Add structs, enums for `mdast`

1 files changed, 1922 insertions, 0 deletions

diff --git a/src/to_html.rs b/src/to_html.rs
new file mode 100644
index 0000000..43be6a7
--- /dev/null
+++ b/src/to_html.rs
@@ -0,0 +1,1922 @@
+//! Turn events into a string of HTML.
+use crate::event::{Event, Kind, Name};
+use crate::util::{
+    constant::{SAFE_PROTOCOL_HREF, SAFE_PROTOCOL_SRC},
+    decode_character_reference::{decode_named, decode_numeric},
+    encode::encode,
+    gfm_tagfilter::gfm_tagfilter,
+    normalize_identifier::normalize_identifier,
+    sanitize_uri::{sanitize, sanitize_with_protocols},
+    skip,
+    slice::{Position, Slice},
+};
+use crate::{LineEnding, Options};
+use alloc::{
+    format,
+    string::{String, ToString},
+    vec,
+    vec::Vec,
+};
+use core::str;
+
+/// Link, image, or footnote call.
+/// Resource or reference.
+/// Reused for temporary definitions as well, in the first pass.
+#[derive(Debug)]
+struct Media {
+    /// Whether this represents an image (`true`) or a link or definition
+    /// (`false`).
+    image: bool,
+    /// The text between the brackets (`x` in `![x]()` and `[x]()`).
+    ///
+    /// Not interpreted.
+    label_id: Option<(usize, usize)>,
+    /// The result of interpreting the text between the brackets
+    /// (`x` in `![x]()` and `[x]()`).
+    ///
+    /// When this is a link, it contains further text content and thus HTML
+    /// tags.
+    /// Otherwise, when an image, text content is also allowed, but resulting
+    /// tags are ignored.
+    label: Option<String>,
+    /// The string between the explicit brackets of the reference (`y` in
+    /// `[x][y]`), as content.
+    ///
+    /// Not interpreted.
+    reference_id: Option<(usize, usize)>,
+    /// The destination (url).
+    ///
+    /// Interpreted string content.
+    destination: Option<String>,
+    /// The destination (url).
+    ///
+    /// Interpreted string content.
+    title: Option<String>,
+}
+
+/// Representation of a definition.
+#[derive(Debug)]
+struct Definition {
+    /// Identifier.
+    id: String,
+    /// The destination (url).
+    ///
+    /// Interpreted string content.
+    destination: Option<String>,
+    /// The title.
+    ///
+    /// Interpreted string content.
+    title: Option<String>,
+}
+
+/// GFM table: column alignment.
+// To do: share with `mdast`.
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
+enum GfmTableAlign {
+    /// No alignment.
+    ///
+    /// ```markdown
+    ///   | | aaa |
+    /// > | | --- |
+    ///       ^^^
+    /// ```
+    None,
+    /// Left alignment.
+    ///
+    /// ```markdown
+    ///   | | aaa |
+    /// > | | :-- |
+    ///       ^^^
+    /// ```
+    Left,
+    /// Center alignment.
+    ///
+    /// ```markdown
+    ///   | | aaa |
+    /// > | | :-: |
+    ///       ^^^
+    /// ```
+    Center,
+    /// Right alignment.
+    ///
+    /// ```markdown
+    ///   | | aaa |
+    /// > | | --: |
+    ///       ^^^
+    /// ```
+    Right,
+}
+
+/// Context used to compile markdown.
+#[allow(clippy::struct_excessive_bools)]
+#[derive(Debug)]
+struct CompileContext<'a> {
+    // Static info.
+    /// List of events.
+    pub events: &'a [Event],
+    /// List of bytes.
+    pub bytes: &'a [u8],
+    /// Configuration.
+    pub options: &'a Options,
+    // Fields used by handlers to track the things they need to track to
+    // compile markdown.
+    /// Rank of heading (atx).
+    pub heading_atx_rank: Option<usize>,
+    /// Buffer of heading (setext) text.
+    pub heading_setext_buffer: Option<String>,
+    /// Whether raw (flow) (code (fenced), math (flow)) or code (indented) contains data.
+    pub raw_flow_seen_data: Option<bool>,
+    /// Number of raw (flow) fences.
+    pub raw_flow_fences_count: Option<usize>,
+    /// Whether we are in code (text).
+    pub raw_text_inside: bool,
+    /// Whether we are in image text.
+    pub image_alt_inside: bool,
+    /// Marker of character reference.
+    pub character_reference_marker: Option<u8>,
+    /// Whether we are expecting the first list item marker.
+    pub list_expect_first_marker: Option<bool>,
+    /// Stack of media (link, image).
+    pub media_stack: Vec<Media>,
+    /// Stack of containers.
+    pub tight_stack: Vec<bool>,
+    /// List of definitions.
+    pub definitions: Vec<Definition>,
+    /// List of definitions.
+    pub gfm_footnote_definitions: Vec<(String, String)>,
+    pub gfm_footnote_definition_calls: Vec<(String, usize)>,
+    pub gfm_footnote_definition_stack: Vec<(usize, usize)>,
+    /// Whether we are in a GFM table head.
+    pub gfm_table_in_head: bool,
+    /// Current GFM table alignment.
+    pub gfm_table_align: Option<Vec<GfmTableAlign>>,
+    /// Current GFM table column.
+    pub gfm_table_column: usize,
+    // Fields used to influance the current compilation.
+    /// Ignore the next line ending.
+    pub slurp_one_line_ending: bool,
+    /// Whether to encode HTML.
+    pub encode_html: bool,
+    // Configuration
+    /// Line ending to use.
+    pub line_ending_default: LineEnding,
+    // Intermediate results.
+    /// Stack of buffers.
+    pub buffers: Vec<String>,
+    /// Current event index.
+    pub index: usize,
+}
+
+impl<'a> CompileContext<'a> {
+    /// Create a new compile context.
+    pub fn new(
+        events: &'a [Event],
+        bytes: &'a [u8],
+        options: &'a Options,
+        line_ending: LineEnding,
+    ) -> CompileContext<'a> {
+        CompileContext {
+            events,
+            bytes,
+            heading_atx_rank: None,
+            heading_setext_buffer: None,
+            raw_flow_seen_data: None,
+            raw_flow_fences_count: None,
+            raw_text_inside: false,
+            character_reference_marker: None,
+            list_expect_first_marker: None,
+            media_stack: vec![],
+            definitions: vec![],
+            gfm_footnote_definitions: vec![],
+            gfm_footnote_definition_calls: vec![],
+            gfm_footnote_definition_stack: vec![],
+            gfm_table_in_head: false,
+            gfm_table_align: None,
+            gfm_table_column: 0,
+            tight_stack: vec![],
+            slurp_one_line_ending: false,
+            image_alt_inside: false,
+            encode_html: true,
+            line_ending_default: line_ending,
+            buffers: vec![String::new()],
+            index: 0,
+            options,
+        }
+    }
+
+    /// Push a buffer.
+    pub fn buffer(&mut self) {
+        self.buffers.push(String::new());
+    }
+
+    /// Pop a buffer, returning its value.
+    pub fn resume(&mut self) -> String {
+        self.buffers.pop().expect("Cannot resume w/o buffer")
+    }
+
+    /// Push a str to the last buffer.
+    pub fn push(&mut self, value: &str) {
+        self.buffers
+            .last_mut()
+            .expect("Cannot push w/o buffer")
+            .push_str(value);
+    }
+
+    /// Add a line ending.
+    pub fn line_ending(&mut self) {
+        let eol = self.line_ending_default.as_str().to_string();
+        self.push(&eol);
+    }
+
+    /// Add a line ending if needed (as in, there’s no eol/eof already).
+    pub fn line_ending_if_needed(&mut self) {
+        let tail = self
+            .buffers
+            .last()
+            .expect("at least one buffer should exist")
+            .as_bytes()
+            .last();
+
+        if !matches!(tail, None | Some(b'\n' | b'\r')) {
+            self.line_ending();
+        }
+    }
+}
+
+/// Turn events and bytes into a string of HTML.
+pub fn compile(events: &[Event], bytes: &[u8], options: &Options) -> String {
+    let mut index = 0;
+    let mut line_ending_inferred = None;
+
+    // First, we figure out what the used line ending style is.
+    // Stop when we find a line ending.
+    while index < events.len() {
+        let event = &events[index];
+
+        if event.kind == Kind::Exit
+            && (event.name == Name::BlankLineEnding || event.name == Name::LineEnding)
+        {
+            line_ending_inferred = Some(LineEnding::from_str(
+                Slice::from_position(bytes, &Position::from_exit_event(events, index)).as_str(),
+            ));
+            break;
+        }
+
+        index += 1;
+    }
+
+    // Figure out which line ending style we’ll use.
+    let line_ending_default =
+        line_ending_inferred.unwrap_or_else(|| options.default_line_ending.clone());
+
+    let mut context = CompileContext::new(events, bytes, options, line_ending_default);
+    let mut definition_indices = vec![];
+    let mut index = 0;
+    let mut definition_inside = false;
+
+    // Handle all definitions first.
+    // We must do two passes because we need to compile the events in
+    // definitions which come after references already.
+    //
+    // To speed things up, we collect the places we can jump over for the
+    // second pass.
+    //
+    // We don’t need to handle GFM footnote definitions like this, because
+    // unlike normal definitions, what they produce is not used in calls.
+    // It would also get very complex, because footnote definitions can be
+    // nested.
+    while index < events.len() {
+        let event = &events[index];
+
+        if definition_inside {
+            handle(&mut context, index);
+        }
+
+        if event.kind == Kind::Enter {
+            if event.name == Name::Definition {
+                handle(&mut context, index); // Also handle start.
+                definition_inside = true;
+                definition_indices.push((index, index));
+            }
+        } else if event.name == Name::Definition {
+            definition_inside = false;
+            definition_indices.last_mut().unwrap().1 = index;
+        }
+
+        index += 1;
+    }
+
+    index = 0;
+    let jump_default = (events.len(), events.len());
+    let mut definition_index = 0;
+    let mut jump = definition_indices
+        .get(definition_index)
+        .unwrap_or(&jump_default);
+
+    while index < events.len() {
+        if index == jump.0 {
+            index = jump.1 + 1;
+            definition_index += 1;
+            jump = definition_indices
+                .get(definition_index)
+                .unwrap_or(&jump_default);
+        } else {
+            handle(&mut context, index);
+            index += 1;
+        }
+    }
+
+    // No section to generate.
+    if !context.gfm_footnote_definition_calls.is_empty() {
+        generate_footnote_section(&mut context);
+    }
+
+    debug_assert_eq!(context.buffers.len(), 1, "expected 1 final buffer");
+    context
+        .buffers
+        .get(0)
+        .expect("expected 1 final buffer")
+        .to_string()
+}
+
+/// Handle the event at `index`.
+fn handle(context: &mut CompileContext, index: usize) {
+    context.index = index;
+
+    if context.events[index].kind == Kind::Enter {
+        enter(context);
+    } else {
+        exit(context);
+    }
+}
+
+/// Handle [`Enter`][Kind::Enter].
+fn enter(context: &mut CompileContext) {
+    match context.events[context.index].name {
+        Name::CodeFencedFenceInfo
+        | Name::CodeFencedFenceMeta
+        | Name::MathFlowFenceMeta
+        | Name::DefinitionLabelString
+        | Name::DefinitionTitleString
+        | Name::GfmFootnoteDefinitionPrefix
+        | Name::HeadingAtxText
+        | Name::HeadingSetextText
+        | Name::Label
+        | Name::MdxEsm
+        | Name::MdxFlowExpression
+        | Name::MdxTextExpression
+        | Name::MdxJsxFlowTag
+        | Name::MdxJsxTextTag
+        | Name::ReferenceString
+        | Name::ResourceTitleString => on_enter_buffer(context),
+
+        Name::BlockQuote => on_enter_block_quote(context),
+        Name::CodeIndented => on_enter_code_indented(context),
+        Name::CodeFenced | Name::MathFlow => on_enter_raw_flow(context),
+        Name::CodeText | Name::MathText => on_enter_raw_text(context),
+        Name::Definition => on_enter_definition(context),
+        Name::DefinitionDestinationString => on_enter_definition_destination_string(context),
+        Name::Emphasis => on_enter_emphasis(context),
+        Name::Frontmatter => on_enter_frontmatter(context),
+        Name::GfmFootnoteDefinition => on_enter_gfm_footnote_definition(context),
+        Name::GfmFootnoteCall => on_enter_gfm_footnote_call(context),
+        Name::GfmStrikethrough => on_enter_gfm_strikethrough(context),
+        Name::GfmTable => on_enter_gfm_table(context),
+        Name::GfmTableBody => on_enter_gfm_table_body(context),
+        Name::GfmTableCell => on_enter_gfm_table_cell(context),
+        Name::GfmTableHead => on_enter_gfm_table_head(context),
+        Name::GfmTableRow => on_enter_gfm_table_row(context),
+        Name::GfmTaskListItemCheck => on_enter_gfm_task_list_item_check(context),
+        Name::HtmlFlow => on_enter_html_flow(context),
+        Name::HtmlText => on_enter_html_text(context),
+        Name::Image => on_enter_image(context),
+        Name::Link => on_enter_link(context),
+        Name::ListItemMarker => on_enter_list_item_marker(context),
+        Name::ListOrdered | Name::ListUnordered => on_enter_list(context),
+        Name::Paragraph => on_enter_paragraph(context),
+        Name::Resource => on_enter_resource(context),
+        Name::ResourceDestinationString => on_enter_resource_destination_string(context),
+        Name::Strong => on_enter_strong(context),
+        _ => {}
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit].
+fn exit(context: &mut CompileContext) {
+    match context.events[context.index].name {
+        Name::CodeFencedFenceMeta
+        | Name::MathFlowFenceMeta
+        | Name::MdxJsxTextTag
+        | Name::MdxTextExpression
+        | Name::Resource => {
+            on_exit_drop(context);
+        }
+        Name::MdxEsm | Name::MdxFlowExpression | Name::MdxJsxFlowTag => on_exit_drop_slurp(context),
+        Name::CharacterEscapeValue | Name::CodeTextData | Name::Data | Name::MathTextData => {
+            on_exit_data(context);
+        }
+        Name::AutolinkEmail => on_exit_autolink_email(context),
+        Name::AutolinkProtocol => on_exit_autolink_protocol(context),
+        Name::BlankLineEnding => on_exit_blank_line_ending(context),
+        Name::BlockQuote => on_exit_block_quote(context),
+        Name::CharacterReferenceMarker => on_exit_character_reference_marker(context),
+        Name::CharacterReferenceMarkerNumeric => {
+            on_exit_character_reference_marker_numeric(context);
+        }
+        Name::CharacterReferenceMarkerHexadecimal => {
+            on_exit_character_reference_marker_hexadecimal(context);
+        }
+        Name::CharacterReferenceValue => on_exit_character_reference_value(context),
+        Name::CodeFenced | Name::CodeIndented | Name::MathFlow => on_exit_raw_flow(context),
+        Name::CodeFencedFence | Name::MathFlowFence => on_exit_raw_flow_fence(context),
+        Name::CodeFencedFenceInfo => on_exit_raw_flow_fence_info(context),
+        Name::CodeFlowChunk | Name::MathFlowChunk => on_exit_raw_flow_chunk(context),
+        Name::CodeText | Name::MathText => on_exit_raw_text(context),
+        Name::Definition => on_exit_definition(context),
+        Name::DefinitionDestinationString => on_exit_definition_destination_string(context),
+        Name::DefinitionLabelString => on_exit_definition_label_string(context),
+        Name::DefinitionTitleString => on_exit_definition_title_string(context),
+        Name::Emphasis => on_exit_emphasis(context),
+        Name::Frontmatter => on_exit_frontmatter(context),
+        Name::GfmAutolinkLiteralEmail => on_exit_gfm_autolink_literal_email(context),
+        Name::GfmAutolinkLiteralMailto => on_exit_gfm_autolink_literal_mailto(context),
+        Name::GfmAutolinkLiteralProtocol => on_exit_gfm_autolink_literal_protocol(context),
+        Name::GfmAutolinkLiteralWww => on_exit_gfm_autolink_literal_www(context),
+        Name::GfmAutolinkLiteralXmpp => on_exit_gfm_autolink_literal_xmpp(context),
+        Name::GfmFootnoteCall => on_exit_gfm_footnote_call(context),
+        Name::GfmFootnoteDefinitionLabelString => {
+            on_exit_gfm_footnote_definition_label_string(context);
+        }
+        Name::GfmFootnoteDefinitionPrefix => on_exit_gfm_footnote_definition_prefix(context),
+        Name::GfmFootnoteDefinition => on_exit_gfm_footnote_definition(context),
+        Name::GfmStrikethrough => on_exit_gfm_strikethrough(context),
+        Name::GfmTable => on_exit_gfm_table(context),
+        Name::GfmTableBody => on_exit_gfm_table_body(context),
+        Name::GfmTableCell => on_exit_gfm_table_cell(context),
+        Name::GfmTableHead => on_exit_gfm_table_head(context),
+        Name::GfmTableRow => on_exit_gfm_table_row(context),
+        Name::GfmTaskListItemCheck => on_exit_gfm_task_list_item_check(context),
+        Name::GfmTaskListItemValueChecked => on_exit_gfm_task_list_item_value_checked(context),
+        Name::HardBreakEscape | Name::HardBreakTrailing => on_exit_break(context),
+        Name::HeadingAtx => on_exit_heading_atx(context),
+        Name::HeadingAtxSequence => on_exit_heading_atx_sequence(context),
+        Name::HeadingAtxText => on_exit_heading_atx_text(context),
+        Name::HeadingSetextText => on_exit_heading_setext_text(context),
+        Name::HeadingSetextUnderlineSequence => on_exit_heading_setext_underline_sequence(context),
+        Name::HtmlFlow | Name::HtmlText => on_exit_html(context),
+        Name::HtmlFlowData | Name::HtmlTextData => on_exit_html_data(context),
+        Name::Image | Name::Link => on_exit_media(context),
+        Name::Label => on_exit_label(context),
+        Name::LabelText => on_exit_label_text(context),
+        Name::LineEnding => on_exit_line_ending(context),
+        Name::ListOrdered | Name::ListUnordered => on_exit_list(context),
+        Name::ListItem => on_exit_list_item(context),
+        Name::ListItemValue => on_exit_list_item_value(context),
+        Name::Paragraph => on_exit_paragraph(context),
+        Name::ReferenceString => on_exit_reference_string(context),
+        Name::ResourceDestinationString => on_exit_resource_destination_string(context),
+        Name::ResourceTitleString => on_exit_resource_title_string(context),
+        Name::Strong => on_exit_strong(context),
+        Name::ThematicBreak => on_exit_thematic_break(context),
+        _ => {}
+    }
+}
+
+/// Handle [`Enter`][Kind::Enter]:`*`.
+///
+/// Buffers data.
+fn on_enter_buffer(context: &mut CompileContext) {
+    context.buffer();
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`BlockQuote`][Name::BlockQuote].
+fn on_enter_block_quote(context: &mut CompileContext) {
+    context.tight_stack.push(false);
+    context.line_ending_if_needed();
+    context.push("<blockquote>");
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`CodeIndented`][Name::CodeIndented].
+fn on_enter_code_indented(context: &mut CompileContext) {
+    context.raw_flow_seen_data = Some(false);
+    context.line_ending_if_needed();
+    context.push("<pre><code>");
+}
+
+/// Handle [`Enter`][Kind::Enter]:{[`CodeFenced`][Name::CodeFenced],[`MathFlow`][Name::MathFlow]}.
+fn on_enter_raw_flow(context: &mut CompileContext) {
+    context.raw_flow_seen_data = Some(false);
+    context.line_ending_if_needed();
+    // Note that no `>` is used, which is added later (due to info)
+    context.push("<pre><code");
+    context.raw_flow_fences_count = Some(0);
+
+    if context.events[context.index].name == Name::MathFlow {
+        context.push(" class=\"language-math math-display\"");
+    }
+}
+
+/// Handle [`Enter`][Kind::Enter]:{[`CodeText`][Name::CodeText],[`MathText`][Name::MathText]}.
+fn on_enter_raw_text(context: &mut CompileContext) {
+    context.raw_text_inside = true;
+    if !context.image_alt_inside {
+        context.push("<code");
+        if context.events[context.index].name == Name::MathText {
+            context.push(" class=\"language-math math-inline\"");
+        }
+        context.push(">");
+    }
+    context.buffer();
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`Definition`][Name::Definition].
+fn on_enter_definition(context: &mut CompileContext) {
+    context.buffer();
+    context.media_stack.push(Media {
+        image: false,
+        label: None,
+        label_id: None,
+        reference_id: None,
+        destination: None,
+        title: None,
+    });
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`DefinitionDestinationString`][Name::DefinitionDestinationString].
+fn on_enter_definition_destination_string(context: &mut CompileContext) {
+    context.buffer();
+    context.encode_html = false;
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`Emphasis`][Name::Emphasis].
+fn on_enter_emphasis(context: &mut CompileContext) {
+    if !context.image_alt_inside {
+        context.push("<em>");
+    }
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`Frontmatter`][Name::Frontmatter].
+fn on_enter_frontmatter(context: &mut CompileContext) {
+    context.buffer();
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`GfmFootnoteDefinition`][Name::GfmFootnoteDefinition].
+fn on_enter_gfm_footnote_definition(context: &mut CompileContext) {
+    context.tight_stack.push(false);
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`GfmFootnoteCall`][Name::GfmFootnoteCall].
+fn on_enter_gfm_footnote_call(context: &mut CompileContext) {
+    context.media_stack.push(Media {
+        image: false,
+        label_id: None,
+        label: None,
+        reference_id: None,
+        destination: None,
+        title: None,
+    });
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`GfmStrikethrough`][Name::GfmStrikethrough].
+fn on_enter_gfm_strikethrough(context: &mut CompileContext) {
+    if !context.image_alt_inside {
+        context.push("<del>");
+    }
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`GfmTable`][Name::GfmTable].
+fn on_enter_gfm_table(context: &mut CompileContext) {
+    // Find the alignment.
+    let mut index = context.index;
+    let mut in_delimiter_row = false;
+    let mut align = vec![];
+
+    while index < context.events.len() {
+        let event = &context.events[index];
+
+        if in_delimiter_row {
+            if event.kind == Kind::Enter {
+                // Start of alignment value: set a new column.
+                if event.name == Name::GfmTableDelimiterCellValue {
+                    align.push(
+                        if context.events[index + 1].name == Name::GfmTableDelimiterMarker {
+                            GfmTableAlign::Left
+                        } else {
+                            GfmTableAlign::None
+                        },
+                    );
+                }
+            } else {
+                // End of alignment value: change the column.
+                if event.name == Name::GfmTableDelimiterCellValue {
+                    if context.events[index - 1].name == Name::GfmTableDelimiterMarker {
+                        let align_index = align.len() - 1;
+                        align[align_index] = if align[align_index] == GfmTableAlign::Left {
+                            GfmTableAlign::Center
+                        } else {
+                            GfmTableAlign::Right
+                        }
+                    }
+                }
+                // Done!
+                else if event.name == Name::GfmTableDelimiterRow {
+                    break;
+                }
+            }
+        } else if event.kind == Kind::Enter && event.name == Name::GfmTableDelimiterRow {
+            in_delimiter_row = true;
+        }
+
+        index += 1;
+    }
+
+    // Generate.
+    context.gfm_table_align = Some(align);
+    context.line_ending_if_needed();
+    context.push("<table>");
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`GfmTableBody`][Name::GfmTableBody].
+fn on_enter_gfm_table_body(context: &mut CompileContext) {
+    context.push("<tbody>");
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`GfmTableCell`][Name::GfmTableCell].
+fn on_enter_gfm_table_cell(context: &mut CompileContext) {
+    let column = context.gfm_table_column;
+    let align = context.gfm_table_align.as_ref().unwrap();
+
+    if column >= align.len() {
+        // Capture cell to ignore it.
+        context.buffer();
+    } else {
+        let value = align[column];
+        context.line_ending_if_needed();
+
+        if context.gfm_table_in_head {
+            context.push("<th");
+        } else {
+            context.push("<td");
+        }
+
+        match value {
+            GfmTableAlign::Left => context.push(" align=\"left\""),
+            GfmTableAlign::Right => context.push(" align=\"right\""),
+            GfmTableAlign::Center => context.push(" align=\"center\""),
+            GfmTableAlign::None => {}
+        }
+
+        context.push(">");
+    }
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`GfmTableHead`][Name::GfmTableHead].
+fn on_enter_gfm_table_head(context: &mut CompileContext) {
+    context.line_ending_if_needed();
+    context.push("<thead>");
+    context.gfm_table_in_head = true;
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`GfmTableRow`][Name::GfmTableRow].
+fn on_enter_gfm_table_row(context: &mut CompileContext) {
+    context.line_ending_if_needed();
+    context.push("<tr>");
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`GfmTaskListItemCheck`][Name::GfmTaskListItemCheck].
+fn on_enter_gfm_task_list_item_check(context: &mut CompileContext) {
+    if !context.image_alt_inside {
+        context.push("<input type=\"checkbox\" disabled=\"\" ");
+    }
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`HtmlFlow`][Name::HtmlFlow].
+fn on_enter_html_flow(context: &mut CompileContext) {
+    context.line_ending_if_needed();
+    if context.options.allow_dangerous_html {
+        context.encode_html = false;
+    }
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`HtmlText`][Name::HtmlText].
+fn on_enter_html_text(context: &mut CompileContext) {
+    if context.options.allow_dangerous_html {
+        context.encode_html = false;
+    }
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`Image`][Name::Image].
+fn on_enter_image(context: &mut CompileContext) {
+    context.media_stack.push(Media {
+        image: true,
+        label_id: None,
+        label: None,
+        reference_id: None,
+        destination: None,
+        title: None,
+    });
+    context.image_alt_inside = true; // Disallow tags.
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`Link`][Name::Link].
+fn on_enter_link(context: &mut CompileContext) {
+    context.media_stack.push(Media {
+        image: false,
+        label_id: None,
+        label: None,
+        reference_id: None,
+        destination: None,
+        title: None,
+    });
+}
+
+/// Handle [`Enter`][Kind::Enter]:{[`ListOrdered`][Name::ListOrdered],[`ListUnordered`][Name::ListUnordered]}.
+fn on_enter_list(context: &mut CompileContext) {
+    let events = &context.events;
+    let mut index = context.index;
+    let mut balance = 0;
+    let mut loose = false;
+    let name = &events[index].name;
+
+    while index < events.len() {
+        let event = &events[index];
+
+        if event.kind == Kind::Enter {
+            balance += 1;
+        } else {
+            balance -= 1;
+
+            if balance < 3 && event.name == Name::BlankLineEnding {
+                // Blank line directly after a prefix:
+                //
+                // ```markdown
+                // > | -␊
+                //      ^
+                //   |   a
+                // ```
+                let mut at_prefix = false;
+                // Blank line directly after item, which is just a prefix.
+                //
+                // ```markdown
+                // > | -␊
+                //      ^
+                //   | - a
+                // ```
+                let mut at_empty_list_item = false;
+                // Blank line at block quote prefix:
+                //
+                // ```markdown
+                // > | * >␊
+                //        ^
+                //   | * a
+                // ```
+                let mut at_empty_block_quote = false;
+
+                if balance == 1 {
+                    let mut before = index - 2;
+
+                    if events[before].name == Name::ListItem {
+                        before -= 1;
+
+                        if events[before].name == Name::SpaceOrTab {
+                            before -= 2;
+                        }
+
+                        if events[before].name == Name::BlockQuote
+                            && events[before - 1].name == Name::BlockQuotePrefix
+                        {
+                            at_empty_block_quote = true;
+                        } else if events[before].name == Name::ListItemPrefix {
+                            at_empty_list_item = true;
+                        }
+                    }
+                } else {
+                    let mut before = index - 2;
+
+                    if events[before].name == Name::SpaceOrTab {
+                        before -= 2;
+                    }
+
+                    if events[before].name == Name::ListItemPrefix {
+                        at_prefix = true;
+                    }
+                }
+
+                if !at_prefix && !at_empty_list_item && !at_empty_block_quote {
+                    loose = true;
+                    break;
+                }
+            }
+
+            // Done.
+            if balance == 0 && event.name == *name {
+                break;
+            }
+        }
+
+        index += 1;
+    }
+
+    context.tight_stack.push(!loose);
+    context.line_ending_if_needed();
+    // Note: no `>`.
+    context.push(if *name == Name::ListOrdered {
+        "<ol"
+    } else {
+        "<ul"
+    });
+    context.list_expect_first_marker = Some(true);
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`ListItemMarker`][Name::ListItemMarker].
+fn on_enter_list_item_marker(context: &mut CompileContext) {
+    if context.list_expect_first_marker.take().unwrap() {
+        context.push(">");
+    }
+
+    context.line_ending_if_needed();
+
+    context.push("<li>");
+    context.list_expect_first_marker = Some(false);
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`Paragraph`][Name::Paragraph].
+fn on_enter_paragraph(context: &mut CompileContext) {
+    let tight = context.tight_stack.last().unwrap_or(&false);
+
+    if !tight {
+        context.line_ending_if_needed();
+        context.push("<p>");
+    }
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`Resource`][Name::Resource].
+fn on_enter_resource(context: &mut CompileContext) {
+    context.buffer(); // We can have line endings in the resource, ignore them.
+    context.media_stack.last_mut().unwrap().destination = Some("".to_string());
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`ResourceDestinationString`][Name::ResourceDestinationString].
+fn on_enter_resource_destination_string(context: &mut CompileContext) {
+    context.buffer();
+    // Ignore encoding the result, as we’ll first percent encode the url and
+    // encode manually after.
+    context.encode_html = false;
+}
+
+/// Handle [`Enter`][Kind::Enter]:[`Strong`][Name::Strong].
+fn on_enter_strong(context: &mut CompileContext) {
+    if !context.image_alt_inside {
+        context.push("<strong>");
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`AutolinkEmail`][Name::AutolinkEmail].
+fn on_exit_autolink_email(context: &mut CompileContext) {
+    generate_autolink(
+        context,
+        Some("mailto:"),
+        Slice::from_position(
+            context.bytes,
+            &Position::from_exit_event(context.events, context.index),
+        )
+        .as_str(),
+        false,
+    );
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`AutolinkProtocol`][Name::AutolinkProtocol].
+fn on_exit_autolink_protocol(context: &mut CompileContext) {
+    generate_autolink(
+        context,
+        None,
+        Slice::from_position(
+            context.bytes,
+            &Position::from_exit_event(context.events, context.index),
+        )
+        .as_str(),
+        false,
+    );
+}
+
+/// Handle [`Exit`][Kind::Exit]:{[`HardBreakEscape`][Name::HardBreakEscape],[`HardBreakTrailing`][Name::HardBreakTrailing]}.
+fn on_exit_break(context: &mut CompileContext) {
+    if !context.image_alt_inside {
+        context.push("<br />");
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`BlankLineEnding`][Name::BlankLineEnding].
+fn on_exit_blank_line_ending(context: &mut CompileContext) {
+    if context.index == context.events.len() - 1 {
+        context.line_ending_if_needed();
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`BlockQuote`][Name::BlockQuote].
+fn on_exit_block_quote(context: &mut CompileContext) {
+    context.tight_stack.pop();
+    context.line_ending_if_needed();
+    context.slurp_one_line_ending = false;
+    context.push("</blockquote>");
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`CharacterReferenceMarker`][Name::CharacterReferenceMarker].
+fn on_exit_character_reference_marker(context: &mut CompileContext) {
+    context.character_reference_marker = Some(b'&');
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`CharacterReferenceMarkerHexadecimal`][Name::CharacterReferenceMarkerHexadecimal].
+fn on_exit_character_reference_marker_hexadecimal(context: &mut CompileContext) {
+    context.character_reference_marker = Some(b'x');
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`CharacterReferenceMarkerNumeric`][Name::CharacterReferenceMarkerNumeric].
+fn on_exit_character_reference_marker_numeric(context: &mut CompileContext) {
+    context.character_reference_marker = Some(b'#');
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`CharacterReferenceValue`][Name::CharacterReferenceValue].
+fn on_exit_character_reference_value(context: &mut CompileContext) {
+    let marker = context
+        .character_reference_marker
+        .take()
+        .expect("expected `character_reference_kind` to be set");
+    let slice = Slice::from_position(
+        context.bytes,
+        &Position::from_exit_event(context.events, context.index),
+    );
+    let value = slice.as_str();
+
+    let value = match marker {
+        b'#' => decode_numeric(value, 10),
+        b'x' => decode_numeric(value, 16),
+        b'&' => decode_named(value),
+        _ => panic!("impossible"),
+    };
+
+    context.push(&encode(&value, context.encode_html));
+}
+
+/// Handle [`Exit`][Kind::Exit]:{[`CodeFlowChunk`][Name::CodeFlowChunk],[`MathFlowChunk`][Name::MathFlowChunk]}.
+fn on_exit_raw_flow_chunk(context: &mut CompileContext) {
+    context.raw_flow_seen_data = Some(true);
+    context.push(&encode(
+        &Slice::from_position(
+            context.bytes,
+            &Position::from_exit_event(context.events, context.index),
+        )
+        // Must serialize to get virtual spaces.
+        .serialize(),
+        context.encode_html,
+    ));
+}
+
+/// Handle [`Exit`][Kind::Exit]:{[`CodeFencedFence`][Name::CodeFencedFence],[`MathFlowFence`][Name::MathFlowFence]}.
+fn on_exit_raw_flow_fence(context: &mut CompileContext) {
+    let count = if let Some(count) = context.raw_flow_fences_count {
+        count
+    } else {
+        0
+    };
+
+    if count == 0 {
+        context.push(">");
+        context.slurp_one_line_ending = true;
+    }
+
+    context.raw_flow_fences_count = Some(count + 1);
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`CodeFencedFenceInfo`][Name::CodeFencedFenceInfo].
+///
+/// Note: math (flow) does not support `info`.
+fn on_exit_raw_flow_fence_info(context: &mut CompileContext) {
+    let value = context.resume();
+    context.push(" class=\"language-");
+    context.push(&value);
+    context.push("\"");
+}
+
+/// Handle [`Exit`][Kind::Exit]:{[`CodeFenced`][Name::CodeFenced],[`CodeIndented`][Name::CodeIndented],[`MathFlow`][Name::MathFlow]}.
+fn on_exit_raw_flow(context: &mut CompileContext) {
+    // One special case is if we are inside a container, and the raw (flow) was
+    // not closed (meaning it runs to the end).
+    // In that case, the following line ending, is considered *outside* the
+    // fenced code and block quote by micromark, but CM wants to treat that
+    // ending as part of the code.
+    if let Some(count) = context.raw_flow_fences_count {
+        // No closing fence.
+        if count == 1
+            // In a container.
+            && !context.tight_stack.is_empty()
+            // Empty (as the closing is right at the opening fence)
+            && !matches!(context.events[context.index - 1].name, Name::CodeFencedFence | Name::MathFlowFence)
+        {
+            context.line_ending();
+        }
+    }
+
+    // But in most cases, it’s simpler: when we’ve seen some data, emit an extra
+    // line ending when needed.
+    if context
+        .raw_flow_seen_data
+        .take()
+        .expect("`raw_flow_seen_data` must be defined")
+    {
+        context.line_ending_if_needed();
+    }
+
+    context.push("</code></pre>");
+
+    if let Some(count) = context.raw_flow_fences_count.take() {
+        if count < 2 {
+            context.line_ending_if_needed();
+        }
+    }
+
+    context.slurp_one_line_ending = false;
+}
+
+/// Handle [`Exit`][Kind::Exit]:{[`CodeText`][Name::CodeText],[`MathText`][Name::MathText]}.
+fn on_exit_raw_text(context: &mut CompileContext) {
+    let result = context.resume();
+    let mut bytes = result.as_bytes().to_vec();
+
+    // If we are in a GFM table, we need to decode escaped pipes.
+    // This is a rather weird GFM feature.
+    if context.gfm_table_align.is_some() {
+        let mut index = 0;
+        let mut len = bytes.len();
+
+        while index < len {
+            if index + 1 < len && bytes[index] == b'\\' && bytes[index + 1] == b'|' {
+                bytes.remove(index);
+                len -= 1;
+            }
+
+            index += 1;
+        }
+    }
+
+    let mut trim = false;
+    let mut index = 0;
+    let mut end = bytes.len();
+
+    if end > 2 && bytes[index] == b' ' && bytes[end - 1] == b' ' {
+        index += 1;
+        end -= 1;
+        while index < end && !trim {
+            if bytes[index] != b' ' {
+                trim = true;
+                break;
+            }
+            index += 1;
+        }
+    }
+
+    if trim {
+        bytes.remove(0);
+        bytes.pop();
+    }
+
+    context.raw_text_inside = false;
+    context.push(str::from_utf8(&bytes).unwrap());
+
+    if !context.image_alt_inside {
+        context.push("</code>");
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:*.
+///
+/// Resumes, and ignores what was resumed.
+fn on_exit_drop(context: &mut CompileContext) {
+    context.resume();
+}
+
+/// Handle [`Exit`][Kind::Exit]:*.
+///
+/// Resumes, ignores what was resumed, and slurps the following line ending.
+fn on_exit_drop_slurp(context: &mut CompileContext) {
+    context.resume();
+    context.slurp_one_line_ending = true;
+}
+
+/// Handle [`Exit`][Kind::Exit]:{[`CodeTextData`][Name::CodeTextData],[`Data`][Name::Data],[`CharacterEscapeValue`][Name::CharacterEscapeValue]}.
+fn on_exit_data(context: &mut CompileContext) {
+    context.push(&encode(
+        Slice::from_position(
+            context.bytes,
+            &Position::from_exit_event(context.events, context.index),
+        )
+        .as_str(),
+        context.encode_html,
+    ));
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`Definition`][Name::Definition].
+fn on_exit_definition(context: &mut CompileContext) {
+    context.resume();
+    let media = context.media_stack.pop().unwrap();
+    let indices = media.reference_id.unwrap();
+    let id =
+        normalize_identifier(Slice::from_indices(context.bytes, indices.0, indices.1).as_str());
+
+    context.definitions.push(Definition {
+        id,
+        destination: media.destination,
+        title: media.title,
+    });
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`DefinitionDestinationString`][Name::DefinitionDestinationString].
+fn on_exit_definition_destination_string(context: &mut CompileContext) {
+    let buf = context.resume();
+    context.media_stack.last_mut().unwrap().destination = Some(buf);
+    context.encode_html = true;
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`DefinitionLabelString`][Name::DefinitionLabelString].
+fn on_exit_definition_label_string(context: &mut CompileContext) {
+    // Discard label, use the source content instead.
+    context.resume();
+    context.media_stack.last_mut().unwrap().reference_id =
+        Some(Position::from_exit_event(context.events, context.index).to_indices());
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`DefinitionTitleString`][Name::DefinitionTitleString].
+fn on_exit_definition_title_string(context: &mut CompileContext) {
+    let buf = context.resume();
+    context.media_stack.last_mut().unwrap().title = Some(buf);
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`Emphasis`][Name::Emphasis].
+fn on_exit_emphasis(context: &mut CompileContext) {
+    if !context.image_alt_inside {
+        context.push("</em>");
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`Frontmatter`][Name::Frontmatter].
+fn on_exit_frontmatter(context: &mut CompileContext) {
+    context.resume();
+    context.slurp_one_line_ending = true;
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmAutolinkLiteralEmail`][Name::GfmAutolinkLiteralEmail].
+fn on_exit_gfm_autolink_literal_email(context: &mut CompileContext) {
+    generate_autolink(
+        context,
+        Some("mailto:"),
+        Slice::from_position(
+            context.bytes,
+            &Position::from_exit_event(context.events, context.index),
+        )
+        .as_str(),
+        true,
+    );
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmAutolinkLiteralMailto`][Name::GfmAutolinkLiteralMailto].
+fn on_exit_gfm_autolink_literal_mailto(context: &mut CompileContext) {
+    generate_autolink(
+        context,
+        None,
+        Slice::from_position(
+            context.bytes,
+            &Position::from_exit_event(context.events, context.index),
+        )
+        .as_str(),
+        true,
+    );
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmAutolinkLiteralProtocol`][Name::GfmAutolinkLiteralProtocol].
+fn on_exit_gfm_autolink_literal_protocol(context: &mut CompileContext) {
+    generate_autolink(
+        context,
+        None,
+        Slice::from_position(
+            context.bytes,
+            &Position::from_exit_event(context.events, context.index),
+        )
+        .as_str(),
+        true,
+    );
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmAutolinkLiteralWww`][Name::GfmAutolinkLiteralWww].
+fn on_exit_gfm_autolink_literal_www(context: &mut CompileContext) {
+    generate_autolink(
+        context,
+        Some("http://"),
+        Slice::from_position(
+            context.bytes,
+            &Position::from_exit_event(context.events, context.index),
+        )
+        .as_str(),
+        true,
+    );
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmAutolinkLiteralXmpp`][Name::GfmAutolinkLiteralXmpp].
+fn on_exit_gfm_autolink_literal_xmpp(context: &mut CompileContext) {
+    generate_autolink(
+        context,
+        None,
+        Slice::from_position(
+            context.bytes,
+            &Position::from_exit_event(context.events, context.index),
+        )
+        .as_str(),
+        true,
+    );
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmFootnoteCall`][Name::GfmFootnoteCall].
+fn on_exit_gfm_footnote_call(context: &mut CompileContext) {
+    let indices = context.media_stack.pop().unwrap().label_id.unwrap();
+    let id =
+        normalize_identifier(Slice::from_indices(context.bytes, indices.0, indices.1).as_str());
+    let safe_id = sanitize(&id.to_lowercase());
+    let mut call_index = 0;
+
+    // See if this has been called before.
+    while call_index < context.gfm_footnote_definition_calls.len() {
+        if context.gfm_footnote_definition_calls[call_index].0 == id {
+            break;
+        }
+        call_index += 1;
+    }
+
+    // New.
+    if call_index == context.gfm_footnote_definition_calls.len() {
+        context.gfm_footnote_definition_calls.push((id, 0));
+    }
+
+    // Increment.
+    context.gfm_footnote_definition_calls[call_index].1 += 1;
+
+    // No call is output in an image alt, though the definition and
+    // backreferences are generated as if it was the case.
+    if context.image_alt_inside {
+        return;
+    }
+
+    context.push("<sup><a href=\"#");
+    if let Some(ref value) = context.options.gfm_footnote_clobber_prefix {
+        context.push(&encode(value, context.encode_html));
+    } else {
+        context.push("user-content-");
+    }
+    context.push("fn-");
+    context.push(&safe_id);
+    context.push("\" id=\"");
+    if let Some(ref value) = context.options.gfm_footnote_clobber_prefix {
+        context.push(&encode(value, context.encode_html));
+    } else {
+        context.push("user-content-");
+    }
+    context.push("fnref-");
+    context.push(&safe_id);
+    if context.gfm_footnote_definition_calls[call_index].1 > 1 {
+        context.push("-");
+        context.push(
+            &context.gfm_footnote_definition_calls[call_index]
+                .1
+                .to_string(),
+        );
+    }
+    context.push("\" data-footnote-ref=\"\" aria-describedby=\"footnote-label\">");
+
+    context.push(&(call_index + 1).to_string());
+    context.push("</a></sup>");
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmFootnoteDefinitionLabelString`][Name::GfmFootnoteDefinitionLabelString].
+fn on_exit_gfm_footnote_definition_label_string(context: &mut CompileContext) {
+    context
+        .gfm_footnote_definition_stack
+        .push(Position::from_exit_event(context.events, context.index).to_indices());
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmFootnoteDefinitionPrefix`][Name::GfmFootnoteDefinitionPrefix].
+fn on_exit_gfm_footnote_definition_prefix(context: &mut CompileContext) {
+    // Drop the prefix.
+    context.resume();
+    // Capture everything until end of definition.
+    context.buffer();
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmFootnoteDefinition`][Name::GfmFootnoteDefinition].
+fn on_exit_gfm_footnote_definition(context: &mut CompileContext) {
+    let value = context.resume();
+    let indices = context.gfm_footnote_definition_stack.pop().unwrap();
+    context.tight_stack.pop();
+    context.gfm_footnote_definitions.push((
+        normalize_identifier(Slice::from_indices(context.bytes, indices.0, indices.1).as_str()),
+        value,
+    ));
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmStrikethrough`][Name::GfmStrikethrough].
+fn on_exit_gfm_strikethrough(context: &mut CompileContext) {
+    if !context.image_alt_inside {
+        context.push("</del>");
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmTable`][Name::GfmTable].
+fn on_exit_gfm_table(context: &mut CompileContext) {
+    context.gfm_table_align = None;
+    context.line_ending_if_needed();
+    context.push("</table>");
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmTableBody`][Name::GfmTableBody].
+fn on_exit_gfm_table_body(context: &mut CompileContext) {
+    context.line_ending_if_needed();
+    context.push("</tbody>");
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmTableCell`][Name::GfmTableCell].
+fn on_exit_gfm_table_cell(context: &mut CompileContext) {
+    let align = context.gfm_table_align.as_ref().unwrap();
+
+    if context.gfm_table_column < align.len() {
+        if context.gfm_table_in_head {
+            context.push("</th>");
+        } else {
+            context.push("</td>");
+        }
+    } else {
+        // Stop capturing.
+        context.resume();
+    }
+
+    context.gfm_table_column += 1;
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmTableHead`][Name::GfmTableHead].
+fn on_exit_gfm_table_head(context: &mut CompileContext) {
+    context.gfm_table_in_head = false;
+    context.line_ending_if_needed();
+    context.push("</thead>");
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmTableRow`][Name::GfmTableRow].
+fn on_exit_gfm_table_row(context: &mut CompileContext) {
+    let mut column = context.gfm_table_column;
+    let len = context.gfm_table_align.as_ref().unwrap().len();
+
+    // Add “phantom” cells, for body rows that are shorter than the delimiter
+    // row (which is equal to the head row).
+    while column < len {
+        on_enter_gfm_table_cell(context);
+        on_exit_gfm_table_cell(context);
+        column += 1;
+    }
+
+    context.gfm_table_column = 0;
+    context.line_ending_if_needed();
+    context.push("</tr>");
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmTaskListItemCheck`][Name::GfmTaskListItemCheck].
+fn on_exit_gfm_task_list_item_check(context: &mut CompileContext) {
+    if !context.image_alt_inside {
+        context.push("/>");
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`GfmTaskListItemValueChecked`][Name::GfmTaskListItemValueChecked].
+fn on_exit_gfm_task_list_item_value_checked(context: &mut CompileContext) {
+    if !context.image_alt_inside {
+        context.push("checked=\"\" ");
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`HeadingAtx`][Name::HeadingAtx].
+fn on_exit_heading_atx(context: &mut CompileContext) {
+    let rank = context
+        .heading_atx_rank
+        .take()
+        .expect("`heading_atx_rank` must be set in headings");
+
+    context.push("</h");
+    context.push(&rank.to_string());
+    context.push(">");
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`HeadingAtxSequence`][Name::HeadingAtxSequence].
+fn on_exit_heading_atx_sequence(context: &mut CompileContext) {
+    // First fence we see.
+    if context.heading_atx_rank.is_none() {
+        let rank = Slice::from_position(
+            context.bytes,
+            &Position::from_exit_event(context.events, context.index),
+        )
+        .len();
+        context.line_ending_if_needed();
+        context.heading_atx_rank = Some(rank);
+        context.push("<h");
+        context.push(&rank.to_string());
+        context.push(">");
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`HeadingAtxText`][Name::HeadingAtxText].
+fn on_exit_heading_atx_text(context: &mut CompileContext) {
+    let value = context.resume();
+    context.push(&value);
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`HeadingSetextText`][Name::HeadingSetextText].
+fn on_exit_heading_setext_text(context: &mut CompileContext) {
+    let buf = context.resume();
+    context.heading_setext_buffer = Some(buf);
+    context.slurp_one_line_ending = true;
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`HeadingSetextUnderlineSequence`][Name::HeadingSetextUnderlineSequence].
+fn on_exit_heading_setext_underline_sequence(context: &mut CompileContext) {
+    let text = context
+        .heading_setext_buffer
+        .take()
+        .expect("`heading_atx_rank` must be set in headings");
+    let head = Slice::from_position(
+        context.bytes,
+        &Position::from_exit_event(context.events, context.index),
+    )
+    .head();
+    let rank = if head == Some(b'-') { "2" } else { "1" };
+
+    context.line_ending_if_needed();
+    context.push("<h");
+    context.push(rank);
+    context.push(">");
+    context.push(&text);
+    context.push("</h");
+    context.push(rank);
+    context.push(">");
+}
+
+/// Handle [`Exit`][Kind::Exit]:{[`HtmlFlow`][Name::HtmlFlow],[`HtmlText`][Name::HtmlText]}.
+fn on_exit_html(context: &mut CompileContext) {
+    context.encode_html = true;
+}
+
+/// Handle [`Exit`][Kind::Exit]:{[`HtmlFlowData`][Name::HtmlFlowData],[`HtmlTextData`][Name::HtmlTextData]}.
+fn on_exit_html_data(context: &mut CompileContext) {
+    let slice = Slice::from_position(
+        context.bytes,
+        &Position::from_exit_event(context.events, context.index),
+    );
+    let value = slice.as_str();
+
+    let encoded = if context.options.gfm_tagfilter && context.options.allow_dangerous_html {
+        encode(&gfm_tagfilter(value), context.encode_html)
+    } else {
+        encode(value, context.encode_html)
+    };
+
+    context.push(&encoded);
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`Label`][Name::Label].
+fn on_exit_label(context: &mut CompileContext) {
+    let buf = context.resume();
+    context.media_stack.last_mut().unwrap().label = Some(buf);
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`LabelText`][Name::LabelText].
+fn on_exit_label_text(context: &mut CompileContext) {
+    context.media_stack.last_mut().unwrap().label_id =
+        Some(Position::from_exit_event(context.events, context.index).to_indices());
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`LineEnding`][Name::LineEnding].
+fn on_exit_line_ending(context: &mut CompileContext) {
+    if context.raw_text_inside {
+        context.push(" ");
+    } else if context.slurp_one_line_ending
+        // Ignore line endings after definitions.
+        || (context.index > 1
+            && (context.events[context.index - 2].name == Name::Definition
+                || context.events[context.index - 2].name == Name::GfmFootnoteDefinition))
+    {
+        context.slurp_one_line_ending = false;
+    } else {
+        context.push(&encode(
+            Slice::from_position(
+                context.bytes,
+                &Position::from_exit_event(context.events, context.index),
+            )
+            .as_str(),
+            context.encode_html,
+        ));
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:{[`ListOrdered`][Name::ListOrdered],[`ListUnordered`][Name::ListUnordered]}.
+fn on_exit_list(context: &mut CompileContext) {
+    context.tight_stack.pop();
+    context.line_ending();
+    context.push(if context.events[context.index].name == Name::ListOrdered {
+        "</ol>"
+    } else {
+        "</ul>"
+    });
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`ListItem`][Name::ListItem].
+fn on_exit_list_item(context: &mut CompileContext) {
+    let tight = context.tight_stack.last().unwrap_or(&false);
+    let before_item = skip::opt_back(
+        context.events,
+        context.index - 1,
+        &[
+            Name::BlankLineEnding,
+            Name::BlockQuotePrefix,
+            Name::LineEnding,
+            Name::SpaceOrTab,
+            // Also ignore things that don’t contribute to the document.
+            Name::Definition,
+            Name::GfmFootnoteDefinition,
+        ],
+    );
+    let previous = &context.events[before_item];
+    let tight_paragraph = *tight && previous.name == Name::Paragraph;
+    let empty_item = previous.name == Name::ListItemPrefix;
+
+    context.slurp_one_line_ending = false;
+
+    if !tight_paragraph && !empty_item {
+        context.line_ending_if_needed();
+    }
+
+    context.push("</li>");
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`ListItemValue`][Name::ListItemValue].
+fn on_exit_list_item_value(context: &mut CompileContext) {
+    if context.list_expect_first_marker.unwrap() {
+        let slice = Slice::from_position(
+            context.bytes,
+            &Position::from_exit_event(context.events, context.index),
+        );
+        let value = slice.as_str().parse::<u32>().ok().unwrap();
+
+        if value != 1 {
+            context.push(" start=\"");
+            context.push(&value.to_string());
+            context.push("\"");
+        }
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:{[`Image`][Name::Image],[`Link`][Name::Link]}.
+fn on_exit_media(context: &mut CompileContext) {
+    let mut is_in_image = false;
+    let mut index = 0;
+
+    // Skip current.
+    let end = context.media_stack.len() - 1;
+    while index < end {
+        if context.media_stack[index].image {
+            is_in_image = true;
+            break;
+        }
+        index += 1;
+    }
+
+    context.image_alt_inside = is_in_image;
+
+    let media = context.media_stack.pop().unwrap();
+    let label = media.label.unwrap();
+    let id = media.reference_id.or(media.label_id).map(|indices| {
+        normalize_identifier(Slice::from_indices(context.bytes, indices.0, indices.1).as_str())
+    });
+
+    let definition_index = if media.destination.is_none() {
+        id.and_then(|id| {
+            let mut index = 0;
+
+            while index < context.definitions.len() {
+                if context.definitions[index].id == id {
+                    return Some(index);
+                }
+
+                index += 1;
+            }
+
+            None
+        })
+    } else {
+        None
+    };
+
+    if !is_in_image {
+        if media.image {
+            context.push("<img src=\"");
+        } else {
+            context.push("<a href=\"");
+        };
+
+        let destination = if let Some(index) = definition_index {
+            context.definitions[index].destination.as_ref()
+        } else {
+            media.destination.as_ref()
+        };
+
+        if let Some(destination) = destination {
+            let url = if context.options.allow_dangerous_protocol {
+                sanitize(destination)
+            } else {
+                sanitize_with_protocols(
+                    destination,
+                    if media.image {
+                        &SAFE_PROTOCOL_SRC
+                    } else {
+                        &SAFE_PROTOCOL_HREF
+                    },
+                )
+            };
+            context.push(&url);
+        }
+
+        if media.image {
+            context.push("\" alt=\"");
+        };
+    }
+
+    if media.image {
+        context.push(&label);
+    }
+
+    if !is_in_image {
+        context.push("\"");
+
+        let title = if let Some(index) = definition_index {
+            context.definitions[index].title.clone()
+        } else {
+            media.title
+        };
+
+        if let Some(title) = title {
+            context.push(" title=\"");
+            context.push(&title);
+            context.push("\"");
+        };
+
+        if media.image {
+            context.push(" /");
+        }
+
+        context.push(">");
+    }
+
+    if !media.image {
+        context.push(&label);
+
+        if !is_in_image {
+            context.push("</a>");
+        }
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`Paragraph`][Name::Paragraph].
+fn on_exit_paragraph(context: &mut CompileContext) {
+    let tight = context.tight_stack.last().unwrap_or(&false);
+
+    if *tight {
+        context.slurp_one_line_ending = true;
+    } else {
+        context.push("</p>");
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`ReferenceString`][Name::ReferenceString].
+fn on_exit_reference_string(context: &mut CompileContext) {
+    // Drop stuff.
+    context.resume();
+
+    context.media_stack.last_mut().unwrap().reference_id =
+        Some(Position::from_exit_event(context.events, context.index).to_indices());
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`ResourceDestinationString`][Name::ResourceDestinationString].
+fn on_exit_resource_destination_string(context: &mut CompileContext) {
+    let buf = context.resume();
+    context.media_stack.last_mut().unwrap().destination = Some(buf);
+    context.encode_html = true;
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`ResourceTitleString`][Name::ResourceTitleString].
+fn on_exit_resource_title_string(context: &mut CompileContext) {
+    let buf = context.resume();
+    context.media_stack.last_mut().unwrap().title = Some(buf);
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`Strong`][Name::Strong].
+fn on_exit_strong(context: &mut CompileContext) {
+    if !context.image_alt_inside {
+        context.push("</strong>");
+    }
+}
+
+/// Handle [`Exit`][Kind::Exit]:[`ThematicBreak`][Name::ThematicBreak].
+fn on_exit_thematic_break(context: &mut CompileContext) {
+    context.line_ending_if_needed();
+    context.push("<hr />");
+}
+
+/// Generate a footnote section.
+fn generate_footnote_section(context: &mut CompileContext) {
+    context.line_ending_if_needed();
+    context.push("<section data-footnotes=\"\" class=\"footnotes\"><");
+    if let Some(ref value) = context.options.gfm_footnote_label_tag_name {
+        context.push(&encode(value, context.encode_html));
+    } else {
+        context.push("h2");
+    }
+    context.push(" id=\"footnote-label\" ");
+    if let Some(ref value) = context.options.gfm_footnote_label_attributes {
+        context.push(value);
+    } else {
+        context.push("class=\"sr-only\"");
+    }
+    context.push(">");
+    if let Some(ref value) = context.options.gfm_footnote_label {
+        context.push(&encode(value, context.encode_html));
+    } else {
+        context.push("Footnotes");
+    }
+    context.push("</");
+    if let Some(ref value) = context.options.gfm_footnote_label_tag_name {
+        context.push(&encode(value, context.encode_html));
+    } else {
+        context.push("h2");
+    }
+    context.push(">");
+    context.line_ending();
+    context.push("<ol>");
+
+    let mut index = 0;
+    while index < context.gfm_footnote_definition_calls.len() {
+        generate_footnote_item(context, index);
+        index += 1;
+    }
+
+    context.line_ending();
+    context.push("</ol>");
+    context.line_ending();
+    context.push("</section>");
+    context.line_ending();
+}
+
+/// Generate a footnote item from a call.
+fn generate_footnote_item(context: &mut CompileContext, index: usize) {
+    let id = &context.gfm_footnote_definition_calls[index].0;
+    let safe_id = sanitize(&id.to_lowercase());
+
+    // Find definition: we’ll always find it.
+    let mut definition_index = 0;
+    while definition_index < context.gfm_footnote_definitions.len() {
+        if &context.gfm_footnote_definitions[definition_index].0 == id {
+            break;
+        }
+        definition_index += 1;
+    }
+
+    debug_assert_ne!(
+        definition_index,
+        context.gfm_footnote_definitions.len(),
+        "expected definition"
+    );
+
+    context.line_ending();
+    context.push("<li id=\"");
+    if let Some(ref value) = context.options.gfm_footnote_clobber_prefix {
+        context.push(&encode(value, context.encode_html));
+    } else {
+        context.push("user-content-");
+    }
+    context.push("fn-");
+    context.push(&safe_id);
+    context.push("\">");
+    context.line_ending();
+
+    // Create one or more backreferences.
+    let mut reference_index = 0;
+    let mut backreferences = String::new();
+    while reference_index < context.gfm_footnote_definition_calls[index].1 {
+        if reference_index != 0 {
+            backreferences.push(' ');
+        }
+        backreferences.push_str("<a href=\"#");
+        if let Some(ref value) = context.options.gfm_footnote_clobber_prefix {
+            backreferences.push_str(&encode(value, context.encode_html));
+        } else {
+            backreferences.push_str("user-content-");
+        }
+        backreferences.push_str("fnref-");
+        backreferences.push_str(&safe_id);
+        if reference_index != 0 {
+            backreferences.push('-');
+            backreferences.push_str(&(reference_index + 1).to_string());
+        }
+        backreferences.push_str("\" data-footnote-backref=\"\" aria-label=\"");
+        if let Some(ref value) = context.options.gfm_footnote_back_label {
+            backreferences.push_str(&encode(value, context.encode_html));
+        } else {
+            backreferences.push_str("Back to content");
+        }
+        backreferences.push_str("\" class=\"data-footnote-backref\">↩");
+        if reference_index != 0 {
+            backreferences.push_str("<sup>");
+            backreferences.push_str(&(reference_index + 1).to_string());
+            backreferences.push_str("</sup>");
+        }
+        backreferences.push_str("</a>");
+
+        reference_index += 1;
+    }
+
+    let value = context.gfm_footnote_definitions[definition_index].1.clone();
+    let bytes = value.as_bytes();
+    let mut byte_index = bytes.len();
+    // Move back past EOL.
+    while byte_index > 0 && matches!(bytes[byte_index - 1], b'\n' | b'\r') {
+        byte_index -= 1;
+    }
+    // Check if it ends in `</p>`.
+    // This is a bit funky if someone wrote a safe paragraph by hand in
+    // there.
+    // But in all other cases, `<` and `>` would be encoded, so we can be
+    // sure that this is generated by our compiler.
+    if byte_index > 3
+        && bytes[byte_index - 4] == b'<'
+        && bytes[byte_index - 3] == b'/'
+        && bytes[byte_index - 2] == b'p'
+        && bytes[byte_index - 1] == b'>'
+    {
+        let (before, after) = bytes.split_at(byte_index - 4);
+        let mut result = String::new();
+        result.push_str(str::from_utf8(before).unwrap());
+        result.push(' ');
+        result.push_str(&backreferences);
+        result.push_str(str::from_utf8(after).unwrap());
+        context.push(&result);
+    } else {
+        context.push(&value);
+        context.line_ending_if_needed();
+        context.push(&backreferences);
+    }
+    context.line_ending_if_needed();
+    context.push("</li>");
+}
+
+/// Generate an autolink (used by unicode autolinks and GFM autolink literals).
+fn generate_autolink(
+    context: &mut CompileContext,
+    protocol: Option<&str>,
+    value: &str,
+    is_gfm_literal: bool,
+) {
+    let mut is_in_link = false;
+    let mut index = 0;
+
+    while index < context.media_stack.len() {
+        if !context.media_stack[index].image {
+            is_in_link = true;
+            break;
+        }
+        index += 1;
+    }
+
+    if !context.image_alt_inside && (!is_in_link || !is_gfm_literal) {
+        context.push("<a href=\"");
+        let url = if let Some(protocol) = protocol {
+            format!("{}{}", protocol, value)
+        } else {
+            value.to_string()
+        };
+
+        let url = if context.options.allow_dangerous_protocol {
+            sanitize(&url)
+        } else {
+            sanitize_with_protocols(&url, &SAFE_PROTOCOL_HREF)
+        };
+
+        context.push(&url);
+        context.push("\">");
+    }
+
+    context.push(&encode(value, context.encode_html));
+
+    if !context.image_alt_inside && (!is_in_link || !is_gfm_literal) {
+        context.push("</a>");
+    }
+}