Add support for definitions

*   Add definitions
*   Add partials for label, destination, title
*   Add `go`, to attempt something, and do something else on `ok`

1 files changed, 318 insertions, 0 deletions

diff --git a/src/construct/definition.rs b/src/construct/definition.rs
new file mode 100644
index 0000000..e540b44
--- /dev/null
+++ b/src/construct/definition.rs
@@ -0,0 +1,318 @@
+//! Definition is a construct that occurs in the [flow] content type.
+//!
+//! They’re formed with the following BNF:
+//!
+//! ```bnf
+//! definition ::= label ':' whitespace destination [ whitespace title ] [ space_or_tab ]
+//!
+//! ; Restriction: maximum `999` codes allowed between brackets.
+//! ; Restriction: no blank lines.
+//! ; Restriction: at least 1 non-space and non-eol code must exist.
+//! label ::= '[' *( label_text | label_escape ) ']'
+//! label_text ::= code - '[' - '\\' - ']'
+//! label_escape ::= '\\' [ '[' | '\\' | ']' ]
+//!
+//! destination ::= destination_enclosed | destination_raw
+//! destination_enclosed ::= '<' *( destination_enclosed_text | destination_enclosed_escape ) '>'
+//! destination_enclosed_text ::= code - '<' - '\\' - eol
+//! destination_enclosed_escape ::= '\\' [ '<' | '\\' | '>' ]
+//! destination_raw ::= 1*( destination_raw_text | destination_raw_escape )
+//! ; Restriction: unbalanced `)` characters are not allowed.
+//! destination_raw_text ::= code - '\\' - ascii_control - space_or_tab - eol
+//! destination_raw_escape ::= '\\' [ '(' | ')' | '\\' ]
+//!
+//! ; Restriction: no blank lines.
+//! ; Restriction: markers must match (in case of `(` with `)`).
+//! title ::= marker [  *( code - '\\' | '\\' [ marker ] ) ] marker
+//! marker ::= '"' | '\'' | '('
+//!
+//! whitespace ::= eol *whitespace | 1*space_or_tab [ eol *whitespace ]
+//! space_or_tab ::= ' ' | '\t'
+//! ```
+//!
+//! Definitions in markdown to not, on their own, relate to anything in HTML.
+//! When connected with a link (reference), they together relate to the `<a>`
+//! element in HTML.
+//! The definition forms its `href`, and optionally `title`, attributes.
+//! See [*§ 4.5.1 The `a` element*][html] in the HTML spec for more info.
+//!
+//! The `label`, `destination`, and `title` parts are interpreted as the
+//! [string][] content type.
+//! That means that character escapes and character reference are allowed.
+//!
+//! ## References
+//!
+//! *   [`definition.js` in `micromark`](https://github.com/micromark/micromark/blob/main/packages/micromark-core-commonmark/dev/lib/definition.js)
+//! *   [*§ 4.7 Link reference definitions* in `CommonMark`](https://spec.commonmark.org/0.30/#link-reference-definitions)
+//!
+//! [flow]: crate::content::flow
+//! [string]: crate::content::string
+//! [html]: https://html.spec.whatwg.org/multipage/text-level-semantics.html#the-a-element
+//!
+//! <!-- To do: link link (reference) -->
+//!
+//! <!-- To do: describe how references and definitions match -->
+
+use crate::construct::{
+    partial_destination::start as destination, partial_label::start as label,
+    partial_title::start as title, partial_whitespace::start as whitespace,
+};
+use crate::tokenizer::{Code, State, StateFnResult, TokenType, Tokenizer};
+
+/// At the start of a definition.
+///
+/// ```markdown
+/// |[a]: b "c"
+/// ```
+pub fn start(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    match code {
+        Code::Char('[') => {
+            tokenizer.enter(TokenType::Definition);
+            tokenizer.go(label, label_after)(tokenizer, code)
+        }
+        _ => (State::Nok, None),
+    }
+}
+
+/// After the label of a definition.
+///
+/// ```markdown
+/// [a]|: b "c"
+/// ```
+pub fn label_after(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    // To do: get the identifier:
+    // identifier = normalizeIdentifier(
+    //   self.sliceSerialize(self.events[self.events.length - 1][1]).slice(1, -1)
+    // )
+
+    match code {
+        Code::Char(':') => {
+            tokenizer.enter(TokenType::DefinitionMarker);
+            tokenizer.consume(code);
+            tokenizer.exit(TokenType::DefinitionMarker);
+            (State::Fn(Box::new(marker_after)), None)
+        }
+        _ => (State::Nok, None),
+    }
+}
+
+/// After the marker of a definition.
+///
+/// ```markdown
+/// [a]:| b "c"
+///
+/// [a]:| ␊
+///  b "c"
+/// ```
+pub fn marker_after(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    tokenizer.attempt(
+        |t, c| whitespace(t, c, TokenType::Whitespace),
+        |_ok| Box::new(marker_after_optional_whitespace),
+    )(tokenizer, code)
+}
+
+/// After the marker, after whitespace.
+///
+/// ```markdown
+/// [a]: |b "c"
+///
+/// [a]: |␊
+///  b "c"
+/// ```
+pub fn marker_after_optional_whitespace(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    match code {
+        Code::CarriageReturnLineFeed | Code::Char('\r' | '\n') => {
+            tokenizer.enter(TokenType::LineEnding);
+            tokenizer.consume(code);
+            tokenizer.exit(TokenType::LineEnding);
+            (State::Fn(Box::new(marker_after_optional_line_ending)), None)
+        }
+        _ => destination_before(tokenizer, code),
+    }
+}
+
+/// After the marker, after a line ending.
+///
+/// ```markdown
+/// [a]:
+/// | b "c"
+/// ```
+pub fn marker_after_optional_line_ending(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    tokenizer.attempt(
+        |t, c| whitespace(t, c, TokenType::Whitespace),
+        |_ok| Box::new(destination_before),
+    )(tokenizer, code)
+}
+
+/// Before a destination.
+///
+/// ```markdown
+/// [a]: |b "c"
+///
+/// [a]:
+///  |b "c"
+/// ```
+pub fn destination_before(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    let event = tokenizer.events.last().unwrap();
+    // Blank line not ok.
+    let char_nok = matches!(
+        code,
+        Code::None | Code::CarriageReturnLineFeed | Code::Char('\r' | '\n')
+    );
+
+    if !char_nok
+        && (event.token_type == TokenType::LineEnding || event.token_type == TokenType::Whitespace)
+    {
+        tokenizer.go(destination, destination_after)(tokenizer, code)
+    } else {
+        (State::Nok, None)
+    }
+}
+
+/// After a destination.
+///
+/// ```markdown
+/// [a]: b| "c"
+///
+/// [a]: b| ␊
+///  "c"
+/// ```
+pub fn destination_after(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    tokenizer.attempt(title_before, |_ok| Box::new(after))(tokenizer, code)
+}
+
+/// After a definition.
+///
+/// ```markdown
+/// [a]: b|
+/// [a]: b "c"|
+/// ```
+pub fn after(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    tokenizer.attempt(
+        |t, c| whitespace(t, c, TokenType::Whitespace),
+        |_ok| Box::new(after_whitespace),
+    )(tokenizer, code)
+}
+
+/// After a definition, after optional whitespace.
+///
+/// ```markdown
+/// [a]: b |
+/// [a]: b "c"|
+/// ```
+pub fn after_whitespace(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    match code {
+        Code::None | Code::CarriageReturnLineFeed | Code::Char('\r' | '\n') => {
+            tokenizer.exit(TokenType::Definition);
+            (State::Ok, Some(vec![code]))
+        }
+        _ => (State::Nok, None),
+    }
+}
+
+/// After a destination, presumably before a title.
+///
+/// ```markdown
+/// [a]: b| "c"
+///
+/// [a]: b| ␊
+///  "c"
+/// ```
+pub fn title_before(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    tokenizer.attempt(
+        |t, c| whitespace(t, c, TokenType::Whitespace),
+        |_ok| Box::new(title_before_after_optional_whitespace),
+    )(tokenizer, code)
+}
+
+/// Before a title, after optional whitespace.
+///
+/// ```markdown
+/// [a]: b |"c"
+///
+/// [a]: b |␊
+///  "c"
+/// ```
+pub fn title_before_after_optional_whitespace(
+    tokenizer: &mut Tokenizer,
+    code: Code,
+) -> StateFnResult {
+    match code {
+        Code::CarriageReturnLineFeed | Code::Char('\r' | '\n') => {
+            tokenizer.enter(TokenType::LineEnding);
+            tokenizer.consume(code);
+            tokenizer.exit(TokenType::LineEnding);
+            (
+                State::Fn(Box::new(title_before_after_optional_line_ending)),
+                None,
+            )
+        }
+        _ => title_before_marker(tokenizer, code),
+    }
+}
+
+/// Before a title, after a line ending.
+///
+/// ```markdown
+/// [a]: b␊
+/// | "c"
+/// ```
+pub fn title_before_after_optional_line_ending(
+    tokenizer: &mut Tokenizer,
+    code: Code,
+) -> StateFnResult {
+    tokenizer.attempt(
+        |t, c| whitespace(t, c, TokenType::Whitespace),
+        |_ok| Box::new(title_before_marker),
+    )(tokenizer, code)
+}
+
+/// Before a title, after a line ending.
+///
+/// ```markdown
+/// [a]: b␊
+/// | "c"
+/// ```
+pub fn title_before_marker(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    let event = tokenizer.events.last().unwrap();
+
+    if event.token_type == TokenType::LineEnding || event.token_type == TokenType::Whitespace {
+        tokenizer.go(title, title_after)(tokenizer, code)
+    } else {
+        (State::Nok, None)
+    }
+}
+
+/// After a title.
+///
+/// ```markdown
+/// [a]: b "c"|
+///
+/// [a]: b␊
+/// "c"|
+/// ```
+pub fn title_after(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
+    tokenizer.attempt(
+        |t, c| whitespace(t, c, TokenType::Whitespace),
+        |_ok| Box::new(title_after_after_optional_whitespace),
+    )(tokenizer, code)
+}
+
+/// After a title, after optional whitespace.
+///
+/// ```markdown
+/// [a]: b "c"|
+///
+/// [a]: b "c" |
+/// ```
+pub fn title_after_after_optional_whitespace(
+    _tokenizer: &mut Tokenizer,
+    code: Code,
+) -> StateFnResult {
+    match code {
+        Code::None | Code::CarriageReturnLineFeed | Code::Char('\r' | '\n') => {
+            (State::Ok, Some(vec![code]))
+        }
+        _ => (State::Nok, None),
+    }
+}