//! Label occurs in [definition][] and label end.
//!
//! They’re formed with the following BNF:
//!
//! ```bnf
//! ; 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 ::= '\\' [ '[' | '\\' | ']' ]
//! ```
//!
//! The maximum allowed size of the label, without the brackets, is `999`
//! (inclusive), which is defined in
//! [`LINK_REFERENCE_SIZE_MAX`][link_reference_size_max].
//!
//! Labels can contain line endings and whitespace, but they are not allowed to
//! contain blank lines, and they must not be blank themselves.
//!
//! The label is interpreted as the [string][] content type.
//! That means that [character escapes][character_escape] and
//! [character references][character_reference] are allowed.
//!
//! > 👉 **Note**: this label relates to, but is not, the initial “label” of
//! > what is know as a reference in markdown:
//! >
//! > | Kind | Link | Image |
//! > | --------- | -------- | --------- |
//! > | Shortcut | `[x]` | `![x]` |
//! > | Collapsed | `[x][]` | `![x][]` |
//! > | Full | `[x][y]` | `![x][y]` |
//! >
//! > The 6 above things are references, in the three kinds they come in, as
//! > links and images.
//! > The label that this module focusses on is only the thing that contains
//! > `y`.
//! >
//! > The thing that contains `x` is not a single thing when parsing markdown,
//! > but instead constists of an opening (label start (image) or label start
//! > (link)) and a closing (label end), so as to allow further phrasing such
//! > as code (text) or attention.
//!
//! ## References
//!
//! * [`micromark-factory-label/index.js` in `micromark`](https://github.com/micromark/micromark/blob/main/packages/micromark-factory-label/dev/index.js)
//!
//! [definition]: crate::construct::definition
//! [string]: crate::content::string
//! [character_escape]: crate::construct::character_escape
//! [character_reference]: crate::construct::character_reference
//! [link_reference_size_max]: crate::constant::LINK_REFERENCE_SIZE_MAX
//!
//! <!-- To do: link label end, label starts. -->
// To do: pass token types in.
use crate::constant::LINK_REFERENCE_SIZE_MAX;
use crate::construct::partial_space_or_tab::space_or_tab_opt;
use crate::tokenizer::{Code, State, StateFnResult, TokenType, Tokenizer};
use crate::util::link::link;
/// State needed to parse labels.
#[derive(Debug)]
struct Info {
/// Whether we’ve seen our first `ChunkString`.
connect: bool,
/// Whether there are non-blank characters in the label.
data: bool,
/// Number of characters in the label.
size: usize,
}
/// Before a label.
///
/// ```markdown
/// |[a]
/// ```
pub fn start(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
match code {
Code::Char('[') => {
tokenizer.enter(TokenType::DefinitionLabel);
tokenizer.enter(TokenType::DefinitionLabelMarker);
tokenizer.consume(code);
tokenizer.exit(TokenType::DefinitionLabelMarker);
tokenizer.enter(TokenType::DefinitionLabelData);
let info = Info {
connect: false,
data: false,
size: 0,
};
(State::Fn(Box::new(|t, c| at_break(t, c, info))), None)
}
_ => (State::Nok, None),
}
}
/// In a label, at something.
///
/// ```markdown
/// [|a]
/// [a|]
/// ```
fn at_break(tokenizer: &mut Tokenizer, code: Code, info: Info) -> StateFnResult {
match code {
Code::None | Code::Char('[') => (State::Nok, None),
Code::Char(']') if !info.data => (State::Nok, None),
_ if info.size > LINK_REFERENCE_SIZE_MAX => (State::Nok, None),
Code::Char(']') => {
tokenizer.exit(TokenType::DefinitionLabelData);
tokenizer.enter(TokenType::DefinitionLabelMarker);
tokenizer.consume(code);
tokenizer.exit(TokenType::DefinitionLabelMarker);
tokenizer.exit(TokenType::DefinitionLabel);
(State::Ok, None)
}
_ => {
tokenizer.enter(TokenType::ChunkString);
if info.connect {
let index = tokenizer.events.len() - 1;
link(&mut tokenizer.events, index);
}
label(tokenizer, code, info)
}
}
}
/// After a line ending.
///
/// ```markdown
/// [a
/// |b]
/// ```
fn line_start(tokenizer: &mut Tokenizer, code: Code, info: Info) -> StateFnResult {
tokenizer.go(space_or_tab_opt(), |t, c| line_begin(t, c, info))(tokenizer, code)
}
/// After a line ending, after optional whitespace.
///
/// ```markdown
/// [a
/// |b]
/// ```
fn line_begin(tokenizer: &mut Tokenizer, code: Code, info: Info) -> StateFnResult {
match code {
// Blank line not allowed.
Code::CarriageReturnLineFeed | Code::Char('\r' | '\n') => (State::Nok, None),
_ => at_break(tokenizer, code, info),
}
}
/// In a label, in text.
///
/// ```markdown
/// [a|b]
/// ```
fn label(tokenizer: &mut Tokenizer, code: Code, mut info: Info) -> StateFnResult {
if !info.connect {
info.connect = true;
}
match code {
Code::None | Code::Char('[' | ']') => {
tokenizer.exit(TokenType::ChunkString);
at_break(tokenizer, code, info)
}
_ if info.size > LINK_REFERENCE_SIZE_MAX => {
tokenizer.exit(TokenType::ChunkString);
at_break(tokenizer, code, info)
}
Code::CarriageReturnLineFeed | Code::Char('\r' | '\n') => {
tokenizer.consume(code);
info.size += 1;
tokenizer.exit(TokenType::ChunkString);
(State::Fn(Box::new(|t, c| line_start(t, c, info))), None)
}
Code::VirtualSpace | Code::Char('\t' | ' ') => {
tokenizer.consume(code);
info.size += 1;
(State::Fn(Box::new(|t, c| label(t, c, info))), None)
}
Code::Char('/') => {
tokenizer.consume(code);
info.size += 1;
if !info.data {
info.data = true;
}
(State::Fn(Box::new(|t, c| escape(t, c, info))), None)
}
Code::Char(_) => {
tokenizer.consume(code);
info.size += 1;
if !info.data {
info.data = true;
}
(State::Fn(Box::new(|t, c| label(t, c, info))), None)
}
}
}
/// After `\` in a label.
///
/// ```markdown
/// [a\|[b]
/// ```
fn escape(tokenizer: &mut Tokenizer, code: Code, mut info: Info) -> StateFnResult {
match code {
Code::Char('[' | '\\' | ']') => {
tokenizer.consume(code);
info.size += 1;
(State::Fn(Box::new(|t, c| label(t, c, info))), None)
}
_ => label(tokenizer, code, info),
}
}
