//! Paragraph is a construct that occurs in the [flow] content type.
//!
//! They’re formed with the following BNF:
//!
//! ```bnf
//! ; Restriction: lines cannot start other flow constructs.
//! ; Restriction: lines cannot be blank.
//! paragraph ::= 1*line *( eol 1*line )
//! ```
//!
//! Paragraphs in markdown relate to the `<p>` element in HTML.
//! See [*§ 4.4.1 The `p` element* in the HTML spec][html] for more info.
//!
//! Paragraphs can contain line endings and whitespace, but they are not
//! allowed to contain blank lines, or to be blank themselves.
//!
//! The paragraph is interpreted as the [text][] content type.
//! That means that [autolinks][autolink], [code (text)][code_text], etc are allowed.
//!
//! ## Tokens
//!
//! * [`Paragraph`][TokenType::Paragraph]
//!
//! ## References
//!
//! * [`content.js` in `micromark`](https://github.com/micromark/micromark/blob/main/packages/micromark-core-commonmark/dev/lib/content.js)
//! * [*§ 4.8 Paragraphs* in `CommonMark`](https://spec.commonmark.org/0.30/#paragraphs)
//!
//! [flow]: crate::content::flow
//! [text]: crate::content::text
//! [autolink]: crate::construct::autolink
//! [code_text]: crate::construct::code_text
//! [html]: https://html.spec.whatwg.org/multipage/grouping-content.html#the-p-element
use crate::tokenizer::{
Code, ContentType, Event, EventType, State, StateFnResult, TokenType, Tokenizer,
};
use crate::util::{edit_map::EditMap, skip::opt as skip_opt};
/// Before a paragraph.
///
/// ```markdown
/// |qwe
/// ```
pub fn start(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
match code {
Code::None | Code::CarriageReturnLineFeed | Code::Char('\n' | '\r') => {
unreachable!("unexpected eol/eof")
}
_ => {
tokenizer.enter(TokenType::Paragraph);
tokenizer.enter_with_content(TokenType::Data, Some(ContentType::Text));
inside(tokenizer, code)
}
}
}
/// In a paragraph.
///
/// ```markdown
/// al|pha
/// ```
fn inside(tokenizer: &mut Tokenizer, code: Code) -> StateFnResult {
match code {
Code::None | Code::CarriageReturnLineFeed | Code::Char('\n' | '\r') => {
tokenizer.exit(TokenType::Data);
tokenizer.exit(TokenType::Paragraph);
tokenizer.register_resolver_before("paragraph".to_string(), Box::new(resolve));
// You’d be interrupting.
tokenizer.interrupt = true;
(State::Ok, Some(vec![code]))
}
_ => {
tokenizer.consume(code);
(State::Fn(Box::new(inside)), None)
}
}
}
/// Merge “`Paragraph`”s, which currently span a single line, into actual
/// `Paragraph`s that span multiple lines.
pub fn resolve(tokenizer: &mut Tokenizer) -> Vec<Event> {
let mut edit_map = EditMap::new();
let len = tokenizer.events.len();
let mut index = 0;
while index < len {
let event = &tokenizer.events[index];
if event.event_type == EventType::Enter && event.token_type == TokenType::Paragraph {
// Exit:Paragraph
let mut exit_index = index + 3;
let mut enter_next_index =
skip_opt(&tokenizer.events, exit_index + 1, &[TokenType::LineEnding]);
// Enter:Paragraph
enter_next_index = skip_opt(
&tokenizer.events,
enter_next_index,
&[TokenType::SpaceOrTab, TokenType::BlockQuotePrefix],
);
// Find future `Paragraphs`.
while enter_next_index < tokenizer.events.len()
&& tokenizer.events[enter_next_index].token_type == TokenType::Paragraph
{
// Remove Exit:Paragraph, Enter:LineEnding, Exit:LineEnding, Enter:Paragraph.
edit_map.add(exit_index, 3, vec![]);
// Remove Enter:Paragraph.
edit_map.add(enter_next_index, 1, vec![]);
// Add Exit:LineEnding position info to Exit:Data.
let line_ending_exit = &tokenizer.events[exit_index + 2];
let line_ending_point = line_ending_exit.point.clone();
let line_ending_index = line_ending_exit.index;
let data_exit = &mut tokenizer.events[exit_index - 1];
data_exit.point = line_ending_point;
data_exit.index = line_ending_index;
// Link Enter:Data on the previous line to Enter:Data on this line.
let data_enter_prev = &mut tokenizer.events[exit_index - 2];
data_enter_prev.next = Some(enter_next_index + 1);
let data_enter_next = &mut tokenizer.events[enter_next_index + 1];
data_enter_next.previous = Some(exit_index - 2);
// Potential next start.
exit_index = enter_next_index + 3;
enter_next_index =
skip_opt(&tokenizer.events, exit_index + 1, &[TokenType::LineEnding]);
enter_next_index = skip_opt(
&tokenizer.events,
enter_next_index,
&[TokenType::SpaceOrTab, TokenType::BlockQuotePrefix],
);
}
// Move to `Exit:Paragraph`.
index = exit_index;
}
index += 1;
}
edit_map.consume(&mut tokenizer.events)
}