//! wikilink occurs in the [[text]][] content type.
//!
//! ## Grammar
//!
//! ```bnf
//! wikilink ::= '[[' label opt_alias opt_heading opt_block ']]'
//!
//! opt_alias ::= '|' label | ''
//! opt_heading ::= '#' label | ''
//! opt_block ::= '^' label | ''
//!
//! ; See the `label` constructs for the BNF of
//! ; those parts.
//! ```
//!

use crate::event::Name;
use crate::state::Name as MoveName;
use crate::state::State;
use crate::tokenizer::{Label, LabelKind, LabelStart, Tokenizer};

/// Start of label (link) start.
///
/// ```markdown
/// > | a [b] c
///       ^
/// ```
pub fn start(tokenizer: &mut Tokenizer) -> State {
    if !tokenizer.parse_state.options.constructs.wikilink {
        return State::Retry(MoveName::TextBeforeLabelStartLink);
    }

    let start_conditions = tokenizer.current == Some(b'[');

    if start_conditions && tokenizer.tokenize_state.size == 0 {
        tokenizer.tokenize_state.size += 1;
        tokenizer.attempt(
            State::Next(MoveName::WikilinkLabelStart),
            State::Next(MoveName::TextBeforeLabelStartLink),
        );

        tokenizer.consume();
        State::Next(MoveName::WikilinkStart)
    } else if start_conditions && tokenizer.tokenize_state.size == 1 {
        tokenizer.tokenize_state.size = 0;
        let start = tokenizer.events.len();

        tokenizer.enter(Name::WikilinkStart);
        // // tokenizer.enter(Name::LabelMarker);
        tokenizer.consume();
        // // tokenizer.exit(Name::LabelMarker);
        tokenizer.exit(Name::WikilinkStart);

        tokenizer.tokenize_state.wikilink_starts.push(LabelStart {
            kind: LabelKind::Link,
            start: (start, tokenizer.events.len()),
            inactive: false,
        });
        State::Ok
    } else {
        tokenizer.tokenize_state.size = 0;

        // Resume the "regular" sequence of state transitions
        State::Nok
        // State::Retry(MoveName::TextBeforeLabelStartLink)
    }
}

pub fn end(tokenizer: &mut Tokenizer) -> State {
    if Some(b']') == tokenizer.current
        && Some(b']') == tokenizer.previous
        && tokenizer.parse_state.options.constructs.wikilink
        && !tokenizer.tokenize_state.wikilink_starts.is_empty()
    {
        let wikilink_start = tokenizer.tokenize_state.wikilink_starts.last().unwrap();
        tokenizer.tokenize_state.end = tokenizer.events.len();

        // If the corresponding label (link) start is marked as inactive,
        // it means we’d be wrapping a link, like this:
        //
        // ```markdown
        // > | a [b [c](d) e](f) g.
        //                  ^
        // ```
        //
        // We can’t have that, so it’s just balanced brackets.
        if wikilink_start.inactive {
            return State::Retry(MoveName::WikilinkEndNok);
        }

        tokenizer.enter(Name::WikilinkEnd);
        tokenizer.consume();
        tokenizer.exit(Name::WikilinkEnd);
        return State::Ok;
    }

    State::Nok
}