//! Several helpers to parse whitespace (`space_or_tab`, `space_or_tab_eol`).
//!
//! ## References
//!
//! *   [`micromark-factory-space/index.js` in `micromark`](https://github.com/micromark/micromark/blob/main/packages/micromark-factory-space/dev/index.js)

use crate::subtokenize::link;
use crate::token::Token;
use crate::tokenizer::{ContentType, State, StateFn, Tokenizer};

/// Options to parse `space_or_tab`.
#[derive(Debug)]
pub struct Options {
    /// Minimum allowed bytes (inclusive).
    pub min: usize,
    /// Maximum allowed bytes (inclusive).
    pub max: usize,
    /// Token type to use for whitespace events.
    pub kind: Token,
    /// Connect this whitespace to the previous.
    pub connect: bool,
    /// Embedded content type to use.
    pub content_type: Option<ContentType>,
}

/// Options to parse `space_or_tab` and one optional eol, but no blank line.
#[derive(Debug)]
pub struct EolOptions {
    /// Connect this whitespace to the previous.
    pub connect: bool,
    /// Embedded content type to use.
    pub content_type: Option<ContentType>,
}

/// One or more `space_or_tab`.
///
/// ```bnf
/// space_or_tab ::= 1*( ' ' '\t' )
/// ```
pub fn space_or_tab() -> Box<StateFn> {
    space_or_tab_min_max(1, usize::MAX)
}

/// Between `x` and `y` `space_or_tab`.
///
/// ```bnf
/// space_or_tab_min_max ::= x*y( ' ' '\t' )
/// ```
pub fn space_or_tab_min_max(min: usize, max: usize) -> Box<StateFn> {
    space_or_tab_with_options(Options {
        kind: Token::SpaceOrTab,
        min,
        max,
        content_type: None,
        connect: false,
    })
}

/// `space_or_tab`, with the given options.
pub fn space_or_tab_with_options(options: Options) -> Box<StateFn> {
    Box::new(|tokenizer| {
        tokenizer.tokenize_state.space_or_tab_connect = options.connect;
        tokenizer.tokenize_state.space_or_tab_content_type = options.content_type;
        tokenizer.tokenize_state.space_or_tab_min = options.min;
        tokenizer.tokenize_state.space_or_tab_max = options.max;
        tokenizer.tokenize_state.space_or_tab_token = options.kind;
        start(tokenizer)
    })
}

/// `space_or_tab`, or optionally `space_or_tab`, one `eol`, and
/// optionally `space_or_tab`.
///
/// ```bnf
/// space_or_tab_eol ::= 1*( ' ' '\t' ) | 0*( ' ' '\t' ) eol 0*( ' ' '\t' )
/// ```
pub fn space_or_tab_eol() -> Box<StateFn> {
    space_or_tab_eol_with_options(EolOptions {
        content_type: None,
        connect: false,
    })
}

/// `space_or_tab_eol`, with the given options.
pub fn space_or_tab_eol_with_options(options: EolOptions) -> Box<StateFn> {
    Box::new(move |tokenizer| {
        tokenizer.tokenize_state.space_or_tab_eol_content_type = options.content_type;
        tokenizer.tokenize_state.space_or_tab_eol_connect = options.connect;

        tokenizer.attempt(
            space_or_tab_with_options(Options {
                kind: Token::SpaceOrTab,
                min: 1,
                max: usize::MAX,
                content_type: tokenizer
                    .tokenize_state
                    .space_or_tab_eol_content_type
                    .clone(),
                connect: tokenizer.tokenize_state.space_or_tab_eol_connect,
            }),
            move |ok| {
                Box::new(move |tokenizer| {
                    if ok {
                        tokenizer.tokenize_state.space_or_tab_eol_ok = ok;
                    }

                    after_space_or_tab(tokenizer)
                })
            },
        )(tokenizer)
    })
}

/// Before `space_or_tab`.
///
/// ```markdown
/// > | a␠␠b
///      ^
/// ```
fn start(tokenizer: &mut Tokenizer) -> State {
    match tokenizer.current {
        Some(b'\t' | b' ') if tokenizer.tokenize_state.space_or_tab_max > 0 => {
            tokenizer.enter_with_content(
                tokenizer.tokenize_state.space_or_tab_token.clone(),
                tokenizer.tokenize_state.space_or_tab_content_type.clone(),
            );

            if tokenizer.tokenize_state.space_or_tab_connect {
                let index = tokenizer.events.len() - 1;
                link(&mut tokenizer.events, index);
            } else if tokenizer.tokenize_state.space_or_tab_content_type.is_some() {
                tokenizer.tokenize_state.space_or_tab_connect = true;
            }

            inside(tokenizer)
        }
        _ => after(tokenizer),
    }
}

/// In `space_or_tab`.
///
/// ```markdown
/// > | a␠␠b
///       ^
/// ```
fn inside(tokenizer: &mut Tokenizer) -> State {
    match tokenizer.current {
        Some(b'\t' | b' ')
            if tokenizer.tokenize_state.space_or_tab_size
                < tokenizer.tokenize_state.space_or_tab_max =>
        {
            tokenizer.consume();
            tokenizer.tokenize_state.space_or_tab_size += 1;
            State::Fn(Box::new(inside))
        }
        _ => {
            tokenizer.exit(tokenizer.tokenize_state.space_or_tab_token.clone());
            after(tokenizer)
        }
    }
}

/// After `space_or_tab`.
///
/// ```markdown
/// > | a␠␠b
///        ^
/// ```
fn after(tokenizer: &mut Tokenizer) -> State {
    let state = if tokenizer.tokenize_state.space_or_tab_size
        >= tokenizer.tokenize_state.space_or_tab_min
    {
        State::Ok
    } else {
        State::Nok
    };
    tokenizer.tokenize_state.space_or_tab_connect = false;
    tokenizer.tokenize_state.space_or_tab_content_type = None;
    tokenizer.tokenize_state.space_or_tab_size = 0;
    tokenizer.tokenize_state.space_or_tab_max = 0;
    tokenizer.tokenize_state.space_or_tab_min = 0;
    tokenizer.tokenize_state.space_or_tab_token = Token::SpaceOrTab;
    state
}

/// `space_or_tab_eol`: after optionally first `space_or_tab`.
///
/// ```markdown
/// > | a
///      ^
///   | b
/// ```
fn after_space_or_tab(tokenizer: &mut Tokenizer) -> State {
    if tokenizer.tokenize_state.space_or_tab_eol_ok
        && tokenizer
            .tokenize_state
            .space_or_tab_eol_content_type
            .is_some()
    {
        tokenizer.tokenize_state.space_or_tab_eol_connect = true;
    }

    if let Some(b'\n') = tokenizer.current {
        tokenizer.enter_with_content(
            Token::LineEnding,
            tokenizer
                .tokenize_state
                .space_or_tab_eol_content_type
                .clone(),
        );

        if tokenizer.tokenize_state.space_or_tab_eol_connect {
            let index = tokenizer.events.len() - 1;
            link(&mut tokenizer.events, index);
        } else if tokenizer
            .tokenize_state
            .space_or_tab_eol_content_type
            .is_some()
        {
            tokenizer.tokenize_state.space_or_tab_eol_connect = true;
        }

        tokenizer.consume();
        tokenizer.exit(Token::LineEnding);
        State::Fn(Box::new(after_eol))
    } else {
        let state = if tokenizer.tokenize_state.space_or_tab_eol_ok {
            State::Ok
        } else {
            State::Nok
        };
        tokenizer.tokenize_state.space_or_tab_eol_content_type = None;
        tokenizer.tokenize_state.space_or_tab_eol_connect = false;
        tokenizer.tokenize_state.space_or_tab_eol_ok = false;
        state
    }
}

/// `space_or_tab_eol`: after eol.
///
/// ```markdown
///   | a
/// > | b
///     ^
/// ```
#[allow(clippy::needless_pass_by_value)]
fn after_eol(tokenizer: &mut Tokenizer) -> State {
    tokenizer.attempt_opt(
        space_or_tab_with_options(Options {
            kind: Token::SpaceOrTab,
            min: 1,
            max: usize::MAX,
            content_type: tokenizer
                .tokenize_state
                .space_or_tab_eol_content_type
                .clone(),
            connect: tokenizer.tokenize_state.space_or_tab_eol_connect,
        }),
        after_more_space_or_tab,
    )(tokenizer)
}

/// `space_or_tab_eol`: after more (optional) `space_or_tab`.
///
/// ```markdown
///   | a
/// > | b
///     ^
/// ```
fn after_more_space_or_tab(tokenizer: &mut Tokenizer) -> State {
    tokenizer.tokenize_state.space_or_tab_eol_content_type = None;
    tokenizer.tokenize_state.space_or_tab_eol_connect = false;
    tokenizer.tokenize_state.space_or_tab_eol_ok = false;

    // Blank line not allowed.
    if matches!(tokenizer.current, None | Some(b'\n')) {
        State::Nok
    } else {
        State::Ok
    }
}