use {SyntaxKind, Token};

#[macro_use]
mod parser;
mod grammar;

/// `Parser` produces a flat list of `Event`s.
/// They are converted to a tree-structure in
/// a separate pass, via `TreeBuilder`.
#[derive(Debug)]
pub(crate) enum Event {
    /// This event signifies the start of the node.
    /// It should be either abandoned (in which case the
    /// `kind` is `TOMBSTONE`, and the event is ignored),
    /// or completed via a `Finish` event.
    ///
    /// All tokens between a `Start` and a `Finish` would
    /// become the children of the respective node.
    ///
    /// For left-recursive syntactic constructs, the parser produces
    /// a child node before it sees a parent. `forward_parent`
    /// exists to allow to tweak parent-child relationships.
    ///
    /// Consider this path
    ///
    /// foo::bar
    ///
    /// The events for it would look like this:
    ///
    ///
    /// START(PATH) IDENT('foo') FINISH START(PATH) COLONCOLON IDENT('bar') FINISH
    ///       |                          /\
    ///       |                          |
    ///       +------forward-parent------+
    ///
    /// And the tree would look like this
    ///
    ///    +--PATH---------+
    ///    |   |           |
    ///    |   |           |
    ///    |  '::'       'bar'
    ///    |
    ///   PATH
    ///    |
    ///   'foo'
    ///
    /// See also `CompleteMarker::precede`.
    Start {
        kind: SyntaxKind,
        forward_parent: Option<u32>,
    },

    /// Complete the previous `Start` event
    Finish,

    /// Produce a single leaf-element.
    /// `n_raw_tokens` is used to glue complex contextual tokens.
    /// For example, lexer tokenizes `>>` as `>`, `>`, and
    /// `n_raw_tokens = 2` is used to produced a single `>>`.
    Token {
        kind: SyntaxKind,
        n_raw_tokens: u8,
    },

    Error {
        message: String,
    },
}

pub(crate) fn parse<'t>(text: &'t str, raw_tokens: &'t [Token]) -> Vec<Event> {
    let mut parser = parser::Parser::new(text, raw_tokens);
    grammar::file(&mut parser);
    parser.into_events()
}