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// This file is part of the pgn-reader library.
// Copyright (C) 2017-2018 Niklas Fiekas <niklas.fiekas@backscattering.de>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.

use shakmaty::Outcome;
use shakmaty::san::SanPlus;

use crate::types::{RawComment, RawHeader, Nag, Skip};

/// Consumes games from a reader.
///
/// ![Flow](https://github.com/niklasf/rust-pgn-reader/blob/master/docs/visitor.png?raw=true)
pub trait Visitor {
    /// Value produced by the visitor after reading a game.
    type Result;

    /// Called at the start of the game.
    fn begin_game(&mut self) { }

    /// Called directly before reading game headers.
    fn begin_headers(&mut self) { }
    /// Called when parsing a game header like `[White "Deep Blue"]`.
    fn header(&mut self, _key: &[u8], _value: RawHeader<'_>) { }
    /// Called after reading the headers of a game. May skip quickly over
    /// the following move text directly to
    /// [`end_game()`](trait.Visitor.html#tymethod.end_game).
    fn end_headers(&mut self) -> Skip { Skip(false) }

    /// Called for each move, like `Nf3+`.
    fn san(&mut self, _san_plus: SanPlus) { }
    /// Called for each numeric annotation glyph like `!?` or `$7`.
    fn nag(&mut self, _nag: Nag) { }
    /// Called for each `{ comment }`.
    fn comment(&mut self, _comment: RawComment<'_>) { }
    /// Called for each `(`. May skip over the following variation directly
    /// to [`end_variation()`](trait.Visitor.html#method.end_variation) (or to
    /// [`end_game()`](trait.Visitor.html#tymethod.end_game) if no matching `)`
    /// follows before the end of the game.
    fn begin_variation(&mut self) -> Skip { Skip(false) }
    /// Called for each `)`. It is *not* guaranteed that there was a
    /// matching `(`.
    fn end_variation(&mut self) { }
    /// Called for each game termination, like `*` or `1-0`.
    fn outcome(&mut self, _outcome: Option<Outcome>) { }

    /// Called after parsing a game. Can produce a custom result.
    fn end_game(&mut self) -> Self::Result;
}

pub(crate) struct SkipVisitor;

impl Visitor for SkipVisitor {
    type Result = ();

    fn end_headers(&mut self) -> Skip { Skip(true) }
    fn begin_variation(&mut self) -> Skip { Skip(true) }
    fn end_game(&mut self) { }
}