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/*******************************************************************************
 * Copyright (c) 2017 Association Cénotélie (cenotelie.fr)
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General
 * Public License along with this program.
 * If not, see <http://www.gnu.org/licenses/>.
 ******************************************************************************/

//! Module for lexers API

pub mod automaton;
pub mod fuzzy;
pub mod impls;

use std::usize;

use crate::errors::ParseErrors;
use crate::lexers::automaton::Automaton;
use crate::tokens::TokenRepository;

/// Identifier of the default context
pub const DEFAULT_CONTEXT: u16 = 0;

/// Provides context information to a lexer
pub trait ContextProvider {
    /// Gets the priority of the specified context required by the specified terminal
    /// The priority is an unsigned integer. The lesser the value the higher the priority.
    /// The absence of value represents the unavailability of the required context.
    fn get_context_priority(
        &self,
        token_count: usize,
        context: u16,
        terminal_id: u32
    ) -> Option<usize>;
}

/// Implementation of the default context provider
pub struct DefaultContextProvider {}

impl ContextProvider for DefaultContextProvider {
    fn get_context_priority(
        &self,
        _token_count: usize,
        context: u16,
        _terminal_id: u32
    ) -> Option<usize> {
        if context == DEFAULT_CONTEXT {
            Some(usize::MAX)
        } else {
            Some(0)
        }
    }
}

/// Represents the kernel of a token, i.e. the identifying information of a token
#[derive(Debug, Default, Copy, Clone)]
pub struct TokenKernel {
    /// The identifier of the matched terminal
    pub terminal_id: u32,
    /// The token's index in its repository
    pub index: u32
}

/// Represents a context-free lexer (lexing rules do not depend on the context)
pub struct LexerData<'s, 't, 'a> {
    /// The token repository for this lexer
    pub repository: TokenRepository<'s, 't, 'a>,
    /// The repository for errors
    pub errors: &'a mut ParseErrors<'s>,
    /// The DFA automaton for this lexer
    pub automaton: Automaton,
    /// Whether the lexer has run yet
    pub has_run: bool,
    /// Symbol ID of the SEPARATOR terminal
    pub separator_id: u32,
    /// The next token in this repository
    pub index: usize,
    /// The maximum Levenshtein distance to go to for the recovery of a matching failure.
    /// A distance of 0 indicates no recovery.
    pub recovery: usize
}

pub use impls::Lexer;