/*
 * This file is part of espanso.
 *
 * Copyright (C) 2019-202 case_insensitive: (), preserve_case_markers: (), left_word: (), right_word: ()1 Federico Terzi
 *
 * espanso 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.
 *
 * espanso 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 espanso.  If not, see <https://www.gnu.org/licenses/>.
 */

use std::collections::HashMap;

use log::error;
use regex::{Regex, RegexSet};

use crate::Matcher;
use crate::{event::Event, MatchResult};

#[derive(Debug)]
pub struct RegexMatch<Id> {
  pub id: Id,
  pub regex: String,
}

impl<Id> RegexMatch<Id> {
  pub fn new(id: Id, regex: &str) -> Self {
    Self {
      id,
      regex: regex.to_string(),
    }
  }
}

#[derive(Clone, Default)]
pub struct RegexMatcherState {
  buffer: String,
}

pub struct RegexMatcherOptions {
  pub max_buffer_size: usize,
}

impl Default for RegexMatcherOptions {
  fn default() -> Self {
    Self {
      max_buffer_size: 30,
    }
  }
}

pub struct RegexMatcher<Id> {
  ids: Vec<Id>,
  // The RegexSet is used to efficiently determine which regexes match
  regex_set: RegexSet,

  // The single regexes are then used to find the captures
  regexes: Vec<Regex>,

  max_buffer_size: usize,
}

impl<'a, Id> Matcher<'a, RegexMatcherState, Id> for RegexMatcher<Id>
where
  Id: Clone,
{
  fn process(
    &'a self,
    prev_state: Option<&RegexMatcherState>,
    event: Event,
  ) -> (RegexMatcherState, Vec<MatchResult<Id>>) {
    let mut buffer = if let Some(prev_state) = prev_state {
      prev_state.buffer.clone()
    } else {
      "".to_string()
    };

    if let Event::Key {
      key: _,
      chars: Some(chars),
    } = event
    {
      buffer.push_str(&chars);
    }

    // Keep the buffer length in check
    if buffer.len() > self.max_buffer_size {
      buffer.remove(0);
    }

    // Find matches
    if self.regex_set.is_match(&buffer) {
      let mut matches = Vec::new();

      for index in self.regex_set.matches(&buffer) {
        if let (Some(id), Some(regex)) = (self.ids.get(index), self.regexes.get(index)) {
          if let Some(captures) = regex.captures(&buffer) {
            let full_match = captures.get(0).map_or("", |m| m.as_str());
            if !full_match.is_empty() {
              // Now extract the captured names as variables
              let variables: HashMap<String, String> = regex
                .capture_names()
                .flatten()
                .filter_map(|n| Some((n.to_string(), captures.name(n)?.as_str().to_string())))
                .collect();

              let result = MatchResult {
                id: (*id).clone(),
                trigger: full_match.to_string(),
                left_separator: None,
                right_separator: None,
                vars: variables,
              };

              matches.push(result);
            }
          }
        } else {
          error!(
            "received inconsistent index from regex set with index: {}",
            index
          );
        }
      }

      if !matches.is_empty() {
        return (RegexMatcherState::default(), matches);
      }
    }

    let current_state = RegexMatcherState { buffer };
    (current_state, Vec::new())
  }
}

impl<Id: Clone> RegexMatcher<Id> {
  pub fn new(matches: &[RegexMatch<Id>], opt: RegexMatcherOptions) -> Self {
    let mut ids = Vec::new();
    let mut regexes = Vec::new();
    let mut good_regexes = Vec::new();

    for m in matches {
      match Regex::new(&m.regex) {
        Ok(regex) => {
          ids.push(m.id.clone());
          good_regexes.push(&m.regex);
          regexes.push(regex);
        }
        Err(err) => {
          error!("unable to compile regex: '{}', error: {:?}", m.regex, err);
        }
      }
    }

    let regex_set = RegexSet::new(&good_regexes).expect("unable to build regex set");

    Self {
      ids,
      regex_set,
      regexes,
      max_buffer_size: opt.max_buffer_size,
    }
  }
}

#[cfg(test)]
mod tests {
  use super::*;
  use crate::util::tests::get_matches_after_str;

  fn match_result<Id: Default>(id: Id, trigger: &str, vars: &[(&str, &str)]) -> MatchResult<Id> {
    let vars: HashMap<String, String> = vars
      .iter()
      .map(|(key, value)| (key.to_string(), value.to_string()))
      .collect();

    MatchResult {
      id,
      trigger: trigger.to_string(),
      left_separator: None,
      right_separator: None,
      vars,
    }
  }

  #[test]
  fn matcher_simple_matches() {
    let matcher = RegexMatcher::new(
      &[
        RegexMatch::new(1, "hello"),
        RegexMatch::new(2, "num\\d{1,3}s"),
      ],
      RegexMatcherOptions::default(),
    );
    assert_eq!(get_matches_after_str("hi", &matcher), vec![]);
    assert_eq!(
      get_matches_after_str("hello", &matcher),
      vec![match_result(1, "hello", &[])]
    );
    assert_eq!(
      get_matches_after_str("say hello", &matcher),
      vec![match_result(1, "hello", &[])]
    );
    assert_eq!(
      get_matches_after_str("num1s", &matcher),
      vec![match_result(2, "num1s", &[])]
    );
    assert_eq!(
      get_matches_after_str("num134s", &matcher),
      vec![match_result(2, "num134s", &[])]
    );
    assert_eq!(get_matches_after_str("nums", &matcher), vec![]);
  }

  #[test]
  fn matcher_with_variables() {
    let matcher = RegexMatcher::new(
      &[
        RegexMatch::new(1, "hello\\((?P<name>.*?)\\)"),
        RegexMatch::new(2, "multi\\((?P<name1>.*?),(?P<name2>.*?)\\)"),
      ],
      RegexMatcherOptions::default(),
    );
    assert_eq!(get_matches_after_str("hi", &matcher), vec![]);
    assert_eq!(
      get_matches_after_str("say hello(mary)", &matcher),
      vec![match_result(1, "hello(mary)", &[("name", "mary")])]
    );
    assert_eq!(get_matches_after_str("hello(mary", &matcher), vec![]);
    assert_eq!(
      get_matches_after_str("multi(mary,jane)", &matcher),
      vec![match_result(
        2,
        "multi(mary,jane)",
        &[("name1", "mary"), ("name2", "jane")]
      )]
    );
  }

  #[test]
  fn matcher_max_buffer_size() {
    let matcher = RegexMatcher::new(
      &[
        RegexMatch::new(1, "hello\\((?P<name>.*?)\\)"),
        RegexMatch::new(2, "multi\\((?P<name1>.*?),(?P<name2>.*?)\\)"),
      ],
      RegexMatcherOptions {
        max_buffer_size: 15,
      },
    );
    assert_eq!(
      get_matches_after_str("say hello(mary)", &matcher),
      vec![match_result(1, "hello(mary)", &[("name", "mary")])]
    );
    assert_eq!(
      get_matches_after_str("hello(very long name over buffer)", &matcher),
      vec![]
    );
  }
}