use crate::engine::util::{contains_upper, regex_match};
use crate::item::RankBuilder;
use crate::{CaseMatching, MatchEngine, MatchRange, MatchResult, SkimItem};
use regex::{Regex, escape};
use std::cmp::min;
use std::fmt::{Display, Error, Formatter};
use std::sync::Arc;

//------------------------------------------------------------------------------
// Exact engine
#[derive(Debug, Copy, Clone, Default)]
#[allow(clippy::struct_excessive_bools)]
pub struct ExactMatchingParam {
    pub prefix: bool,
    pub postfix: bool,
    pub inverse: bool,
    pub case: CaseMatching,
    __non_exhaustive: bool,
}

#[derive(Debug)]
pub struct ExactEngine {
    #[allow(dead_code)]
    query: String,
    query_regex: Option<Regex>,
    rank_builder: Arc<RankBuilder>,
    inverse: bool,
}

impl ExactEngine {
    pub fn builder(query: &str, param: ExactMatchingParam) -> Self {
        let case_sensitive = match param.case {
            CaseMatching::Respect => true,
            CaseMatching::Ignore => false,
            CaseMatching::Smart => contains_upper(query),
        };

        let mut query_builder = String::new();
        if !case_sensitive {
            query_builder.push_str("(?i)");
        }

        if param.prefix {
            query_builder.push('^');
        }

        query_builder.push_str(&escape(query));

        if param.postfix {
            query_builder.push('$');
        }

        let query_regex = if query.is_empty() {
            None
        } else {
            Regex::new(&query_builder).ok()
        };

        ExactEngine {
            query: query.to_string(),
            query_regex,
            rank_builder: Default::default(),
            inverse: param.inverse,
        }
    }

    pub fn rank_builder(mut self, rank_builder: Arc<RankBuilder>) -> Self {
        self.rank_builder = rank_builder;
        self
    }

    pub fn build(self) -> Self {
        self
    }
}

impl MatchEngine for ExactEngine {
    fn match_item(&self, item: &dyn SkimItem) -> Option<MatchResult> {
        let mut matched_result = None;
        let item_text = item.text();
        let default_range = [(0, item_text.len())];
        let ranges = item.get_matching_ranges().unwrap_or(&default_range);

        if ranges.is_empty() {
            // Nothing to match against (e.g. every `--nth` index is out of range): the item
            // stays unmatched, inverse or not.
        } else if self.query_regex.is_none() {
            matched_result = Some((0, 0));
        } else {
            for &(start, end) in ranges {
                let start = min(start, item_text.len());
                let end = min(end, item_text.len());

                matched_result =
                    regex_match(&item_text[start..end], self.query_regex.as_ref()).map(|(s, e)| (s + start, e + start));

                if matched_result.is_some() {
                    break;
                }
            }

            // An inverse query has to be evaluated over *all* the matching ranges: the item
            // only matches when none of them contains the query.  Inverting inside the loop
            // would let the first non-matching field short-circuit the scan and wrongly
            // accept an item whose later fields do contain the query.
            if self.inverse {
                matched_result = matched_result.xor(Some((0, 0)));
            }
        }

        let (begin, end) = matched_result?;
        let score = i32::try_from(end - begin).unwrap_or(i32::MAX);
        Some(MatchResult {
            rank: self.rank_builder.build_rank(score, begin, end, &item_text),
            matched_range: MatchRange::ByteRange(begin, end),
        })
    }
}

impl Display for ExactEngine {
    fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
        write!(
            f,
            "(Exact|{}{})",
            if self.inverse { "!" } else { "" },
            self.query_regex.as_ref().map_or("", regex::Regex::as_str)
        )
    }
}

#[cfg(test)]
#[path = "exact_tests.rs"]
mod tests;
