use std::collections::BTreeSet;

use heed::RoTxn;
use roaring::RoaringBitmap;

use super::db_cache::DatabaseCache;
use super::resolve_query_graph::resolve_query_graph;
use super::{QueryGraph, QueryNode, RankingRule, RankingRuleOutput};
use crate::{Index, Result, TermsMatchingStrategy};

pub struct Words {
    exhausted: bool,
    query_graph: Option<QueryGraph>,
    iterating: bool,
    positions_to_remove: Vec<i8>,
    terms_matching_strategy: TermsMatchingStrategy,
}
impl Words {
    pub fn new(terms_matching_strategy: TermsMatchingStrategy) -> Self {
        Self {
            exhausted: true,
            query_graph: None,
            iterating: false,
            positions_to_remove: vec![],
            terms_matching_strategy,
        }
    }
}

impl<'transaction> RankingRule<'transaction, QueryGraph> for Words {
    fn start_iteration(
        &mut self,
        _index: &Index,
        _txn: &'transaction RoTxn,
        _db_cache: &mut DatabaseCache<'transaction>,
        parent_candidates: &RoaringBitmap,
        parent_query_graph: &QueryGraph,
    ) -> Result<()> {
        // println!("Words: start iteration");
        self.exhausted = false;
        self.query_graph = Some(parent_query_graph.clone());

        // TODO: a phrase can contain many positions, but represents a single node.
        // That's a problem.
        let positions_to_remove = match self.terms_matching_strategy {
            TermsMatchingStrategy::Last => {
                let mut all_positions = BTreeSet::new();
                for n in parent_query_graph.nodes.iter() {
                    match n {
                        QueryNode::Term(term) => {
                            all_positions.extend(term.positions.clone().into_iter());
                        }
                        QueryNode::Deleted | QueryNode::Start | QueryNode::End => {}
                    }
                }
                all_positions.into_iter().collect()
            }
            TermsMatchingStrategy::All => vec![],
        };
        // println!("positions to remove: {positions_to_remove:?}");
        self.positions_to_remove = positions_to_remove;
        self.iterating = true;
        Ok(())
    }

    fn next_bucket(
        &mut self,
        index: &Index,
        txn: &'transaction RoTxn,
        db_cache: &mut DatabaseCache<'transaction>,
        universe: &RoaringBitmap,
    ) -> Result<Option<RankingRuleOutput<QueryGraph>>> {
        // println!("Words: next bucket");
        assert!(self.iterating);
        assert!(universe.len() > 1);
        if self.exhausted {
            return Ok(None);
        }
        let Some(query_graph) = &mut self.query_graph else { panic!() };
        // let graphviz = query_graph.graphviz();
        // println!("\n===={graphviz}\n====");
        let this_bucket = resolve_query_graph(index, txn, db_cache, query_graph, universe)?;
        // println!("WORDS: this bucket: {this_bucket:?}");
        let child_query_graph = query_graph.clone();
        // this_bucket is the one that must be returned now
        // self.cur_bucket is set to the next bucket
        // TODO: Check whether a position exists in the graph before removing it and
        // returning the next bucket.
        // while graph.does_not_contain(positions_to_remove.last()) { positions_to_remove.pop() }
        if self.positions_to_remove.is_empty() {
            self.exhausted = true;
        } else {
            let position_to_remove = self.positions_to_remove.pop().unwrap();
            query_graph.remove_words_at_position(position_to_remove);
        }

        Ok(Some(RankingRuleOutput { query: child_query_graph, candidates: this_bucket }))
    }

    fn end_iteration(
        &mut self,
        _index: &Index,
        _txn: &'transaction RoTxn,
        _db_cache: &mut DatabaseCache<'transaction>,
    ) {
        // println!("Words: end iteration");
        self.iterating = false;
        self.exhausted = true;
        self.positions_to_remove = vec![];
    }
}

#[cfg(test)]
mod tests {
    // use charabia::Tokenize;
    // use roaring::RoaringBitmap;

    // use crate::{
    //     index::tests::TempIndex,
    //     search::{criteria::CriteriaBuilder, new::QueryGraphOrPlaceholder},
    // };

    // use super::Words;

    // fn placeholder() {
    //     let qt = QueryGraphOrPlaceholder::Placeholder;
    //     let index = TempIndex::new();
    //     let rtxn = index.read_txn().unwrap();

    //     let query = "a beautiful summer house by the beach overlooking what seems";
    //     // let mut builder = QueryTreeBuilder::new(&rtxn, &index).unwrap();
    //     // let (qt, parts, matching_words) = builder.build(query.tokenize()).unwrap().unwrap();

    //     // let cb = CriteriaBuilder::new(&rtxn, &index).unwrap();
    //     // let x = cb
    //     //     .build(
    //     //         Some(qt),
    //     //         Some(parts),
    //     //         None,
    //     //         None,
    //     //         false,
    //     //         None,
    //     //         crate::CriterionImplementationStrategy::OnlySetBased,
    //     //     )
    //     //     .unwrap();

    //     // let rr = Words::new(&index, &RoaringBitmap::from_sorted_iter(0..1000)).unwrap();
    // }
}