use crate::core::SegmentReader;
use crate::docset::{DocSet, TERMINATED};
use crate::query::boost_query::BoostScorer;
use crate::query::explanation::does_not_match;
use crate::query::{EnableScoring, Explanation, Query, Scorer, Weight};
use crate::{DocId, Score};

/// Query that matches all of the documents.
///
/// All of the document get the score 1.0.
#[derive(Clone, Debug)]
pub struct AllQuery;

impl Query for AllQuery {
    fn weight(&self, _: EnableScoring<'_>) -> crate::Result<Box<dyn Weight>> {
        Ok(Box::new(AllWeight))
    }
}

/// Weight associated with the `AllQuery` query.
pub struct AllWeight;

impl Weight for AllWeight {
    fn scorer(&self, reader: &SegmentReader, boost: Score) -> crate::Result<Box<dyn Scorer>> {
        let all_scorer = AllScorer {
            doc: 0u32,
            max_doc: reader.max_doc(),
        };
        Ok(Box::new(BoostScorer::new(all_scorer, boost)))
    }

    fn explain(&self, reader: &SegmentReader, doc: DocId) -> crate::Result<Explanation> {
        if doc >= reader.max_doc() {
            return Err(does_not_match(doc));
        }
        Ok(Explanation::new("AllQuery", 1.0))
    }
}

/// Scorer associated with the `AllQuery` query.
pub struct AllScorer {
    doc: DocId,
    max_doc: DocId,
}

impl DocSet for AllScorer {
    fn advance(&mut self) -> DocId {
        if self.doc + 1 >= self.max_doc {
            self.doc = TERMINATED;
            return TERMINATED;
        }
        self.doc += 1;
        self.doc
    }

    fn doc(&self) -> DocId {
        self.doc
    }

    fn size_hint(&self) -> u32 {
        self.max_doc
    }
}

impl Scorer for AllScorer {
    fn score(&mut self) -> Score {
        1.0
    }
}

#[cfg(test)]
mod tests {
    use super::AllQuery;
    use crate::docset::TERMINATED;
    use crate::query::{EnableScoring, Query};
    use crate::schema::{Schema, TEXT};
    use crate::Index;

    fn create_test_index() -> crate::Result<Index> {
        let mut schema_builder = Schema::builder();
        let field = schema_builder.add_text_field("text", TEXT);
        let schema = schema_builder.build();
        let index = Index::create_in_ram(schema);
        let mut index_writer = index.writer_for_tests()?;
        index_writer.add_document(doc!(field=>"aaa"))?;
        index_writer.add_document(doc!(field=>"bbb"))?;
        index_writer.commit()?;
        index_writer.add_document(doc!(field=>"ccc"))?;
        index_writer.commit()?;
        Ok(index)
    }

    #[test]
    fn test_all_query() -> crate::Result<()> {
        let index = create_test_index()?;
        let reader = index.reader()?;
        let searcher = reader.searcher();
        let weight = AllQuery.weight(EnableScoring::disabled_from_schema(&index.schema()))?;
        {
            let reader = searcher.segment_reader(0);
            let mut scorer = weight.scorer(reader, 1.0)?;
            assert_eq!(scorer.doc(), 0u32);
            assert_eq!(scorer.advance(), 1u32);
            assert_eq!(scorer.doc(), 1u32);
            assert_eq!(scorer.advance(), TERMINATED);
        }
        {
            let reader = searcher.segment_reader(1);
            let mut scorer = weight.scorer(reader, 1.0)?;
            assert_eq!(scorer.doc(), 0u32);
            assert_eq!(scorer.advance(), TERMINATED);
        }
        Ok(())
    }

    #[test]
    fn test_all_query_with_boost() -> crate::Result<()> {
        let index = create_test_index()?;
        let reader = index.reader()?;
        let searcher = reader.searcher();
        let weight = AllQuery.weight(EnableScoring::disabled_from_schema(searcher.schema()))?;
        let reader = searcher.segment_reader(0);
        {
            let mut scorer = weight.scorer(reader, 2.0)?;
            assert_eq!(scorer.doc(), 0u32);
            assert_eq!(scorer.score(), 2.0);
        }
        {
            let mut scorer = weight.scorer(reader, 1.5)?;
            assert_eq!(scorer.doc(), 0u32);
            assert_eq!(scorer.score(), 1.5);
        }
        Ok(())
    }
}
