#![allow(dead_code)]

use common::HasLen;

use crate::docset::{DocSet, TERMINATED};
use crate::DocId;

/// Simulate a `Postings` objects from a `VecPostings`.
/// `VecPostings` only exist for testing purposes.
///
/// Term frequencies always return 1.
/// No positions are returned.
pub struct VecDocSet {
    doc_ids: Vec<DocId>,
    cursor: usize,
}

impl From<Vec<DocId>> for VecDocSet {
    fn from(doc_ids: Vec<DocId>) -> VecDocSet {
        // We do not use `slice::is_sorted`, as we want to check for doc ids to be strictly
        // sorted.
        assert!(doc_ids.windows(2).all(|w| w[0] < w[1]));
        VecDocSet { doc_ids, cursor: 0 }
    }
}

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

    fn doc(&self) -> DocId {
        if self.cursor == self.doc_ids.len() {
            return TERMINATED;
        }
        self.doc_ids[self.cursor]
    }

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

impl HasLen for VecDocSet {
    fn len(&self) -> usize {
        self.doc_ids.len()
    }
}

#[cfg(test)]
pub(crate) mod tests {

    use super::*;
    use crate::docset::COLLECT_BLOCK_BUFFER_LEN;

    #[test]
    pub fn test_vec_postings() {
        let doc_ids: Vec<DocId> = (0u32..1024u32).map(|e| e * 3).collect();
        let mut postings = VecDocSet::from(doc_ids);
        assert_eq!(postings.doc(), 0u32);
        assert_eq!(postings.advance(), 3u32);
        assert_eq!(postings.doc(), 3u32);
        assert_eq!(postings.seek(14u32), 15u32);
        assert_eq!(postings.doc(), 15u32);
        assert_eq!(postings.seek(300u32), 300u32);
        assert_eq!(postings.doc(), 300u32);
        assert_eq!(postings.seek(6000u32), TERMINATED);
    }

    #[test]
    pub fn test_fill_buffer() {
        let doc_ids: Vec<DocId> = (1u32..=(COLLECT_BLOCK_BUFFER_LEN as u32 * 2 + 9)).collect();
        let mut postings = VecDocSet::from(doc_ids);
        let mut buffer = [0u32; COLLECT_BLOCK_BUFFER_LEN];
        assert_eq!(postings.fill_buffer(&mut buffer), COLLECT_BLOCK_BUFFER_LEN);
        for i in 0u32..COLLECT_BLOCK_BUFFER_LEN as u32 {
            assert_eq!(buffer[i as usize], i + 1);
        }
        assert_eq!(postings.fill_buffer(&mut buffer), COLLECT_BLOCK_BUFFER_LEN);
        for i in 0u32..COLLECT_BLOCK_BUFFER_LEN as u32 {
            assert_eq!(buffer[i as usize], i + 1 + COLLECT_BLOCK_BUFFER_LEN as u32);
        }
        assert_eq!(postings.fill_buffer(&mut buffer), 9);
    }
}