use super::*;

#[test]
fn segment_filename_format() {
    assert_eq!(
        segment_filename(ShardId::SINGLE, 1),
        "wal-00000000000000000001.seg"
    );
    assert_eq!(
        segment_filename(ShardId::SINGLE, 0),
        "wal-00000000000000000000.seg"
    );
    assert_eq!(
        segment_filename(ShardId::SINGLE, u64::MAX),
        "wal-18446744073709551615.seg"
    );
}

#[test]
fn parse_segment_seq_valid() {
    assert_eq!(parse_segment_seq("wal-00000000000000000001.seg"), Some(1));
    assert_eq!(parse_segment_seq("wal-00000000000000000000.seg"), Some(0));
}

#[test]
fn parse_segment_seq_invalid() {
    assert_eq!(parse_segment_seq("not-a-segment.txt"), None);
    assert_eq!(parse_segment_seq("wal-.seg"), None);
    assert_eq!(parse_segment_seq("wal-abc.seg"), None);
    assert_eq!(parse_segment_seq(""), None);
}

#[test]
fn write_and_check_size() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    let mut writer =
        SegmentWriter::open(dir.path(), ShardId::SINGLE, 1, 1024).expect("open should succeed");
    // A fresh segment starts at the versioned header's size (m11p4).
    assert_eq!(writer.current_size(), SEGMENT_HEADER_SIZE as u64);

    let data = [0xABu8; 100];
    writer
        .write_batch_bytes(&data)
        .expect("write should succeed");
    assert_eq!(writer.current_size(), SEGMENT_HEADER_SIZE as u64 + 100);
}

#[test]
fn rotation_creates_new_file() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    let mut writer =
        SegmentWriter::open(dir.path(), ShardId::SINGLE, 1, 100).expect("open should succeed");

    writer
        .write_batch_bytes(&[0u8; 50])
        .expect("write should succeed");
    writer.rotate(100).expect("rotate should succeed");

    // The rotated-to segment starts at its own versioned header.
    assert_eq!(writer.current_size(), SEGMENT_HEADER_SIZE as u64);
    assert_eq!(writer.first_seq(), 100);

    let segments = list_segments(dir.path()).expect("list should succeed");
    assert_eq!(segments.len(), 2);
    assert_eq!(segments[0].0, 1);
    assert_eq!(segments[1].0, 100);
}

#[test]
fn needs_rotation_threshold() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    let mut writer =
        SegmentWriter::open(dir.path(), ShardId::SINGLE, 1, 100).expect("open should succeed");
    assert!(!writer.needs_rotation());

    writer
        .write_batch_bytes(&[0u8; 100])
        .expect("write should succeed");
    assert!(writer.needs_rotation());
}

#[test]
fn list_segments_sorted() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    // Create segments out of order
    let _ = SegmentWriter::open(dir.path(), ShardId::SINGLE, 300, 1024);
    let _ = SegmentWriter::open(dir.path(), ShardId::SINGLE, 100, 1024);
    let _ = SegmentWriter::open(dir.path(), ShardId::SINGLE, 200, 1024);

    let segments = list_segments(dir.path()).expect("list should succeed");
    assert_eq!(segments.len(), 3);
    assert_eq!(segments[0].0, 100);
    assert_eq!(segments[1].0, 200);
    assert_eq!(segments[2].0, 300);
}

#[test]
fn list_segments_empty_dir() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    let segments = list_segments(dir.path()).expect("list should succeed");
    assert!(segments.is_empty());
}

#[test]
fn list_segments_ignores_non_segment_files() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    fs::write(dir.path().join("checkpoint.meta"), "seq=1\nts=1\n").expect("write should succeed");
    fs::write(dir.path().join("random.txt"), "hello").expect("write should succeed");
    let _ = SegmentWriter::open(dir.path(), ShardId::SINGLE, 1, 1024);

    let segments = list_segments(dir.path()).expect("list should succeed");
    assert_eq!(segments.len(), 1);
}

#[test]
fn delete_segments_before_removes_older() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    let _ = SegmentWriter::open(dir.path(), ShardId::SINGLE, 1, 1024);
    let _ = SegmentWriter::open(dir.path(), ShardId::SINGLE, 100, 1024);
    let _ = SegmentWriter::open(dir.path(), ShardId::SINGLE, 200, 1024);

    let deleted = delete_segments_before(dir.path(), 200).expect("delete should succeed");
    assert_eq!(deleted, 2);

    let remaining = list_segments(dir.path()).expect("list should succeed");
    assert_eq!(remaining.len(), 1);
    assert_eq!(remaining[0].0, 200);
}

#[test]
fn delete_segments_before_none_to_delete() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    let _ = SegmentWriter::open(dir.path(), ShardId::SINGLE, 100, 1024);

    let deleted = delete_segments_before(dir.path(), 50).expect("delete should succeed");
    assert_eq!(deleted, 0);
}

#[test]
fn sync_does_not_error() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    let writer =
        SegmentWriter::open(dir.path(), ShardId::SINGLE, 1, 1024).expect("open should succeed");
    writer.sync().expect("sync should succeed");
}

// -- Multi-shard naming tests --

#[test]
fn segment_filename_multi_shard() {
    let name = segment_filename(ShardId(3), 42);
    assert_eq!(name, "wal-s00003-00000000000000000042.seg");
}

#[test]
fn segment_filename_single_shard_backward_compat() {
    // ShardId::SINGLE retains old format exactly
    assert_eq!(
        segment_filename(ShardId::SINGLE, 1),
        "wal-00000000000000000001.seg"
    );
    assert_eq!(
        segment_filename(ShardId(0), 42),
        "wal-00000000000000000042.seg"
    );
}

#[test]
fn parse_segment_filename_both_formats() {
    assert_eq!(
        parse_segment_filename("wal-00000000000000000001.seg"),
        Some((ShardId::SINGLE, 1))
    );
    assert_eq!(
        parse_segment_filename("wal-s00003-00000000000000000042.seg"),
        Some((ShardId(3), 42))
    );
    assert_eq!(parse_segment_filename("not-a-segment.txt"), None);
}

#[test]
fn parse_segment_filename_edge_cases() {
    // Empty filename
    assert_eq!(parse_segment_filename(""), None);
    // Missing .seg suffix
    assert_eq!(parse_segment_filename("wal-00000000000000000001"), None);
    // Shard format but missing seq
    assert_eq!(parse_segment_filename("wal-s00003.seg"), None);
    // Non-numeric shard
    assert_eq!(
        parse_segment_filename("wal-sXYZ-00000000000000000001.seg"),
        None
    );
}

#[test]
fn list_segments_for_shard_filters_correctly() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");

    // Create single-shard segment files (v1 format)
    let _ = SegmentWriter::open(dir.path(), ShardId::SINGLE, 1, 1024);
    let _ = SegmentWriter::open(dir.path(), ShardId::SINGLE, 100, 1024);

    // Create multi-shard segment files (v2 format) manually
    let s3_name = segment_filename(ShardId(3), 50);
    fs::write(dir.path().join(s3_name), []).expect("write should succeed");
    let s3_name2 = segment_filename(ShardId(3), 200);
    fs::write(dir.path().join(s3_name2), []).expect("write should succeed");
    let s5_name = segment_filename(ShardId(5), 75);
    fs::write(dir.path().join(s5_name), []).expect("write should succeed");

    // list_segments returns ALL segment files (backward compat)
    let all = list_segments(dir.path()).expect("list should succeed");
    assert_eq!(all.len(), 5);

    // list_segments_for_shard returns only matching shard
    let single = list_segments_for_shard(dir.path(), ShardId::SINGLE).expect("list should succeed");
    assert_eq!(single.len(), 2);
    assert_eq!(single[0].0, 1);
    assert_eq!(single[1].0, 100);

    let shard3 = list_segments_for_shard(dir.path(), ShardId(3)).expect("list should succeed");
    assert_eq!(shard3.len(), 2);
    assert_eq!(shard3[0].0, 50);
    assert_eq!(shard3[1].0, 200);

    let shard5 = list_segments_for_shard(dir.path(), ShardId(5)).expect("list should succeed");
    assert_eq!(shard5.len(), 1);
    assert_eq!(shard5[0].0, 75);

    // Non-existent shard returns empty
    let empty = list_segments_for_shard(dir.path(), ShardId(99)).expect("list should succeed");
    assert!(empty.is_empty());
}

#[test]
fn list_segments_for_shard_missing_dir() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    let missing = dir.path().join("does-not-exist");
    let result = list_segments_for_shard(&missing, ShardId::SINGLE)
        .expect("should handle missing dir gracefully");
    assert!(result.is_empty());
}

#[test]
fn segment_writer_stores_shard_id() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    let writer = SegmentWriter::open(dir.path(), ShardId(7), 1, 1024).expect("open should succeed");
    assert_eq!(writer.shard_id(), ShardId(7));

    // Verify the on-disk filename uses the v2 format.
    let expected = segment_filename(ShardId(7), 1);
    assert!(
        dir.path().join(&expected).exists(),
        "expected file {expected} to exist in WAL dir"
    );
}

#[test]
fn rotation_preserves_shard_id_in_filename() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    let mut writer =
        SegmentWriter::open(dir.path(), ShardId(3), 1, 100).expect("open should succeed");
    writer
        .write_batch_bytes(&[0u8; 50])
        .expect("write should succeed");
    writer.rotate(100).expect("rotate should succeed");

    let seg1 = segment_filename(ShardId(3), 1);
    let seg2 = segment_filename(ShardId(3), 100);
    assert!(
        dir.path().join(&seg1).exists(),
        "first segment {seg1} must exist"
    );
    assert!(
        dir.path().join(&seg2).exists(),
        "rotated segment {seg2} must exist"
    );
    assert_eq!(writer.shard_id(), ShardId(3));
}

// ── Segment format versioning (m11p4) ──────────────────────────────────────

#[test]
fn new_segment_leads_with_versioned_header() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    let _ = SegmentWriter::open(dir.path(), ShardId::SINGLE, 1, 1024).expect("open");

    let bytes = fs::read(dir.path().join(segment_filename(ShardId::SINGLE, 1))).expect("read");
    assert_eq!(
        bytes,
        segment_header(),
        "fresh segment = exactly the header"
    );
    assert_eq!(&bytes[..4], b"TSEG");
    assert_eq!(bytes[4], SEGMENT_FORMAT_VERSION);
    assert_eq!(&bytes[5..8], &[0, 0, 0], "reserved bytes must be zero");
}

#[test]
fn reopening_existing_segment_writes_no_second_header() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    {
        let mut writer =
            SegmentWriter::open(dir.path(), ShardId::SINGLE, 1, 1024).expect("open should succeed");
        writer.write_batch_bytes(&[0xAB; 10]).expect("write");
    }
    let writer =
        SegmentWriter::open(dir.path(), ShardId::SINGLE, 1, 1024).expect("reopen should succeed");
    assert_eq!(
        writer.current_size(),
        SEGMENT_HEADER_SIZE as u64 + 10,
        "reopen must append, not re-write the header"
    );
}

#[test]
fn reopening_legacy_headerless_segment_stays_legacy() {
    // A pre-m11p4 file (batch bytes at offset 0): appends must NOT inject a
    // header mid-file — the segment keeps its legacy layout.
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    let path = dir.path().join(segment_filename(ShardId::SINGLE, 1));
    fs::write(&path, [0xCD; 32]).expect("write should succeed");

    let writer =
        SegmentWriter::open(dir.path(), ShardId::SINGLE, 1, 1024).expect("open should succeed");
    assert_eq!(writer.current_size(), 32);
    let bytes = fs::read(&path).expect("read");
    assert_eq!(&bytes[..4], &[0xCD; 4], "legacy leading bytes untouched");
}

#[test]
fn unparseable_seg_filename_is_format_unknown() {
    let dir = tempfile::tempdir().expect("tempdir creation should succeed");
    let _ = SegmentWriter::open(dir.path(), ShardId::SINGLE, 1, 1024).expect("open");
    fs::write(dir.path().join("wal-mystery.seg"), [0u8; 8]).expect("write should succeed");

    assert!(
        matches!(
            list_segments(dir.path()),
            Err(WalError::SegmentFormatUnknown { .. })
        ),
        "an unparseable .seg filename must refuse loudly, not read as absent"
    );
    assert!(
        matches!(
            list_segments_for_shard(dir.path(), ShardId::SINGLE),
            Err(WalError::SegmentFormatUnknown { .. })
        ),
        "the per-shard listing must refuse identically"
    );
}

mod proptests {
    use proptest::prelude::*;

    use super::*;

    proptest! {
        #[test]
        fn filename_roundtrip(seq: u64) {
            let name = segment_filename(ShardId::SINGLE, seq);
            let parsed = parse_segment_seq(&name);
            prop_assert_eq!(parsed, Some(seq));
        }

        #[test]
        fn shard_filename_roundtrip(shard_id in 0u16..100u16, seq in proptest::num::u64::ANY) {
            let shard = ShardId(shard_id);
            let name = segment_filename(shard, seq);
            let parsed = parse_segment_filename(&name);
            prop_assert_eq!(parsed, Some((shard, seq)));
        }
    }
}