/*
    This file is part of jellything (https://codeberg.org/metamuffin/jellything)
    which is licensed under the GNU Affero General Public License (version 3); see /COPYING.
    Copyright (C) 2025 metamuffin <metamuffin.org>
*/
use jellybase::common::Node;
use std::{io::Write, ops::Range, path::PathBuf};

// struct ClusterLayout {
//     position: usize,
//     timestamp: u64,
//     source_offsets: Vec<Option<u64>>,
//     blocks: Vec<(usize, BlockIndex)>,
// }

pub fn remux_stream_into(
    _writer: impl Write,
    _range: Range<usize>,
    _path_base: PathBuf,
    _item: &Node,
    _selection: Vec<usize>,
    _webm: bool,
) -> anyhow::Result<()> {
    // info!("remuxing {:?} to have tracks {selection:?}", item.title);
    // let writer = TrimWriter::new(BufWriter::new(writer), range.clone());
    // let mut output = EbmlWriter::new(writer, 0);

    // struct ReaderC {
    //     info: SourceTrack,
    //     reader: EbmlReader,
    //     mapped: u64,
    //     index: Arc<SeekIndex>,
    //     source_track_index: usize,
    //     codec_private: Option<Vec<u8>>,
    //     layouting_progress_index: usize,
    // }

    // let timing_cp = Instant::now();

    // let mut inputs = selection
    //     .iter()
    //     .enumerate()
    //     .map(|(index, sel)| {
    //         let info = item
    //             .media
    //             .as_ref()
    //             .unwrap()
    //             .tracks
    //             .get(*sel)
    //             .ok_or(anyhow!("track not available"))?
    //             .to_owned();
    //         let source_path = path_base.join(&private.path);
    //         let mapped = index as u64 + 1;
    //         info!("\t- {sel} {source_path:?} ({} => {mapped})", private.track);
    //         info!("\t    {}", info);
    //         let file = File::open(&source_path).context("opening source file")?;
    //         let index = get_seek_index(&source_path)?;
    //         let index = index
    //             .get(&(private.track as u64))
    //             .ok_or(anyhow!("track missing 3"))?
    //             .to_owned();
    //         debug!("\t    seek index: {} blocks loaded", index.blocks.len());
    //         let reader = EbmlReader::new(BufReader::new(file));
    //         Ok(ReaderC {
    //             index,
    //             reader,
    //             info,
    //             mapped,
    //             source_track_index: private.track,
    //             codec_private: private.codec_private.clone(),
    //             layouting_progress_index: 0,
    //         })
    //     })
    //     .collect::<anyhow::Result<Vec<_>>>()?;

    // info!("(perf) prepare inputs: {:?}", Instant::now() - timing_cp);
    // let timing_cp = Instant::now();

    // output.write_tag(&ebml_header(webm))?;

    // output.write_tag(&MatroskaTag::Segment(Master::Start))?;
    // let segment_offset = output.position();

    // output.write_tag(&MatroskaTag::Info(Master::Collected(vec![
    //     MatroskaTag::TimestampScale(1_000_000),
    //     MatroskaTag::Duration(item.media.as_ref().unwrap().duration * 1000.0),
    //     MatroskaTag::Title(item.title.clone().unwrap_or_default()),
    //     MatroskaTag::MuxingApp("jellyremux".to_string()),
    //     MatroskaTag::WritingApp("jellything".to_string()),
    // ])))?;

    // let tracks_header = inputs
    //     .iter_mut()
    //     .map(|rc| ebml_track_entry(rc.mapped, rc.mapped, &rc.info, rc.codec_private.take()))
    //     .collect();
    // output.write_tag(&MatroskaTag::Tracks(Master::Collected(tracks_header)))?;

    // let mut segment_layout: Vec<ClusterLayout> = {
    //     let mut cluster_pts = 0;
    //     let mut clusters = vec![];
    //     let mut cluster = vec![];
    //     let mut source_offsets = vec![None; inputs.len()];
    //     let mut gp = 0usize; // cluster position (in the segment)
    //     let mut p = 0usize; // block position (in the cluster)
    //     loop {
    //         let (track, block) = {
    //             let mut best_block = BlockIndex {
    //                 pts: u64::MAX,
    //                 size: 0,
    //                 source_off: 0,
    //             };
    //             let mut best_track = 0;
    //             for (i, r) in inputs.iter().enumerate() {
    //                 if let Some(v) = r.index.blocks.get(r.layouting_progress_index) {
    //                     if v.pts < best_block.pts {
    //                         best_block = v.to_owned();
    //                         best_track = i;
    //                     }
    //                 };
    //             }
    //             (best_track, best_block)
    //         };
    //         inputs[track].layouting_progress_index += 1;
    //         source_offsets[track].get_or_insert(block.source_off);
    //         if block.pts > cluster_pts + 1_000 {
    //             let cluster_content_size = 1 + 1 // timestamp {tag, size}
    //                  + bad_vint_length(cluster_pts) // timestamp tag value
    //                  + p;
    //             let cluster_size = 4 // tag length
    //                   + vint_length(cluster_content_size as u64) // size varint
    //                   + cluster_content_size;
    //             clusters.push(ClusterLayout {
    //                 position: gp, // relative to the first cluster
    //                 timestamp: cluster_pts,
    //                 source_offsets,
    //                 blocks: std::mem::take(&mut cluster),
    //             });

    //             cluster_pts = block.pts;
    //             source_offsets = vec![None; inputs.len()];
    //             gp += cluster_size;
    //             p = 0;
    //         }
    //         if block.pts == u64::MAX {
    //             break;
    //         }

    //         let simpleblock_size = 1 + 2 + 1 // block {tracknum, pts_off, flags}
    //                                         // TODO does not work, if more than 127 tracks are present
    //                                         + block.size; // block payload
    //         p += 1; // simpleblock tag
    //         p += vint_length(simpleblock_size as u64); // simpleblock size vint
    //         p += simpleblock_size;

    //         cluster.push((track, block))
    //     }
    //     info!("segment layout computed ({} clusters)", clusters.len());
    //     clusters
    // };
    // info!(
    //     "(perf) compute segment layout: {:?}",
    //     Instant::now() - timing_cp
    // );
    // let timing_cp = Instant::now();

    // let max_cue_size = 4 // cues id
    //         + 8 // cues len
    //         + ( // cues content
    //             1 // cp id
    //             + 1 // cp len
    //             + ( // cp content
    //                 1 // ctime id,
    //                 + 1 // ctime len
    //                 + 8 // ctime content uint
    //                 + ( // ctps
    //                     1 // ctp id
    //                     + 8 // ctp len
    //                     + (// ctp content
    //                         1 // ctrack id
    //                         + 1 // ctrack size
    //                         + 1 // ctrack content int
    //                             // TODO this breaks if inputs.len() >= 127
    //                         + 1 // ccp id
    //                         + 1 // ccp len
    //                         + 8 // ccp content offset
    //                     )
    //                 )
    //             ) * inputs.len()
    //         ) * segment_layout.len()
    //         + 1 // void id
    //         + 8; // void len

    // let first_cluster_offset_predict = max_cue_size + output.position();

    // // make the cluster position relative to the segment start as they should
    // segment_layout
    //     .iter_mut()
    //     .for_each(|e| e.position += first_cluster_offset_predict - segment_offset);

    // output.write_tag(&MatroskaTag::Cues(Master::Collected(
    //     segment_layout
    //         .iter()
    //         .map(|cluster| {
    //             MatroskaTag::CuePoint(Master::Collected(
    //                 Some(MatroskaTag::CueTime(cluster.timestamp))
    //                     .into_iter()
    //                     // TODO: Subtitles should not have cues for every cluster
    //                     .chain(inputs.iter().map(|i| {
    //                         MatroskaTag::CueTrackPositions(Master::Collected(vec![
    //                             MatroskaTag::CueTrack(i.mapped),
    //                             MatroskaTag::CueClusterPosition(cluster.position as u64),
    //                         ]))
    //                     }))
    //                     .collect(),
    //             ))
    //         })
    //         .collect(),
    // )))?;
    // output.write_padding(first_cluster_offset_predict)?;
    // let first_cluster_offset = output.position();
    // assert_eq!(first_cluster_offset, first_cluster_offset_predict);

    // let mut skip = 0;
    // // TODO binary search
    // for (i, cluster) in segment_layout.iter().enumerate() {
    //     if (cluster.position + segment_offset) >= range.start {
    //         break;
    //     }
    //     skip = i;
    // }

    // if skip != 0 {
    //     info!("skipping {skip} clusters");
    //     output.seek(SeekFrom::Start(
    //         (segment_layout[skip].position + segment_offset) as u64,
    //     ))?;
    // }

    // struct ReaderD<'a> {
    //     stream: SegmentExtractIter<'a>,
    //     mapped: u64,
    // }

    // let mut track_readers = inputs
    //     .iter_mut()
    //     .enumerate()
    //     .map(|(i, inp)| {
    //         inp.reader
    //             .seek(
    //                 // the seek target might be a hole; we continue until the next cluster of that track.
    //                 // this should be fine since tracks are only read according to segment_layout
    //                 find_first_cluster_with_off(&segment_layout, skip, i)
    //                     .ok_or(anyhow!("cluster hole at eof"))?,
    //                 MatroskaTag::Cluster(Master::Start), // TODO shouldn't this be a child of cluster?
    //             )
    //             .context("seeking in input")?;
    //         let stream = SegmentExtractIter::new(&mut inp.reader, inp.source_track_index as u64);

    //         Ok(ReaderD {
    //             mapped: inp.mapped,
    //             stream,
    //         })
    //     })
    //     .collect::<anyhow::Result<Vec<_>>>()?;

    // info!("(perf) seek inputs: {:?}", Instant::now() - timing_cp);

    // for (cluster_index, cluster) in segment_layout.into_iter().enumerate().skip(skip) {
    //     debug!(
    //         "writing cluster {cluster_index} (pts_base={}) with {} blocks",
    //         cluster.timestamp,
    //         cluster.blocks.len()
    //     );
    //     {
    //         let cue_error = cluster.position as i64 - (output.position() - segment_offset) as i64;
    //         if cue_error != 0 {
    //             warn!("calculation was {} bytes off", cue_error);
    //         }
    //     }

    //     let mut cluster_blocks = vec![MatroskaTag::Timestamp(cluster.timestamp)];
    //     for (block_track, index_block) in cluster.blocks {
    //         let track_reader = &mut track_readers[block_track];
    //         // TODO handle duration
    //         let mut block = track_reader.stream.next_block()?.0;

    //         assert_eq!(index_block.size, block.data.len(), "seek index is wrong");

    //         block.track = track_reader.mapped;
    //         block.timestamp_off = (index_block.pts - cluster.timestamp).try_into().unwrap();
    //         trace!("n={} tso={}", block.track, block.timestamp_off);

    //         cluster_blocks.push(MatroskaTag::SimpleBlock(block))
    //     }
    //     output.write_tag(&MatroskaTag::Cluster(Master::Collected(cluster_blocks)))?;
    // }
    // // output.write_tag(&MatroskaTag::Segment(Master::End))?;
    // Ok(())
    todo!()
}

// fn find_first_cluster_with_off(
//     segment_layout: &[ClusterLayout],
//     skip: usize,
//     track: usize,
// ) -> Option<u64> {
//     for cluster in segment_layout.iter().skip(skip) {
//         if let Some(off) = cluster.source_offsets[track] {
//             return Some(off);
//         }
//     }
//     None
// }