/// <reference types="node"/>
import {Int64BE, Uint64BE} from "int64-buffer";
import * as EBML from "./EBML";
import Encoder from "./EBMLEncoder";
import * as _Buffer from "buffer";
import _tools from "./tools-ebml";
import * as _block from "ebml-block";

export const Buffer: typeof global.Buffer = _Buffer.Buffer;
export const readVint: (buffer: Buffer, start: number)=> null | ({length: number; value: number; }) = _tools.readVint;
export const writeVint: (val: number)=> Buffer = _tools.writeVint;

export const ebmlBlock: (buf: Buffer)=> EBML.SimpleBlock = _block;
export function readBlock(buf: ArrayBuffer): EBML.SimpleBlock {
  return ebmlBlock(new Buffer(buf));
}

/**
  * @param end - if end === false then length is unknown
  */
export function encodeTag(tagId: Buffer, tagData: Buffer, unknownSize=false): Buffer {
  return concat([
    tagId,
    unknownSize ?
      new Buffer('01ffffffffffffff', 'hex') : 
      writeVint(tagData.length),
    tagData
  ]);
}

/**
 * WebP ファイルにできる SimpleBlock の パスフィルタ
 */
export function WebPBlockFilter(elms: EBML.EBMLElementDetail[]): (EBML.BinaryElement & EBML.ElementDetail & {data: Buffer})[] {
  return elms.reduce<(EBML.BinaryElement & EBML.ElementDetail & {data: Buffer})[]>((lst, elm)=>{
    if(elm.type !== "b"){ return lst; }
    if(elm.name !== "SimpleBlock"){ return lst; }
    const o = ebmlBlock(elm.data);
    const hasWebP = o.frames.some((frame)=>{
      // https://tools.ietf.org/html/rfc6386#section-19.1
      const startcode = frame.slice(3, 6).toString("hex");
      return startcode === "9d012a";
    });
    if(!hasWebP){ return lst; }
    return lst.concat(elm);
  }, []);
}

/**
 * @param frame - VP8 BitStream のうち startcode をもつ frame
 * @return - WebP ファイルの ArrayBuffer
 */
export function VP8BitStreamToRiffWebPBuffer(frame: Buffer): Buffer {
  const VP8Chunk = createRIFFChunk("VP8 ", frame);
  const WebPChunk = concat([
    new Buffer("WEBP", "ascii"),
    VP8Chunk
  ]);
  return createRIFFChunk("RIFF", WebPChunk);
}

/**
 * RIFF データチャンクを作る
 */
export function createRIFFChunk(FourCC: string, chunk: Buffer): Buffer {
  const chunkSize = new Buffer(4);
  chunkSize.writeUInt32LE(chunk.byteLength , 0);
  return concat([
    new Buffer(FourCC.substr(0, 4), "ascii"),
    chunkSize,
    chunk,
    new Buffer(chunk.byteLength % 2 === 0 ? 0 : 1) // padding
  ]);
}


/* Original Metadata

 m  0	EBML
 u  1	  EBMLVersion 1
 u  1	  EBMLReadVersion 1
 u  1	  EBMLMaxIDLength 4
 u  1	  EBMLMaxSizeLength 8
 s  1	  DocType webm
 u  1	  DocTypeVersion 4
 u  1	  DocTypeReadVersion 2
 m  0	Segment
 m  1	  Info                                segmentContentStartPos, all CueClusterPositions provided in info.cues will be relative to here and will need adjusted
 u  2	    TimecodeScale 1000000
 8  2	    MuxingApp Chrome
 8  2	    WritingApp Chrome
 m  1	  Tracks                              tracksStartPos
 m  2	    TrackEntry
 u  3	      TrackNumber 1
 u  3	      TrackUID 31790271978391090
 u  3	      TrackType 2
 s  3	      CodecID A_OPUS
 b  3	      CodecPrivate <Buffer 19>
 m  3	      Audio
 f  4	        SamplingFrequency 48000
 u  4	        Channels 1
 m  2	    TrackEntry
 u  3	      TrackNumber 2
 u  3	      TrackUID 24051277436254136
 u  3	      TrackType 1
 s  3	      CodecID V_VP8
 m  3	      Video
 u  4	        PixelWidth 1024
 u  4	        PixelHeight 576
 m  1	  Cluster                             clusterStartPos
 u  2	    Timecode 0
 b  2	    SimpleBlock track:2 timecode:0	keyframe:true	invisible:false	discardable:false	lacing:1
*/

/* Desired Metadata

 m	0 EBML
 u	1   EBMLVersion 1
 u	1   EBMLReadVersion 1
 u	1   EBMLMaxIDLength 4
 u	1   EBMLMaxSizeLength 8
 s	1   DocType webm
 u	1   DocTypeVersion 4
 u	1   DocTypeReadVersion 2
 m	0 Segment
 m	1   SeekHead                            -> This is SeekPosition 0, so all SeekPositions can be calculated as (bytePos - segmentContentStartPos), which is 44 in this case
 m	2     Seek
 b	3       SeekID                          -> Buffer([0x15, 0x49, 0xA9, 0x66])  Info
 u	3       SeekPosition                    -> infoStartPos = 
 m	2     Seek
 b	3       SeekID                          -> Buffer([0x16, 0x54, 0xAE, 0x6B])  Tracks
 u	3       SeekPosition { tracksStartPos }
 m	2     Seek
 b	3       SeekID                          -> Buffer([0x1C, 0x53, 0xBB, 0x6B])  Cues
 u	3       SeekPosition { cuesStartPos }   
 m	1   Info
 f	2     Duration 32480                    -> overwrite, or insert if it doesn't exist
 u	2     TimecodeScale 1000000
 8	2     MuxingApp Chrome
 8	2     WritingApp Chrome
 m	1   Tracks
 m	2     TrackEntry
 u	3       TrackNumber 1
 u	3       TrackUID 31790271978391090
 u	3       TrackType 2
 s	3       CodecID A_OPUS
 b	3       CodecPrivate <Buffer 19>
 m	3       Audio
 f	4         SamplingFrequency 48000
 u	4         Channels 1
 m	2     TrackEntry
 u	3       TrackNumber 2
 u	3       TrackUID 24051277436254136
 u	3       TrackType 1
 s	3       CodecID V_VP8
 m	3       Video
 u	4         PixelWidth 1024
 u	4         PixelHeight 576
 m  1   Cues                                -> cuesStartPos
 m  2     CuePoint
 u  3       CueTime 0
 m  3       CueTrackPositions
 u  4         CueTrack 1
 u  4         CueClusterPosition 3911
 m  2     CuePoint
 u  3       CueTime 600
 m  3       CueTrackPositions
 u  4         CueTrack 1
 u  4         CueClusterPosition 3911
 m  1   Cluster
 u  2     Timecode 0
 b  2     SimpleBlock track:2 timecode:0	keyframe:true	invisible:false	discardable:false	lacing:1
*/

/**
 * convert the metadata from a streaming webm bytestream to a seekable file by inserting Duration, Seekhead and Cues
 * @param originalMetadata - orginal metadata (everything before the clusters start) from media recorder
 * @param duration - Duration (TimecodeScale)
 * @param cues - cue points for clusters
 */
export function makeMetadataSeekable( 
  originalMetadata: EBML.EBMLElementDetail[], 
  duration: number,
  cuesInfo: {CueTrack: number; CueClusterPosition: number; CueTime: number; }[] )

  : ArrayBuffer {

  // extract the header, we can reuse this as-is
  let header = extractElement("EBML", originalMetadata);
  let headerSize = encodedSizeOfEbml(header);
  //console.error("Header size: " + headerSize);
  //printElementIds(header);

  // After the header comes the Segment open tag, which in this implementation is always 12 bytes (4 byte id, 8 byte 'unknown length')
  // After that the segment content starts. All SeekPositions and CueClusterPosition must be relative to segmentContentStartPos
  let segmentContentStartPos = headerSize + 12;
  //console.error("segmentContentStartPos: " + segmentContentStartPos);    

  // find the original metadata size, and adjust it for header size and Segment start element so we can keep all positions relative to segmentContentStartPos
  
  let originalMetadataSize = originalMetadata[originalMetadata.length-1].dataEnd - segmentContentStartPos;
  //console.error("Original Metadata size: " + originalMetadataSize);
  //printElementIds(originalMetadata);

  // extract the segment info, remove the potentially existing Duration element, and add our own one.
  let info : EBML.EBMLElementBuffer[] = extractElement("Info", originalMetadata);
  removeElement("Duration", info);
  info.splice(1,0, {name: "Duration", type: "f", data: createFloatBuffer(duration, 8) })
  let infoSize = encodedSizeOfEbml(info);
  //console.error("Info size: " + infoSize);
  //printElementIds(info);  

  // extract the track info, we can re-use this as is
  let tracks = extractElement("Tracks", originalMetadata)
  let tracksSize = encodedSizeOfEbml(tracks);
  //console.error("Tracks size: " + tracksSize);
  //printElementIds(tracks);  

  let seekHeadSize = 47;                        // Initial best guess, but could be slightly larger if the Cues element is huge.
  let seekHead : EBML.EBMLElementBuffer[] = [];

  let cuesSize = 5 + cuesInfo.length * 15;      // very rough initial approximation, depends a lot on file size and number of CuePoints                   
  let cues : EBML.EBMLElementBuffer[] = [];

  let lastSizeDifference = -1;  // 

  // The size of SeekHead and Cues elements depends on how many bytes the offsets values can be encoded in.
  // The actual offsets in CueClusterPosition depend on the final size of the SeekHead and Cues elements
  // We need to iteratively converge to a stable solution.

  const maxIterations = 10;
  for (let i = 0; i < maxIterations; i++) {

    // SeekHead starts at 0
    let infoStart = seekHeadSize;                 // Info comes directly after SeekHead
    let tracksStart = infoStart + infoSize;       // Tracks comes directly after Info
    let cuesStart = tracksStart + tracksSize;     // Cues starts directly after 
    let newMetadataSize = cuesStart + cuesSize;   // total size of metadata  

    // This is the offset all CueClusterPositions should be adjusted by due to the metadata size changing.
    let sizeDifference = newMetadataSize - originalMetadataSize;
    // console.error(`infoStart: ${infoStart}, infoSize: ${infoSize}`);
    // console.error(`tracksStart: ${tracksStart}, tracksSize: ${tracksSize}`);
    // console.error(`cuesStart: ${cuesStart}, cuesSize: ${cuesSize}`);
    // console.error(`originalMetadataSize: ${originalMetadataSize}, newMetadataSize: ${newMetadataSize}, sizeDifference: ${sizeDifference}`); 

    // create the SeekHead element
    seekHead = [];
    seekHead.push({name: "SeekHead", type: "m", isEnd: false});
      seekHead.push({name: "Seek", type: "m", isEnd: false});
        seekHead.push({name: "SeekID", type: "b", data: new Buffer([0x15, 0x49, 0xA9, 0x66])});   // Info
        seekHead.push({name: "SeekPosition", type: "u", data: createUIntBuffer(infoStart)});
      seekHead.push({name: "Seek", type: "m", isEnd: true});
      seekHead.push({name: "Seek", type: "m", isEnd: false});
        seekHead.push({name: "SeekID", type: "b", data: new Buffer([0x16, 0x54, 0xAE, 0x6B])});   // Tracks
        seekHead.push({name: "SeekPosition", type: "u", data: createUIntBuffer(tracksStart)});
      seekHead.push({name: "Seek", type: "m", isEnd: true});
      seekHead.push({name: "Seek", type: "m", isEnd: false});
        seekHead.push({name: "SeekID", type: "b", data: new Buffer([0x1C, 0x53, 0xBB, 0x6B])});   // Cues
        seekHead.push({name: "SeekPosition", type: "u", data: createUIntBuffer(cuesStart)});
      seekHead.push({name: "Seek", type: "m", isEnd: true});        
    seekHead.push({name: "SeekHead", type: "m", isEnd: true});

    seekHeadSize = encodedSizeOfEbml(seekHead);
    //console.error("SeekHead size: " + seekHeadSize);
    //printElementIds(seekHead);  

    // create the Cues element
    cues = [];
    cues.push({name: "Cues", type: "m", isEnd: false}) 
      cuesInfo.forEach(({ CueTrack, CueClusterPosition, CueTime }) => {
        cues.push({ name: "CuePoint", type: "m", isEnd: false });
          cues.push({ name: "CueTime", type: "u", data: createUIntBuffer(CueTime) });
          cues.push({ name: "CueTrackPositions", type: "m", isEnd: false });
            cues.push({ name: "CueTrack", type: "u", data: createUIntBuffer(CueTrack) });
            //console.error(`CueClusterPosition: ${CueClusterPosition}, Corrected to: ${CueClusterPosition - segmentContentStartPos}  , offset by ${sizeDifference} to become ${(CueClusterPosition - segmentContentStartPos) + sizeDifference - segmentContentStartPos}`);
            // EBMLReader returns CueClusterPosition with absolute byte offsets. The Cues section expects them as offsets from the first level 1 element of the Segment, so we need to adjust it.
            CueClusterPosition -= segmentContentStartPos;
            // We also need to adjust to take into account the change in metadata size from when EBMLReader read the original metadata.
            CueClusterPosition += sizeDifference;
            cues.push({ name: "CueClusterPosition", type: "u", data: createUIntBuffer(CueClusterPosition) });
          cues.push({ name: "CueTrackPositions", type: "m", isEnd: true });
        cues.push({ name: "CuePoint", type: "m", isEnd: true });
      });
    cues.push({name: "Cues", type: "m", isEnd: true}) 

    cuesSize = encodedSizeOfEbml(cues);
    //console.error("Cues size: " + cuesSize);   
    //console.error("Cue count: " + cuesInfo.length);
    //printElementIds(cues);      

    // If the new MetadataSize is not the same as the previous iteration, we need to run once more.
    if (lastSizeDifference !== sizeDifference){
      lastSizeDifference = sizeDifference;

      if (i === maxIterations-1) {
        throw new Error("Failed to converge to a stable metadata size");
      }

    } else {
      // We're done! Construct the new metadata from all individual components and return.
      //console.error(`Final size: ${newMetadataSize}, difference: ${sizeDifference}`);
      break;
    }
  }

  let finalMetadata: EBML.EBMLElementDetail[] = [].concat.apply([],
    [
      header,
      { name: "Segment", type: "m", isEnd: false, unknownSize: true },
      seekHead,
      info,
      tracks,
      cues
    ]);
  
  let result = new Encoder().encode(finalMetadata);
  //printElementIds(finalMetadata);
  //console.error(`Final metadata buffer size: ${result.byteLength}`);
  //console.error(`Final metadata buffer size without header and segment: ${result.byteLength-segmentContentStartPos}`);
  return result;  
}

/**
 * print all element id names in a list

 * @param metadata - array of EBML elements to print
 *
export function printElementIds(metadata: EBML.EBMLElementBuffer[]) {

  let result: EBML.EBMLElementBuffer[] = [];
  let start: number = -1;

  for (let i = 0; i < metadata.length; i++) {
    console.error("\t id: " + metadata[i].name);
  }
}
*/

/**
 * remove all occurances of an EBML element from an array of elements
 * If it's a MasterElement you will also remove the content. (everything between start and end)
 * @param idName - name of the EBML Element to remove.
 * @param metadata - array of EBML elements to search
 */
export function removeElement(idName: string, metadata: EBML.EBMLElementBuffer[]) {

  let result: EBML.EBMLElementBuffer[] = [];
  let start: number = -1;

  for (let i = 0; i < metadata.length; i++) {

    let element = metadata[i];

    if (element.name === idName) {

      // if it's a Master element, extract the start and end element, and everything in between
      if (element.type === "m") {

        if (!element.isEnd) {
          start = i;
        } else {
          // we've reached the end, extract the whole thing
          if (start == -1)
            throw new Error(`Detected ${idName} closing element before finding the start`)

          metadata.splice(start, i - start + 1);
          return;
        }

      } else {
        // not a Master element, so we've found what we're looking for.
        metadata.splice(i, 1);
        return;
      }
    }
  }
}

/**
 * extract the first occurance of an EBML tag from a flattened array of EBML data. 
 * If it's a MasterElement you will also get the content. (everything between start and end)
 * @param idName - name of the EBML Element to extract.
 * @param metadata - array of EBML elements to search
 */
export function extractElement(idName: string, metadata: EBML.EBMLElementBuffer[]): EBML.EBMLElementBuffer[] {

  let result: EBML.EBMLElementBuffer[] = [];
  let start: number = -1;

  for (let i = 0; i < metadata.length; i++) {

    let element = metadata[i];

    if (element.name === idName) {

      // if it's a Master element, extract the start and end element, and everything in between
      if (element.type === "m") {

        if (!element.isEnd) {
          start = i;
        } else {
          // we've reached the end, extract the whole thing
          if (start == -1)
            throw new Error(`Detected ${idName} closing element before finding the start`)

          result = metadata.slice(start, i + 1);
          break;
        }

      } else {
        // not a Master element, so we've found what we're looking for.
        result.push(metadata[i]);
        break;
      }
    }
  }

  return result;
}

/**
 * @deprecated
 * metadata に対して duration と seekhead を追加した metadata を返す
 * @param metadata - 変更前の webm における ファイル先頭から 最初の Cluster 要素までの 要素
 * @param duration - Duration (TimecodeScale)
 * @param cues - cue points for clusters
 * @deprecated @param clusterPtrs - 変更前の webm における SeekHead に追加する Cluster 要素 への start pointer
 * @deprecated @param cueInfos - please use cues.
 */
export function putRefinedMetaData(
  metadata: EBML.EBMLElementDetail[],
  info: {
    duration?: number,
    cues?: {CueTrack: number; CueClusterPosition: number; CueTime: number; }[],
    clusterPtrs?: number[],
    cueInfos?: {CueTrack: number; CueClusterPosition: number; CueTime: number; }[],
  }
): ArrayBuffer {
  if(Array.isArray(info.cueInfos) && !Array.isArray(info.cues)){
    console.warn("putRefinedMetaData: info.cueInfos property is deprecated. please use info.cues");
    info.cues = info.cueInfos;
  }
  let ebml: EBML.EBMLElementDetail[] = [];
  let payload: EBML.EBMLElementDetail[] = [];
  for(let i=0; i<metadata.length; i++){
    const elm = metadata[i];
    if(elm.type === "m" && elm.name === "Segment"){
      ebml = metadata.slice(0, i);
      payload = metadata.slice(i);
      if(elm.unknownSize){
        payload.shift(); // remove segment tag
        break;
      }
      throw new Error("this metadata is not streaming webm file");
    }
  }
  // *0    *4    *5  *36      *40   *48=segmentOffset              *185=originalPayloadOffsetEnd
  // |     |     |   |        |     |                              |
  // [EBML][size]....[Segment][size][Info][size][Duration][size]...[Cluster]
  // |               |        |^inf |                              |
  // |               +segmentSiz(12)+                              |
  // +-ebmlSize(36)--+        |     +-payloadSize(137)-------------+offsetEndDiff+
  //                 |        |     +-newPayloadSize(??)-------------------------+
  //                 |        |     |                                            |
  //                 [Segment][size][Info][size][Duration][size]....[size][value][Cluster]
  //                           ^                                                 |
  //                           |                                                 *??=newPayloadOffsetEnd
  //                           inf
  if(!(payload[payload.length-1].dataEnd > 0)){ throw new Error("metadata dataEnd has wrong number"); }
  const originalPayloadOffsetEnd = payload[payload.length-1].dataEnd; // = first cluster ptr
  const ebmlSize = ebml[ebml.length-1].dataEnd; // = first segment ptr
  const refinedEBMLSize = new Encoder().encode(ebml).byteLength;
  const offsetDiff = refinedEBMLSize - ebmlSize;
  const payloadSize = originalPayloadOffsetEnd - payload[0].tagStart;
  const segmentSize = payload[0].tagStart - ebmlSize;
  const segmentOffset = payload[0].tagStart;
  const segmentTagBuf = new Buffer([0x18, 0x53, 0x80, 0x67]); // Segment
  const segmentSizeBuf = new Buffer('01ffffffffffffff', 'hex'); // Segmentの最後の位置は無数の Cluster 依存なので。 writeVint(newPayloadSize).byteLength ではなく、 infinity.
  const _segmentSize = segmentTagBuf.byteLength + segmentSizeBuf.byteLength; // == segmentSize
  let newPayloadSize = payloadSize;
  // We need the size to be stable between two refinements in order for our offsets to be correct
  // Bound the number of possible refinements so we can't go infinate if something goes wrong
  let i;
  for(i = 1; i < 20; i++) {
    const newPayloadOffsetEnd = ebmlSize + _segmentSize + newPayloadSize;
    const offsetEndDiff = newPayloadOffsetEnd - originalPayloadOffsetEnd;
    const sizeDiff = offsetDiff + offsetEndDiff;
    const refined = refineMetadata(payload, sizeDiff, info);
    const newNewRefinedSize = new Encoder().encode(refined).byteLength; // 一旦 seekhead を作って自身のサイズを調べる
    if(newNewRefinedSize === newPayloadSize) {
      // Size is stable
      return new Encoder().encode(
        (<EBML.EBMLElementBuffer[]>[]).concat(
          ebml,
          [{type: "m", name: "Segment", isEnd: false, unknownSize: true}],
          refined,
        )
      );
    }
    newPayloadSize = newNewRefinedSize;
  }
  throw new Error("unable to refine metadata, stable size could not be found in " + i + " iterations!");
}
// Given a list of EBMLElementBuffers, returns their encoded size in bytes
function encodedSizeOfEbml(refinedMetaData: EBML.EBMLElementBuffer[]): number {
  const encorder = new Encoder();
  return refinedMetaData.reduce<ArrayBuffer[]>((lst, elm)=> lst.concat(encorder.encode([elm])), []).reduce((o, buf)=> o + buf.byteLength, 0);
}

function refineMetadata(
  mesetadata: EBML.EBMLElementDetail[],
  sizeDiff: number,
  info: {
    duration?: number,
    clusterPtrs?: number[],
    cues?: {CueTrack: number; CueClusterPosition: number; CueTime: number; }[]
  }
): EBML.EBMLElementBuffer[] {
  const {duration, clusterPtrs, cues} = info;
  let _metadata: EBML.EBMLElementBuffer[] = mesetadata.slice(0);
  if(typeof duration === "number"){
    // duration を追加する
    let overwrited = false;
    _metadata.forEach((elm)=>{
      if(elm.type === "f" && elm.name === "Duration"){
        overwrited = true;
        elm.data = createFloatBuffer(duration, 8);
      }
    });
    if(!overwrited){
      insertTag(_metadata, "Info", [{name: "Duration", type: "f", data: createFloatBuffer(duration, 8) }]);
    }
  }
  if(Array.isArray(cues)){
    insertTag(_metadata, "Cues", create_cue(cues, sizeDiff));
  }

  let seekhead_children: EBML.EBMLElementBuffer[] = [];
  if(Array.isArray(clusterPtrs)){
    console.warn("append cluster pointers to seekhead is deprecated. please use cues");
    seekhead_children = create_seek_from_clusters(clusterPtrs, sizeDiff);
  }
  // remove seek info
  /*
  _metadata = _metadata.filter((elm)=> !(
    elm.name === "Seek" ||
    elm.name === "SeekID" ||
    elm.name === "SeekPosition") );
  */
  // working on progress
  //seekhead_children = seekhead_children.concat(create_seekhead(_metadata));
  

  insertTag(_metadata, "SeekHead", seekhead_children, true);

  return _metadata;
}

function create_seekhead(metadata: (EBML.EBMLElementDetail|EBML.EBMLElementBuffer)[], sizeDiff: number): EBML.EBMLElementBuffer[] {
  const seeks: EBML.EBMLElementBuffer[] = [];
  ["Info", "Tracks", "Cues"].forEach((tagName)=>{
    const tagStarts = metadata.filter((elm)=> elm.type === "m" && elm.name === tagName && elm.isEnd === false).map((elm)=> elm["tagStart"]);
    const tagStart = tagStarts[0];
    if(typeof tagStart !== "number"){ return; }
    seeks.push({name: "Seek", type: "m", isEnd: false});
    switch(tagName){
      case "Info": seeks.push({name: "SeekID", type: "b", data: new Buffer([0x15, 0x49, 0xA9, 0x66]) }); break;
      case "Tracks": seeks.push({name: "SeekID", type: "b", data: new Buffer([0x16, 0x54, 0xAE, 0x6B]) }); break;
      case "Cues": seeks.push({name: "SeekID", type: "b", data: new Buffer([0x1C, 0x53, 0xBB, 0x6B]) }); break;
    }
    seeks.push({name: "SeekPosition", type: "u", data: createUIntBuffer(tagStart +  sizeDiff)});
    seeks.push({name: "Seek", type: "m", isEnd: true});
  });
  return seeks;
}

function create_seek_from_clusters(clusterPtrs: number[], sizeDiff: number): EBML.EBMLElementBuffer[] {
  const seeks: EBML.EBMLElementBuffer[] = [];
  clusterPtrs.forEach((start)=>{
    seeks.push({name: "Seek", type: "m", isEnd: false});
      // [0x1F, 0x43, 0xB6, 0x75] で Cluster 意
      seeks.push({name: "SeekID", type: "b", data: new Buffer([0x1F, 0x43, 0xB6, 0x75]) });
      seeks.push({name: "SeekPosition", type: "u", data: createUIntBuffer(start +  sizeDiff)});
    seeks.push({name: "Seek", type: "m", isEnd: true});
  });
  return seeks;
}

function create_cue(cueInfos: {CueTrack: number; CueClusterPosition: number; CueTime: number; }[], sizeDiff: number): EBML.EBMLElementBuffer[] {
  const cues: EBML.EBMLElementBuffer[] = [];
  cueInfos.forEach(({CueTrack, CueClusterPosition, CueTime})=>{
    cues.push({name: "CuePoint", type: "m", isEnd: false});
      cues.push({name: "CueTime", type: "u", data: createUIntBuffer(CueTime) });
      cues.push({name: "CueTrackPositions", type: "m", isEnd: false});
        cues.push({name: "CueTrack", type: "u", data: createUIntBuffer(CueTrack) }); // video track
        cues.push({name: "CueClusterPosition", type: "u", data: createUIntBuffer(CueClusterPosition +  sizeDiff) });
      cues.push({name: "CueTrackPositions", type: "m", isEnd: true});
    cues.push({name: "CuePoint", type: "m", isEnd: true});
  });
  return cues;
}

function insertTag(_metadata: EBML.EBMLElementBuffer[], tagName: string, children: EBML.EBMLElementBuffer[], insertHead: boolean = false): void {
  // find the tagname from _metadata
  let idx = -1;
  for(let i=0; i<_metadata.length; i++){
    const elm = _metadata[i];
    if(elm.type === "m" && elm.name === tagName && elm.isEnd === false){
      idx = i;
      break;
    }
  }
  if(idx >= 0){
    // insert [<CuePoint />] to <Cues />
    Array.prototype.splice.apply(_metadata, [<any>idx+1, 0].concat(children));
  }else if(insertHead){
    (<EBML.EBMLElementBuffer[]>[]).concat(
      [{name: tagName, type: "m", isEnd: false}],
      children,
      [{name: tagName, type: "m", isEnd: true}],
    ).reverse().forEach((elm)=>{ _metadata.unshift(elm); });
  }else{
    // metadata 末尾に <Cues /> を追加
    // insert <Cues />
    _metadata.push({name: tagName, type: "m", isEnd: false});
    children.forEach((elm)=>{ _metadata.push(elm); });
    _metadata.push({name: tagName, type: "m", isEnd: true});
  }
}


export function concat(list: Buffer[]): Buffer {
  return Buffer.concat(list);
}

export function encodeValueToBuffer(elm: EBML.MasterElement): EBML.MasterElement;
export function encodeValueToBuffer(elm: EBML.ChildElementsValue): EBML.ChildElementBuffer;
export function encodeValueToBuffer(elm: EBML.EBMLElementValue): EBML.EBMLElementBuffer {
  let data = new Buffer(0);
  if(elm.type === "m"){ return elm; }
  switch(elm.type){
    case "u": data = createUIntBuffer(elm.value); break;
    case "i": data = createIntBuffer(elm.value); break;
    case "f": data = createFloatBuffer(elm.value); break;
    case "s": data = new Buffer(elm.value, 'ascii'); break;
    case "8": data = new Buffer(elm.value, 'utf8'); break;
    case "b": data = elm.value; break;
    case "d": data = new Int64BE(elm.value.getTime().toString()).toBuffer(); break;
  }
  return Object.assign({}, elm, {data});
}

export function createUIntBuffer(value: number): Buffer {
  // Big-endian, any size from 1 to 8
  // but js number is float64, so max 6 bit octets
  let bytes: 1|2|3|4|5|6 = 1;
  for(; value >= Math.pow(2, 8*bytes); bytes++){}
  if(bytes >= 7){
    console.warn("7bit or more bigger uint not supported.");
    return new Uint64BE(value).toBuffer();
  }
  const data = new Buffer(bytes);
  data.writeUIntBE(value, 0, bytes);
  return data;
}

export function createIntBuffer(value: number): Buffer {
  // Big-endian, any size from 1 to 8 octets
  // but js number is float64, so max 6 bit
  let bytes: 1|2|3|4|5|6 = 1;
  for(; value >= Math.pow(2, 8*bytes); bytes++){}
  if(bytes >= 7){
    console.warn("7bit or more bigger uint not supported.");
    return new Int64BE(value).toBuffer();
  }
  const data = new Buffer(bytes);
  data.writeIntBE(value, 0, bytes);
  return data;
}

export function createFloatBuffer(value: number, bytes: 4|8 = 8): Buffer {
  // Big-endian, defined for 4 and 8 octets (32, 64 bits)
  // js number is float64 so 8 bytes.
  if(bytes === 8){
    // 64bit
    const data = new Buffer(8);
    data.writeDoubleBE(value, 0);
    return data;
  }else if(bytes === 4){
    // 32bit
    const data = new Buffer(4);
    data.writeFloatBE(value, 0);
    return data;
  }else{
    throw new Error("float type bits must 4bytes or 8bytes");
  }
}

export function convertEBMLDateToJSDate(int64str: number | string | Date): Date {
  if(int64str instanceof Date){ return int64str; }
  return new Date(new Date("2001-01-01T00:00:00.000Z").getTime() +  (Number(int64str)/1000/1000));
}