const fs = require("fs");
const path = require("path");
const tar = require("tar-stream");
const tarPack = tar.pack();
const ZstdCodec = require("zstd-codec").ZstdCodec;
const util = require("util");

const COMPRESSION_LEVEL = 5;

const SUPPORTED_FORMATS = [
  [/\.(jpg|png|gif|svg|bmp)$/i, "images"],
  [/\.(mp4|m4v|mkv|webm|flv|f4v|ogv)$/i, "videos"],
  [/\.(mp3|m4a|aac|wav|flac|ogg|opus)$/i, "audios"]
];

function getMediaType(fileName) {
  const res = SUPPORTED_FORMATS.reduce((ret, testpair) => {
    const [regex, mediaType] = testpair;

    return regex.test(ret) ? mediaType : ret;
  }, fileName);

  return res !== fileName ? res : "others";
}

function mkdirSyncRecursive(dir) {
  let segments = dir.split(path.sep);

  for (let i = 1; i <= segments.length; i++) {
    let segment = segments.slice(0, i).join("/");
    if (segment.length > 0 && !fs.existsSync(segment)) {
      fs.mkdirSync(segment);
    }
  }
}

// async readdir
const readdir = async (path, options) => {
  return new Promise(resolve => {
    fs.readdir(path, options, (err, files) => {
      if (err) {
        throw err;
      }
      resolve(files);
    });
  });
};

// async readFile
const readFile = util.promisify(fs.readFile);

function generateFirstEntry(options) {
  return "{}";
}

function writeFirstEntry(options, tarPack) {
  tarPack.entry({ name: "." }, generateFirstEntry(options), err => {
    if (err) {
      throw err;
    }
  });
}

function getFileReadStream(options) {
  const fileName = options.fileName || "package.lbry";
  return fs.createReadStream(fileName);
}

function getFileWriteStream(options) {
  const fileName = options.fileName || "package.lbry";
  return fs.createWriteStream(fileName);
}

async function getZstd() {
  return new Promise((resolve, reject) => {
    try {
      ZstdCodec.run(zstd => {
        const Streaming = new zstd.Streaming();
        resolve(Streaming);
      });
    } catch (e) {
      reject(e);
    }
  });
}

async function catagoriseFilesIndex(runCommand, root, index) {
  const files = { images: "", audios: "", videos: "", others: "" };

  for (let file of index) {
    const mediaType = getMediaType(path.basename(file));
    files[mediaType] += `"${file}",`;
  }

  let contents = "";
  for (let mediaType in files) {
    contents += `${mediaType}=[${files[mediaType]}];\n`;
  }

  const bufferedContents = Buffer.from(contents);
  const relativeFilePath = path.join(root, "files.js");
  await runCommand(relativeFilePath, bufferedContents);
}

async function processTemplate(runCommand, root, userDefinedTemplate) {
  const template = userDefinedTemplate
    ? userDefinedTemplate
    : require("./templates").default;

  for (const resource of template.resources) {
    if (resource.type === "static") {
      const bufferedContents = Buffer.from(resource.contents);
      const relativeFilePath = path.join(root, resource.name);
      await runCommand(relativeFilePath, bufferedContents);
    }
  }
}

async function walkAndRun(runCommand, dir, root) {
  let files = await readdir(dir);

  for (let file of files) {
    const currentPath = path.join(dir, file);

    if (fs.statSync(currentPath).isDirectory()) {
      await walkAndRun(runCommand, currentPath);
    } else {
      const fileContents = await readFile(path.normalize(currentPath));
      await runCommand(currentPath, fileContents);
    }
  }
}

async function writeStream(stream, data) {
  return new Promise(resolve => {
    stream.write(data);
    stream.end(resolve);
  });
}

async function packDirectory(directory, options = {}) {
  let filesIndex = [];

  const zstd = await getZstd();
  const packRoot = directory;
  const fileWriteStream = getFileWriteStream(options);

  tarPack.pipe(fileWriteStream);
  writeFirstEntry(options, tarPack);

  const makeChunkIterator = contents => {
    const chunkSize = 2048;
    let position = 0;

    const iterator = {
      next: function() {
        const endIndex = position + chunkSize;
        const result = {
          value: contents.slice(position, endIndex),
          done: position >= contents.length
        };

        position = endIndex;
        return result;
      },
      [Symbol.iterator]: function() {
        return this;
      }
    };
    return iterator;
  };

  const createEntry = async (file, contents) => {
    const chunkIterator = makeChunkIterator(contents);
    contents = zstd.compressChunks(
      chunkIterator,
      contents.length,
      COMPRESSION_LEVEL
    );
    let name = path.relative(packRoot, file).replace("\\", "/");
    if (/^\.\//.test(name)) {
      name = name.slice(2);
    }
    const entry = tarPack.entry({ name, size: contents.length }, err => {
      if (err) {
        throw err;
      }
    });
    await writeStream(entry, contents);
    entry.end();
    filesIndex.push(name);
  };

  await walkAndRun(createEntry, directory, packRoot);
  if (options.useTemplate === true) {
    await processTemplate(createEntry, packRoot);
    await catagoriseFilesIndex(createEntry, packRoot, filesIndex);
  }
  tarPack.finalize();
}

function strToBuffer(string) {
  let arrayBuffer = new ArrayBuffer(string.length * 1);
  let newUint = new Uint8Array(arrayBuffer);
  newUint.forEach((_, i) => {
    newUint[i] = string.charCodeAt(i);
  });
  return newUint;
}

function streamToBuffer(stream) {
  const chunks = [];
  return new Promise((resolve, reject) => {
    stream.on("data", chunk => chunks.push(chunk));
    stream.on("error", reject);
    stream.on("end", () => resolve(Buffer.concat(chunks)));
  });
}

async function unpackDirectory(directory, options = {}) {
  return new Promise(async resolve => {
    if (!fs.existsSync(directory)) {
      mkdirSyncRecursive(directory);
    }

    const fileReadStream = getFileReadStream(options);
    const zstd = await getZstd();

    const extract = tar.extract();

    extract.on("entry", async (header, fileStream, next) => {
      let contents = await streamToBuffer(fileStream);
      contents = new Uint8Array(contents);

      // Must be chunked to avoid issues with fixed memory limits.
      const chunkIterator = (() => {
        const chunkSize = 2048;
        let position = 0;

        const iterator = {
          next: function() {
            const endIndex = position + chunkSize;
            const result = {
              value: contents.slice(position, endIndex),
              done: position >= contents.length
            };

            position = endIndex;
            return result;
          },
          [Symbol.iterator]: function() {
            return this;
          }
        };
        return iterator;
      })();

      contents = zstd.decompressChunks(chunkIterator);

      if (!/^\./.test(header.name)) {
        const writePath = path.join(directory, header.name);

        try {
          mkdirSyncRecursive(path.dirname(writePath));
        } catch (e) {
          console.log(e);
          // Directory exists
        }
        const fileWriteStream = fs.createWriteStream(writePath);
        fileWriteStream.write(contents);
        fileWriteStream.end();
        next();
      } else {
        fileStream.resume();
        next();
      }
    });

    extract.on("finish", () => {
      resolve(true);
    });

    fileReadStream.pipe(extract);
  });
}

/*
// DO NOT USE until converted to use `compressChunks`
async function packPaths(root, pathsArray, options = {}) {
  const fileWriteStream = getFileWriteStream(options);
  const zstd = await getZstd();

  tarPack.pipe(fileWriteStream);
  writeFirstEntry(options, tarPack);

  for(let name of pathsArray) {
    let contents = await readFile(path.join(root, name));

    contents = new Uint8Array(contents);
    contents = zstd.compress(contents, COMPRESSION_LEVEL);

    if(/^\.\//.test(name)) {
      name = name.slice(2);
    }

    const entry = tarPack.entry({ name, size: contents.length }, (err) => {
      if(err) {
        throw err;
      }
    });

    entry.end(contents);
  }
  tarPack.finalize();
}
*/

module.exports = {
  packDirectory,
  unpackDirectory
};