var util = require('./util');
// 按照文件特征值，缓存 UploadId
var cacheKey = 'cos_sdk_upload_cache';
var expires = 30 * 24 * 3600;
var store;
var cache;
var timer;

var getCache = function () {
  var val,
    opt = { configName: 'cos-nodejs-sdk-v5-storage' };
  if (this.options.ConfCwd) opt.cwd = this.options.ConfCwd;
  try {
    var Conf = require('conf');
    store = new Conf(opt);
    val = store.get(cacheKey);
  } catch (e) {}
  if (!val || !(val instanceof Array)) val = [];
  cache = val;
};
var setCache = function () {
  try {
    if (cache.length) store.set(cacheKey, cache);
    else store.delete(cacheKey);
  } catch (e) {}
};

var init = function () {
  if (cache) return;
  getCache.call(this);
  // 清理太老旧的数据
  var changed = false;
  var now = Math.round(Date.now() / 1000);
  for (var i = cache.length - 1; i >= 0; i--) {
    var mtime = cache[i][2];
    if (!mtime || mtime + expires < now) {
      cache.splice(i, 1);
      changed = true;
    }
  }
  changed && setCache();
};

// 把缓存存到本地
var save = function () {
  if (timer) return;
  timer = setTimeout(function () {
    setCache();
    timer = null;
  }, 400);
};

var mod = {
  using: {},
  // 标记 UploadId 正在使用
  setUsing: function (uuid) {
    mod.using[uuid] = true;
  },
  // 标记 UploadId 已经没在使用
  removeUsing: function (uuid) {
    delete mod.using[uuid];
  },
  // 用上传参数生成哈希值
  getFileId: function (FileStat, ChunkSize, Bucket, Key) {
    if (FileStat && FileStat.FilePath && FileStat.size && FileStat.ctime && FileStat.mtime && ChunkSize) {
      return (
        util.md5([FileStat.FilePath].join('::')) +
        '-' +
        util.md5([FileStat.size, FileStat.ctime, FileStat.mtime, ChunkSize, Bucket, Key].join('::'))
      );
    } else {
      return null;
    }
  },
  // 用上传参数生成哈希值
  getCopyFileId: function (copySource, sourceHeaders, ChunkSize, Bucket, Key) {
    var size = sourceHeaders['content-length'];
    var etag = sourceHeaders.etag || '';
    var lastModified = sourceHeaders['last-modified'];
    if (copySource && ChunkSize) {
      return util.md5([copySource, size, etag, lastModified, ChunkSize, Bucket, Key].join('::'));
    } else {
      return null;
    }
  },
  // 获取文件对应的 UploadId 列表
  getUploadIdList: function (uuid) {
    if (!uuid) return null;
    init.call(this);
    var list = [];
    for (var i = 0; i < cache.length; i++) {
      if (cache[i][0] === uuid) list.push(cache[i][1]);
    }
    return list.length ? list : null;
  },
  // 缓存 UploadId
  saveUploadId: function (uuid, UploadId, limit) {
    init.call(this);
    if (!uuid) return;
    // 清理没用的 UploadId
    var part1 = uuid.substr(0, uuid.indexOf('-') + 1);
    for (var i = cache.length - 1; i >= 0; i--) {
      var item = cache[i];
      if (item[0] === uuid && item[1] === UploadId) {
        cache.splice(i, 1);
      } else if (uuid !== item[0] && item[0].indexOf(part1) === 0) {
        // 文件路径相同，但其他信息不同，说明文件改变了或上传参数（存储桶、路径、分片大小）变了，直接清理掉
        cache.splice(i, 1);
      }
    }
    cache.unshift([uuid, UploadId, Math.round(Date.now() / 1000)]);
    if (cache.length > limit) cache.splice(limit);
    save();
  },
  // UploadId 已用完，移除掉
  removeUploadId: function (UploadId) {
    init.call(this);
    delete mod.using[UploadId];
    for (var i = cache.length - 1; i >= 0; i--) {
      if (cache[i][1] === UploadId) cache.splice(i, 1);
    }
    save();
  },
};

module.exports = mod;