'use strict';

var PromiseA = require('bluebird');
var path = require('path');
var fs = PromiseA.promisifyAll(require('fs'));
var jwt = require('jsonwebtoken');
var crypto = require('crypto');

module.exports.create = function (deps, conf) {
  var hrIds = require('human-readable-ids').humanReadableIds;
  var scmp = require('scmp');
  var storageDir = path.join(__dirname, '..', 'var');

  function read(fileName) {
    return fs.readFileAsync(path.join(storageDir, fileName))
    .then(JSON.parse, function (err) {
      if (err.code === 'ENOENT') {
        return {};
      }
      throw err;
    });
  }
  function write(fileName, obj) {
    return fs.mkdirAsync(storageDir).catch(function (err) {
      if (err.code !== 'EEXIST') {
        console.error('failed to mkdir', storageDir, err.toString());
      }
    }).then(function () {
      return fs.writeFileAsync(path.join(storageDir, fileName), JSON.stringify(obj), 'utf8');
    });
  }

  var owners = {
    _filename: 'owners.json'
  , all: function () {
      return read(this._filename).then(function (owners) {
        return Object.keys(owners).map(function (id) {
          var owner = owners[id];
          owner.id = id;
          return owner;
        });
      });
    }
  , get: function (id) {
      // While we could directly read the owners file and access the id directly from
      // the resulting object I'm not sure of the details of how the object key lookup
      // works or whether that would expose us to timing attacks.
      // See https://codahale.com/a-lesson-in-timing-attacks/
      return this.all().then(function (owners) {
        return owners.filter(function (owner) {
          return scmp(id, owner.id);
        })[0];
      });
    }
  , exists: function (id) {
      return this.get(id).then(function (owner) {
        return !!owner;
      });
    }
  , set: function (id, obj) {
      var self = this;
      return read(self._filename).then(function (owners) {
        obj.id = id;
        owners[id] = obj;
        return write(self._filename, owners);
      });
    }
  };

  var confCb;
  var config = {
    save: function (changes) {
      deps.messenger.send({
        type: 'com.daplie.goldilocks/config'
      , changes: changes
      });

      return new deps.PromiseA(function (resolve, reject) {
        var timeoutId = setTimeout(function () {
          reject(new Error('Did not receive config update from main process in a reasonable time'));
          confCb = null;
        }, 15*1000);

        confCb = function (config) {
          confCb = null;
          clearTimeout(timeoutId);
          resolve(config);
        };
      });
    }
  };
  function updateConf(config) {
    if (confCb) {
      confCb(config);
    }
  }

  var userTokens = {
    _filename: 'user-tokens.json'
  , _cache: {}
  , _convertToken: function convertToken(id, token) {
      // convert the token into something that looks more like what OAuth3 uses internally
      // as sessions so we can use it with OAuth3. We don't use OAuth3's internal session
      // storage because it effectively only supports storing tokens based on provider URI.
      // We also use the token as the `access_token` instead of `refresh_token` because the
      // refresh functionality is closely tied to the storage.
      var decoded = jwt.decode(token);
      if (!decoded) {
        return null;
      }
      return {
        id:           id
      , access_token: token
      , token:        decoded
      , provider_uri: decoded.iss || decoded.issuer || decoded.provider_uri
      , client_uri:   decoded.azp
      , scope:        decoded.scp || decoded.scope || decoded.grants
      };
    }
  , all: function allUserTokens() {
      var self = this;
      if (self._cacheComplete) {
        return deps.PromiseA.resolve(Object.values(self._cache));
      }

      return read(self._filename).then(function (tokens) {
        // We will read every single token into our cache, so it will be complete once we finish
        // creating the result (it's set out of order so we can directly return the result).
        self._cacheComplete = true;

        return Object.keys(tokens).map(function (id) {
          self._cache[id] = self._convertToken(id, tokens[id]);
          return self._cache[id];
        });
      });
    }
  , get: function getUserToken(id) {
      var self = this;
      if (self._cache.hasOwnProperty(id) || self._cacheComplete) {
        return deps.PromiseA.resolve(self._cache[id] || null);
      }

      return read(self._filename).then(function (tokens) {
        self._cache[id] = self._convertToken(id, tokens[id]);
        return self._cache[id];
      });
    }
  , save: function saveUserToken(newToken) {
      var self = this;
      return read(self._filename).then(function (tokens) {
        var rawToken;
        if (typeof newToken === 'string') {
          rawToken = newToken;
        } else {
          rawToken = newToken.refresh_token || newToken.access_token;
        }
        if (typeof rawToken !== 'string') {
          throw new Error('cannot save invalid session: missing refresh_token and access_token');
        }

        var decoded = jwt.decode(rawToken);
        var idHash = crypto.createHash('sha256');
        idHash.update(decoded.sub || decoded.ppid || decoded.appScopedId || '');
        idHash.update(decoded.iss || decoded.issuer || '');
        idHash.update(decoded.aud || decoded.audience || '');

        var scope = decoded.scope || decoded.scp || decoded.grants || '';
        idHash.update(scope.split(/[,\s]+/mg).sort().join(','));

        var id = idHash.digest('hex');
        tokens[id] = rawToken;
        return write(self._filename, tokens).then(function () {
          // Delete the current cache so that if this is an update it will refresh
          // the cache once we read the ID.
          delete self._cache[id];
          return self.get(id);
        });
      });
    }
  , remove: function removeUserToken(id) {
      var self = this;
      return read(self._filename).then(function (tokens) {
        var present = delete tokens[id];
        if (!present) {
          return present;
        }

        return write(self._filename, tokens).then(function () {
          delete self._cache[id];
          return true;
        });
      });
    }
  };

  var mdnsId = {
    _filename: 'mdns-id'
  , get: function () {
      var self = this;
      return read("mdns-id").then(function (result) {
        if (typeof result !== 'string') {
          throw new Error('mDNS ID not present');
        }
        return result;
      }).catch(function () {
        return self.set(hrIds.random());
      });
    }

  , set: function (value) {
      var self = this;
      return write(self._filename, value).then(function () {
        return self.get();
      });
    }
  };

  return {
    owners: owners
  , config: config
  , updateConf: updateConf
  , tokens: userTokens
  , mdnsId: mdnsId
  };
};