'use strict';

const assert = require('assert');
const async = require('async');
const Error = require('http-errors');
const Stream = require('stream');
const Local = require('./local-storage');
const Logger = require('./logger');
const MyStreams = require('./streams');
const Proxy = require('./up-storage');
const Utils = require('./utils');

/**
 * Implements Storage interface
 * (same for storage.js, local-storage.js, up-storage.js).
 */
class Storage {

  /**
   *
   * @param {*} config
   */
  constructor(config) {
    this.config = config;
    // we support a number of uplinks, but only one local storage
    // Proxy and Local classes should have similar API interfaces
    this.uplinks = {};
    for (let p in config.uplinks) {
      if (Object.prototype.hasOwnProperty.call(config.uplinks, p)) {
        // instance for each up-link definition
        this.uplinks[p] = new Proxy(config.uplinks[p], config);
        this.uplinks[p].upname = p;
      }
    }
    // an instance for local storage
    this.local = new Local(config);
    this.logger = Logger.logger.child();
  }

  /**
   *  Add a {name} package to a system
      Function checks if package with the same name is available from uplinks.
      If it isn't, we create package locally
      Used storages: local (write) && uplinks
   * @param {*} name
   * @param {*} metadata
   * @param {*} callback
   */
  add_package(name, metadata, callback) {
    let self = this;

    // NOTE:
    // - when we checking package for existance, we ask ALL uplinks
    // - when we publishing package, we only publish it to some of them
    // so all requests are necessary

    check_package_local(function(err) {
      if (err) return callback(err);

      check_package_remote(function(err) {
        if (err) return callback(err);

        publish_package(function(err) {
          if (err) return callback(err);
          callback();
        });
      });
    });

    /**
     * Check whether a package it is already a local package
     * @param {*} cb the callback method
     */
    function check_package_local(cb) {
      self.local.get_package(name, {}, function(err, results) {
        if (err && err.status !== 404) {
           return cb(err);
        }
        if (results) {
          return cb( Error[409]('this package is already present') );
        }
        cb();
      });
    }

    /**
     * Check whether a package exist in any of the uplinks.
     * @param {*} cb the callback method
     */
    function check_package_remote(cb) {
      self._sync_package_with_uplinks(name, null, {}, function(err, results, err_results) {
        // something weird
        if (err && err.status !== 404) {
           return cb(err);
        }
        // checking package
        if (results) {
          return cb( Error[409]('this package is already present') );
        }
        for (let i=0; i<err_results.length; i++) {
          // checking error
          // if uplink fails with a status other than 404, we report failure
          if (err_results[i][0] != null) {
            if (err_results[i][0].status !== 404) {
              return cb( Error[503]('one of the uplinks is down, refuse to publish') );
            }
          }
        }

        return cb();
      });
    }

    /**
     * Add a package to the local database
     * @param {*} cb callback method
     */
    function publish_package(cb) {
      self.local.add_package(name, metadata, callback);
    }
  }

  /**
   * Add a new version of package {name} to a system
     Used storages: local (write)
   * @param {*} name
   * @param {*} version
   * @param {*} metadata
   * @param {*} tag
   * @param {*} callback
   */
  add_version(name, version, metadata, tag, callback) {
    this.local.add_version(name, version, metadata, tag, callback);
  }

  /**
   * Tags a package version with a provided tag
     Used storages: local (write)
   * @param {*} name
   * @param {*} tag_hash
   * @param {*} callback
   */
  merge_tags(name, tag_hash, callback) {
    this.local.merge_tags(name, tag_hash, callback);
  }

  /**
   * Tags a package version with a provided tag
     Used storages: local (write)
   * @param {*} name
   * @param {*} tag_hash
   * @param {*} callback
   */
  replace_tags(name, tag_hash, callback) {
    this.local.replace_tags(name, tag_hash, callback);
  }

  /**
   * Change an existing package (i.e. unpublish one version)
     Function changes a package info from local storage and all uplinks with write access./
     Used storages: local (write)
   * @param {*} name
   * @param {*} metadata
   * @param {*} revision
   * @param {*} callback
   */
  change_package(name, metadata, revision, callback) {
    this.local.change_package(name, metadata, revision, callback);
  }

  /**
   * Remove a package from a system
     Function removes a package from local storage
     Used storages: local (write)
   * @param {*} name
   * @param {*} callback
   */
  remove_package(name, callback) {
    this.local.remove_package(name, callback);
  }

  /**
    Remove a tarball from a system
    Function removes a tarball from local storage.
    Tarball in question should not be linked to in any existing
    versions, i.e. package version should be unpublished first.
    Used storages: local (write)
   * @param {*} name
   * @param {*} filename
   * @param {*} revision
   * @param {*} callback
   */
  remove_tarball(name, filename, revision, callback) {
    this.local.remove_tarball(name, filename, revision, callback);
  }

  /**
   * Upload a tarball for {name} package
    Function is syncronous and returns a WritableStream
    Used storages: local (write)
   * @param {*} name
   * @param {*} filename
   * @return {Stream}
   */
  add_tarball(name, filename) {
    return this.local.add_tarball(name, filename);
  }

  /**
    Get a tarball from a storage for {name} package
    Function is syncronous and returns a ReadableStream
    Function tries to read tarball locally, if it fails then it reads package
    information in order to figure out where we can get this tarball from
    Used storages: local || uplink (just one)
   * @param {*} name
   * @param {*} filename
   * @return {Stream}
   */
  get_tarball(name, filename) {
    let stream = MyStreams.readTarballStream();
    stream.abort = function() {};

    let self = this;

    // if someone requesting tarball, it means that we should already have some
    // information about it, so fetching package info is unnecessary

    // trying local first
    let rstream = self.local.get_tarball(name, filename);
    let is_open = false;
    rstream.on('error', function(err) {
      if (is_open || err.status !== 404) {
        return stream.emit('error', err);
      }

      // local reported 404
      let err404 = err;
      rstream.abort();
      rstream = null; // gc
      self.local.get_package(name, function(err, info) {
        if (!err && info._distfiles && info._distfiles[filename] != null) {
          // information about this file exists locally
          serve_file(info._distfiles[filename]);
        } else {
          // we know nothing about this file, trying to get information elsewhere
          self._sync_package_with_uplinks(name, info, {}, function(err, info) {
            if (err) {
               return stream.emit('error', err);
            }
            if (!info._distfiles || info._distfiles[filename] == null) {
              return stream.emit('error', err404);
            }
            serve_file(info._distfiles[filename]);
          });
        }
      });
    });
    rstream.on('content-length', function(v) {
      stream.emit('content-length', v);
    });
    rstream.on('open', function() {
      is_open = true;
      rstream.pipe(stream);
    });
    return stream;

    /**
     * Fetch and cache local/remote packages.
     * @param {Object} file define the package shape
     */
    function serve_file(file) {
      let uplink = null;
      for (let p in self.uplinks) {
        if (self.uplinks[p].can_fetch_url(file.url)) {
          uplink = self.uplinks[p];
        }
      }
      if (uplink == null) {
        uplink = new Proxy({
          url: file.url,
          _autogenerated: true,
        }, self.config);
      }
      let savestream = self.local.add_tarball(name, filename);
      let on_open = function() {
        // prevent it from being called twice
        on_open = function() {};
        let rstream2 = uplink.get_url(file.url);
        rstream2.on('error', function(err) {
          if (savestream) {
            savestream.abort();
          }
          savestream = null;
          stream.emit('error', err);
        });
        rstream2.on('end', function() {
          if (savestream) {
            savestream.done();
          }
        });

        rstream2.on('content-length', function(v) {
          stream.emit('content-length', v);
          if (savestream) {
            savestream.emit('content-length', v);
          }
        });
        rstream2.pipe(stream);
        if (savestream) {
          rstream2.pipe(savestream);
        }
      };

      savestream.on('open', function() {
        on_open();
      });

      savestream.on('error', function(err) {
        self.logger.warn( {err: err}
                        , 'error saving file: @{err.message}\n@{err.stack}' );
        if (savestream) {
          savestream.abort();
        }
        savestream = null;
        on_open();
      });
    }
  }

  /**
    Retrieve a package metadata for {name} package
      Function invokes local.get_package and uplink.get_package for every
      uplink with proxy_access rights against {name} and combines results
      into one json object
    Used storages: local && uplink (proxy_access)
   * @param {*} name
   * @param {*} options
   * @param {*} callback
   */
  get_package(name, options, callback) {
    if (typeof(options) === 'function') {
      callback = options, options = {};
    }

    this.local.get_package(name, options, (err, data) => {
      if (err && (!err.status || err.status >= 500)) {
        // report internal errors right away
        return callback(err);
      }

      this._sync_package_with_uplinks(name, data, options, function(err, result, uplink_errors) {
        if (err) return callback(err);
        const whitelist = ['_rev', 'name', 'versions', 'dist-tags', 'readme'];
        for (let i in result) {
          if (whitelist.indexOf(i) === -1) delete result[i];
        }

        Utils.normalize_dist_tags(result);

        // npm can throw if this field doesn't exist
        result._attachments = {};

        callback(null, result, uplink_errors);
      });
    });
  }

  /**
    Retrieve remote and local packages more recent than {startkey}
    Function streams all packages from all uplinks first, and then
    local packages.
      Note that local packages could override registry ones just because
      they appear in JSON last. That's a trade-off we make to avoid
      memory issues.
      Used storages: local && uplink (proxy_access)
   * @param {*} startkey
   * @param {*} options
   * @return {Stream}
   */
  search(startkey, options) {
    let self = this;
    // stream to write a tarball
    let stream = new Stream.PassThrough({objectMode: true});

    async.eachSeries(Object.keys(this.uplinks), function(up_name, cb) {
      // shortcut: if `local=1` is supplied, don't call uplinks
      if (options.req.query.local !== undefined) {
         return cb();
      }
      // search by keyword for each uplink
      let lstream = self.uplinks[up_name].search(startkey, options);
      // join streams
      lstream.pipe(stream, {end: false});
      lstream.on('error', function(err) {
        self.logger.error({err: err}, 'uplink error: @{err.message}');
        cb(), cb = function() {};
      });
      lstream.on('end', function() {
        cb(), cb = function() {};
      });

      stream.abort = function() {
        if (lstream.abort) {
          lstream.abort();
        }
        cb(), cb = function() {};
      };
    },
    // executed after all series
    function() {
      // attach a local search results
      let lstream = self.local.search(startkey, options);
      stream.abort = function() {
        lstream.abort();
      };
      lstream.pipe(stream, {end: true});
      lstream.on('error', function(err) {
        self.logger.error({err: err}, 'search error: @{err.message}');
        stream.end();
      });
    });

    return stream;
  }

  /**
   *
   * @param {*} callback
   */
  get_local(callback) {
    let self = this;
    let locals = this.config.localList.get();
    let packages = [];

    const getPackage = function(i) {
      self.local.get_package(locals[i], function(err, info) {
        if (!err) {
          let latest = info['dist-tags'].latest;
          if (latest && info.versions[latest]) {
            packages.push(info.versions[latest]);
          } else {
            self.logger.warn( {package: locals[i]}
                            , 'package @{package} does not have a "latest" tag?' );
          }
        }

        if (i >= locals.length - 1) {
          callback(null, packages);
        } else {
          getPackage(i + 1);
        }
      });
    };

    if (locals.length) {
      getPackage(0);
    } else {
      callback(null, []);
    }
  }

  /**
   * Function fetches package information from uplinks and synchronizes it with local data
     if package is available locally, it MUST be provided in pkginfo
     returns callback(err, result, uplink_errors)
   * @param {*} name
   * @param {*} pkginfo
   * @param {*} options
   * @param {*} callback
   */
  _sync_package_with_uplinks(name, pkginfo, options, callback) {
    let self = this;
    let exists = false;
    if (!pkginfo) {
      exists = false;

      pkginfo = {
        'name': name,
        'versions': {},
        'dist-tags': {},
        '_uplinks': {},
      };
    } else {
      exists = true;
    }

    let uplinks = [];
    for (let i in self.uplinks) {
      if (self.config.can_proxy_to(name, i)) {
        uplinks.push(self.uplinks[i]);
      }
    }

    async.map(uplinks, function(up, cb) {
      let _options = Object.assign({}, options);
      if (Utils.is_object(pkginfo._uplinks[up.upname])) {
        let fetched = pkginfo._uplinks[up.upname].fetched;
        if (fetched && fetched > (Date.now() - up.maxage)) {
          return cb();
        }

        _options.etag = pkginfo._uplinks[up.upname].etag;
      }

      up.get_package(name, _options, function(err, up_res, etag) {
        if (err && err.status === 304) {
          pkginfo._uplinks[up.upname].fetched = Date.now();
        }

        if (err || !up_res) {
          return cb(null, [err || Error('no data')]);
        }

        try {
          Utils.validate_metadata(up_res, name);
        } catch(err) {
          self.logger.error({
            sub: 'out',
            err: err,
          }, 'package.json validating error @{!err.message}\n@{err.stack}');
          return cb(null, [err]);
        }

        pkginfo._uplinks[up.upname] = {
          etag: etag,
          fetched: Date.now(),
        };
        for (let i in up_res.versions) {
           if (Object.prototype.hasOwnProperty.call(up_res.versions, i)) {
            // this won't be serialized to json,
            // kinda like an ES6 Symbol
            // FIXME: perhaps Symbol('_verdaccio_uplink') here?
            Object.defineProperty(up_res.versions[i], '_verdaccio_uplink', {
              value: up.upname,
              enumerable: false,
              configurable: false,
              writable: true,
            });
          }
        }

        try {
          Storage._merge_versions(pkginfo, up_res, self.config);
        } catch(err) {
          self.logger.error({
            sub: 'out',
            err: err,
          }, 'package.json parsing error @{!err.message}\n@{err.stack}');
          return cb(null, [err]);
        }

        // if we got to this point, assume that the correct package exists
        // on the uplink
        exists = true;
        cb();
      });
    }, function(err, uplink_errors) {
      assert(!err && Array.isArray(uplink_errors));

      if (!exists) {
        return callback( Error[404]('no such package available')
                      , null
                      , uplink_errors );
      }

      self.local.update_versions(name, pkginfo, function(err, pkginfo) {
        if (err) return callback(err);
        return callback(null, pkginfo, uplink_errors);
      });
    });
  }

  /**
   * Function gets a local info and an info from uplinks and tries to merge it
     exported for unit tests only.
   * @param {*} local
   * @param {*} up
   * @param {*} config
   */
  static _merge_versions(local, up, config) {
    // copy new versions to a cache
    // NOTE: if a certain version was updated, we can't refresh it reliably
    for (let i in up.versions) {
      if (local.versions[i] == null) {
        local.versions[i] = up.versions[i];
      }
    }

    // refresh dist-tags
    for (let i in up['dist-tags']) {
      if (local['dist-tags'][i] !== up['dist-tags'][i]) {
        local['dist-tags'][i] = up['dist-tags'][i];
        if (i === 'latest') {
          // if remote has more fresh package, we should borrow its readme
          local.readme = up.readme;
        }
      }
    }
  }

}

module.exports = Storage;