"use strict";

var utils = require('./utils');
var merge = require('./merge');
var errors = require('./deps/errors');
var EventEmitter = require('events').EventEmitter;
var upsert = require('./deps/upsert');
var Changes = require('./changes');
var Promise = utils.Promise;

/*
 * A generic pouch adapter
 */

// returns first element of arr satisfying callback predicate
function arrayFirst(arr, callback) {
  for (var i = 0; i < arr.length; i++) {
    if (callback(arr[i], i) === true) {
      return arr[i];
    }
  }
  return false;
}

// Wrapper for functions that call the bulkdocs api with a single doc,
// if the first result is an error, return an error
function yankError(callback) {
  return function (err, results) {
    if (err || (results[0] && results[0].error)) {
      callback(err || results[0]);
    } else {
      callback(null, results.length ? results[0]  : results);
    }
  };
}

// for every node in a revision tree computes its distance from the closest
// leaf
function computeHeight(revs) {
  var height = {};
  var edges = [];
  merge.traverseRevTree(revs, function (isLeaf, pos, id, prnt) {
    var rev = pos + "-" + id;
    if (isLeaf) {
      height[rev] = 0;
    }
    if (prnt !== undefined) {
      edges.push({from: prnt, to: rev});
    }
    return rev;
  });

  edges.reverse();
  edges.forEach(function (edge) {
    if (height[edge.from] === undefined) {
      height[edge.from] = 1 + height[edge.to];
    } else {
      height[edge.from] = Math.min(height[edge.from], 1 + height[edge.to]);
    }
  });
  return height;
}

function allDocsKeysQuery(api, opts, callback) {
  var keys =  ('limit' in opts) ?
      opts.keys.slice(opts.skip, opts.limit + opts.skip) :
      (opts.skip > 0) ? opts.keys.slice(opts.skip) : opts.keys;
  if (opts.descending) {
    keys.reverse();
  }
  if (!keys.length) {
    return api._allDocs({limit: 0}, callback);
  }
  var finalResults = {
    offset: opts.skip
  };
  return Promise.all(keys.map(function (key) {
    var subOpts = utils.extend(true, {key: key, deleted: 'ok'}, opts);
    ['limit', 'skip', 'keys'].forEach(function (optKey) {
      delete subOpts[optKey];
    });
    return new Promise(function (resolve, reject) {
      api._allDocs(subOpts, function (err, res) {
        if (err) {
          return reject(err);
        }
        finalResults.total_rows = res.total_rows;
        resolve(res.rows[0] || {key: key, error: 'not_found'});
      });
    });
  })).then(function (results) {
    finalResults.rows = results;
    return finalResults;
  });
}

utils.inherits(AbstractPouchDB, EventEmitter);
module.exports = AbstractPouchDB;

function AbstractPouchDB() {
  var self = this;
  EventEmitter.call(this);

  var listeners = 0, changes;
  var eventNames = ['change', 'delete', 'create', 'update'];
  this.on('newListener', function (eventName) {
    if (~eventNames.indexOf(eventName)) {
      if (listeners) {
        listeners++;
        return;
      } else {
        listeners++;
      }
    } else {
      return;
    }
    var lastChange = 0;
    changes = this.changes({
      conflicts: true,
      include_docs: true,
      continuous: true,
      since: 'now',
      onChange: function (change) {
        if (change.seq <= lastChange) {
          return;
        }
        lastChange = change.seq;
        self.emit('change', change);
        if (change.doc._deleted) {
          self.emit('delete', change);
        } else if (change.doc._rev.split('-')[0] === '1') {
          self.emit('create', change);
        } else {
          self.emit('update', change);
        }
      }
    });
  });
  this.on('removeListener', function (eventName) {
    if (~eventNames.indexOf(eventName)) {
      listeners--;
      if (listeners) {
        return;
      }
    } else {
      return;
    }
    changes.cancel();
  });
}

AbstractPouchDB.prototype.post =
  utils.adapterFun('post', function (doc, opts, callback) {
  if (typeof opts === 'function') {
    callback = opts;
    opts = {};
  }
  if (typeof doc !== 'object' || Array.isArray(doc)) {
    return callback(errors.error(errors.NOT_AN_OBJECT));
  }
  this.bulkDocs({docs: [doc]}, opts, yankError(callback));
});

AbstractPouchDB.prototype.put =
  utils.adapterFun('put', utils.getArguments(function (args) {
  var temp, temptype, opts, callback;
  var doc = args.shift();
  var id = '_id' in doc;
  if (typeof doc !== 'object' || Array.isArray(doc)) {
    callback = args.pop();
    return callback(errors.error(errors.NOT_AN_OBJECT));
  }
  doc = utils.clone(doc);
  while (true) {
    temp = args.shift();
    temptype = typeof temp;
    if (temptype === "string" && !id) {
      doc._id = temp;
      id = true;
    } else if (temptype === "string" && id && !('_rev' in doc)) {
      doc._rev = temp;
    } else if (temptype === "object") {
      opts = temp;
    } else if (temptype === "function") {
      callback = temp;
    }
    if (!args.length) {
      break;
    }
  }
  opts = opts || {};
  var error = utils.invalidIdError(doc._id);
  if (error) {
    return callback(error);
  }
  if (utils.isLocalId(doc._id) && typeof this._putLocal === 'function') {
    if (doc._deleted) {
      return this._removeLocal(doc, callback);
    } else {
      return this._putLocal(doc, callback);
    }
  }
  this.bulkDocs({docs: [doc]}, opts, yankError(callback));
}));

AbstractPouchDB.prototype.putAttachment =
  utils.adapterFun('putAttachment', function (docId, attachmentId, rev,
                                              blob, type, callback) {
  var api = this;
  if (typeof type === 'function') {
    callback = type;
    type = blob;
    blob = rev;
    rev = null;
  }
  if (typeof type === 'undefined') {
    type = blob;
    blob = rev;
    rev = null;
  }

  function createAttachment(doc) {
    doc._attachments = doc._attachments || {};
    doc._attachments[attachmentId] = {
      content_type: type,
      data: blob
    };
    return api.put(doc);
  }

  return api.get(docId).then(function (doc) {
    if (doc._rev !== rev) {
      throw errors.error(errors.REV_CONFLICT);
    }

    return createAttachment(doc);
  }, function (err) {
     // create new doc
    if (err.reason === errors.MISSING_DOC.message) {
      return createAttachment({_id: docId});
    } else {
      throw err;
    }
  });
});

AbstractPouchDB.prototype.removeAttachment =
  utils.adapterFun('removeAttachment', function (docId, attachmentId, rev,
                                                 callback) {
  var self = this;
  self.get(docId, function (err, obj) {
    if (err) {
      callback(err);
      return;
    }
    if (obj._rev !== rev) {
      callback(errors.error(errors.REV_CONFLICT));
      return;
    }
    if (!obj._attachments) {
      return callback();
    }
    delete obj._attachments[attachmentId];
    if (Object.keys(obj._attachments).length === 0) {
      delete obj._attachments;
    }
    self.put(obj, callback);
  });
});

AbstractPouchDB.prototype.remove =
  utils.adapterFun('remove', function (docOrId, optsOrRev, opts, callback) {
  var doc;
  if (typeof optsOrRev === 'string') {
    // id, rev, opts, callback style
    doc = {
      _id: docOrId,
      _rev: optsOrRev
    };
    if (typeof opts === 'function') {
      callback = opts;
      opts = {};
    }
  } else {
    // doc, opts, callback style
    doc = docOrId;
    if (typeof optsOrRev === 'function') {
      callback = optsOrRev;
      opts = {};
    } else {
      callback = opts;
      opts = optsOrRev;
    }
  }
  opts = utils.clone(opts || {});
  opts.was_delete = true;
  var newDoc = {_id: doc._id, _rev: (doc._rev || opts.rev)};
  newDoc._deleted = true;
  if (utils.isLocalId(newDoc._id) && typeof this._removeLocal === 'function') {
    return this._removeLocal(doc, callback);
  }
  this.bulkDocs({docs: [newDoc]}, opts, yankError(callback));
});

AbstractPouchDB.prototype.revsDiff =
  utils.adapterFun('revsDiff', function (req, opts, callback) {
  if (typeof opts === 'function') {
    callback = opts;
    opts = {};
  }
  opts = utils.clone(opts);
  var ids = Object.keys(req);

  if (!ids.length) {
    return callback(null, {});
  }

  var count = 0;
  var missing = new utils.Map();

  function addToMissing(id, revId) {
    if (!missing.has(id)) {
      missing.set(id, {missing: []});
    }
    missing.get(id).missing.push(revId);
  }

  function processDoc(id, rev_tree) {
    // Is this fast enough? Maybe we should switch to a set simulated by a map
    var missingForId = req[id].slice(0);
    merge.traverseRevTree(rev_tree, function (isLeaf, pos, revHash, ctx,
      opts) {
        var rev = pos + '-' + revHash;
        var idx = missingForId.indexOf(rev);
        if (idx === -1) {
          return;
        }

        missingForId.splice(idx, 1);
        if (opts.status !== 'available') {
          addToMissing(id, rev);
        }
      });

    // Traversing the tree is synchronous, so now `missingForId` contains
    // revisions that were not found in the tree
    missingForId.forEach(function (rev) {
      addToMissing(id, rev);
    });
  }

  ids.map(function (id) {
    this._getRevisionTree(id, function (err, rev_tree) {
      if (err && err.status === 404 && err.message === 'missing') {
        missing.set(id, {missing: req[id]});
      } else if (err) {
        return callback(err);
      } else {
        processDoc(id, rev_tree);
      }

      if (++count === ids.length) {
        // convert LazyMap to object
        var missingObj = {};
        missing.forEach(function (value, key) {
          missingObj[key] = value;
        });
        return callback(null, missingObj);
      }
    });
  }, this);
});

// compact one document and fire callback
// by compacting we mean removing all revisions which
// are further from the leaf in revision tree than max_height
AbstractPouchDB.prototype.compactDocument =
  utils.adapterFun('compactDocument', function (docId, maxHeight, callback) {
  var self = this;
  this._getRevisionTree(docId, function (err, revTree) {
    if (err) {
      return callback(err);
    }
    var height = computeHeight(revTree);
    var candidates = [];
    var revs = [];
    Object.keys(height).forEach(function (rev) {
      if (height[rev] > maxHeight) {
        candidates.push(rev);
      }
    });

    merge.traverseRevTree(revTree, function (isLeaf, pos, revHash, ctx, opts) {
      var rev = pos + '-' + revHash;
      if (opts.status === 'available' && candidates.indexOf(rev) !== -1) {
        revs.push(rev);
      }
    });
    self._doCompaction(docId, revs, callback);
  });
});

// compact the whole database using single document
// compaction
AbstractPouchDB.prototype.compact =
  utils.adapterFun('compact', function (opts, callback) {
  if (typeof opts === 'function') {
    callback = opts;
    opts = {};
  }
  var self = this;

  opts = utils.clone(opts || {});

  self.get('_local/compaction').catch(function () {
    return false;
  }).then(function (doc) {
    if (typeof self._compact === 'function') {
      if (doc && doc.last_seq) {
        opts.last_seq = doc.last_seq;
      }
      return self._compact(opts, callback);
    }

  });
});
AbstractPouchDB.prototype._compact = function (opts, callback) {
  var self = this;
  var changesOpts = {
    returnDocs: false,
    last_seq: opts.last_seq || 0
  };
  var promises = [];

  function onChange(row) {
    promises.push(self.compactDocument(row.id, 0));
  }
  function onComplete(resp) {
    var lastSeq = resp.last_seq;
    Promise.all(promises).then(function () {
      return upsert(self, '_local/compaction', function deltaFunc(doc) {
        if (!doc.last_seq || doc.last_seq < lastSeq) {
          doc.last_seq = lastSeq;
          return doc;
        }
        return false; // somebody else got here first, don't update
      });
    }).then(function () {
      callback(null, {ok: true});
    }).catch(callback);
  }
  self.changes(changesOpts)
    .on('change', onChange)
    .on('complete', onComplete)
    .on('error', callback);
};
/* Begin api wrappers. Specific functionality to storage belongs in the 
   _[method] */
AbstractPouchDB.prototype.get =
  utils.adapterFun('get', function (id, opts, callback) {
  if (typeof opts === 'function') {
    callback = opts;
    opts = {};
  }
  if (typeof id !== 'string') {
    return callback(errors.error(errors.INVALID_ID));
  }
  if (utils.isLocalId(id) && typeof this._getLocal === 'function') {
    return this._getLocal(id, callback);
  }
  var leaves = [], self = this;

  function finishOpenRevs() {
    var result = [];
    var count = leaves.length;
    if (!count) {
      return callback(null, result);
    }
    // order with open_revs is unspecified
    leaves.forEach(function (leaf) {
      self.get(id, {
        rev: leaf,
        revs: opts.revs,
        attachments: opts.attachments
      }, function (err, doc) {
        if (!err) {
          result.push({ok: doc});
        } else {
          result.push({missing: leaf});
        }
        count--;
        if (!count) {
          callback(null, result);
        }
      });
    });
  }

  if (opts.open_revs) {
    if (opts.open_revs === "all") {
      this._getRevisionTree(id, function (err, rev_tree) {
        if (err) {
          return callback(err);
        }
        leaves = merge.collectLeaves(rev_tree).map(function (leaf) {
          return leaf.rev;
        });
        finishOpenRevs();
      });
    } else {
      if (Array.isArray(opts.open_revs)) {
        leaves = opts.open_revs;
        for (var i = 0; i < leaves.length; i++) {
          var l = leaves[i];
          // looks like it's the only thing couchdb checks
          if (!(typeof(l) === "string" && /^\d+-/.test(l))) {
            return callback(errors.error(errors.INVALID_REV));
          }
        }
        finishOpenRevs();
      } else {
        return callback(errors.error(errors.UNKNOWN_ERROR,
          'function_clause'));
      }
    }
    return; // open_revs does not like other options
  }

  return this._get(id, opts, function (err, result) {
    opts = utils.clone(opts);
    if (err) {
      return callback(err);
    }

    var doc = result.doc;
    var metadata = result.metadata;
    var ctx = result.ctx;

    if (opts.conflicts) {
      var conflicts = merge.collectConflicts(metadata);
      if (conflicts.length) {
        doc._conflicts = conflicts;
      }
    }

    if (utils.isDeleted(metadata, doc._rev)) {
      doc._deleted = true;
    }

    if (opts.revs || opts.revs_info) {
      var paths = merge.rootToLeaf(metadata.rev_tree);
      var path = arrayFirst(paths, function (arr) {
        return arr.ids.map(function (x) { return x.id; })
          .indexOf(doc._rev.split('-')[1]) !== -1;
      });

      var indexOfRev = path.ids.map(function (x) {return x.id; })
        .indexOf(doc._rev.split('-')[1]) + 1;
      var howMany = path.ids.length - indexOfRev;
      path.ids.splice(indexOfRev, howMany);
      path.ids.reverse();

      if (opts.revs) {
        doc._revisions = {
          start: (path.pos + path.ids.length) - 1,
          ids: path.ids.map(function (rev) {
            return rev.id;
          })
        };
      }
      if (opts.revs_info) {
        var pos =  path.pos + path.ids.length;
        doc._revs_info = path.ids.map(function (rev) {
          pos--;
          return {
            rev: pos + '-' + rev.id,
            status: rev.opts.status
          };
        });
      }
    }

    if (opts.local_seq) {
      utils.info('The "local_seq" option is deprecated and will be removed');
      doc._local_seq = result.metadata.seq;
    }

    if (opts.attachments && doc._attachments) {
      var attachments = doc._attachments;
      var count = Object.keys(attachments).length;
      if (count === 0) {
        return callback(null, doc);
      }
      Object.keys(attachments).forEach(function (key) {
        this._getAttachment(attachments[key],
                            {encode: true, ctx: ctx}, function (err, data) {
          var att = doc._attachments[key];
          att.data = data;
          delete att.stub;
          delete att.length;
          if (!--count) {
            callback(null, doc);
          }
        });
      }, self);
    } else {
      if (doc._attachments) {
        for (var key in doc._attachments) {
          if (doc._attachments.hasOwnProperty(key)) {
            doc._attachments[key].stub = true;
          }
        }
      }
      callback(null, doc);
    }
  });
});

AbstractPouchDB.prototype.getAttachment =
  utils.adapterFun('getAttachment', function (docId, attachmentId, opts,
                                              callback) {
  var self = this;
  if (opts instanceof Function) {
    callback = opts;
    opts = {};
  }
  opts = utils.clone(opts);
  this._get(docId, opts, function (err, res) {
    if (err) {
      return callback(err);
    }
    if (res.doc._attachments && res.doc._attachments[attachmentId]) {
      opts.ctx = res.ctx;
      self._getAttachment(res.doc._attachments[attachmentId], opts, callback);
    } else {
      return callback(errors.error(errors.MISSING_DOC));
    }
  });
});

AbstractPouchDB.prototype.allDocs =
  utils.adapterFun('allDocs', function (opts, callback) {
  if (typeof opts === 'function') {
    callback = opts;
    opts = {};
  }
  opts = utils.clone(opts);
  opts.skip = typeof opts.skip !== 'undefined' ? opts.skip : 0;
  if ('keys' in opts) {
    if (!Array.isArray(opts.keys)) {
      return callback(new TypeError('options.keys must be an array'));
    }
    var incompatibleOpt =
      ['startkey', 'endkey', 'key'].filter(function (incompatibleOpt) {
      return incompatibleOpt in opts;
    })[0];
    if (incompatibleOpt) {
      callback(errors.error(errors.QUERY_PARSE_ERROR,
        'Query parameter `' + incompatibleOpt +
        '` is not compatible with multi-get'
      ));
      return;
    }
    if (this.type() !== 'http') {
      return allDocsKeysQuery(this, opts, callback);
    }
  }

  return this._allDocs(opts, callback);
});

AbstractPouchDB.prototype.changes = function (opts, callback) {
  if (typeof opts === 'function') {
    callback = opts;
    opts = {};
  }
  return new Changes(this, opts, callback);
};

AbstractPouchDB.prototype.close =
  utils.adapterFun('close', function (callback) {
  this._closed = true;
  return this._close(callback);
});

AbstractPouchDB.prototype.info = utils.adapterFun('info', function (callback) {
  var self = this;
  this._info(function (err, info) {
    if (err) {
      return callback(err);
    }
    // assume we know better than the adapter, unless it informs us
    info.db_name = info.db_name || self._db_name;
    info.auto_compaction = !!(self.auto_compaction && self.type() !== 'http');
    callback(null, info);
  });
});

AbstractPouchDB.prototype.id = utils.adapterFun('id', function (callback) {
  return this._id(callback);
});

AbstractPouchDB.prototype.type = function () {
  return (typeof this._type === 'function') ? this._type() : this.adapter;
};

AbstractPouchDB.prototype.bulkDocs =
  utils.adapterFun('bulkDocs', function (req, opts, callback) {
  if (typeof opts === 'function') {
    callback = opts;
    opts = {};
  }

  opts = utils.clone(opts);

  if (Array.isArray(req)) {
    req = {
      docs: req
    };
  }

  if (!req || !req.docs || !Array.isArray(req.docs)) {
    return callback(errors.error(errors.MISSING_BULK_DOCS));
  }

  for (var i = 0; i < req.docs.length; ++i) {
    if (typeof req.docs[i] !== 'object' || Array.isArray(req.docs[i])) {
      return callback(errors.error(errors.NOT_AN_OBJECT));
    }
  }

  req = utils.clone(req);
  if (!('new_edits' in opts)) {
    if ('new_edits' in req) {
      opts.new_edits = req.new_edits;
    } else {
      opts.new_edits = true;
    }
  }

  if (!opts.new_edits && this.type() !== 'http') {
    // ensure revisions of the same doc are sorted, so that
    // the local adapter processes them correctly (#2935)
    req.docs.sort(function (a, b) {
      var idCompare = utils.compare(a._id, b._id);
      if (idCompare !== 0) {
        return idCompare;
      }
      var aStart = a._revisions ? a._revisions.start : 0;
      var bStart = b._revisions ? b._revisions.start : 0;
      return utils.compare(aStart, bStart);
    });
  }

  req.docs.forEach(function (doc) {
    if (doc._deleted) {
      delete doc._attachments; // ignore atts for deleted docs
    }
  });

  return this._bulkDocs(req, opts, function (err, res) {
    if (err) {
      return callback(err);
    }
    if (!opts.new_edits) {
      // this is what couch does when new_edits is false
      res = res.filter(function (x) {
        return x.error;
      });
    }
    callback(null, res);
  });
});

AbstractPouchDB.prototype.registerDependentDatabase =
  utils.adapterFun('registerDependentDatabase', function (dependentDb,
                                                          callback) {
  var depDB = new this.constructor(dependentDb, this.__opts || {});

  function diffFun(doc) {
    doc.dependentDbs = doc.dependentDbs || {};
    if (doc.dependentDbs[dependentDb]) {
      return false; // no update required
    }
    doc.dependentDbs[dependentDb] = true;
    return doc;
  }
  upsert(this, '_local/_pouch_dependentDbs', diffFun, function (err) {
    if (err) {
      return callback(err);
    }
    return callback(null, {db: depDB});
  });
});