(function(){

  class YArray {
    constructor (os, _model, idArray, valArray) {
      this.os = os;
      this._model = _model;
      // Array of all the operation id's
      this.idArray = idArray;
      // Array of all the values
      this.valArray = valArray;
      this.eventHandler = new EventHandler( ops =>{
        var userEvents = [];
        for (var i in ops) {
          var op = ops[i];
          if (op.struct === "Insert") {
            let pos;
            // we check op.left only!,
            // because op.right might not be defined when this is called
            if (op.left === null) {
              pos = 0;
            } else {
              var sid = JSON.stringify(op.left);
              pos = this.idArray.indexOf(sid) + 1;
              if (pos <= 0) {
                throw new Error("Unexpected operation!");
              }
            }
            this.idArray.splice(pos, 0, JSON.stringify(op.id));
            this.valArray.splice(pos, 0, op.content);
            userEvents.push({
              type: "insert",
              object: this,
              index: pos,
              length: 1
            });
          } else if (op.struct === "Delete") {
            let pos = this.idArray.indexOf(JSON.stringify(op.target));
            this.idArray.splice(pos, 1);
            this.valArray.splice(pos, 1);
            userEvents.push({
              type: "delete",
              object: this,
              index: pos,
              length: 1
            });
          } else {
            throw new Error("Unexpected struct!");
          }
        }
        this.eventHandler.callUserEventListeners(userEvents);
      });
    }
    get (pos) {
      if (pos == null || typeof pos !== "number") {
          throw new Error("pos must be a number!");
      }
      return this.valArray[pos];
    }
    toArray() {
      return this.valArray.slice();
    }
    insert (pos, contents) {
      if (typeof pos !== "number") {
        throw new Error("pos must be a number!");
      }
      if (!(contents instanceof Array)) {
        throw new Error("contents must be an Array of objects!");
      }
      if (contents.length === 0) {
        return;
      }
      if (pos > this.idArray.length || pos < 0) {
        throw new Error("This position exceeds the range of the array!");
      }
      var mostLeft = pos === 0 ? null : JSON.parse(this.idArray[pos - 1]);

      var ops = [];
      var prevId = mostLeft;
      for (var i = 0; i < contents.length; i++) {
        var op = {
          left: prevId,
          origin: prevId,
          // right: mostRight,
          // NOTE: I intentionally do not define right here, because it could be deleted
          // at the time of creating this operation, and is therefore not defined in idArray
          parent: this._model,
          content: contents[i],
          struct: "Insert",
          id: this.os.getNextOpId()
        };
        ops.push(op);
        prevId = op.id;
      }
      var eventHandler = this.eventHandler;
      eventHandler.awaitAndPrematurelyCall(ops);
      this.os.requestTransaction(function*(){
        // now we can set the right reference.
        var mostRight;
        if (mostLeft != null) {
          mostRight = (yield* this.getOperation(mostLeft)).right;
        } else {
          mostRight = (yield* this.getOperation(ops[0].parent)).start;
        }
        for (var j in ops) {
          ops[j].right = mostRight;
        }
        yield* this.applyCreatedOperations(ops);
        eventHandler.awaitedLastInserts(ops.length);
      });
    }
    delete (pos, length = 1) {
      if (typeof length !== "number") {
        throw new Error("pos must be a number!");
      }
      if (typeof pos !== "number") {
        throw new Error("pos must be a number!");
      }
      if (pos + length > this.idArray.length || pos < 0 || length < 0) {
        throw new Error("The deletion range exceeds the range of the array!");
      }
      var eventHandler = this.eventHandler;
      var newLeft = pos > 0 ? JSON.parse(this.idArray[pos - 1]) : null;
      var dels = [];
      for (var i = 0; i < length; i++) {
        dels.push({
          target: JSON.parse(this.idArray[pos + i]),
          struct: "Delete"
        });
      }
      eventHandler.awaitAndPrematurelyCall(dels);
      this.os.requestTransaction(function*(){
        yield* this.applyCreatedOperations(dels);
        eventHandler.awaitedLastDeletes(dels.length, newLeft);
      });
    }
    observe (f) {
      this.eventHandler.addUserEventListener(f);
    }
    *_changed (transaction, op) {
      if (op.struct === "Insert") {
        var l = op.left;
        var left;
        while (l != null) {
          left = yield* transaction.getOperation(l);
          if (!left.deleted) {
            break;
          }
          l = left.left;
        }
        op.left = l;
      }
      this.eventHandler.receivedOp(op);
    }
  }

  Y.Array = function* _YArray(){
    var model = {
      start: null,
      end: null,
      struct: "List",
      type: "Array",
      id: this.store.getNextOpId()
    };
    yield* this.applyCreatedOperations([model]);
    return yield* this.createType(model);
  };
  Y.Array.create = function* YArrayCreate(os, model){
    var valArray = [];
    var idArray = yield* Y.Struct.List.map.call(this, model, function(c){
      valArray.push(c.content);
      return JSON.stringify(c.id);
    });
    return new YArray(os, model.id, idArray, valArray);
  };
})();