/**
 * Copyright 2013-2014 Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * @providesModule ReactComponent
 */

"use strict";

var ReactDescriptor = require('ReactDescriptor');
var ReactOwner = require('ReactOwner');
var ReactUpdates = require('ReactUpdates');

var invariant = require('invariant');
var keyMirror = require('keyMirror');
var merge = require('merge');

/**
 * Every React component is in one of these life cycles.
 */
var ComponentLifeCycle = keyMirror({
  /**
   * Mounted components have a DOM node representation and are capable of
   * receiving new props.
   */
  MOUNTED: null,
  /**
   * Unmounted components are inactive and cannot receive new props.
   */
  UNMOUNTED: null
});

var injected = false;

/**
 * Optionally injectable environment dependent cleanup hook. (server vs.
 * browser etc). Example: A browser system caches DOM nodes based on component
 * ID and must remove that cache entry when this instance is unmounted.
 *
 * @private
 */
var unmountIDFromEnvironment = null;

/**
 * The "image" of a component tree, is the platform specific (typically
 * serialized) data that represents a tree of lower level UI building blocks.
 * On the web, this "image" is HTML markup which describes a construction of
 * low level `div` and `span` nodes. Other platforms may have different
 * encoding of this "image". This must be injected.
 *
 * @private
 */
var mountImageIntoNode = null;

/**
 * Components are the basic units of composition in React.
 *
 * Every component accepts a set of keyed input parameters known as "props" that
 * are initialized by the constructor. Once a component is mounted, the props
 * can be mutated using `setProps` or `replaceProps`.
 *
 * Every component is capable of the following operations:
 *
 *   `mountComponent`
 *     Initializes the component, renders markup, and registers event listeners.
 *
 *   `receiveComponent`
 *     Updates the rendered DOM nodes to match the given component.
 *
 *   `unmountComponent`
 *     Releases any resources allocated by this component.
 *
 * Components can also be "owned" by other components. Being owned by another
 * component means being constructed by that component. This is different from
 * being the child of a component, which means having a DOM representation that
 * is a child of the DOM representation of that component.
 *
 * @class ReactComponent
 */
var ReactComponent = {

  injection: {
    injectEnvironment: function(ReactComponentEnvironment) {
      invariant(
        !injected,
        'ReactComponent: injectEnvironment() can only be called once.'
      );
      mountImageIntoNode = ReactComponentEnvironment.mountImageIntoNode;
      unmountIDFromEnvironment =
        ReactComponentEnvironment.unmountIDFromEnvironment;
      ReactComponent.BackendIDOperations =
        ReactComponentEnvironment.BackendIDOperations;
      injected = true;
    }
  },

  /**
   * @internal
   */
  LifeCycle: ComponentLifeCycle,

  /**
   * Injected module that provides ability to mutate individual properties.
   * Injected into the base class because many different subclasses need access
   * to this.
   *
   * @internal
   */
  BackendIDOperations: null,

  /**
   * Base functionality for every ReactComponent constructor. Mixed into the
   * `ReactComponent` prototype, but exposed statically for easy access.
   *
   * @lends {ReactComponent.prototype}
   */
  Mixin: {

    /**
     * Checks whether or not this component is mounted.
     *
     * @return {boolean} True if mounted, false otherwise.
     * @final
     * @protected
     */
    isMounted: function() {
      return this._lifeCycleState === ComponentLifeCycle.MOUNTED;
    },

    /**
     * Sets a subset of the props.
     *
     * @param {object} partialProps Subset of the next props.
     * @param {?function} callback Called after props are updated.
     * @final
     * @public
     */
    setProps: function(partialProps, callback) {
      // Merge with the pending descriptor if it exists, otherwise with existing
      // descriptor props.
      var descriptor = this._pendingDescriptor || this._descriptor;
      this.replaceProps(
        merge(descriptor.props, partialProps),
        callback
      );
    },

    /**
     * Replaces all of the props.
     *
     * @param {object} props New props.
     * @param {?function} callback Called after props are updated.
     * @final
     * @public
     */
    replaceProps: function(props, callback) {
      invariant(
        this.isMounted(),
        'replaceProps(...): Can only update a mounted component.'
      );
      invariant(
        this._mountDepth === 0,
        'replaceProps(...): You called `setProps` or `replaceProps` on a ' +
        'component with a parent. This is an anti-pattern since props will ' +
        'get reactively updated when rendered. Instead, change the owner\'s ' +
        '`render` method to pass the correct value as props to the component ' +
        'where it is created.'
      );
      // This is a deoptimized path. We optimize for always having a descriptor.
      // This creates an extra internal descriptor.
      this._pendingDescriptor = ReactDescriptor.cloneAndReplaceProps(
        this._pendingDescriptor || this._descriptor,
        props
      );
      ReactUpdates.enqueueUpdate(this, callback);
    },

    /**
     * Schedule a partial update to the props. Only used for internal testing.
     *
     * @param {object} partialProps Subset of the next props.
     * @param {?function} callback Called after props are updated.
     * @final
     * @internal
     */
    _setPropsInternal: function(partialProps, callback) {
      // This is a deoptimized path. We optimize for always having a descriptor.
      // This creates an extra internal descriptor.
      var descriptor = this._pendingDescriptor || this._descriptor;
      this._pendingDescriptor = ReactDescriptor.cloneAndReplaceProps(
        descriptor,
        merge(descriptor.props, partialProps)
      );
      ReactUpdates.enqueueUpdate(this, callback);
    },

    /**
     * Base constructor for all React components.
     *
     * Subclasses that override this method should make sure to invoke
     * `ReactComponent.Mixin.construct.call(this, ...)`.
     *
     * @param {ReactDescriptor} descriptor
     * @internal
     */
    construct: function(descriptor) {
      // This is the public exposed props object after it has been processed
      // with default props. The descriptor's props represents the true internal
      // state of the props.
      this.props = descriptor.props;
      // Record the component responsible for creating this component.
      // This is accessible through the descriptor but we maintain an extra
      // field for compatibility with devtools and as a way to make an
      // incremental update. TODO: Consider deprecating this field.
      this._owner = descriptor._owner;

      // All components start unmounted.
      this._lifeCycleState = ComponentLifeCycle.UNMOUNTED;

      // See ReactUpdates.
      this._pendingCallbacks = null;

      // We keep the old descriptor and a reference to the pending descriptor
      // to track updates.
      this._descriptor = descriptor;
      this._pendingDescriptor = null;
    },

    /**
     * Initializes the component, renders markup, and registers event listeners.
     *
     * NOTE: This does not insert any nodes into the DOM.
     *
     * Subclasses that override this method should make sure to invoke
     * `ReactComponent.Mixin.mountComponent.call(this, ...)`.
     *
     * @param {string} rootID DOM ID of the root node.
     * @param {ReactReconcileTransaction|ReactServerRenderingTransaction} transaction
     * @param {number} mountDepth number of components in the owner hierarchy.
     * @return {?string} Rendered markup to be inserted into the DOM.
     * @internal
     */
    mountComponent: function(rootID, transaction, mountDepth) {
      invariant(
        !this.isMounted(),
        'mountComponent(%s, ...): Can only mount an unmounted component. ' +
        'Make sure to avoid storing components between renders or reusing a ' +
        'single component instance in multiple places.',
        rootID
      );
      var props = this._descriptor.props;
      if (props.ref != null) {
        var owner = this._descriptor._owner;
        ReactOwner.addComponentAsRefTo(this, props.ref, owner);
      }
      this._rootNodeID = rootID;
      this._lifeCycleState = ComponentLifeCycle.MOUNTED;
      this._mountDepth = mountDepth;
      // Effectively: return '';
    },

    /**
     * Releases any resources allocated by `mountComponent`.
     *
     * NOTE: This does not remove any nodes from the DOM.
     *
     * Subclasses that override this method should make sure to invoke
     * `ReactComponent.Mixin.unmountComponent.call(this)`.
     *
     * @internal
     */
    unmountComponent: function() {
      invariant(
        this.isMounted(),
        'unmountComponent(): Can only unmount a mounted component.'
      );
      var props = this.props;
      if (props.ref != null) {
        ReactOwner.removeComponentAsRefFrom(this, props.ref, this._owner);
      }
      unmountIDFromEnvironment(this._rootNodeID);
      this._rootNodeID = null;
      this._lifeCycleState = ComponentLifeCycle.UNMOUNTED;
    },

    /**
     * Given a new instance of this component, updates the rendered DOM nodes
     * as if that instance was rendered instead.
     *
     * Subclasses that override this method should make sure to invoke
     * `ReactComponent.Mixin.receiveComponent.call(this, ...)`.
     *
     * @param {object} nextComponent Next set of properties.
     * @param {ReactReconcileTransaction} transaction
     * @internal
     */
    receiveComponent: function(nextDescriptor, transaction) {
      invariant(
        this.isMounted(),
        'receiveComponent(...): Can only update a mounted component.'
      );
      this._pendingDescriptor = nextDescriptor;
      this.performUpdateIfNecessary(transaction);
    },

    /**
     * If `_pendingDescriptor` is set, update the component.
     *
     * @param {ReactReconcileTransaction} transaction
     * @internal
     */
    performUpdateIfNecessary: function(transaction) {
      if (this._pendingDescriptor == null) {
        return;
      }
      var prevDescriptor = this._descriptor;
      var nextDescriptor = this._pendingDescriptor;
      this._descriptor = nextDescriptor;
      this.props = nextDescriptor.props;
      this._owner = nextDescriptor._owner;
      this._pendingDescriptor = null;
      this.updateComponent(transaction, prevDescriptor);
    },

    /**
     * Updates the component's currently mounted representation.
     *
     * @param {ReactReconcileTransaction} transaction
     * @param {object} prevDescriptor
     * @internal
     */
    updateComponent: function(transaction, prevDescriptor) {
      var nextDescriptor = this._descriptor;

      // If either the owner or a `ref` has changed, make sure the newest owner
      // has stored a reference to `this`, and the previous owner (if different)
      // has forgotten the reference to `this`. We use the descriptor instead
      // of the public this.props because the post processing cannot determine
      // a ref. The ref conceptually lives on the descriptor.

      // TODO: Should this even be possible? The owner cannot change because
      // it's forbidden by shouldUpdateReactComponent. The ref can change
      // if you swap the keys of but not the refs. Reconsider where this check
      // is made. It probably belongs where the key checking and
      // instantiateReactComponent is done.

      if (nextDescriptor._owner !== prevDescriptor._owner ||
          nextDescriptor.props.ref !== prevDescriptor.props.ref) {
        if (prevDescriptor.props.ref != null) {
          ReactOwner.removeComponentAsRefFrom(
            this, prevDescriptor.props.ref, prevDescriptor._owner
          );
        }
        // Correct, even if the owner is the same, and only the ref has changed.
        if (nextDescriptor.props.ref != null) {
          ReactOwner.addComponentAsRefTo(
            this,
            nextDescriptor.props.ref,
            nextDescriptor._owner
          );
        }
      }
    },

    /**
     * Mounts this component and inserts it into the DOM.
     *
     * @param {string} rootID DOM ID of the root node.
     * @param {DOMElement} container DOM element to mount into.
     * @param {boolean} shouldReuseMarkup If true, do not insert markup
     * @final
     * @internal
     * @see {ReactMount.renderComponent}
     */
    mountComponentIntoNode: function(rootID, container, shouldReuseMarkup) {
      var transaction = ReactUpdates.ReactReconcileTransaction.getPooled();
      transaction.perform(
        this._mountComponentIntoNode,
        this,
        rootID,
        container,
        transaction,
        shouldReuseMarkup
      );
      ReactUpdates.ReactReconcileTransaction.release(transaction);
    },

    /**
     * @param {string} rootID DOM ID of the root node.
     * @param {DOMElement} container DOM element to mount into.
     * @param {ReactReconcileTransaction} transaction
     * @param {boolean} shouldReuseMarkup If true, do not insert markup
     * @final
     * @private
     */
    _mountComponentIntoNode: function(
        rootID,
        container,
        transaction,
        shouldReuseMarkup) {
      var markup = this.mountComponent(rootID, transaction, 0);
      mountImageIntoNode(markup, container, shouldReuseMarkup);
    },

    /**
     * Checks if this component is owned by the supplied `owner` component.
     *
     * @param {ReactComponent} owner Component to check.
     * @return {boolean} True if `owners` owns this component.
     * @final
     * @internal
     */
    isOwnedBy: function(owner) {
      return this._owner === owner;
    },

    /**
     * Gets another component, that shares the same owner as this one, by ref.
     *
     * @param {string} ref of a sibling Component.
     * @return {?ReactComponent} the actual sibling Component.
     * @final
     * @internal
     */
    getSiblingByRef: function(ref) {
      var owner = this._owner;
      if (!owner || !owner.refs) {
        return null;
      }
      return owner.refs[ref];
    }
  }
};

module.exports = ReactComponent;
