/**
 * GameLib.EntityManager
 * @constructor
 */
GameLib.EntityManager = function() {

    this.id = GameLib.Utils.RandomId();

    this.name = 'Entity Manager (' + this.id + ')';

    this.entities = [];

    GameLib.Component.call(
        this,
        GameLib.Component.COMPONENT_ENTITY_MANAGER,
        {
            'entities' : [GameLib.Entity]
        },
        null
    );

    this.loaded = [];

    this.dependencies = {};

    this.subscriptions = [];

    this.registerCallbacks();
};

GameLib.EntityManager.prototype = Object.create(GameLib.Component.prototype);
GameLib.EntityManager.prototype.constructor = GameLib.EntityManager;

GameLib.EntityManager.prototype.createInstance = function() {
    return GameLib.EntityManager.Instance;
};

/**
 * Creates an GameLib.Entity and adds it to entities array
 * @returns {*}
 */
GameLib.EntityManager.prototype.createEntity = function(name) {

    var apiEntity = new GameLib.API.Entity(
        null,
        name,
        null,
        null,
        this
    );

    var entity = new GameLib.Entity(
        this.graphics,
        apiEntity
    );

    this.entities.push(entity);

    GameLib.Event.Emit(
        GameLib.Event.NEW_ENTITY,
        {
            entity : entity
        }
    );

    return entity;
};

/**
 * Returns an entity by ID or null
 * @param id
 * @returns {*}
 */
GameLib.EntityManager.prototype.findEntityById = function(id) {

    return this.entities.reduce(
        function(result, entity){

            if (entity.id === id) {
                result = entity;
            }

            return result;
        },
        null
    );
};

GameLib.EntityManager.prototype.findHelperByObject = function(object) {

    return this.entities.reduce(
        function(result, entity) {
            var helpers = entity.getComponents(GameLib.D3.Helper);
            var helper = helpers.reduce(
                function(helperResult, tmpHelper) {

                    if (tmpHelper.object === object) {
                        helperResult = tmpHelper;
                    }

                    return helperResult;
                },
                null
            );

            if (helper) {
                result = helper;
            }

            return result;
        },
        null
    );

};

/**
 * Adds an entity to this manager
 * @param entity GameLib.Entity
 */
GameLib.EntityManager.prototype.addEntity = function(entity) {
    entity.parentEntityManager = this;
    this.entities.push(entity);
};

// /**
//  * Adds a system to this manager
//  * @param system GameLib.System
//  */
// GameLib.EntityManager.prototype.addSystem = function(system) {
// 	this.systems.push(system);
// };

/**
 * Returns entity by name
 * @param name
 * @returns {*}
 */
GameLib.EntityManager.prototype.queryByName = function(name) {
    return this.entities.reduce(
        function(result, entity){
            if (entity.name === name) {
                result = entity;
            }
            return result;
        },
        null
    )
};

/**
 * Removes an entity - do we remove all its components as well?
 * @param entity GameLib.D3.Entity
 * @returns boolean true if successful
 */
GameLib.EntityManager.prototype.removeEntity = function(entity) {

    var index = this.entities.indexOf(entity);

    if (index === -1) {
        console.log('failed to remove entity : ', entity);
        return false;
    }

    entity.parentEntityManager = null;

    this.entities.splice(index, 1);
    return true;
};

/**
 * Returns all the entities with the following components
 * @param components GameLib.Component[]
 */
GameLib.EntityManager.prototype.query = function(components) {

    var entities = this.entities.reduce(
        function(result, entity) {

            var hasAllComponents = components.reduce(
                function(componentResult, component) {
                    if (!entity.hasComponent(component)) {
						componentResult = false;
                    }
                    return componentResult;
                },
                true
            );

            if (hasAllComponents) {
                result.push(entity);
            }

            return result;
        },
        []
    );

    return entities;
};

/**
 * Returns all actual components of all entities that contain this component
 * @param constructor
 */
GameLib.EntityManager.prototype.queryComponents = function(constructor) {

    var entities = this.query([constructor]);

    var components = entities.reduce(
        function(result, entity){
            var ecs = entity.getComponents(constructor);
            ecs.map(function(ec){
                result.push(ec);
            });
            return result;
        },
        []
    );

    return components;
};

/**
 * Converts a GameLib.Entity to GameLib.API.Entity
 * @returns {GameLib.API.EntityManager}
 */
GameLib.EntityManager.prototype.toApiObject = function() {

    var apiEntities = this.entities.map(
        function (entity) {
            return entity.toApiObject();
        }
    );

	// var apiSystems = this.systems.map(
	// 	function (system) {
	// 		return system.toApiObject();
	// 	}
	// );

    var apiEntityManager = new GameLib.API.EntityManager(
        this.id,
        this.name,
        apiEntities,
		// apiSystems,
        this.parentEntity
    );

    return apiEntityManager;
};

/**
 * Returns an EntityManager from an Object entity manager
 * @param graphics
 * @param objectEntityManager Object
 * @constructor
 */
GameLib.EntityManager.FromObject = function(objectEntityManager) {

    var apiEntityManager = GameLib.API.EntityManager.FromObject(objectEntityManager);

    var entityManager = new GameLib.EntityManager(apiEntityManager);

    return entityManager;
};

/**
 * Defines what should happen when a parent scene changes
 * @param data
 */
GameLib.EntityManager.prototype.onParentSceneChange = function(data) {

	if (
	    data.object instanceof GameLib.D3.Mesh ||
        data.object instanceof GameLib.D3.Light
    ) {

		/**
		 * We remove the helper (if any) from the old scene and add it to the new scene
		 */
		var helper = this.findHelperByObject(data.object);
		if (helper) {

		    if (data.originalScene && data.originalScene.instance) {
                data.originalScene.instance.remove(helper.instance);
            }
			data.newScene.instance.add(helper.instance);
		}

		/**
		 * We remove the mesh from the old scene and add it to the new scene
		 */
		if (data.originalScene && data.originalScene.removeObject) {
		    data.originalScene.removeObject(data.object);
        }
		data.newScene.addObject(data.object);

		/**
		 * We inherit the parent entity of this new scene
		 */
		var originalEntity = null;
		var newEntity = null;

		if (data.object.hasOwnProperty('parentEntity')) {
			originalEntity = data.object.parentEntity
		}

		if (data.newScene.hasOwnProperty('parentEntity')) {
			newEntity = data.newScene.parentEntity;
		}

		var gui = null;

		if (originalEntity) {

            if (originalEntity.removeComponent) {
                if (helper) {
                    originalEntity.removeComponent(helper);
                }
                originalEntity.removeComponent(data.object);
            }

            if (originalEntity.getFirstComponent) {
                gui = originalEntity.getFirstComponent(GameLib.GUI);
                if (gui) {
                    gui.removeObject(data.object);
                    gui.build(this);
                }
            }
        }

		if (newEntity) {

		    if (newEntity.addComponent) {
		        if (helper) {
                    newEntity.addComponent(helper);
                }
                newEntity.addComponent(data.object);
            }

            if (newEntity.getFirstComponent) {
                gui = newEntity.getFirstComponent(GameLib.GUI);
                if (gui) {
                    gui.addObject(data.object);
                    gui.build(this);
                }
            }
		}
	}

};

/**
 * Change parent entity
 * TODO: also change parent entity of children objects
 * @param data
 */
GameLib.EntityManager.prototype.onParentEntityChange = function(data) {

    if (data.originalEntity) {
        data.originalEntity.removeComponent(data.object);
    }

	data.newEntity.addComponent(data.object);

    // - ok not so cool - we may have parent entities of entities -
    // - so not all children should inherit the parent entity
    // data.object.buildIdToObject();
    //
    // for (var property in data.object.idToObject) {
    //     if (data.object.idToObject.hasOwnProperty(property)) {
    //         if (data.object.idToObject[property].hasOwnProperty('parentEntity')) {
    //             data.object.idToObject[property].parentEntity = data.newEntity;
    //         }
    //     }
    // }

};

GameLib.EntityManager.prototype.componentCreated = function(data) {

    console.log('component created : ' + data.component.name);

    /**
     * If we notify ourselves - ignore it
     */
    if (data.component === this) {
        return;
    }

    /**
     * Store this component into our 'loaded' list
     */
    this.loaded.push(data.component);

    /**
     * Store the dependencies too
     */
    data.component.dependencies.map(function(id) {

        if (GameLib.Utils.UndefinedOrNull(this.dependencies[id])) {
            this.dependencies[id] = [];
        }

        this.dependencies[id].push(data.component);

    }.bind(this));

    /**
     * Now find all the dependencies of this component
     */
    var dependencies = this.dependencies[data.component.id];
    if (GameLib.Utils.UndefinedOrNull(dependencies)) {

        /**
         * We have no dependencies, so mark our component as loaded and create an instance
         */
        data.component.loaded = true;
        data.component.instance = data.component.createInstance();

        /**
         * If we have none, we are done and can exit
         */
        return;
    }

    /**
     * Otherwise, now - for each dependency - update 'idToObject' and check if its loaded
     */
    dependencies.map(function(component){
        component.idToObject[data.component.id] = data.component;

        var loaded = true;

        for (var property in component.idToObject) {
            if (
                component.idToObject.hasOwnProperty(property) &&
                component.idToObject[property] === null
            ) {
                loaded = false
            }
        }

        component.loaded = loaded;

        if (component.loaded) {
            /**
             * Our component is fully loaded, time to create an instance of it
             */
            component.instance = component.createInstance();
        }

    })

};

/**
 *
 */
GameLib.EntityManager.prototype.registerCallbacks = function() {

    this.subscriptions.push(
        this.subscribe(
            GameLib.Event.PARENT_SCENE_CHANGE,
            this.onParentSceneChange
        )
    );

    this.subscriptions.push(
        this.subscribe(
            GameLib.Event.PARENT_ENTITY_CHANGE,
            this.onParentEntityChange
        )
    );

    this.subscriptions.push(
        this.subscribe(
            GameLib.Event.COMPONENT_CREATED,
            this.componentCreated
        )
    );
};

/**
 * Links object Ids to actual objects
 * @param idToObject
 */
// GameLib.EntityManager.prototype.linkObjects = function(idToObject) {
//
//     this.entities.map(
//         function(entity) {
//             entity.components.map(
//                 function (componentId, index, array) {
//                     if (componentId instanceof GameLib.Component) {
//                         array[index] = componentId;
//                     } else {
//                         array[index] = idToObject[componentId];
//                     }
//
//                     Object.keys(array[index].linkedObjects).map(
//                         function (propertyName) {
//                             array[index][propertyName] = idToObject[array[index][propertyName]];
//                         }
//                     );
//
//                     array[index].loaded = true;
//                 }
//             )
//         }
//     );
//
// };