/**
 * Storage System takes care loading and linking components and dependencies
 * @param graphics
 * @param apiSystem GameLib.API.System
 * @param apiUrl
 * @param token
 * @param apiUploadUrl
 * @param onImageLoaded
 * @param onImageProgress
 * @param onImageError
 * @param onComponentLoaded
 * @param onComponentProgress
 * @param onComponentError
 * @constructor
 */
GameLib.System.Storage = function(
    graphics,
    apiSystem,
    apiUrl,
    token,
    apiUploadUrl,
    onImageLoaded,
    onImageProgress,
    onImageError,
    onComponentLoaded,
    onComponentProgress,
    onComponentError
) {
    this.graphics = graphics;
    this.graphics.isNotThreeThrow();

    GameLib.System.call(
        this,
        apiSystem
    );

    if (GameLib.Utils.UndefinedOrNull(apiUrl)) {
        console.warn('Need an API URL for a storage system');
        apiUrl = '';
    }
    this.apiUrl = apiUrl;

    if (GameLib.Utils.UndefinedOrNull(token)) {
        token = null;
    }
    this.token = token;

    if (GameLib.Utils.UndefinedOrNull(apiUploadUrl)) {
        console.warn('Need an API Upload URL for a storage system');
        apiUploadUrl = '';
    }
    this.apiUploadUrl = apiUploadUrl;

    if (GameLib.Utils.UndefinedOrNull(onImageLoaded)) {
        onImageLoaded = null;
    }
    this.onImageLoaded = onImageLoaded;

    if (GameLib.Utils.UndefinedOrNull(onImageProgress)) {
        onImageProgress = null;
    }
    this.onImageProgress = onImageProgress;

    if (GameLib.Utils.UndefinedOrNull(onImageError)) {
        onImageError = null;
    }
    this.onImageError = onImageError;

    if (GameLib.Utils.UndefinedOrNull(onComponentLoaded)) {
        onComponentLoaded = null;
    }
    this.onComponentLoaded = onComponentLoaded;

    if (GameLib.Utils.UndefinedOrNull(onComponentProgress)) {
        onComponentProgress = null;
    }
    this.onComponentProgress = onComponentProgress;

    if (GameLib.Utils.UndefinedOrNull(onComponentError)) {
        onComponentError = null;
    }
    this.onComponentError = onComponentError;

	this.loginSubscription = null;
	this.saveSubscription  = null;
	this.loadSubscription  = null;
	this.loadImageSubscription = null;
};

GameLib.System.Storage.prototype = Object.create(GameLib.System.prototype);
GameLib.System.Storage.prototype.constructor = GameLib.System.Storage;

GameLib.System.Storage.prototype.start = function() {

	this.loginSubscription = this.subscribe(
		GameLib.Event.LOGGED_IN,
		function(data) {
			this.token = data.token;
		}
	);

	this.saveSubscription = this.subscribe(
		GameLib.Event.SAVE_COMPONENT,
		this.save
	);

	this.loadSubscription = this.subscribe(
		GameLib.Event.LOAD_COMPONENT,
		this.load
	);

	this.loadImageSubscription = this.subscribe(
	    GameLib.Event.LOAD_IMAGE,
        this.loadImage
    );
};

/**
 * 'Saves' data to baseURL
 */
GameLib.System.Storage.prototype.save = function(data) {

    if (typeof XMLHttpRequest === 'undefined') {
        console.log('Implement server side save here');
        return;
    }

    var xhr = new XMLHttpRequest();

    xhr.open(
        'POST',
        this.apiUrl + '/component/create'
    );

    xhr.setRequestHeader("Accept", "application/json");
    xhr.setRequestHeader("Content-Type", "application/json");

    xhr.onreadystatechange = function () {
        if (this.readyState === 4) {
            try {
                var response = JSON.parse(this.responseText)
            } catch (error) {
                GameLib.Event.Emit(
                    GameLib.Event.SAVE_COMPONENT_ERROR,
                    {
                        message: this.responseText
                    }
                )
            }

            if (response.result === 'success') {
                GameLib.Event.Emit(
                    GameLib.Event.COMPONENT_SAVED,
                    {
                        message: response.message || 'Successfully saved the component'
                    }
                )
            } else {
                GameLib.Event.Emit(
                    GameLib.Event.SAVE_COMPONENT_ERROR,
                    {
                        message: response.message || 'The server responded but failed to save the component'
                    }
                )
            }
        }
    };

    xhr.send(JSON.stringify({
        component : data,
        session : this.token
    }));

};

GameLib.System.Storage.prototype.loadComponent = function(toProcess, includeDependencies) {

    var loaded = [];

    var loading = [];

    toProcess.map(function(id) {
        if (loading.indexOf(id) === -1) {
            loading.push(id);
        }
    });

    return function download(id, parentEntity) {

        var onComponentLoaded = this.onComponentLoaded;

        var onComponentProgress = this.onComponentProgress;

        var onComponentError = this.onComponentError;

        var xhr = new XMLHttpRequest();

        xhr.onload = function(__system) {

            return function () {

                try {
                    var object = JSON.parse(this.responseText);
                } catch (error) {

                    if (onComponentError) {
                        onComponentError(error);
                    }

                    GameLib.Event.Emit(
                        GameLib.Event.LOAD_COMPONENT_ERROR,
                        {
                            error: error
                        }
                    );

                    return;
                }

                if (object.result !== 'success') {

                    if (onComponentError) {
                        onComponentError(id, object);
                    }

                    GameLib.Event.Emit(
                        GameLib.Event.LOAD_COMPONENT_ERROR,
                        {error : object}
                    );

                    return;
                }

                /**
                 * Now we need to create the runtime component - this happens systematically.
                 * First, we create an API object from the Object, then a Runtime object from the API object
                 * Each component has a function 'FromObject' which essentially does this for you
                 */
                object.component.map(function (component) {

                    var componentName = GameLib.Component.GetComponentName(component.componentType);

                    var componentClass = eval(componentName);

                    var fn = componentClass['FromObject'];

                    var runtimeComponent = null;

                    if (component.componentType === GameLib.Component.COMPONENT_ENTITY) {
                        runtimeComponent = fn(component, GameLib.EntityManager.Instance);
                        runtimeComponent.parentEntity = parentEntity;
                        parentEntity = runtimeComponent;
                    } else {
                        runtimeComponent = fn(__system.graphics, component);
                        runtimeComponent.parentEntity = parentEntity;
                    }

                    if (runtimeComponent instanceof GameLib.D3.Image) {
                        GameLib.Event.Emit(
                            GameLib.Event.LOAD_IMAGE,
                            {
                                image : runtimeComponent
                            }
                        )
                    }

                    loaded.push(runtimeComponent);

                    if (includeDependencies) {
                        /**
                         * Before we announce the creation of this component, we should get
                         * a list of all dependencies of this component, because once we announce
                         * the creation of this component - the linking system will attempt to resolve
                         * all dependencies
                         */
                        var dependencies = runtimeComponent.getDependencies();

                        /**
                         * Now - we should systematically check if we have the dependency already
                         * loaded (in our runtime environment) - if we have - we just ignore loading this dependency (for now)
                         *
                         * We don't override runtime versions of the same component in the database because the user
                         * could be working with it and it should be the latest version.
                         */

                        dependencies = dependencies.reduce(
                            function (result, dependency) {

                                if (GameLib.EntityManager.Instance.findComponentById(dependency)) {
                                    /**
                                     * Don't add the dependency
                                     */
                                } else {
                                    result.push(dependency);
                                }

                                return result;
                            },
                            []
                        );

                        /**
                         * Also check if we did not already load this component quite recently
                         */
                        dependencies = dependencies.reduce(
                            function (result, dependency) {

                                var found = loaded.reduce(
                                    function (result, component) {
                                        if (component.id === dependency) {
                                            result = true;
                                        }
                                        return result;
                                    },
                                    false
                                );

                                if (!found) {
                                    result.push(dependency);
                                }

                                return result;
                            },
                            []
                        );

                        /**
                         * We should now check our 'loading' list and add all dependencies which are not already in there
                         */
                        dependencies.map(
                            function (dependency) {
                                if (loading.indexOf(dependency) === -1) {
                                    loading.push(dependency);
                                }
                            }
                        )
                    }

                    /**
                     * Ok - now we have a super good idea of which components still need to load -
                     * they live in the 'loading' list.
                     *
                     * At this point - the runtime components are created, but they are not ready
                     * to be used. They may have dependencies to other components, which still need
                     * to load, or may never be loaded.
                     *
                     * It is however safe, to announce, that we created the
                     * runtime version of it, however it could still have some dependencies.
                     *
                     * The Linking system will then kick in and try to resolve all dependencies
                     */

                    if (onComponentLoaded) {
                        onComponentLoaded(runtimeComponent);
                    }

                    GameLib.Event.Emit(
                        GameLib.Event.COMPONENT_CREATED,
                        {
                            component: runtimeComponent
                        }
                    );

                    var toProcess = GameLib.Utils.Difference(loaded.map(function(component){return component.id}), loading);

                    if (toProcess.length === 0) {
                        GameLib.Event.Emit(
                            GameLib.Event.COMPONENT_DOWNLOAD_COMPLETE,
                            {
                                loaded: loaded
                            }
                        )
                    } else {
                        download.bind(__system)(toProcess.pop(), parentEntity);
                    }
                });
            };
        }(this);

        xhr.onprogress = function(__id) {
            return function (progressEvent) {

                var progress = 0;

                if (progressEvent.total !== 0) {
                    progress = Number(progressEvent.loaded / progressEvent.total);
                    progress *= 100;
                }

                if (onComponentProgress) {
                    onComponentProgress(__id, progress)
                }
            };
        }(id);

        xhr.onerror = function(__id) {
            return function (error) {
                console.warn('component load failed for component ID ' + __id);
                if (onComponentError) {
                    onComponentError(__id, error)
                }
            };
        }(id);

        xhr.open(
            'GET',
            this.apiUrl + '/component/load/' + id
        );

        xhr.send();
    }.bind(this);

};

/**
 * 'Loads' data from a url
 */
GameLib.System.Storage.prototype.load = function(data) {

    if (typeof XMLHttpRequest === 'undefined') {
        console.log('Implement server side load here');
        return;
    }

    if (data.ids && data.ids.length > 0) {
        this.loadComponent(data.ids, data.includeDependencies)(data.ids[0], null);
    } else {
        console.log('No components selected');
    }

};

GameLib.System.Storage.prototype.loadImage = function(data) {

    console.log('loading image : ' + data.image.name);

    var onLoaded = this.onImageLoaded;

    var onProgress = this.onImageProgress;

    var onError = this.onImageError;

    var image = data.image;

    var url = this.apiUploadUrl + image.path + '?ts=' + Date.now();

    var preflight = new XMLHttpRequest();

    preflight.withCredentials = true;

    preflight.open(
        'OPTIONS',
        url
    );

    preflight.setRequestHeader('Content-Type', 'application/json');

    preflight.onload = function() {

        var xhr = new XMLHttpRequest();

        xhr.withCredentials = true;

        xhr.open('GET', url);

        xhr.setRequestHeader('Content-Type', image.contentType);

        xhr.responseType = 'blob';

        xhr.onload = function() {

            try {
                if (this.response.type !== 'application/json') {
                    var url = window.URL.createObjectURL(this.response);
                } else {
                    if (onError) {
                        onError(image, {message:'Image not found'});
                        return;
                    }
                }
            } catch (error) {
                if (onError) {
                    onError(image, {message:'Image not found'});
                    return;
                }
            }
            var img = document.createElement('img');

            img.onload = function() {

                window.URL.revokeObjectURL(url);

                image.instance = img;
                image.loaded = true;
                image.publish(
                    GameLib.Event.IMAGE_INSTANCE_CREATED,
                    {
                        image: image
                    }
                );

                if (onLoaded) {
                    onLoaded(image);
                }
            };

            img.src = url;
        };

        xhr.onprogress = function(progressEvent) {

            var progress = 0;

            if (progressEvent.total !== 0) {
                progress = Number(progressEvent.loaded / progressEvent.total);
                progress *= 100;
            }

            if (onProgress) {
                onProgress(image, progress);
            }

            image.size = progressEvent.total;
        };

        xhr.onerror = function(error) {
            console.warn('image load failed for image ' + image.name);
            if (onError) {
                onError(image, error)
            }
        };

        xhr.send();
    };

    preflight.onerror = function(error) {
        console.warn('image pre-flight request failed for image ' + image.name);
        if (onError) {
            onError(image, error);
        }
    };

    preflight.send();
};

GameLib.System.Storage.prototype.stop = function() {
    this.loginSubscription.remove();
	this.loadSubscription.remove();
	this.saveSubscription.remove();
    this.loadImageSubscription.remove();
};