"use strict";
const path = require('path');
const fs = require('fs');

const {BasicError, LoadError, FileError} = require("./errors")
const LoadingFile = require("./loadingFile");
const Queue = require("./queue");
const Dependency = require("./dependency");
const Type = Dependency.Type;
const Module = require("./module");
class Mimicry {
    /**
     * Creates an instance of the Mimicry.
     *
     * @param {Object}                     [config] - configuration of the Mimicry.
     * @param {Number} [config.maxParallelLoadings] - amount of files that are loaded in parallel.
     * @param {String}             [config.baseUrl] - URL prefix that will be added to every.
     * @param {String}                [config.seed] - request optional component allowing to drop user cached files.
     */
    constructor (config) {
        instances.push(this);

        this._queue = new Queue();
        this._loadedFiles = new Set();
        this._config = Object.create(null);
        this._loadingFiles = new Map();
        this._plannedFiles = Object.create(null);
        this._modules = new Map();
        this._typePaths = new Map();
        this._loadedAssets = new Map();
        this._libs = new Map();
        this._errors = new Map();
        this._moduleErrors = [];
        this._errorHandlers = [];
        this._progressHandlers = [];

        Object.assign(this._config, defaultOptions, config);

        this._baseUrl = this._config.baseUrl;
        if (this._baseUrl && !this._baseUrl.endsWith("/"))
            this._baseUrl += "/";

        this._globalErrorHandler = onGlobalError.bind(this);
        //window.addEventListener("error", this._globalErrorHandler);
    }

    /**
     * Finalizes Mimicry, clears as much memory as it can, forgets all the handlers and contexts
     * */
    destructor () {
        //window.off("error", this._globalErrorHandler);

        const index = instances.indexOf(this);
        instances.splice(index, 1);

        delete this._queue;
        delete this._loadedFiles;
        delete this._config;
        delete this._loadingFiles;
        delete this._plannedFiles;
        delete this._modules;
        delete this._typePaths;
        delete this._loadedAssets;
        delete this._libs;
        delete this._errors;
        delete this._moduleErrors;
        delete this._errorHandlers;
        delete this._progressHandlers;
        delete this._globalErrorHandler;
        delete this._baseUrl;

        this.destroyed = true;
    }

    /**
     * Loads a file, calls the callback if it has loaded successfully,
     * calls error callback if there was any sort of error
     *
     * @param {String}                                path - path to the module
     * @param {Function}            [callback=contentType] - a callback that is called after module is loaded
     * @param {Function}               [error=contentType] - a callback that is called if there was an error
     * @param {Mimicry.Type} [contentType=Mimicry.Type.js] - type of the content to load
     */
    load (path, callback, error, contentType) {
        if (!(error instanceof Function) && contentType === undefined) {
            contentType = error;
            error = undefined;
        }
        if (!(callback instanceof Function) && contentType === undefined) {
            contentType = callback;
            callback = undefined;
        }
        if (!contentType)
            contentType = Type.js;

        scheduleLoad.call(this,
            Dependency.refinePath(path, contentType, this._baseUrl, this._typePaths, this._libs),
            callback, error, contentType, path);
    }

    /**
     * Declares a module.
     * The mainstream way to use Mimicry is to declare modules.
     * It's best If you declare one module per file.
     *
     * The best way to export anything from the module is to return it from the callback
     *
     * @param {Array<String>} dependencies - list of module names that this module depends on
     * @param {Function}        [callback] - module body that will be executed as soon all dependencies are resolved
     */
    module (dependencies, callback) {
        const href = getCurrentHref();
        if (!href.length)
            throw new Error("Couldn't understand module path");

        const moduleName = Dependency.nameFromHref(href, this._baseUrl, this._typePaths, this._libs);
        if (this._modules.has(moduleName))
            throw new Error("An attempt to declare more than one module per file (" + moduleName + ")");

        const {deps, body} = Dependency.refineModuleArguments(dependencies, callback);
        const module = new Module(deps, body);
        this._modules.set(moduleName, module);

        for (let i = 0; i < deps.length; ++i) {
            const element = deps[i];
            const contentType = element.contentType;
            const elName = element.name;

            this.load(elName, loadedFileForModule.bind(this, module, elName), contentType);
        }

        if (module.allDependenciesResolved)
            module.execute(this, global);
    }

    /**
     * Synchronously returns the module value if it was
     * already loaded and executed, returns undefined otherwise
     * */
    getModule(/*String*/moduleName) {
        const module = this._modules.get(moduleName);
        if (module && module.executed)
            return module.value;
    }

    /**
     * Synchronously returns the asses if it was already loaded, returns undefined otherwise
     * */
    getAsset(/*String*/assetName) {
        const asset = this._loadedAssets.get(assetName);
        if (asset)
            return asset;
    }

    /**
     * If you wish to keep all files of some types in a designated folder of your project
     * you can declare it using this function.
     *
     * Say, you want to have all JSON files in "json" folder, and all CSS files in "styles/css" folder.
     * After calling "mimicry.setTypePath(Mimicry.Type.json, 'json')" and
     * "mimicry.setTypePath(Mimicry.Type.css, 'styles/css')" you can access files from those folders
     * in a following manner
     *
     * "mimicry.load('json/config/main', () => {}, Mimicry.Type.json)" changes to
     * "mimicry.load('config/main', () => {}, Mimicry.Type.json)", and
     *
     * "mimicry.load('styles/css/basic', () => {}, Mimicry.Type.css)" to
     * "mimicry.load('basic', () => {}, Mimicry.Type.css)"
     * */
    setTypePath (/*Type*/type, /*String*/path) {
        if (path && !path.endsWith("/"))
            path += "/";

        this._typePaths.set(type, path);
    }

    /**
     * You might want to include other projects in your project. I will call those imported subprojects libraries
     * In mimicry there is a way to hide actual path behind library name.
     *
     * Say you included a library called "flame", and placed in "libs/external/flame".
     * After calling "mimicry.setLibPath('flame', 'libs/external/flame')" you can access files from those libraries
     * in a following manner
     *
     * "mimicry.load('libs/external/flame/index', () => {})" changes to
     * "mimicry.load('@flame/index', () => {})"
     * */
    setLibPath (/*String*/libraryName, /*String*/libraryPath) {
        const path = this._libs.get(libraryName);
        if (path && path !== libraryPath)
            throw new Error("Mimicry error: library " + libraryName + " already had a path " + path +
                ", assigning new path " + libraryPath + " would probably break everything");

        this._libs.set(libraryName, libraryPath);
    }
    /**
     * Adds a handler for you to handle errors that this instance of mimicry
     * faces loading and evaluating files.
     *
     * These handlers get called after (if there was any) error callbacks passed to load operations.
     *
     * @param {Function} handler - a handler that would be called in case of error
     *
     * Handler is called with a single argument of error, which can one of the following types:
     * - Mimicry.FileError - if there was an error on file evaluation
     * - Mimicry.LoadError - if mimicry could not load a file
     * */
    addErrorHandler (handler) {
        this._errorHandlers.push(handler);
    }

    /**
     * Method provides you information about the progress of your loads.
     * Sometimes when you load lots of files in bulk you wish to show a progress indicator.
     *
     * @param {Function} handler - a handler which is called when the progress changes
     * Passed handler is called with following arguments:
     *  {Number}  loaded - how many files mimicry have loaded so far
     *  {Number} pending - how many files are currently loading or in a queue
     *  {Number}   total - how many files does mimicry even know about
     * */
    addProgressHandler (handler) {
        this._progressHandlers.push(handler);
    }
    /**
     * If you use Mimicry in a script file included right after mimicry
     * it might not be able to work yet: it doesn't yet have some classes for normal work.
     * In this "unready" state you can not
     * - access Mimicry.FileError nad Mimicry.LoadError classes
     * - access Mimicry.Type enum.
     *
     * You can, however, perform default (meaning Mimicry.type.js) loads, declare modules,
     * set up paths, and subscribe to handlers.
     *
     * @returns {Boolean} - if the instance is ready to be used
     * */
    get ready () {return true;}

    /**
     * @returns {Number} - amount of files that are currently loading or in a queue
     * */
    get pendingFilesAmount () {return this._loadingFiles.size + this._queue.length;}

    /**
     * @returns {Number} - amount of files mimicry have loaded until this moment
     * */
    get loadedFilesAmount () {return this._loadedFiles.size;}

    /**
     * @returns {Object} - default mimicry options object
     * */
    static get defaultOptions () {return defaultOptions;}

    /**
     * If you use Mimicry in a script file included right after mimicry
     * it might not be able to work yet: it doesn't yet have some classes for normal work.
     * In this "unready" state you can not
     * - access Mimicry.FileError nad Mimicry.LoadError classes
     * - access Mimicry.Type enum.
     *
     * You can, however, perform default (meaning Mimicry.type.js) loads, declare modules,
     * set up paths, and subscribe to handlers.
     *
     * This state is on the static level: once all necessary files are loaded all mimicry instances are
     * ready and don't need to be waited on
     *
     * @returns {Boolean} - if the Mimicry system is ready to be used
     * */
    static get ready () {return true;}

    /**
     * Normally mimicry loads .js files, but you can also load other stuff like json, or css, or binary
     * I expect you to pass values from this enum to specify what exactly you are loading if it is not a
     * JavaScript file
     *
     * @returns {Mimicry.Type} - type of content
     * */
    static get Type () {return Type;}
    static get FileError() {return FileError;}
    static get LoadError() {return LoadError;}
}

const defaultOptions = {
    maxParallelLoadings: 10,
    baseUrl: "",
    seed: ""
};
Object.freeze(defaultOptions)

function callCallback(/*Function*/callback, /*String*/originalName) {
    if (callback instanceof Function) {
        const module = this._modules.get(originalName);
        if (module) {
            module.addCallback(callback, global);
        } else {
            const asset = this._loadedAssets.get(originalName);
            if (asset)
                callback(asset);
            else
                callback(global);
        }
    }
}

/**
 * @param {String}         path
 * @param {Function}   callback
 * @param {Function}      error
 * @param {Type}    contentType
 * @param {String} originalName
 * */
function scheduleLoad (path, callback, error, contentType, originalName) {
    if (this._loadedFiles.has(path))
        return callCallback.call(this, callback, originalName);

    let loadingFile = this._loadingFiles.get(path);
    if (loadingFile === undefined)
        loadingFile = this._plannedFiles[path];

    if (loadingFile) {
        Dependency.checkContentType(loadingFile.contentType, contentType, path);
        loadingFile.addSuccessHandler(callback);
        loadingFile.addErrorHandler(error);
        return;
    }

    loadingFile = new LoadingFile(contentType, originalName, callback, error);
    if (this._loadingFiles.size < this._config.maxParallelLoadings) {
        executeLoad.call(this, path, loadingFile);
    } else {
        this._queue.push(path);
        this._plannedFiles[path] = loadingFile;
    }

    notifyProgressSubscribers.call(this);
}

function executeLoad (/*String*/path, /*LoadingFile*/loadingFile) {
    this._loadingFiles.set(path, loadingFile);

    const boundLoad = onLoaded.bind(this, path);
    const boundError = onError.bind(this, path);
    switch (loadingFile.contentType) {
        case Type.js:
            try {
                require("./" + path);
                this._loadedFiles.add(path);
                setTimeout(boundLoad, 0);
            } catch (e) {
                this._errors.set(path, e);
                setTimeout(boundError, 0);
            }
            break;
        case Type.json:
            try {
                const json = require("./" + path);
                this._loadedFiles.add(path);
                setTimeout(onLoaded.bind(this, path, json), 0);
            } catch (e) {
                this._errors.set(path, e);
                setTimeout(boundError, 0);
            }
            break;
        case Type.css:
            setTimeout(boundLoad, 0);   //todo just for now, don't know what to do yet with css here
            //getStylesheetWithTag(path, boundLoad, boundError, this._config.seed);
            break;
        case Type.binary:
            //getByXHR(path, boundLoad, boundError, "arraybuffer", this._config.seed);
            break;
        case Type.text:
            fs.readFile(path, "utf8", onFileRead.bind(this, path));
            //getByXHR(path, boundLoad, boundError, "text", this._config.seed);
            break;
    }
}

function notifyProgressSubscribers() {
    const pending = this.pendingFilesAmount;
    const loaded = this.loadedFilesAmount;
    for (let i = 0; i < this._progressHandlers.length; ++i) {
        const handler = this._progressHandlers[i];
        handler(loaded, pending, loaded + pending);
    }
}

function onLoaded(/*String*/path, /*any*/value) {
    if (this._moduleErrors.length)
        return onModuleError.call(this, path, value);

    const loading = this._loadingFiles.get(path);
    this._loadedFiles.add(path);
    switch (loading.contentType) {
        case Type.json:
        case Type.binary:
        case Type.text:
            this._loadedAssets.set(loading.originalName, value);
            break;
    }
    loading.callSuccessHandlers(callCallback, this);
    cleanUp.call(this, path);
    checkNextElement.call(this);
    notifyProgressSubscribers.call(this);
}

function onFileRead (/*String*/path, err, value) {
    if (err) {
        this._errors.set(path, err);
        onError.call(this, path)
    } else {
        onLoaded.call(this, path, value);
    }
}

function onError (/*String*/path) {
    const loading = this._loadingFiles.get(path);
    let error = this._errors.get(path);
    if (!(error instanceof BasicError))
        error = new LoadError(path, loading.originalName);

    loading.callErrorHandlers(error);
    for (let i = 0; i < this._errorHandlers.length; ++i)
        this._errorHandlers[i](error);

    cleanUp.call(this, path);
    checkNextElement.call(this);
    notifyProgressSubscribers.call(this);
}

function onModuleError (/*String*/path) {
    for (let i = 0; i < this._moduleErrors.length; ++i) {
        const error = this._moduleErrors[i];
        error.path = path;

        for (let i = 0; i < this._errorHandlers.length; ++i)
            this._errorHandlers[i](error)
    }
    this._moduleErrors = [];
    cleanUp.call(this, path);
    checkNextElement.call(this);
    notifyProgressSubscribers.call(this);
}

function cleanUp (/*String*/path) {
    const loading = this._loadingFiles.get(path);
    this._loadingFiles.delete(path);
    this._errors.delete(path);
    switch (loading.contentType) {
        case Type.js:
            //todo don't know yet
            break;
        case Type.css:
            //todo don't know yet
            break;
        case Type.json:
        case Type.binary:
        case Type.text:
            //todo dont know yet
            break
    }
    loading.destructor();
}

function onGlobalError (event, url, line, col, errorObj) {
    let message;
    if (event instanceof ErrorEvent) {
        url = event.filename;
        line = event.lineno;
        col = event.colno;
        errorObj = event.error;
        message = event.message;
    } else {
        message = event;
    }
    if (url && url.indexOf(location.origin) === 0)
        url = url.slice(location.origin.length);

    if (!setFileError(url, message, line, col, errorObj)) {
        let href = getCurrentHref();
        const index = url.lastIndexOf(href);
        if (href.length && index === url.length - href.length)
            setFileError(href, message, line, col, errorObj)
    }
}

function setFileError(name, message, line, col, errorObj) {
    let result = true;
    let loading = this._loadingFiles.get(name);
    if (loading instanceof LoadingFile)
        this._errors.set(name, new FileError(name, loading.originalName, message, line, col, errorObj));
    else
        result = false;

    return result;
}

function checkNextElement () {
    while (!this._queue.empty && (this._loadingFiles.size < this._config.maxParallelLoadings)) {
        const path = this._queue.pop();
        const loadingFile = this._plannedFiles[path];
        delete this._plannedFiles[path];
        executeLoad.call(this, path, loadingFile);
    }
}

function getCurrentHref() {
    return path.relative(__dirname, _getCallerFile());
}

function _getCallerFile() {
    let caller;
    try {
        const err = new Catcher();
        let current = err.stack.shift().getFileName();

        while (err.stack.length) {
            caller = err.stack.shift().getFileName();

            if (current !== caller)
                break;
        }
    } catch (e) {}

    return caller;
}

class Catcher {
    constructor(...args) {
        const err = new Error(args);
        Error.prepareStackTrace = Catcher.prepareStackTrace;
        this._stack = err.stack;
        Error.prepareStackTrace = defaultPrepareStackTrace;
    }
    get stack () {return this._stack;}
    static prepareStackTrace (err, stack) {return stack;}
}
const defaultPrepareStackTrace = Error.prepareStackTrace;

function loadedFileForModule (/*Module*/requester, /*String*/fileName) {
    const dep = this._modules.get(fileName);
    if (dep)
        dep.addCallback(requester.incrementDependency.bind(requester, this, global), global);
    else
        requester.incrementDependency(this, global);
}

const instances = [];

module.exports = Mimicry;