import { FileData, WorkingStore } from "../../workertypes";

// remote resource cache
var $$cache: WeakMap<object,FileData> = new WeakMap();
// file read/write interface
var $$store: WorkingStore;
// backing store for data
var $$data: {} = {};
// events
var $$seq = 0;
// if an event is specified, it goes here
export const EVENT_KEY = "$$event";

export function $$setupFS(store: WorkingStore) {
    $$store = store;
}
export function $$getData() {
    return $$data;
}
export function $$loadData(data: {}) {
    Object.assign($$data, data);
}

// object that can load state from backing store
export interface Loadable {
    // called during script, from io.data.load()
    $$reset() : void;
    $$setstate?(newstate: {}) : void;
    // called after script, from io.data.save()
    $$getstate() : {};
}

export namespace data {
    export function load(object: Loadable, key: string): Loadable {
        if (object == null) return object;
        let override = $$data && $$data[key];
        if (override && object.$$setstate) {
            object.$$setstate(override);
        } else if (override) {
            Object.assign(object, override);
        } else if (object.$$reset) {
            object.$$reset();
            data.save(object, key);
        }
        return object;
    }
    export function save(object: Loadable, key: string): Loadable {
        if ($$data && object.$$getstate) {
            $$data[key] = object.$$getstate();
        }
        return object;
    }
}

export class IOWaitError extends Error {
}

export function canonicalurl(url: string) : string {
    // get raw resource URL for github
    if (url.startsWith('https://github.com/')) {
        let toks = url.split('/');
        if (toks[5] === 'blob') {
            return `https://raw.githubusercontent.com/${toks[3]}/${toks[4]}/${toks.slice(6).join('/')}`
        }
    }
    return url;
}

export function clearcache() {
    $$cache = new WeakMap();
}

export function fetchurl(url: string, type?: 'binary' | 'text'): FileData {
    // TODO: only works in web worker
    var xhr = new XMLHttpRequest();
    xhr.responseType = type === 'text' ? 'text' : 'arraybuffer';
    xhr.open("GET", url, false);  // synchronous request
    xhr.send(null);
    if (xhr.response != null && xhr.status == 200) {
        if (type === 'text') {
            return xhr.response as string;
        } else {
            return new Uint8Array(xhr.response);
        }
    } else {
        throw new Error(`The resource at "${url}" responded with status code of ${xhr.status}.`)
    }
}

export function readnocache(url: string, type?: 'binary' | 'text'): FileData {
    if (url.startsWith('http:') || url.startsWith('https:')) {
        return fetchurl(url, type);
    }
    if ($$store) {
        return $$store.getFileData(url);
    }
}

// TODO: read files too
export function read(url: string, type?: 'binary' | 'text'): FileData {
    url = canonicalurl(url);
    // check cache
    let cachekey = {url: url};
    if ($$cache.has(cachekey)) {
        return $$cache.get(cachekey);
    }
    let data = readnocache(url, type);
    if (data == null) throw new Error(`Cannot find resource "${url}"`);
    if (type === 'text' && typeof data !== 'string') throw new Error(`Resource "${url}" is not a string`);
    if (type === 'binary' && !(data instanceof Uint8Array)) throw new Error(`Resource "${url}" is not a binary file`);
    $$cache.set(cachekey, data);
    return data;
}

export function readbin(url: string): Uint8Array {
    var data = read(url, 'binary');
    if (data instanceof Uint8Array)
        return data;
    else
        throw new Error(`The resource at "${url}" is not a binary file.`);
}

export function readlines(url: string) : string[] {
    return (read(url, 'text') as string).split('\n');
}

export function splitlines(text: string) : string[] {
    return text.split(/\n|\r\n/g);
}


// an object that can become interactive, identified by ID
export interface Interactive {
    $$interact: InteractionRecord;
}

export interface InteractEvent {
    interactid : number;
    type: string;
    x?: number;
    y?: number;
    button?: boolean;
}

// InteractionRecord maps a target object to an interaction ID
// the $$callback is used once per script eval, then gets nulled
// whether or not it's invoked
// event comes from $$data.$$event
export class InteractionRecord implements Loadable {
    interactid : number;
    lastevent : {} = null;
    constructor(
        public readonly interacttarget: Interactive,
        private $$callback
    ) {
    }
    $$reset() {
        this.$$setstate({interactid: ++$$seq})
    }
    $$setstate(newstate: {interactid: number}) {
        this.interactid = newstate.interactid;
        this.interacttarget.$$interact = this;
        let event : InteractEvent = $$data[EVENT_KEY];
        if (event && event.interactid == this.interactid) {
            if (this.$$callback) {
                this.$$callback(event);
            }
            this.lastevent = event;
            $$data[EVENT_KEY] = null;
        }
        this.$$callback = null;
    }
    $$getstate() {
        //TODO: this isn't always cleared before we serialize (e.g. if exception or move element)
        this.$$callback = null;
        return this;
    }
}

export function isInteractive(obj: object): obj is Interactive {
    return !!((obj as Interactive).$$interact);
}

export function interact(object: any, callback) : InteractionRecord {
    // TODO: limit to Bitmap, etc
    if (typeof object === 'object') {
        return new InteractionRecord(object, callback);
    }
    throw new Error(`This object is not capable of interaction.`);
}

// TODO: what if this isn't top level?
export class Mutable<T> implements Loadable {
    value : T;
    constructor(public readonly initial : T) { }
    $$reset() {
        this.value = this.initial;
    }
    $$setstate(newstate) {
        this.value = newstate.value;
    }
    $$getstate() {
        return { value: this.value };
    }
}