import {
    HomeServerError,
    RequestAbortError,
    NetworkError
} from "./error.js";

class RequestWrapper {
    constructor(promise, controller) {
        if (!controller) {
            const abortPromise = new Promise((_, reject) => {
                this._controller = {
                    abort() {
                        const err = new Error("fetch request aborted");
                        err.name = "AbortError";
                        reject(err);
                    }
                };
            });
            this._promise = Promise.race([promise, abortPromise]);
        } else {
            this._promise = promise;
            this._controller = controller;
        }
    }

    abort() {
        this._controller.abort();
    }

    response() {
        return this._promise;
    }
}

// todo: everywhere here, encode params in the url that could have slashes ... mainly event ids?
export default class HomeServerApi {
    constructor(homeserver, accessToken) {
        // store these both in a closure somehow so it's harder to get at in case of XSS?
        // one could change the homeserver as well so the token gets sent there, so both must be protected from read/write
        this._homeserver = homeserver;
        this._accessToken = accessToken;
    }

    _url(csPath) {
        return `${this._homeserver}/_matrix/client/r0${csPath}`;
    }

    _request(method, csPath, queryParams = {}, body) {
        const queryString = Object.entries(queryParams)
            .filter(([, value]) => value !== undefined)
            .map(([name, value]) => `${encodeURIComponent(name)}=${encodeURIComponent(value)}`)
            .join("&");
        const url = this._url(`${csPath}?${queryString}`);
        let bodyString;
        const headers = new Headers();
        if (this._accessToken) {
            headers.append("Authorization", `Bearer ${this._accessToken}`);
        }
        headers.append("Accept", "application/json");
        if (body) {
            headers.append("Content-Type", "application/json");
            bodyString = JSON.stringify(body);
        }
        const controller = typeof AbortController === "function" ? new AbortController() : null;
        // TODO: set authenticated headers with second arguments, cache them
        let promise = fetch(url, {
            method,
            headers,
            body: bodyString,
            signal: controller && controller.signal
        });
        promise = promise.then(async (response) => {
            if (response.ok) {
                return await response.json();
            } else {
                switch (response.status) {
                    default:
                        throw new HomeServerError(method, url, await response.json())
                }
            }
        }, err => {
            if (err.name === "AbortError") {
                throw new RequestAbortError();
            } else if (err instanceof TypeError) {
                // Network errors are reported as TypeErrors, see
                // https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch#Checking_that_the_fetch_was_successful
                // this can either mean user is offline, server is offline, or a CORS error (server misconfiguration).
                // 
                // One could check navigator.onLine to rule out the first
                // but the 2 later ones are indistinguishable from javascript.
                throw new NetworkError(err.message);
            }
            throw err;
        });
        return new RequestWrapper(promise, controller);
    }

    _post(csPath, queryParams, body) {
        return this._request("POST", csPath, queryParams, body);
    }

    _put(csPath, queryParams, body) {
        return this._request("PUT", csPath, queryParams, body);
    }

    _get(csPath, queryParams, body) {
        return this._request("GET", csPath, queryParams, body);
    }

    sync(since, filter, timeout) {
        return this._get("/sync", {since, timeout, filter});
    }

    // params is from, dir and optionally to, limit, filter.
    messages(roomId, params) {
        return this._get(`/rooms/${roomId}/messages`, params);
    }

    send(roomId, eventType, txnId, content) {
        return this._put(`/rooms/${roomId}/send/${eventType}/${txnId}`, {}, content);
    }

    passwordLogin(username, password) {
        return this._post("/login", undefined, {
          "type": "m.login.password",
          "identifier": {
            "type": "m.id.user",
            "user": username
          },
          "password": password
        });
    }
}