import {createEnum} from "../utils/enum.js";
import {ObservableValue} from "../observable/ObservableValue.js";
import {HomeServerApi} from "./net/HomeServerApi.js";
import {Reconnector, ConnectionStatus} from "./net/Reconnector.js";
import {ExponentialRetryDelay} from "./net/ExponentialRetryDelay.js";
import {HomeServerError, ConnectionError, AbortError} from "./error.js";
import {Sync, SyncStatus} from "./Sync.js";
import {Session} from "./Session.js";

export const LoadStatus = createEnum(
    "NotLoading",
    "Login",
    "LoginFailed",
    "Loading",
    "Migrating",    //not used atm, but would fit here
    "FirstSync",
    "Error",
    "Ready",
);

export const LoginFailure = createEnum(
    "Connection",
    "Credentials",
    "Unknown",
);

export class SessionContainer {
    constructor({clock, random, onlineStatus, request, storageFactory, sessionInfoStorage}) {
        this._random = random;
        this._clock = clock;
        this._onlineStatus = onlineStatus;
        this._request = request;
        this._storageFactory = storageFactory;
        this._sessionInfoStorage = sessionInfoStorage;

        this._status = new ObservableValue(LoadStatus.NotLoading);
        this._error = null;
        this._loginFailure = null;
        this._reconnector = null;
        this._session = null;
        this._sync = null;
        this._sessionId = null;
        this._storage = null;
    }

    createNewSessionId() {
        return (Math.floor(this._random() * Number.MAX_SAFE_INTEGER)).toString();
    }

    async startWithExistingSession(sessionId) {
        if (this._status.get() !== LoadStatus.NotLoading) {
            return;
        }
        this._status.set(LoadStatus.Loading);
        try {
            const sessionInfo = await this._sessionInfoStorage.get(sessionId);
            if (!sessionInfo) {
                throw new Error("Invalid session id: " + sessionId);
            }
            await this._loadSessionInfo(sessionInfo);
        } catch (err) {
            this._error = err;
            this._status.set(LoadStatus.Error);
        }
    }

    async startWithLogin(homeServer, username, password) {
        if (this._status.get() !== LoadStatus.NotLoading) {
            return;
        }
        this._status.set(LoadStatus.Login);
        let sessionInfo;
        try {
            const hsApi = new HomeServerApi({homeServer, request: this._request, createTimeout: this._clock.createTimeout});
            const loginData = await hsApi.passwordLogin(username, password).response();
            const sessionId = this.createNewSessionId();
            sessionInfo = {
                id: sessionId,
                deviceId: loginData.device_id,
                userId: loginData.user_id,
                homeServer: homeServer,
                accessToken: loginData.access_token,
                lastUsed: this._clock.now()
            };
            await this._sessionInfoStorage.add(sessionInfo);            
        } catch (err) {
            this._error = err;
            if (err instanceof HomeServerError) {
                if (err.errcode === "M_FORBIDDEN") {
                    this._loginFailure = LoginFailure.Credentials;
                } else {
                    this._loginFailure = LoginFailure.Unknown;
                }
                this._status.set(LoadStatus.LoginFailed);
            } else if (err instanceof ConnectionError) {
                this._loginFailure = LoginFailure.Connection;
                this._status.set(LoadStatus.LoginFailed);
            } else {
                this._status.set(LoadStatus.Error);
            }
            return;
        }
        // loading the session can only lead to
        // LoadStatus.Error in case of an error,
        // so separate try/catch
        try {
            await this._loadSessionInfo(sessionInfo);
        } catch (err) {
            this._error = err;
            this._status.set(LoadStatus.Error);
        }
    }

    async _loadSessionInfo(sessionInfo) {
        this._status.set(LoadStatus.Loading);
        this._reconnector = new Reconnector({
            onlineStatus: this._onlineStatus,
            retryDelay: new ExponentialRetryDelay(this._clock.createTimeout),
            createMeasure: this._clock.createMeasure
        });
        const hsApi = new HomeServerApi({
            homeServer: sessionInfo.homeServer,
            accessToken: sessionInfo.accessToken,
            request: this._request,
            reconnector: this._reconnector,
            createTimeout: this._clock.createTimeout
        });
        this._sessionId = sessionInfo.id;
        this._storage = await this._storageFactory.create(sessionInfo.id);
        // no need to pass access token to session
        const filteredSessionInfo = {
            deviceId: sessionInfo.deviceId,
            userId: sessionInfo.userId,
            homeServer: sessionInfo.homeServer,
        };
        this._session = new Session({storage: this._storage, sessionInfo: filteredSessionInfo, hsApi});
        await this._session.load();
        
        this._sync = new Sync({hsApi, storage: this._storage, session: this._session});
        // notify sync and session when back online
        this._reconnectSubscription = this._reconnector.connectionStatus.subscribe(state => {
            if (state === ConnectionStatus.Online) {
                this._sync.start();
                this._session.start(this._reconnector.lastVersionsResponse);
            }
        });
        await this._waitForFirstSync();

        this._status.set(LoadStatus.Ready);

        // if the sync failed, and then the reconnector
        // restored the connection, it would have already
        // started to session, so check first
        // to prevent an extra /versions request
        
        // TODO: this doesn't look logical, but works. Why?
        // I think because isStarted is true by default. That's probably not what we intend.
        // I think there is a bug here, in that even if the reconnector already started the session, we'd still do this.
        if (this._session.isStarted) {
            const lastVersionsResponse = await hsApi.versions({timeout: 10000}).response();
            this._session.start(lastVersionsResponse);
        }
    }

    async _waitForFirstSync() {
        try {
            this._sync.start();
            this._status.set(LoadStatus.FirstSync);
        } catch (err) {
            // swallow ConnectionError here and continue,
            // as the reconnector above will call 
            // sync.start again to retry in this case
            if (!(err instanceof ConnectionError)) {
                throw err;
            }
        }
        // only transition into Ready once the first sync has succeeded
        this._waitForFirstSyncHandle = this._sync.status.waitFor(s => s === SyncStatus.Syncing || s === SyncStatus.Stopped);
        try {
            await this._waitForFirstSyncHandle.promise;
            if (this._sync.status.get() === SyncStatus.Stopped) {
                if (this._sync.error) {
                    throw this._sync.error;
                }
            }
        } catch (err) {
            // if dispose is called from stop, bail out
            if (err instanceof AbortError) {
                return;
            }
            throw err;
        } finally {
            this._waitForFirstSyncHandle = null;
        }
    }


    get loadStatus() {
        return this._status;
    }

    get loadError() {
        return this._error;
    }

    /** only set at loadStatus InitialSync, CatchupSync or Ready */
    get sync() {
        return this._sync;
    }

    /** only set at loadStatus InitialSync, CatchupSync or Ready */
    get session() {
        return this._session;
    }

    get reconnector() {
        return this._reconnector;
    }

    stop() {
        this._reconnectSubscription();
        this._reconnectSubscription = null;
        this._sync.stop();
        this._session.stop();
        if (this._waitForFirstSyncHandle) {
            this._waitForFirstSyncHandle.dispose();
            this._waitForFirstSyncHandle = null;
        }
        if (this._storage) {
            this._storage.close();
            this._storage = null;
        }
    }

    async deleteSession() {
        if (this._sessionId) {
            // if one fails, don't block the other from trying
            // also, run in parallel
            await Promise.all([
                this._storageFactory.delete(this._sessionId),
                this._sessionInfoStorage.delete(this._sessionId),
            ]);
            this._sessionId = null;
        }
    }
}