/*
Copyright 2024 New Vector Ltd.
Copyright 2020-2024 The Matrix.org Foundation C.I.C.

SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
Please see LICENSE files in the repository root for full details.
*/

import EventEmitter from "events";
import {
    type KeyBackupInfo,
    VerificationPhase,
    type VerificationRequest,
    VerificationRequestEvent,
    CryptoEvent,
} from "matrix-js-sdk/src/crypto-api";
import { logger } from "matrix-js-sdk/src/logger";
import { type Device, type SecretStorage } from "matrix-js-sdk/src/matrix";

import { MatrixClientPeg } from "../MatrixClientPeg";
import { AccessCancelledError, accessSecretStorage } from "../SecurityManager";
import { asyncSome } from "../utils/arrays";
import { initialiseDehydrationIfEnabled } from "../utils/device/dehydration";

export enum Phase {
    Loading = 0,
    Intro = 1,
    Busy = 2,
    Done = 3, // final done stage, but still showing UX
    ConfirmSkip = 4,
    Finished = 5, // UX can be closed
    ConfirmReset = 6,
}

/**
 * Logic for setting up 4S and/or verifying the user's device: a process requiring
 * ongoing interaction with the user, as distinct from InitialCryptoSetupStore which
 * a (usually) non-interactive process that happens immediately after registration.
 */
export class SetupEncryptionStore extends EventEmitter {
    private started?: boolean;
    public phase?: Phase;
    public verificationRequest: VerificationRequest | null = null;
    public backupInfo: KeyBackupInfo | null = null;
    // ID of the key that the secrets we want are encrypted with
    public keyId: string | null = null;
    // Descriptor of the key that the secrets we want are encrypted with
    public keyInfo: SecretStorage.SecretStorageKeyDescription | null = null;
    public hasDevicesToVerifyAgainst?: boolean;

    public static sharedInstance(): SetupEncryptionStore {
        if (!window.mxSetupEncryptionStore) window.mxSetupEncryptionStore = new SetupEncryptionStore();
        return window.mxSetupEncryptionStore;
    }

    public start(): void {
        if (this.started) {
            return;
        }
        this.started = true;
        this.phase = Phase.Loading;

        const cli = MatrixClientPeg.safeGet();
        cli.on(CryptoEvent.VerificationRequestReceived, this.onVerificationRequest);
        cli.on(CryptoEvent.UserTrustStatusChanged, this.onUserTrustStatusChanged);

        const requestsInProgress = cli.getCrypto()!.getVerificationRequestsToDeviceInProgress(cli.getUserId()!);
        if (requestsInProgress.length) {
            // If there are multiple, we take the most recent. Equally if the user sends another request from
            // another device after this screen has been shown, we'll switch to the new one, so this
            // generally doesn't support multiple requests.
            this.setActiveVerificationRequest(requestsInProgress[requestsInProgress.length - 1]);
        }

        this.fetchKeyInfo();
    }

    public stop(): void {
        if (!this.started) {
            return;
        }
        this.started = false;
        this.verificationRequest?.off(VerificationRequestEvent.Change, this.onVerificationRequestChange);

        const cli = MatrixClientPeg.get();
        if (!!cli) {
            cli.removeListener(CryptoEvent.VerificationRequestReceived, this.onVerificationRequest);
            cli.removeListener(CryptoEvent.UserTrustStatusChanged, this.onUserTrustStatusChanged);
        }
    }

    public async fetchKeyInfo(): Promise<void> {
        if (!this.started) return; // bail if we were stopped
        const cli = MatrixClientPeg.safeGet();
        const keys = await cli.secretStorage.isStored("m.cross_signing.master");
        if (keys === null || Object.keys(keys).length === 0) {
            this.keyId = null;
            this.keyInfo = null;
        } else {
            // If the secret is stored under more than one key, we just pick an arbitrary one
            this.keyId = Object.keys(keys)[0];
            this.keyInfo = keys[this.keyId];
        }

        const ownUserId = cli.getUserId()!;
        const crypto = cli.getCrypto()!;
        // do we have any other verified devices which are E2EE which we can verify against?
        const userDevices: Iterable<Device> =
            (await crypto.getUserDeviceInfo([ownUserId])).get(ownUserId)?.values() ?? [];
        this.hasDevicesToVerifyAgainst = await asyncSome(userDevices, async (device) => {
            // Ignore dehydrated devices. MSC3814 proposes that devices
            // should set a `dehydrated` flag in the device key.
            if (device.dehydrated) return false;

            // ignore devices without an identity key
            if (!device.getIdentityKey()) return false;

            const verificationStatus = await crypto.getDeviceVerificationStatus(ownUserId, device.deviceId);
            return !!verificationStatus?.signedByOwner;
        });

        this.phase = Phase.Intro;
        this.emit("update");
    }

    public async usePassPhrase(): Promise<void> {
        logger.debug("SetupEncryptionStore.usePassphrase");
        this.phase = Phase.Busy;
        this.emit("update");
        try {
            const cli = MatrixClientPeg.safeGet();
            const backupInfo = (await cli.getCrypto()?.getKeyBackupInfo()) ?? null;
            this.backupInfo = backupInfo;
            this.emit("update");

            await new Promise((resolve: (value?: unknown) => void, reject: (reason?: any) => void) => {
                accessSecretStorage(async (): Promise<void> => {
                    // `accessSecretStorage` will call `boostrapCrossSigning` and `bootstrapSecretStorage`, so that
                    // should be enough to ensure that our device is correctly cross-signed.
                    //
                    // The remaining tasks (device dehydration and restoring key backup) may take some time due to
                    // processing many to-device messages in the case of device dehydration, or having many keys to
                    // restore in the case of key backups, so we allow the dialog to advance before this.
                    //
                    // However, we need to keep the 4S key cached, so we stay inside `accessSecretStorage`.
                    logger.debug(
                        "SetupEncryptionStore.usePassphrase: cross-signing and secret storage set up; checking " +
                            "dehydration and backup in the background",
                    );
                    resolve();

                    await initialiseDehydrationIfEnabled(cli);

                    if (backupInfo) {
                        await cli.getCrypto()?.loadSessionBackupPrivateKeyFromSecretStorage();
                        await cli.getCrypto()?.restoreKeyBackup();
                    }
                }).catch(reject);
            });

            if (await cli.getCrypto()?.getCrossSigningKeyId()) {
                logger.debug("SetupEncryptionStore.usePassphrase: done");
                this.phase = Phase.Done;
                this.emit("update");
            }
        } catch (e) {
            if (e instanceof AccessCancelledError) {
                logger.debug("SetupEncryptionStore.usePassphrase: user cancelled access to secret storage");
            } else {
                logger.log("SetupEncryptionStore.usePassphrase: error", e);
            }

            this.phase = Phase.Intro;
            this.emit("update");
        }
    }

    private onUserTrustStatusChanged = async (userId: string): Promise<void> => {
        if (userId !== MatrixClientPeg.safeGet().getSafeUserId()) return;
        const publicKeysTrusted = await MatrixClientPeg.safeGet().getCrypto()?.getCrossSigningKeyId();
        if (publicKeysTrusted) {
            this.phase = Phase.Done;
            this.emit("update");
        }
    };

    public onVerificationRequest = (request: VerificationRequest): void => {
        this.setActiveVerificationRequest(request);
    };

    public onVerificationRequestChange = async (): Promise<void> => {
        if (this.verificationRequest?.phase === VerificationPhase.Cancelled) {
            this.verificationRequest.off(VerificationRequestEvent.Change, this.onVerificationRequestChange);
            this.verificationRequest = null;
            this.emit("update");
        } else if (this.verificationRequest?.phase === VerificationPhase.Done) {
            this.verificationRequest.off(VerificationRequestEvent.Change, this.onVerificationRequestChange);
            this.verificationRequest = null;
            // At this point, the verification has finished, we just need to wait for
            // cross signing to be ready to use, so wait for the user trust status to
            // change (or change to DONE if it's already ready).
            const publicKeysTrusted = await MatrixClientPeg.safeGet().getCrypto()?.getCrossSigningKeyId();
            this.phase = publicKeysTrusted ? Phase.Done : Phase.Busy;
            this.emit("update");
        }
    };

    public skip(): void {
        this.phase = Phase.ConfirmSkip;
        this.emit("update");
    }

    public skipConfirm(): void {
        this.phase = Phase.Finished;
        this.emit("update");
    }

    public returnAfterSkip(): void {
        this.phase = Phase.Intro;
        this.emit("update");
    }

    public reset(): void {
        this.phase = Phase.ConfirmReset;
        this.emit("update");
    }

    public async resetConfirm(): Promise<void> {
        try {
            // If we've gotten here, the user presumably lost their
            // secret storage key if they had one. Start by resetting
            // secret storage and setting up a new recovery key, then
            // create new cross-signing keys once that succeeds.
            await accessSecretStorage(
                async (): Promise<void> => {
                    this.phase = Phase.Finished;
                },
                {
                    forceReset: true,
                    resetCrossSigning: true,
                },
            );
        } catch (e) {
            logger.error("Error resetting cross-signing", e);
            this.phase = Phase.Intro;
        }
        this.emit("update");
    }

    public returnAfterReset(): void {
        this.phase = Phase.Intro;
        this.emit("update");
    }

    public done(): void {
        this.phase = Phase.Finished;
        this.emit("update");
    }

    private async setActiveVerificationRequest(request: VerificationRequest): Promise<void> {
        if (!this.started) return; // bail if we were stopped
        if (request.otherUserId !== MatrixClientPeg.safeGet().getUserId()) return;

        if (this.verificationRequest) {
            this.verificationRequest.off(VerificationRequestEvent.Change, this.onVerificationRequestChange);
        }
        this.verificationRequest = request;
        await request.accept();
        request.on(VerificationRequestEvent.Change, this.onVerificationRequestChange);
        this.emit("update");
    }

    public lostKeys(): boolean {
        return !this.hasDevicesToVerifyAgainst && !this.keyInfo;
    }
}