Custodian integration for in-wallet browsers and browser extensions

interface TonConnectBridge {
    deviceInfo: DeviceInfo; // see Requests/Responses spec
    walletInfo?: WalletInfo;
    protocolVersion: number; // max supported Ton Connect version (e.g. 2)
    isWalletBrowser: boolean; // if the page is opened into wallet's browser
    connect(protocolVersion: number, message: ConnectRequest): Promise<ConnectEvent>;
    restoreConnection(): Promise<ConnectEvent>;
    send(message: AppRequest): Promise<WalletResponse>;
    listen(callback: (event: WalletEvent) => void): () => void;
}

npm install @tonconnect/protocol

import {
    AppRequest,
    CHAIN,
    CONNECT_EVENT_ERROR_CODES,
    ConnectEvent,
    ConnectEventSuccess,
    ConnectManifest,
    ConnectRequest,
    DeviceInfo,
    RpcMethod,
    SendTransactionRpcRequest,
    SendTransactionRpcResponseError,
    SendTransactionRpcResponseSuccess,
    TonAddressItem,
    TonProofItem,
    WalletEvent,
    WalletResponse,
} from '@tonconnect/protocol';

export type TonConnectCallback = (event: WalletEvent | DisconnectEvent) => void;

// https://github.com/ton-connect/sdk/blob/main/packages/sdk/src/provider/injected/models/injected-wallet-api.ts
export interface TonConnectBridge {
    deviceInfo: DeviceInfo; // see Requests/Responses spec
    walletInfo?: WalletInfo;
    protocolVersion: number; // max supported Ton Connect version (e.g. 2)
    isWalletBrowser: boolean; // if the page is opened into the wallet's browser
    connect(
        protocolVersion: number,
        message: ConnectRequest,
    ): Promise<ConnectEvent>;

    restoreConnection(): Promise<ConnectEvent>;

    send<T extends RpcMethod>(message: AppRequest<T>): Promise<WalletResponse<T>>;

    listen(callback: TonConnectCallback): () => void;
}

export interface DisconnectEvent {
    event: 'disconnect';
    id: number | string;
    payload: Record<string, never>;
}

export interface WalletInfo {
    name: string;
    image: string; // <png image url>
    tondns?: string;
    about_url: string;
}

// Instance of this class should be injected into the window.[custodian].tonconnect property.
export class JsBridge implements TonConnectBridge {
    deviceInfo: DeviceInfo = {
        platform: 'browser',
        appName: '[custodian]',     // Must match your manifest app_name
        appVersion: '1.0.0',        // Your wallet version
        maxProtocolVersion: 2,      // TON Connect protocol version, currently 2
        features: [
            'SendTransaction',        // Keep 'SendTransaction' as string for backward compatibility
            {                         // And pass the object of 'SendTransaction' feature
                name: 'SendTransaction',
                maxMessages: 4,
                extraCurrencySupported: false
            }
        ]
    };

    isWalletBrowser: boolean = true;
    protocolVersion: number = 2;
    walletInfo: WalletInfo = {
        name: 'walletName',
        about_url: 'about.com',
        image: 'image.png',
    };

    // Refer to https://github.com/ton-blockchain/ton-connect/blob/main/spec/connect.md#connectrequest documentation for more details.
    async connect(protocolVersion: number, request: ConnectRequest): Promise<ConnectEvent> {
        if (protocolVersion > this.protocolVersion) {
            throw new Error('Invalid TON Connect URL');
        }
        // Check if the ton_addr is requested in the connection request, if not, throw an error
        const tonAddrItemRequest: TonAddressItem | null = request.items.find(p => p.name === 'ton_addr') ?? null;
        if (!tonAddrItemRequest) {
            throw new Error("`ton_addr` item is required in the connection request");
        }
        // Check if the ton_proof is requested in the connection request, optional
        const tonProofItemRequest: TonProofItem | null = request.items.find(p => p.name === 'ton_proof') ?? null;

        // Load app manifest
        const manifestUrl: string = request.manifestUrl; // app manifest url
        const manifest: ConnectManifest = await fetch(manifestUrl).then(res => res.json());
        if (!manifest) {
            throw new Error("Failed to load app manifest");
        }

        // 2. Show the connection approval dialog to the user
        const userApproved = await confirm(`Allow ${request.manifestUrl} to connect to your wallet?`);
        if (!userApproved) {
            // User rejected the connection
            throw new Error('User rejected connection'); //
        }

        // 3. Get the user's wallet data from the custodian API
        const walletAddress = '0:9C60B85...57805AC'; // Replace with actual address from custodian API
        const walletPublicKey = 'ADA60BC...1B56B86'; // Replace with actual wallet's public key from custodian API
        const walletStateInit = 'te6cckEBBAEA...PsAlxCarA=='; // Replace with actual wallet's `StateInit` from custodian API

        // 4. Create the connect event
        return {
            event: 'connect',
            id: 0, // The id field is 0 for connect events
            payload: {
                items: [
                    {
                        name: 'ton_addr',
                        address: walletAddress,
                        network: CHAIN.MAINNET,
                        publicKey: walletPublicKey,
                        walletStateInit: walletStateInit
                    }
                    // If ton_proof was requested in the connection request, include it here:
                    // Note: how to get the proof is described in a separate section
                    // {
                    //   name: 'ton_proof',
                    //   proof: {
                    //     // Signed proof data
                    //   }
                    // }
                ],
                device: this.deviceInfo
            }
        };
    }

    private listeners: TonConnectCallback[] = [];

    listen(callback: TonConnectCallback): () => void {
        this.listeners.push(callback);
        return () => {
            this.listeners = this.listeners.filter(listener => listener !== callback);
        }
    }

    // Function to disconnect from a dApp
    // Refer to the https://github.com/ton-blockchain/ton-connect/blob/main/spec/rpc.md#wallet-events documentation for more details.
    async disconnectFromDApp() {
        // Create a disconnect event
        // The id field should be incremented for each sent message
        const disconnectEvent = {
            event: 'disconnect',
            id: nextEventId++,
            payload: {
                reason: 'user_disconnected'
            }
        } as const;

        this.listeners.map(listener => listener(disconnectEvent));
    }


    async restoreConnection(): Promise<ConnectEvent> {
        // 1. Get the user's wallet data from custodian API
        const walletAddress = '0:9C60B85...57805AC'; // Replace with actual address from custodian API
        const walletPublicKey = 'ADA60BC...1B56B86'; // Replace with actual wallet's public key from custodian API
        const walletStateInit = 'te6cckEBBAEA...PsAlxCarA=='; // Replace with actual wallet's `StateInit` from custodian API

        // 2. Create the connect event
        return {
            event: 'connect',
            id: 0, // The id field is 0 for connect events
            payload: {
                items: [
                    {
                        name: 'ton_addr',
                        address: walletAddress,
                        network: CHAIN.MAINNET,
                        publicKey: walletPublicKey,
                        walletStateInit: walletStateInit
                    }
                    // If ton_proof was requested in the connection request, include it here:
                    // Note: how to get the proof is described in a separate section
                    // {
                    //   name: 'ton_proof',
                    //   proof: {
                    //     // Signed proof data
                    //   }
                    // }
                ],
                device: this.deviceInfo
            }
        };
    }

    // Handle messages from dApps
    // Refer to the https://github.com/ton-blockchain/ton-connect/blob/main/spec/rpc.md#sendtransaction documentation for more details.
    // Parameters:
    // - request: The request from the dApp
    send<T extends RpcMethod>(request: AppRequest<T>): Promise<WalletResponse<T>> {
        console.log(`Received message:`, request);

        // Check the message type
        if (request.method === 'sendTransaction') {
            // Handle transaction request
            await handleTransactionRequest(request);
        } else if (request.method === 'disconnect') {
            // Handle disconnect request
            await handleDisconnectRequest(request);
        } else {
            console.warn(`Unknown message method: ${request.method}`);
        }
    }
}

// Handle transaction request
// Parameters:
// - request: The transaction request object from the dApp
async function handleTransactionRequest(request: SendTransactionRpcRequest) {
    // Extract transaction details
    const {id, params} = request;
    let [{network, from, valid_until, messages}] = JSON.parse(params[0]);

    // The wallet should check all the parameters of the request; if any of the checks fail, it should send an error response back to the dApp

    // Check if the selected network is valid
    if (network !== CHAIN.MAINNET) {
        return {
            id: request.id,
            error: {code: 1, message: 'Invalid network ID'},
        } satisfies SendTransactionRpcResponseError;
    }

    // Check if the selected wallet address is valid
    if (!Address.parse(from).equals(Address.parse(sessionData.walletAddress))) {
        return {
            id: request.id,
            error: {
                code: 1,
                message: 'Invalid wallet address'
            },
        } satisfies SendTransactionRpcResponseError;
    }

    // Set limit for valid_until
    const limit = 60 * 5; // 5 minutes
    const now = Math.round(Date.now() / 1000);
    valid_until = Math.min(valid_until ?? Number.MAX_SAFE_INTEGER, now + limit);

    // Check if the transaction is still valid
    if (valid_until < now) {
        return {
            id: request.id,
            error: {
                code: 1,
                message: 'Transaction expired'
            },
        } satisfies SendTransactionRpcResponseError;
    }

    // Check if the messages are valid
    for (const message of messages) {
        if (!message.to || !Address.isFriendly(message.to)) {
            return {
                id: request.id,
                error: {
                    code: 1,
                    message: 'Address is not friendly'
                },
            } satisfies SendTransactionRpcResponseError;
        }

        // Check if the value is a string of digits
        if (!(typeof message.value === 'string' && /^[0-9]+$/.test(message.value))) {
            return {
                id: request.id,
                error: {
                    code: 1,
                    message: 'Value is not a string of digits'
                },
            } satisfies SendTransactionRpcResponseError;
        }

        // Check if the payload is a valid BoC
        if (message.payload) {
            try {
                const payload = Cell.fromBoc(message.payload)[0];
            } catch (e) {
                return {
                    id: request.id,
                    error: {
                        code: 1,
                        message: 'Payload is not valid BoC'
                    },
                } satisfies SendTransactionRpcResponseError;
            }
        }

        // Check if the stateInit is valid BoC
        if (message.stateInit) {
            try {
                const stateInit = Cell.fromBoc(message.stateInit)[0];
            } catch (e) {
                return {
                    id: request.id,
                    error: {
                        code: 1,
                        message: 'StateInit is not valid BoC'
                    },
                } satisfies SendTransactionRpcResponseError;
            }
        }
    }

    if (messages.length === 0) {
        return {
            id: request.id,
            error: {
                code: 1,
                message: 'No messages'
            },
        } satisfies SendTransactionRpcResponseError;
    }

    // Show transaction approval UI to the user
    const userApproved = await confirm(`Approve transaction from ${dAppName}?`);

    // User rejected the transaction - send error response
    if (!userApproved) {
        return {
            id: request.id,
            error: {
                code: 300,
                message: 'Transaction rejected by user'
            },
        } satisfies SendTransactionRpcResponseError;
    }

    if (messages.length > 4) {
        return {
            id: request.id,
            error: {
                code: 1,
                message: 'Too many messages'
            },
        } satisfies SendTransactionRpcResponseError;
    }

    // User approved the transaction - sign it using the custodian API, send signed BoC to the blockchain, and send a success response
    try {
        // Sign the transaction (implementation would depend on custodian API)
        const signedBoc = await signTransactionWithMpcApi(sessionData.walletAddress, messages);

        // Send the signed transaction to the blockchain and wait for the result
        const isSuccess = await sendTransactionToBlockchain(signedBoc);
        if (!isSuccess) {
            throw new Error('Transaction send failed');
        }

        return {
            id: request.id,
            result: signedBoc,
        } satisfies SendTransactionRpcResponseSuccess;
    } catch (error) {
        return {
            id: request.id,
            error: {
                code: 100,
                message: 'Transaction signing failed'
            },
        } satisfies SendTransactionRpcResponseError;
    }
}