expo-ble-app-demo/ble/core/BleClient.ts

import {BleManager, Device, Characteristic, ScanOptions} from 'react-native-ble-plx';
import {Platform} from 'react-native';
import {BleDevice, ConnectionState, BleError, ScanResult} from './types';
import {BLE_UUIDS} from "../protocol/Constants";

export class BleClient {
    private static instance: BleClient;
    private manager: BleManager | null = null;
    private connectedDevice: Device | null = null;

    // Simple event system
    private listeners: Map<string, Set<Function>> = new Map();

    private constructor() {
        if (Platform.OS !== 'web') {
            this.manager = new BleManager();
        }
    }

    public static getInstance(): BleClient {
        if (!BleClient.instance) {
            BleClient.instance = new BleClient();
        }
        return BleClient.instance;
    }

    public addListener(event: string, callback: Function) {
        if (!this.listeners.has(event)) {
            this.listeners.set(event, new Set());
        }
        this.listeners.get(event)!.add(callback);
    }

    public removeListener(event: string, callback: Function) {
        if (this.listeners.has(event)) {
            this.listeners.get(event)!.delete(callback);
        }
    }

    private emit(event: string, ...args: any[]) {
        if (this.listeners.has(event)) {
            this.listeners.get(event)!.forEach(cb => cb(...args));
        }
    }

    public async startScan(
        serviceUUIDs: string[] | null = null,
        options: ScanOptions = {},
        onDeviceFound: (result: ScanResult) => void
    ): Promise<void> {
        if (!this.manager) {
            console.warn('BLE not supported on web');
            return;
        }
        const state = await this.manager.state();
        if (state !== 'PoweredOn') {
            throw new Error(`Bluetooth is not powered on. State: ${state}`);
        }

        this.manager.startDeviceScan(serviceUUIDs, options, (error, device) => {
            if (error) {
                this.emit('scanError', error);
                return;
            }
            if (device) {
                onDeviceFound({
                    device,
                    rssi: device.rssi,
                    localName: device.name
                });
            }
        });
    }

    public async getConnectedDevices(serviceUUIDs: string[]): Promise<BleDevice[]> {
        if (!this.manager) return [];
        try {
            const devices = await this.manager.connectedDevices(serviceUUIDs);
            return devices as BleDevice[];
        } catch (e) {
            throw this.normalizeError(e);
        }
    }

    public stopScan() {
        if (!this.manager) return;
        this.manager.stopDeviceScan();
    }

    public async connect(deviceId: string): Promise<BleDevice> {
        if (!this.manager) throw new Error('BLE not supported on web');
        try {
            this.emit('connectionStateChange', {deviceId, state: ConnectionState.CONNECTING});
            let device = await this.manager.connectToDevice(deviceId, {
                autoConnect: false,
                requestMTU: BLE_UUIDS.REQUEST_MTU
            });
            if (device.mtu < BLE_UUIDS.REQUEST_MTU) {
                console.log(`MTU ${device.mtu} not supported, requesting default to ${BLE_UUIDS.REQUEST_MTU}`);
                device = await device.requestMTU(BLE_UUIDS.REQUEST_MTU);
                // Give some time for the stack to stabilize after MTU change
                await new Promise(resolve => setTimeout(resolve, 500));
            }
            console.log("Connected to device with MTU = ", device.mtu);
            this.connectedDevice = await device.discoverAllServicesAndCharacteristics();
            this.emit('connectionStateChange', {deviceId, state: ConnectionState.CONNECTED});

            // Handle disconnection monitoring
            device.onDisconnected((error, disconnectedDevice) => {
                this.connectedDevice = null;
                this.emit('connectionStateChange', {
                    deviceId: disconnectedDevice.id,
                    state: ConnectionState.DISCONNECTED
                });
                this.emit('disconnected', disconnectedDevice);
            });

            return this.connectedDevice;
        } catch (error: any) {
            this.emit('connectionStateChange', {deviceId, state: ConnectionState.DISCONNECTED});
            throw this.normalizeError(error);
        }
    }

    public async disconnect(deviceId?: string): Promise<void> {
        const id = deviceId || this.connectedDevice?.id;
        if (!id) return;
        if (!this.manager) return;

        try {
            this.emit('connectionStateChange', {deviceId: id, state: ConnectionState.DISCONNECTING});
            await this.manager.cancelDeviceConnection(id);
            // onDisconnected callback will handle the state update
        } catch (error: any) {
            throw this.normalizeError(error);
        }
    }

    public async read(
        deviceId: string,
        serviceUUID: string,
        characteristicUUID: string
    ): Promise<string> {
        if (!this.manager) throw new Error('BLE not supported on web');
        try {
            const char = await this.manager.readCharacteristicForDevice(
                deviceId,
                serviceUUID,
                characteristicUUID
            );
            return char.value || ''; // Base64 string
        } catch (e) {
            throw this.normalizeError(e);
        }
    }

    public async write(
        deviceId: string,
        serviceUUID: string,
        characteristicUUID: string,
        dataBase64: string,
        response: boolean = true
    ): Promise<Characteristic> {
        if (!this.manager) throw new Error('BLE not supported on web');
        let result: Characteristic | null;
        try {
            if (response) {
                result = await this.manager.writeCharacteristicWithResponseForDevice(
                    deviceId, serviceUUID, characteristicUUID, dataBase64
                );
            } else {
                result = await this.manager.writeCharacteristicWithoutResponseForDevice(
                    deviceId, serviceUUID, characteristicUUID, dataBase64
                );
            }
            return result
        } catch (e) {
            throw this.normalizeError(e);
        }
    }

    public async monitor(
        deviceId: string,
        serviceUUID: string,
        characteristicUUID: string,
        listener: (error: BleError | null, value: string | null) => void
    ) {
        if (!this.manager) {
            listener({message: 'BLE not supported on web', errorCode: 0, reason: null}, null);
            return {
                remove: () => {
                }
            };
        }
        return this.manager.monitorCharacteristicForDevice(
            deviceId,
            serviceUUID,
            characteristicUUID,
            (error, char) => {
                if (error) {
                    listener(this.normalizeError(error), null);
                } else {
                    listener(null, char?.value || null);
                }
            }
        );
    }

    public async requestMtu(deviceId: string, mtu: number): Promise<number> {
        if (!this.manager) return 23;
        try {
            const device = await this.manager.requestMTUForDevice(deviceId, mtu);
            return device.mtu;
        } catch (e) {
            console.warn("MTU negotiation failed", e);
            // iOS doesn't allow explicit MTU request usually, so we might ignore or return default
            return 23;
        }
    }

    public getConnectedDevice(): Device | null {
        return this.connectedDevice;
    }

    private normalizeError(e: any): BleError {
        // wrapper to convert PlxError to our BleError
        return {
            errorCode: e.errorCode || 0,
            message: e.message || 'Unknown error',
            reason: e.reason
        };
    }
}