import { get } from 'svelte/store';
import { injectDummyDevices, isConnected, isPaired, isConnecting, pairedDevices, availableDevices, activeDeviceId, saveConnectionState, loadConnectionState, targetDeviceId, resetLocal, resetRemote } from './store';
import { BLE } from './protocol/constants';
import { parseIncomingFrame } from './protocol';
import { registerTransport, handleTransportDisconnect, handleTransportConnect } from './transport';
import { addToast, clearAllToasts } from './toast';
import { SETTINGS } from './settings';

let rxCharacteristic: BluetoothRemoteGATTCharacteristic | null = null;
let txCharacteristic: BluetoothRemoteGATTCharacteristic | null = null;
let device: BluetoothDevice | null = null;

export async function restoreSession() {
    try {
        const devices = await getPairedDevices();
        if (devices.length > 0) {
            isPaired.set(true);
            startScanningAdvertisements(devices);

            const savedState = loadConnectionState();
            if (savedState && savedState.autoConnect && savedState.transport === 'ble') {
                const targetDev = devices.find(d => d.id === savedState.deviceId);
                if (targetDev) {
                    addToast("Versuche automatische Wiederverbindung...", "info");
                    await connectBuzzer(targetDev);
                }
            } else if (savedState) {
                targetDeviceId.set(savedState.deviceId);
                device = devices.find(d => d.id === savedState.deviceId) || devices[0];
            } else {
                device = devices[0];
            }
        }
    } catch (error) {
        console.error("Session-Wiederherstellung fehlgeschlagen:", error);
    }
}

async function startScanningAdvertisements(devices: BluetoothDevice[]) {
    for (const dev of devices) {
        // Sicherheits-Check für Mock-Objekte
        if (typeof dev.addEventListener !== 'function') continue;

        dev.addEventListener('advertisementreceived', () => {
            availableDevices.update(set => {
                const newSet = new Set(set);
                newSet.add(dev.id);
                return newSet;
            });
        });

        try {
            // Auch hier vorher prüfen
            if (typeof dev.watchAdvertisements === 'function') {
                await dev.watchAdvertisements();
            }
        } catch (e) {
            console.warn("Scanning für Gerät nicht möglich:", dev.name);
        }
    }
}

export async function pairBuzzer() {
    try {
        const newDevice = await navigator.bluetooth.requestDevice({
            filters: [{ services: [BLE.SERVICE_UUID] }]
        });

        isPaired.set(true);

        const devices = await getPairedDevices();
        startScanningAdvertisements(devices);

        await connectBuzzer(newDevice);

    } catch (error) {
        console.error("Pairing abgebrochen oder fehlgeschlagen", error);
    }
}

export async function connectBuzzer(targetDevice?: BluetoothDevice | Event) {
    console.debug("connectBuzzer aufgerufen");
    if (targetDevice instanceof Event) {
        targetDevice = undefined;
    }

    if (get(isConnecting)) return;

    if (targetDevice) {
        if (device && device.gatt?.connected && device.id !== (targetDevice as BluetoothDevice).id) {
            device.gatt.disconnect();
        }
        device = targetDevice as BluetoothDevice;
    }

    clearAllToasts();

    if (!device) return;

    device.removeEventListener('gattserverdisconnected', handleDisconnect);
    device.addEventListener('gattserverdisconnected', handleDisconnect);

    isConnecting.set(true);
    console.debug("connectBuzzer: Verbindungsversuch mit", device.name);

    const connectionTimeout = setTimeout(() => {
        isConnecting.set(false);
        addToast("Verbindungsaufbau fehlgeschlagen (Timeout).", "error", true);
        handleTransportDisconnect();
    }, SETTINGS.bluetooth.connectionTimeoutMs);

    try {
        const server = await device.gatt?.connect();
        if (!server) throw new Error("GATT Server nicht gefunden");

        const service = await server.getPrimaryService(BLE.SERVICE_UUID);
        rxCharacteristic = await service.getCharacteristic(BLE.RX_UUID);
        txCharacteristic = await service.getCharacteristic(BLE.TX_UUID);

        await txCharacteristic.startNotifications();
        txCharacteristic.addEventListener('characteristicvaluechanged', handleIncomingData);

        clearTimeout(connectionTimeout);

        // Hardware-Setup ist fertig -> Übergabe an den Transport-Layer
        activeDeviceId.set(device.id);
        saveConnectionState({ transport: 'ble', deviceId: device.id, autoConnect: true });
        targetDeviceId.set(device.id);

        addToast(`Verbunden mit <b>${device.name}</b>`, "success");

        // Führt die Requests aus und setzt $isConnected = true
        await handleTransportConnect(sendBleFrame);

    } catch (error) {
        clearTimeout(connectionTimeout);
        const errMsg = error instanceof Error ? error.message : String(error);
        console.error("Bluetooth Fehler während connectBuzzer:", errMsg);

        if (errMsg.includes("no longer in range")) {
            addToast("Geräte-Referenz veraltet (Out of Range). Bitte über den 'Pairen'-Button neu autorisieren.", "error", true);

            if (device) {
                const deadId = device.id;
                pairedDevices.update(devices => devices.filter(d => d.id !== deadId));
                availableDevices.update(set => {
                    const newSet = new Set(set);
                    newSet.delete(deadId);
                    return newSet;
                });
            }
        } else {
            addToast("Verbindungsfehler: " + errMsg, "error");
        }

        handleTransportDisconnect();
    } finally {
        isConnecting.set(false);
    }
}

export function disconnectBuzzer() {
    console.debug("disconnectBuzer aufgerufen");

    if (device) {
        saveConnectionState({
            transport: 'ble',
            deviceId: device.id,
            autoConnect: false
        });

        isConnected.set(false);

        if (device.gatt?.connected) {
            device.gatt.disconnect();
        }
    }
    resetRemote();
    addToast("Verbindung mit <b>" + device.name + "</b> getrennt", "info");
}

export async function forgetDevice(targetDevice: BluetoothDevice) {
    console.debug("forgetDevice aufgerufen");
    try {
        if (targetDevice.gatt?.connected) {
            targetDevice.gatt.disconnect();
        }
        await targetDevice.forget();
        addToast(`Gerät ${targetDevice.name} vergessen`, "success");

        const devices = await getPairedDevices();
        if (devices.length === 0) {
            isPaired.set(false);
        }
    } catch (error) {
        console.error("Fehler beim Löschen des Geräts:", error);
        addToast("Konnte Gerät nicht entfernen", "error", true);
    }
}

export async function getPairedDevices() {
    let rawDevices: BluetoothDevice[] = [];

    // 1. Physische Geräte abrufen, falls die API verfügbar ist
    if ('bluetooth' in navigator && 'getDevices' in navigator.bluetooth) {
        try {
            rawDevices = await navigator.bluetooth.getDevices();
        } catch (error) {
            console.error("Fehler beim Abrufen der gekoppelten Geräte:", error);
        }
    }

    // 2. Physische Geräte in den Store schreiben
    pairedDevices.set(rawDevices);

    // 3. Testdaten anfügen
    injectDummyDevices();

    // 4. Den aktualisierten Store-Inhalt (inkl. Dummies) für die weiterverarbeitenden Funktionen zurückgeben
    return get(pairedDevices);
}

function handleDisconnect() {
    console.debug("handleDisconnect aufgerufen");

    if (get(isConnected)) {
        addToast("Verbindung zu Buzzer verloren", "warning");
    }

    resetRemote();
    registerTransport(null);
    rxCharacteristic = null;
    txCharacteristic = null;
}

function handleIncomingData(event: Event) {
    const target = event.target as BluetoothRemoteGATTCharacteristic;
    if (target.value) {
        parseIncomingFrame(target.value, (buffer) => sendBleFrame(buffer));
    }
}

export async function sendBleFrame(buffer: ArrayBuffer) {
    // TODO: MTU Check einfügen!
    if (!rxCharacteristic) return;
    await rxCharacteristic.writeValueWithoutResponse(buffer);
}