import { createBluetooth } from "node-ble";
import type NodeBle from "node-ble";
import { ConnectionError } from "../../utils/errors.ts";
import { logger } from "../../utils/logger.ts";
import type {
  BleBackend,
  BleCharacteristic,
  DiscoveredDevice,
} from "../backend.ts";
import type {
  AdapterInternal,
  BluezInterfacesMap,
  DbusObjectManager,
} from "../../../types/node-ble.d.ts";

const POLL_INTERVAL_MS = 1000;

class DBusCharacteristic implements BleCharacteristic {
  private valueChangedListener: ((buffer: Buffer) => void) | null = null;

  constructor(
    private characteristic: NodeBle.GattCharacteristic,
    public readonly uuid: string,
  ) {}

  async write(data: Buffer, withoutResponse: boolean): Promise<void> {
    if (withoutResponse) {
      await this.characteristic.writeValueWithoutResponse(data);
    } else {
      await this.characteristic.writeValueWithResponse(data);
    }
  }

  async subscribe(onData: (data: Buffer) => void): Promise<void> {
    this.valueChangedListener = onData;
    this.characteristic.on("valuechanged", onData);
    await this.characteristic.startNotifications();
  }

  async unsubscribe(): Promise<void> {
    if (this.valueChangedListener) {
      this.characteristic.removeListener(
        "valuechanged",
        this.valueChangedListener,
      );
      this.valueChangedListener = null;
    }
    await this.characteristic.stopNotifications().catch(() => {});
  }
}

export class DBusBackend implements BleBackend {
  readonly name = "dbus";

  private bluetooth: NodeBle.Bluetooth | null = null;
  private destroy: (() => void) | null = null;
  private adapter: NodeBle.Adapter | null = null;
  private device: NodeBle.Device | null = null;
  private scanning = false;

  async init(): Promise<void> {
    if (this.bluetooth) {
      return;
    }

    const { bluetooth, destroy } = createBluetooth();
    this.bluetooth = bluetooth;
    this.destroy = destroy;

    try {
      this.adapter = await bluetooth.defaultAdapter();
    } catch {
      throw new ConnectionError(
        "No Bluetooth adapter found (is bluetoothd running?)",
      );
    }

    if (!(await this.adapter.isPowered())) {
      throw new ConnectionError("Bluetooth adapter is not powered on");
    }
  }

  private async ensureDiscovering(): Promise<void> {
    if (!this.adapter) {
      throw new ConnectionError("Bluetooth adapter not initialized");
    }
    if (!(await this.adapter.isDiscovering())) {
      await this.adapter.startDiscovery();
    }
    this.scanning = true;
  }

  async scanFor(
    matcher: (device: DiscoveredDevice) => boolean,
    timeoutMs: number,
  ): Promise<DiscoveredDevice | null> {
    if (!this.adapter) {
      throw new ConnectionError("Bluetooth adapter not initialized");
    }

    await this.ensureDiscovering();

    const adapter = this.adapter;
    const named = new Map<string, string | null>();
    const deadline = Date.now() + timeoutMs;

    while (Date.now() < deadline) {
      const addresses = await adapter.devices();

      for (const address of addresses) {
        if (named.get(address)) {
          continue;
        }

        let name: string | null = null;
        try {
          const remoteDevice = await adapter.getDevice(address);
          name = await remoteDevice.getName().catch(async () => {
            return await remoteDevice.getAlias().catch(() => null);
          });
        } catch {
          // device vanished mid-scan??
        }

        if (name && named.get(address) !== name) {
          logger.debug(`Discovered device: ${name} (${address})`);
        }
        named.set(address, name);

        const candidate: DiscoveredDevice = { address, name };
        if (matcher(candidate)) {
          await this.stopScan();
          this.device = await adapter.getDevice(address);
          return candidate;
        }
      }

      await new Promise((resolve) => setTimeout(resolve, POLL_INTERVAL_MS));
    }

    await this.stopScan();
    return null;
  }

  async scanForAll(
    matcher: (device: DiscoveredDevice) => boolean,
    timeoutMs: number,
    onDeviceFound?: (device: DiscoveredDevice) => void,
    signal?: AbortSignal,
  ): Promise<DiscoveredDevice[]> {
    if (!this.adapter) {
      throw new ConnectionError("Bluetooth adapter not initialized");
    }

    await this.ensureDiscovering();

    const adapter = this.adapter;
    const found = new Map<string, DiscoveredDevice>();

    return new Promise<DiscoveredDevice[]>((resolve) => {
      const dbus = (adapter as AdapterInternal).dbus;

      let objectManager: DbusObjectManager | null = null;

      const finish = async () => {
        clearTimeout(timeoutId);
        signal?.removeEventListener("abort", finish);
        if (objectManager) {
          objectManager.removeAllListeners("InterfacesAdded");
        }
        await this.stopScan();
        resolve(Array.from(found.values()));
      };

      const timeoutId = setTimeout(finish, timeoutMs);
      signal?.addEventListener("abort", finish, { once: true });

      const handleDevice = async (
        objectPath: string,
        interfaces: BluezInterfacesMap,
      ) => {
        if (!objectPath.includes("/dev_")) return;
        const iface = interfaces["org.bluez.Device1"];
        if (!iface) return;

        const address: string =
          iface.Address?.value ??
          objectPath.split("/dev_")[1]?.replace(/_/g, ":") ??
          "";
        if (!address || found.has(address)) return;

        const name: string | null =
          iface.Name?.value ?? iface.Alias?.value ?? null;

        if (name) {
          logger.debug(`Discovered device: ${name} (${address})`);
        }

        const candidate: DiscoveredDevice = { address, name };
        if (matcher(candidate)) {
          found.set(address, candidate);
          if (!this.device) {
            this.device = await adapter.getDevice(address).catch(() => null);
          }
          onDeviceFound?.(candidate);
        }
      };

      dbus
        .getProxyObject("org.bluez", "/")
        .then((rootObj) => {
          objectManager = rootObj.getInterface(
            "org.freedesktop.DBus.ObjectManager",
          );
          objectManager.on("InterfacesAdded", handleDevice);

          objectManager
            .GetManagedObjects()
            .then((objects) => {
              for (const [objectPath, interfaces] of Object.entries(objects)) {
                handleDevice(objectPath, interfaces);
              }
            })
            .catch(() => {});
        })
        .catch(() => {
          const poll = async () => {
            if (signal?.aborted) return;
            try {
              const addresses = await adapter.devices();
              for (const address of addresses) {
                if (found.has(address)) continue;
                let name: string | null = null;
                try {
                  const remoteDevice = await adapter.getDevice(address);
                  name = await remoteDevice
                    .getName()
                    .catch(async () =>
                      remoteDevice.getAlias().catch(() => null),
                    );
                } catch {
                  /* ignore */
                }
                if (name)
                  logger.debug(`Discovered device: ${name} (${address})`);
                const candidate: DiscoveredDevice = { address, name };
                if (matcher(candidate)) {
                  found.set(address, candidate);
                  if (!this.device)
                    this.device = await adapter
                      .getDevice(address)
                      .catch(() => null);
                  onDeviceFound?.(candidate);
                }
              }
            } catch {
              /* ignore */
            }
            if (!signal?.aborted) setTimeout(poll, POLL_INTERVAL_MS);
          };
          poll();
        });
    });
  }

  async stopScan(): Promise<void> {
    if (this.adapter && this.scanning) {
      await this.adapter.stopDiscovery().catch(() => {});
      this.scanning = false;
    }
  }

  async connect(address: string): Promise<void> {
    if (!this.adapter) {
      throw new ConnectionError("Bluetooth adapter not initialized");
    }

    if (!this.device) {
      this.device = await this.adapter.getDevice(address);
    }

    if (await this.device.isConnected().catch(() => false)) {
      await this.device.disconnect().catch(() => {});
      await new Promise((resolve) => setTimeout(resolve, 500));
    }

    await this.device.connect();
  }

  onDisconnect(callback: () => void): void {
    this.device?.once("disconnect", callback);
  }

  async discoverCharacteristics(
    writeUUID: string,
    notifyUUID: string,
    normalizeUUID: (uuid: string) => string,
  ): Promise<{ write: BleCharacteristic; notify: BleCharacteristic }> {
    if (!this.device) {
      throw new ConnectionError("Not connected to device");
    }

    const gattServer = await this.device.gatt();
    const serviceUuids = await gattServer.services();

    const normalizedWriteUuid = normalizeUUID(writeUUID);
    const normalizedNotifyUuid = normalizeUUID(notifyUUID);

    let writeChar: { char: NodeBle.GattCharacteristic; uuid: string } | null =
      null;
    let notifyChar: { char: NodeBle.GattCharacteristic; uuid: string } | null =
      null;

    for (const serviceUuid of serviceUuids) {
      const service = await gattServer.getPrimaryService(serviceUuid);
      const charUuids = await service.characteristics();

      for (const charUuid of charUuids) {
        const normalizedCharUuid = normalizeUUID(charUuid);

        if (normalizedCharUuid === normalizedWriteUuid && !writeChar) {
          writeChar = {
            char: await service.getCharacteristic(charUuid),
            uuid: charUuid,
          };
        }
        if (normalizedCharUuid === normalizedNotifyUuid && !notifyChar) {
          notifyChar = {
            char: await service.getCharacteristic(charUuid),
            uuid: charUuid,
          };
        }
      }
    }

    if (!writeChar || !notifyChar) {
      throw new ConnectionError("Could not find required characteristics");
    }

    return {
      write: new DBusCharacteristic(writeChar.char, writeChar.uuid),
      notify: new DBusCharacteristic(notifyChar.char, notifyChar.uuid),
    };
  }

  async disconnect(): Promise<void> {
    try {
      await this.stopScan();

      if (this.device) {
        this.device.removeAllListeners();

        const address = await this.device.getAddress().catch(() => null);

        if (await this.device.isConnected().catch(() => false)) {
          await this.device.disconnect().catch(() => {});
        }

        if (address && this.adapter) {
          const internal = this.adapter as AdapterInternal;
          const devicePath = `/org/bluez/${internal.adapter}/dev_${address.replace(/:/g, "_").toUpperCase()}`;
          await internal.helper.callMethod("RemoveDevice", devicePath).catch(() => {});
        }

        this.device = null;
      }

      this.destroy?.();
      this.destroy = null;
      this.bluetooth = null;
      this.adapter = null;
    } catch {
      // best-effort cleanup
    }
  }
}