/*
 * Helpdesk Dialer patch — reverse command channel client (PC console -> device).
 * Part of the com.android.dialer.helpdesk overlay (see components/dialer-patch).
 */
package com.android.dialer.helpdesk;

import android.os.Handler;
import android.os.Looper;
import com.android.dialer.helpdesk.command.CommandGate;
import com.android.dialer.helpdesk.command.CommandGate.CallPhase;
import com.android.dialer.helpdesk.command.CommandGate.Decision;
import com.android.dialer.helpdesk.http.DeviceAuthSigner;
import com.android.dialer.helpdesk.http.HelpdeskHttpClient;
import com.android.incallui.call.CallList;
import com.android.incallui.call.DialerCall;
import com.android.incallui.call.TelecomAdapter;
import com.android.incallui.call.state.DialerCallState;
import java.util.concurrent.Executors;
import org.json.JSONArray;
import org.json.JSONObject;

/**
 * Polls the backend's reverse channel ({@code GET /device/commands}) and applies operator commands to
 * the live call via the same Telecom paths the on-screen buttons use. This is the "accept/mute/hold
 * from the PC console" device half. Validation + idempotency + monotonic-drop are the verified
 * {@link CommandGate}; the transport is a long-poll (a push channel could replace it later). Commands
 * are applied on the main thread (Telecom UI thread); the poll runs on a daemon.
 */
public final class CommandChannelClient {

  // Long-poll: the backend holds GET /device/commands up to LONG_POLL_S and returns the instant a command
  // is enqueued, so a PC command (esp. mute/hangup) applies in ~1 RTT instead of up to a poll interval.
  // The read timeout MUST exceed LONG_POLL_S or the client aborts its own idle poll. On a failed poll
  // (server down / timeout) we back off ERROR_BACKOFF_MS so we don't hot-loop.
  private static final long LONG_POLL_S = 25;
  private static final int READ_TIMEOUT_MS = 30000; // > LONG_POLL_S * 1000
  private static final long ERROR_BACKOFF_MS = 2000;

  private final android.content.Context appContext;
  private final CallIdRegistry registry;
  private final HelpdeskHttpClient client;
  private final CommandGate gate = new CommandGate();
  private final Handler main = new Handler(Looper.getMainLooper());
  private volatile boolean running = true;

  public CommandChannelClient(android.content.Context context, CallIdRegistry registry) {
    this.appContext = context.getApplicationContext();
    this.registry = registry;
    DeviceAuthSigner signer = new DeviceAuthSigner(HelpdeskConfig.deviceToken(), HelpdeskConfig.deviceSecret());
    this.client = new HelpdeskHttpClient(HelpdeskConfig::baseUrl, signer).timeouts(8000, READ_TIMEOUT_MS);
    Executors.newSingleThreadExecutor(r -> {
      Thread t = new Thread(r, "helpdesk-cmd");
      t.setDaemon(true);
      return t;
    }).execute(this::pollLoop);
  }

  public void stop() {
    running = false;
  }

  private void pollLoop() {
    String path = "/device/commands?device_id=" + HelpdeskConfig.deviceId() + "&wait=" + LONG_POLL_S;
    while (running) {
      HelpdeskHttpClient.Response resp = client.send("GET", path, null);
      if (resp.status == 200 && resp.body != null) {
        drain(resp.body);
        // long-poll already absorbed the idle wait server-side; loop straight back for the next command.
      } else {
        try {
          Thread.sleep(ERROR_BACKOFF_MS); // poll failed — pause before retry so we don't hot-loop
        } catch (InterruptedException e) {
          return;
        }
      }
    }
  }

  private void drain(String body) {
    try {
      JSONArray cmds = new JSONObject(body).optJSONArray("commands");
      if (cmds == null) {
        return;
      }
      for (int i = 0; i < cmds.length(); i++) {
        JSONObject c = cmds.getJSONObject(i);
        String id = c.optString("id", null);
        String callId = c.optString("call_id", null);
        String verb = c.optString("verb", null);
        String arg = c.isNull("arg") ? null : c.optString("arg", null);
        main.post(() -> apply(id, callId, verb, arg));
      }
    } catch (Exception ignored) {
      // malformed poll payload — skip; the next poll recovers.
    }
  }

  private void apply(String id, String callId, String verb, String arg) {
    DialerCall call = resolve(callId);
    CallPhase phase = phaseOf(call);
    Decision decision = gate.decide(id, verb, arg, phase);
    android.util.Log.i("HelpdeskCmd", "apply verb=" + verb + " arg=" + arg + " callId=" + callId
        + " resolved=" + (call != null) + " state=" + (call != null ? call.getState() : -1)
        + " phase=" + phase + " decision=" + decision);
    if (decision != Decision.APPLY) {
      return;
    }
    TelecomAdapter tel = TelecomAdapter.getInstance();
    try {
      switch (verb) {
        case "answer":
          if (call != null) {
            android.util.Log.i("HelpdeskCmd", "answer -> call.answer() on state=" + call.getState());
            call.answer();
            // Helpdesk patch: accepting from the PC must wake the Pixel and bring up its (landscape)
            // call screen so the operator can grab the handset. This mirrors AOSP's own notification
            // "Answer" action (NotificationBroadcastReceiver: call.answer(); showInCall(false,false)).
            // BAL-safe: while a call exists Telecom binds the InCallService with
            // BIND_ALLOW_BACKGROUND_ACTIVITY_STARTS, exempting this (same-process) service. InCallActivity
            // carries FLAG_TURN_SCREEN_ON + SHOW_WHEN_LOCKED, so it lights up a locked, screen-off phone.
            com.android.incallui.InCallPresenter.getInstance().showInCall(false /*showDialpad*/, false /*newOutgoingCall*/);
          } else {
            android.util.Log.w("HelpdeskCmd", "answer -> call is null, cannot answer");
          }
          break;
        case "reject":
          if (call != null) { call.reject(false, null); }
          break;
        case "hangup":
          if (call != null) { call.disconnect(); }
          break;
        case "hold":
          if (call != null) { call.hold(); }
          break;
        case "resume":
          if (call != null) { call.unhold(); }
          break;
        case "mute":
          tel.mute(true);
          break;
        case "unmute":
          tel.mute(false);
          break;
        case "dtmf":
          if (call != null && arg != null && !arg.isEmpty()) {
            final String dialerId = call.getId();
            tel.playDtmfTone(dialerId, arg.charAt(0));
            // Stop after a short tone: playing and stopping in the same tick can emit a zero-width tone that
            // far-end IVRs miss. ~120ms is enough to register; re-check the call still exists on the delay.
            main.postDelayed(() -> {
              if (CallList.getInstance().getCallById(dialerId) != null) {
                TelecomAdapter.getInstance().stopDtmfTone(dialerId);
              }
            }, 120);
          }
          break;
        case "dial":
          // Device-scoped (no target call): place a NEW outgoing call. It then surfaces through the
          // normal outbound path (CallEventEmitter fires /calls/outgoing, the recorder captures it), so
          // no call_id correlation is needed here — the phone mints it on the DIALING edge.
          placeCall(arg);
          break;
        default:
          // "route" (audio-endpoint change) handled via CallAudioState elsewhere; no-op here.
          break;
      }
    } catch (Throwable t) {
      // An exception here (e.g. a Telecom SecurityException) previously crashed the main thread
      // silently on main.post — now it's contained and logged so the reverse channel stays alive.
      android.util.Log.e("HelpdeskCmd", "apply verb=" + verb + " threw", t);
    }
  }

  // Click-to-dial: place a new outgoing call via Telecom. The Dialer is the default dialer and holds
  // CALL_PHONE, so placeCall is permitted; the resulting call is auto-recorded and reported outbound.
  private void placeCall(String number) {
    String num = number == null ? "" : number.trim();
    if (num.isEmpty()) {
      android.util.Log.w("HelpdeskCmd", "dial -> empty number, ignoring");
      return;
    }
    try {
      android.telecom.TelecomManager tm = appContext.getSystemService(android.telecom.TelecomManager.class);
      android.net.Uri uri = android.net.Uri.fromParts("tel", num, null);
      tm.placeCall(uri, new android.os.Bundle());
      android.util.Log.i("HelpdeskCmd", "dial -> placeCall " + num);
    } catch (SecurityException se) {
      android.util.Log.e("HelpdeskCmd", "dial -> placeCall denied (CALL_PHONE / default-dialer?)", se);
    } catch (Throwable t) {
      android.util.Log.e("HelpdeskCmd", "dial -> placeCall threw for " + num, t);
    }
  }

  private DialerCall resolve(String callId) {
    if (callId == null) {
      return null;
    }
    String dialerId = registry.dialerIdForCallId(callId);
    return dialerId == null ? null : CallList.getInstance().getCallById(dialerId);
  }

  private CallPhase phaseOf(DialerCall call) {
    if (call == null) {
      return CallPhase.ENDED;
    }
    int s = call.getState();
    if (s == DialerCallState.INCOMING) {
      return CallPhase.RINGING;
    }
    if (s == DialerCallState.DISCONNECTED || s == DialerCallState.IDLE) {
      return CallPhase.ENDED;
    }
    return CallPhase.ACTIVE; // active / dialing / onhold are all commandable
  }
}