// components/AgentVoiceReply.tsx
// The "Ysterbaard speaks back to me" loop.
//
// Watches the upstream InputMode (driven by VoiceField's onInputModeChange
// callback). When the user submits in voice mode and speak-back is enabled,
// this component auto-narrates the reply through window.speechSynthesis.
// When the user submits in text mode, it stays silent.
//
// The reply text is provided by the parent (the actual agent response).
// This component is purely the orchestration layer — it doesn't generate
// replies itself. Plug it in front of any text-producing assistant.

"use client";

import { useCallback, useEffect, useRef } from "react";
import { useSpeech } from "@/lib/voice/useSpeech";
import type { InputMode } from "@/components/VoiceField";

interface Props {
  /** What the agent wants to say. Empty string = nothing to speak. */
  replyText: string;
  /** Most recent input mode from the upstream VoiceField. */
  inputMode: InputMode;
  /** BCP-47 lang. Defaults to en-ZA. */
  lang?: string;
  /**
   * Whether speak-back is currently enabled by the user. Persisted in
   * localStorage by VoiceField, but the parent can override.
   */
  speakBackEnabled?: boolean;
  /**
   * Bumped each time the parent wants the reply re-spoken (e.g. a new
   * reply arrived). Increments force the speak() effect to re-fire
   * even if the reply text is identical to the previous one.
   */
  replyVersion?: number;
}

const SPEAK_BACK_STORAGE_KEY = "wf:speakBackEnabled";

/**
 * Side-effect component that auto-speaks the agent reply when:
 *   • replyText is non-empty
 *   • the most recent user input was voice
 *   • speak-back is enabled
 *   • a new replyVersion has been emitted
 *
 * Renders nothing visible. Drop it as a sibling of VoiceField.
 *
 *   <VoiceField onInputModeChange={setMode} ... />
 *   <AgentVoiceReply
 *     replyText={agentReply}
 *     inputMode={mode}
 *     speakBackEnabled={speakBackEnabled}
 *     replyVersion={replyVersion}
 *   />
 */
export default function AgentVoiceReply({
  replyText,
  inputMode,
  lang = "en-ZA",
  speakBackEnabled,
  replyVersion = 0
}: Props) {
  const speech = useSpeech({ lang });

  // Read speak-back preference from localStorage if the parent didn't pass one.
  const [persistedEnabled, setPersistedEnabled] = useStatePersistedBoolean(
    SPEAK_BACK_STORAGE_KEY,
    true
  );

  const effectiveEnabled =
    typeof speakBackEnabled === "boolean" ? speakBackEnabled : persistedEnabled;

  const lastSpokenVersionRef = useRef<number>(-1);

  useEffect(() => {
    const trimmed = replyText?.trim();
    if (!trimmed) return;
    if (!effectiveEnabled) return;
    if (inputMode !== "voice") return;
    if (replyVersion === lastSpokenVersionRef.current) return;

    lastSpokenVersionRef.current = replyVersion;
    // Tiny defer so the caller can finish painting the reply text first.
    const t = setTimeout(() => speech.speak(trimmed), 60);
    return () => clearTimeout(t);
  }, [replyText, replyVersion, inputMode, effectiveEnabled, speech]);

  // Cancel any in-flight speech on unmount.
  useEffect(() => {
    return () => {
      speech.cancel();
    };
  }, [speech]);

  // No UI — this is a pure side-effect component.
  return null;
}

/** Tiny localStorage-backed boolean state without a real hook import. */
function useStatePersistedBoolean(
  key: string,
  fallback: boolean
): [boolean, (next: boolean) => void] {
  // We import useState lazily so we don't pay for it when the parent overrides.
  // eslint-disable-next-line @typescript-eslint/no-var-requires
  const { useState, useEffect } = require("react") as typeof import("react");

  const [value, setValue] = useState<boolean>(() => {
    if (typeof window === "undefined") return fallback;
    try {
      const raw = window.localStorage.getItem(key);
      if (raw === null) return fallback;
      return raw === "1";
    } catch {
      return fallback;
    }
  });

  useEffect(() => {
    try {
      window.localStorage.setItem(key, value ? "1" : "0");
    } catch {
      /* ignore */
    }
  }, [key, value]);

  const setter = useCallback((next: boolean) => setValue(next), []);
  return [value, setter];
}