"use client";
import * as React from "react";

/** Minimal typing for the Web Speech API (not in lib.dom for every TS target). */
interface SpeechRecognitionLike {
  lang: string;
  continuous: boolean;
  interimResults: boolean;
  start(): void;
  stop(): void;
  abort(): void;
  onresult: ((ev: { resultIndex: number; results: ArrayLike<ArrayLike<{ transcript: string }> & { isFinal: boolean }> }) => void) | null;
  onerror: ((ev: { error: string }) => void) | null;
  onend: (() => void) | null;
}
type SpeechRecognitionCtor = new () => SpeechRecognitionLike;

function getCtor(): SpeechRecognitionCtor | null {
  if (typeof window === "undefined") return null;
  const w = window as unknown as { SpeechRecognition?: SpeechRecognitionCtor; webkitSpeechRecognition?: SpeechRecognitionCtor };
  return w.SpeechRecognition ?? w.webkitSpeechRecognition ?? null;
}

/**
 * Voice dictation via `SpeechRecognition` / `webkitSpeechRecognition`. `supported` is false where the
 * API is missing (Firefox, some WebViews) so the microphone button can be hidden entirely.
 * `onText(final, interim)` receives the accumulated final transcript and the live interim text.
 */
export function useSpeechDictation(onText: (final: string, interim: string) => void, opts: { lang?: string } = {}) {
  const supported = React.useSyncExternalStore(
    () => () => {},
    () => getCtor() !== null,
    () => false,
  );
  const [listening, setListening] = React.useState(false);
  const [error, setError] = React.useState<string | null>(null);
  const recRef = React.useRef<SpeechRecognitionLike | null>(null);
  const finalRef = React.useRef("");
  const cbRef = React.useRef(onText);
  React.useEffect(() => {
    cbRef.current = onText;
  }, [onText]);

  const stop = React.useCallback(() => {
    recRef.current?.stop();
  }, []);

  const start = React.useCallback(() => {
    const Ctor = getCtor();
    if (!Ctor) return;
    const rec = new Ctor();
    rec.lang = opts.lang ?? (typeof navigator !== "undefined" ? navigator.language : "en-US");
    rec.continuous = true;
    rec.interimResults = true;
    finalRef.current = "";
    rec.onresult = (ev) => {
      let interim = "";
      for (let i = ev.resultIndex; i < ev.results.length; i++) {
        const r = ev.results[i];
        const t = r[0]?.transcript ?? "";
        if (r.isFinal) finalRef.current += (finalRef.current && !/\s$/.test(finalRef.current) ? " " : "") + t.trim();
        else interim += t;
      }
      cbRef.current(finalRef.current, interim);
    };
    rec.onerror = (ev) => {
      setError(ev.error === "not-allowed" ? "Microphone access was denied." : ev.error === "no-speech" ? null : `Dictation error: ${ev.error}`);
    };
    rec.onend = () => {
      setListening(false);
      recRef.current = null;
    };
    recRef.current = rec;
    setError(null);
    setListening(true);
    try {
      rec.start();
    } catch {
      setListening(false);
      recRef.current = null;
    }
  }, [opts.lang]);

  const toggle = React.useCallback(() => {
    if (listening) stop();
    else start();
  }, [listening, start, stop]);

  React.useEffect(() => () => recRef.current?.abort(), []);

  return { supported, listening, error, start, stop, toggle };
}