/*
Copyright 2026 Element Creations Ltd.

SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
Please see LICENSE in the repository root for full details.
*/

import { type FC, useState } from "react";
import { useTranslation } from "react-i18next";
import {
  MicOnIcon,
  MicOffIcon,
} from "@vector-im/compound-design-tokens/assets/web/icons";
import classNames from "classnames";

import styles from "./AudioLevelMeter.module.css";
import {
  useMicrophoneLevel,
  type MicrophoneLevelState,
} from "./useMicrophoneLevel";

// The level is quantised into this many bars. They share the row, so the
// count also sets how thick they are.
const BAR_COUNT = 18;
/**
 * Level below which the meter reads as silent. Above the noise floor of a
 * typical desk microphone, so an idle room does not announce itself as sound.
 */
const SPEECH_THRESHOLD = 0.06;

export interface AudioLevelMeterProps {
  state: MicrophoneLevelState;
}

/**
 * A live indicator of the signal level at the selected microphone.
 *
 * Focusable, so that a screen reader user can put it in focus and hear whether
 * the microphone is picking anything up; the bars alone carry that information
 * for everyone else.
 */
export const AudioLevelMeter: FC<AudioLevelMeterProps> = ({ state }) => {
  const { t } = useTranslation();
  const [focused, setFocused] = useState(false);

  // Bars resting at zero would read as a microphone that hears nothing, which
  // is a different thing and the one people act on.
  if (state.type === "absent")
    return (
      <div className={styles.message} data-testid="mic_absent">
        <MicOffIcon width={24} height={24} aria-hidden />
        <span>{t("audio_menu.mic_absent")}</span>
      </div>
    );

  if (state.type === "denied")
    return (
      <div className={styles.message} data-testid="mic_level_denied">
        <MicOffIcon width={24} height={24} aria-hidden />
        <span>{t("audio_menu.mic_permission_denied")}</span>
      </div>
    );

  const unavailable = state.type === "unavailable";
  const level = state.type === "active" ? state.level : 0;
  const litBars = unavailable ? 0 : Math.round(level * BAR_COUNT);
  const speaking = !unavailable && level >= SPEECH_THRESHOLD;
  const stateText = unavailable
    ? t("audio_menu.mic_unavailable")
    : speaking
      ? t("audio_menu.mic_level_active")
      : t("audio_menu.mic_level_silent");

  return (
    <div
      className={classNames(styles.meter, {
        [styles.unavailable]: unavailable,
      })}
      data-testid="mic_level_meter"
      data-unavailable={unavailable || undefined}
      role="meter"
      // The meter is the only place the "is my microphone working?" answer
      // lives, so it has to be reachable without a pointer even though a
      // meter is not an interactive control.
      // eslint-disable-next-line jsx-a11y/no-noninteractive-tabindex
      tabIndex={0}
      onFocus={() => setFocused(true)}
      onBlur={() => setFocused(false)}
      aria-label={t("audio_menu.mic_level_label")}
      aria-valuemin={0}
      aria-valuemax={1}
      aria-valuenow={level}
      aria-valuetext={stateText}
    >
      <MicOnIcon width={24} height={24} className={styles.icon} aria-hidden />
      <div className={styles.bars}>
        {Array.from({ length: BAR_COUNT }, (_, i) => (
          <span
            key={i}
            className={classNames(styles.bar, { [styles.lit]: i < litBars })}
          />
        ))}
      </div>
      {/* Announces changes only while the meter holds focus, so the level does
          not talk over a screen reader reading the rest of the menu. The text
          stays in the DOM either way: removing it on blur would hand the
          menu's focus trap an empty active element mid-Tab, and it would pull
          focus back into the menu instead of letting it reach the slider. */}
      <span className={styles.srOnly} aria-live={focused ? "polite" : "off"}>
        {stateText}
      </span>
    </div>
  );
};

export interface MicrophoneLevelProps {
  /** The microphone to follow, or undefined if none is selected. */
  deviceId: string | undefined;
  /** Whether to hold a capture and report a level at all. */
  active: boolean;
}

/**
 * The level meter, following a microphone of its own.
 *
 * Re-renders when the level moves to another bar, and only itself.
 */
export const MicrophoneLevel: FC<MicrophoneLevelProps> = ({
  deviceId,
  active,
}) => (
  <AudioLevelMeter state={useMicrophoneLevel(deviceId, active, BAR_COUNT)} />
);