// Assets/_Project/Scripts/Audio/AudioVolumeSettings.cs
using UnityEngine;

namespace TD.Audio
{
    /// <summary>
    /// Player-facing volume mix, persisted in <see cref="PlayerPrefs"/> and shared by
    /// every audio consumer in the game. Two buses:
    /// <list type="bullet">
    ///   <item><b>Music</b> — the looping scene track played by <see cref="MusicPlayer"/>.</item>
    ///   <item><b>SFX</b> — everything routed through <see cref="AudioManager"/>
    ///         (spells, tower fire, build/land, enemy death, sell, UI clicks).</item>
    /// </list>
    /// </summary>
    /// <remarks>
    /// <para><b>Why not named AudioSettings.</b> <c>UnityEngine.AudioSettings</c> already
    /// exists, so a <c>TD.Audio.AudioSettings</c> would be an ambiguous reference in any
    /// file that has both <c>using UnityEngine;</c> and <c>using TD.Audio;</c>.</para>
    ///
    /// <para><b>Units.</b> Public values are ints 0..100 — the numbers the settings slider
    /// shows. Consumers multiply by <see cref="MusicScalar"/> / <see cref="SfxScalar"/>,
    /// which apply a squared taper so the slider's lower half isn't perceptually dead
    /// (linear amplitude drops off much faster than perceived loudness). At 100 the
    /// scalar is exactly 1, so the default mix is byte-identical to the pre-settings
    /// behaviour.</para>
    ///
    /// <para><b>Live updates.</b> <see cref="OnChanged"/> fires on every mutation.
    /// Continuous sources (music) subscribe and re-apply; one-shots read the scalar at
    /// play time, so a mid-flight SFX keeps the volume it started with. That's fine —
    /// they're all short.</para>
    /// </remarks>
    public static class AudioVolumeSettings
    {
        public const int MinVolume = 0;
        public const int MaxVolume = 100;

        private const int    DefaultVolume = 100;
        private const string MusicKey      = "td.audio.music";
        private const string SfxKey        = "td.audio.sfx";

        /// <summary>Raised whenever music or SFX volume changes.</summary>
        public static event System.Action OnChanged;

        // -1 = not yet read from PlayerPrefs. Statics are cleared on domain reload
        // (entering play mode in the editor), so the lazy load re-runs each session.
        private static int music = -1;
        private static int sfx   = -1;

        public static int MusicVolume
        {
            get
            {
                if (music < 0) music = PlayerPrefs.GetInt(MusicKey, DefaultVolume);
                return music;
            }
            set => Set(ref music, MusicKey, value);
        }

        public static int SfxVolume
        {
            get
            {
                if (sfx < 0) sfx = PlayerPrefs.GetInt(SfxKey, DefaultVolume);
                return sfx;
            }
            set => Set(ref sfx, SfxKey, value);
        }

        /// <summary>Amplitude multiplier (0..1) for the music bus.</summary>
        public static float MusicScalar => ToScalar(MusicVolume);

        /// <summary>Amplitude multiplier (0..1) for the sound-effects bus.</summary>
        public static float SfxScalar => ToScalar(SfxVolume);

        /// <summary>
        /// Flushes PlayerPrefs to disk. Setters only write the in-memory pref (cheap
        /// enough to call on every frame of a slider drag); call this once when the
        /// settings UI closes so the choice survives a crash.
        /// </summary>
        public static void Flush() => PlayerPrefs.Save();

        private static void Set(ref int field, string key, int value)
        {
            int clamped = Mathf.Clamp(value, MinVolume, MaxVolume);
            if (field == clamped) return;
            field = clamped;
            PlayerPrefs.SetInt(key, clamped);
            OnChanged?.Invoke();
        }

        private static float ToScalar(int volume)
        {
            float linear = Mathf.Clamp01(volume / (float)MaxVolume);
            return linear * linear;
        }
    }
}