using UnityEngine;

namespace NecromancerTome
{
	/// <summary>
	/// Drains the colour out of the world while the necromancer is channelling something, and
	/// lets it back in when he stops (user request 2026-09-14: "эффект, когда мир становится
	/// тёмным и чёрнобелым... повесить его на момент ожидания применения порталов и на момент
	/// ожидания утаскивания блока", with "желательно плавно... секунды за 3" in both directions).
	/// Shared by both channels so the look, the timing and the name of the effect live in one
	/// place rather than drifting apart in two files.
	///
	/// IT IS THE GAME'S OWN POST-PROCESS, not a reimplementation. EntityPlayerLocal carries a
	/// ScreenEffects component - ScreenEffectManager - whose SetScreenEffect(name, intensity,
	/// fadeTime) is what the engine itself calls for dying ("Dying"), for spawning in
	/// ("VibrantDeSat") and for every buff in the game that tints the screen. THE FADE IS THAT
	/// THIRD ARGUMENT: three seconds in and three seconds out cost nothing to implement, because
	/// the ramp is the effect system's own.
	///
	/// THE EFFECT IS "Greyscale", AND THE CHOICE IS ABOUT WHO ELSE TOUCHES IT. These effects are
	/// a flat namespace of materials loaded from Resources/ScreenEffects - anyone writing to a
	/// name overwrites whatever was there, so picking one is mostly picking a fight to avoid:
	///
	///   - "Greyscale" is written by exactly two things in the whole game, twitch_buffMonochrome
	///     and sandbox_blackandwhite - a Twitch-integration reward and a game-mode toggle. Neither
	///     happens in an ordinary session, so the channel owns it in practice.
	///   - "Dying" and "Dead" are the death visuals the user was describing, and they are exactly
	///     the ones NOT to borrow: EntityPlayerLocal.Update writes "Dying" from the player's own
	///     health every time it changes, so any damage mid-channel would take the effect over -
	///     and being hit mid-channel is a thing that happens.
	///   - "Dark" would have supplied the darkening half. It belongs to buffCrouching, which
	///     fires on every crouch with a 0.2s fade and would stamp on this one.
	///
	/// SO THE DARKENING HALF IS DELIBERATELY NOT DONE. Both effects that dim the screen are owned
	/// by something that fights for them - crouching, and dying - and losing that fight looks like
	/// a bug in this mod rather than in the effect system. Greyscale alone reads as the world
	/// going wrong, which is what was actually asked for; if it wants to be darker too, the list
	/// below takes a second entry and nothing else changes.
	///
	/// NOTHING HERE TOUCHES INPUT. The effect is a camera post-process and outlives the timer
	/// window on purpose: the three-second fade back keeps running while the player walks away,
	/// which is the point of asking for a fade rather than a switch.
	/// </summary>
	public static class ChannelVision
	{
		/// <summary>Seconds to fade in, and to fade back out.</summary>
		public const float FadeSeconds = 3f;

		/// <summary>What to fade, and how far. A list rather than a single name so a second layer
		/// is one entry and not a rewrite - see the class comment on the darkening half.</summary>
		public static readonly string[] EffectNames = { "Greyscale" };

		/// <summary>Full strength per effect, in the same order as EffectNames.</summary>
		public static readonly float[] EffectIntensities = { 1f };

		/// <summary>Colour drains out over FadeSeconds.</summary>
		public static void Begin(EntityPlayerLocal _player)
		{
			Apply(_player, _fullStrength: true);
		}

		/// <summary>Colour comes back over FadeSeconds. Safe to call when nothing is running -
		/// fading an effect that is already at zero to zero does nothing - which is what lets
		/// every exit path call it without first working out whether it is the one that has to.
		/// </summary>
		public static void End(EntityPlayerLocal _player)
		{
			Apply(_player, _fullStrength: false);
		}

		public static void Apply(EntityPlayerLocal _player, bool _fullStrength)
		{
			if (_player == null || _player.ScreenEffectManager == null)
			{
				return;
			}
			for (int i = 0; i < EffectNames.Length; i++)
			{
				float intensity = _fullStrength ? EffectIntensities[i] : 0f;
				_player.ScreenEffectManager.SetScreenEffect(EffectNames[i], intensity, FadeSeconds);
			}
		}
	}
}