using UnityEngine;
using UnityEngine.InputSystem;
using System;

/// <summary>
/// Manages gameplay input via Unity's Input System, creating InputActions at runtime
/// and capturing sub-frame press timestamps (AudioSettings.dspTime) for precise judgement.
/// Replaces legacy Input.GetKeyDown polling with event-driven callbacks.
/// </summary>
public class GameplayInputActions : MonoBehaviour
{
    public static GameplayInputActions Instance { get; private set; }

    // Track press/release events. Args: (trackIndex, dspTime at the input event) for sub-frame precision.
    public static event Action<int, double> OnTrackPressed;
    public static event Action<int, double> OnTrackReleased;

    private InputAction[] trackActions = new InputAction[5];
    private InputAction secondaryTrack3Action;
    private bool isEnabled;

    private void Awake()
    {
        if (Instance == null)
        {
            Instance = this;
        }
        else
        {
            Destroy(gameObject);
            return;
        }

        CreateActions();
    }

    private void OnEnable()
    {
        EnableActions();
    }

    private void OnDisable()
    {
        DisableActions();
    }

    private void OnDestroy()
    {
        DisableActions();
        DisposeActions();

        if (Instance == this)
            Instance = null;
    }

    /// <summary>
    /// Create InputActions at runtime and bind them to the keys from KeyBindingManager.
    /// Called once at Awake.
    /// </summary>
    private void CreateActions()
    {
        string[] colors = { "red", "green", "yellow", "purple", "blue" };

        for (int i = 0; i < 5; i++)
        {
            trackActions[i] = new InputAction($"Track{i}", InputActionType.Button);
            string bindingPath = KeyBindingManager.GetBindingPathForTrack(i);
            if (!string.IsNullOrEmpty(bindingPath))
            {
                trackActions[i].AddBinding(bindingPath);
            }

            int trackIndex = i; // capture for closure
            trackActions[i].started += ctx => HandleTrackPress(trackIndex, ctx);
            trackActions[i].canceled += ctx => HandleTrackRelease(trackIndex, ctx);
        }

        // Secondary track 3 key (yellow副键)
        secondaryTrack3Action = new InputAction("Track3Secondary", InputActionType.Button);
        string secondaryPath = KeyBindingManager.GetSecondaryTrack3BindingPath();
        if (!string.IsNullOrEmpty(secondaryPath))
        {
            secondaryTrack3Action.AddBinding(secondaryPath);
        }
        secondaryTrack3Action.started += ctx => HandleTrackPress(2, ctx); // track 2 = yellow
        secondaryTrack3Action.canceled += ctx => HandleTrackRelease(2, ctx);
    }

    private void EnableActions()
    {
        if (isEnabled) return;

        foreach (var action in trackActions)
        {
            action?.Enable();
        }
        secondaryTrack3Action?.Enable();

        isEnabled = true;
    }

    private void DisableActions()
    {
        if (!isEnabled) return;

        foreach (var action in trackActions)
        {
            action?.Disable();
        }
        secondaryTrack3Action?.Disable();

        isEnabled = false;
    }

    private void DisposeActions()
    {
        foreach (var action in trackActions)
        {
            action?.Dispose();
        }
        secondaryTrack3Action?.Dispose();
    }

    /// <summary>
    /// Refresh bindings from KeyBindingManager after user rebinds a key.
    /// Uses ApplyBindingOverride so the action objects (and their event subscriptions) stay intact;
    /// each action has exactly one binding (index 0) created in CreateActions.
    /// </summary>
    public void RefreshBindings()
    {
        bool wasEnabled = isEnabled;
        DisableActions();

        for (int i = 0; i < 5; i++)
        {
            if (trackActions[i] == null) continue;
            string path = KeyBindingManager.GetBindingPathForTrack(i);
            ApplySingleBinding(trackActions[i], path);
        }

        if (secondaryTrack3Action != null)
        {
            string secondaryPath = KeyBindingManager.GetSecondaryTrack3BindingPath();
            ApplySingleBinding(secondaryTrack3Action, secondaryPath);
        }

        if (wasEnabled) EnableActions();
    }

    // Set an action's single binding path. Actions are created with exactly one binding (index 0);
    // if none exists yet (empty path at creation), add one now.
    private static void ApplySingleBinding(InputAction action, string path)
    {
        if (string.IsNullOrEmpty(path)) return;

        if (action.bindings.Count == 0)
        {
            action.AddBinding(path);
        }
        else
        {
            action.ApplyBindingOverride(0, path);
        }
    }

    private void HandleTrackPress(int trackIndex, InputAction.CallbackContext context)
    {
        // Sub-frame precise timestamp: convert the Input System event time (realtime base)
        // into the dspTime axis the whole judgement chain already runs on.
        OnTrackPressed?.Invoke(trackIndex, ResolveEventDspTime(context));
    }

    private void HandleTrackRelease(int trackIndex, InputAction.CallbackContext context)
    {
        OnTrackReleased?.Invoke(trackIndex, ResolveEventDspTime(context));
    }

    // Upper bound (seconds) on how far back an event timestamp may sit before we distrust it.
    // Real input latency between the event occurring and this callback is a few ms at most;
    // anything larger means the timestamp is unusable (e.g. synthetic/queued event) and we
    // fall back to the previous behaviour for exact equivalence.
    private const double MaxEventLatencySeconds = 0.05;

    /// <summary>
    /// Convert an Input System event time (Time.realtimeSinceStartup base) to the
    /// AudioSettings.dspTime axis used by GameplayClock. The event physically occurred
    /// `latency` seconds before this callback runs, so the equivalent dsp instant is
    /// dspTime(now) - latency. Recovers sub-audio-buffer precision without introducing any
    /// systematic offset. Degrades EXACTLY to AudioSettings.dspTime (the prior behaviour)
    /// whenever the event timestamp is missing or out of a sane range — business logic equivalent.
    /// </summary>
    private static double ResolveEventDspTime(InputAction.CallbackContext context)
    {
        double dspNow = AudioSettings.dspTime;

        double eventTime = context.time;
        if (eventTime <= 0d) return dspNow; // no usable timestamp

        double realtimeNow = Time.realtimeSinceStartupAsDouble;
        double latency = realtimeNow - eventTime;

        // Negative (clock skew) or implausibly large latency → distrust, keep old behaviour.
        if (latency < 0d || latency > MaxEventLatencySeconds) return dspNow;

        return dspNow - latency;
    }
}