using UnityEngine;
#if ENABLE_INPUT_SYSTEM
using UnityEngine.InputSystem;
#endif

/// <summary>
/// Fixed lobby camera. The view doesn't move on its own or with the mouse: left clicking a
/// ViewTarget (the tank, the computer monitor) glides the camera face on and close to it, and
/// right clicking glides back to the lobby view the scene was built with.
/// </summary>
[RequireComponent(typeof(Camera))]
public class LobbyCamera : MonoBehaviour
{
    [Tooltip("Seconds for the glide between views.")]
    public float moveTime = 0.8f;
    [Tooltip("The lobby view, set by the scene builder. Used on start and for Back, whatever pose the camera was saved in.")]
    public bool hasHomePose;
    public Vector3 homePosition;
    public Quaternion homeRotation = Quaternion.identity;

    Camera cam;
    Vector3 homePos, fromPos, toPos;
    Quaternion homeRot, fromRot, toRot;
    float t = 1f;
    ViewTarget current, hover;
    /// <summary>Label of the close-up the camera is in, or null in the lobby view.</summary>
    public static string CurrentLabel { get; private set; }
    /// <summary>When true (a browser has the keyboard), only F1 leaves the close-up; Esc/Backspace/scroll are passed through.</summary>
    public static bool CaptureKeys;
    static LobbyCamera instance;
    public static void RequestView(ViewTarget t) { if (instance != null) instance.GoTo(t); }
    ILobbyClickable hoverClick;

    void Start()
    {
        cam = GetComponent<Camera>();
        instance = this;
        if (hasHomePose) transform.SetPositionAndRotation(homePosition, homeRotation);
        homePos = toPos = transform.position;
        homeRot = toRot = transform.rotation;
    }

    void ReadMouse(out Vector2 pos, out bool left, out bool right)
    {
        // "Back" is a right click, Esc, Backspace, or scrolling the wheel toward you
#if ENABLE_INPUT_SYSTEM
        var m = Mouse.current; var k = Keyboard.current;
        pos = m != null ? m.position.ReadValue() : Vector2.zero;
        left = m != null && m.leftButton.wasPressedThisFrame;
        right = (m != null && (m.rightButton.wasPressedThisFrame || m.scroll.ReadValue().y < -0.1f))
             || (k != null && (k.escapeKey.wasPressedThisFrame || k.backspaceKey.wasPressedThisFrame));
#else
        pos = Input.mousePosition;
        left = Input.GetMouseButtonDown(0);
        right = Input.GetMouseButtonDown(1) || Input.mouseScrollDelta.y < -0.1f || Input.GetKeyDown(KeyCode.Escape) || Input.GetKeyDown(KeyCode.Backspace);
#endif
    }

    void Update()
    {
        ReadMouse(out var mouse, out bool left, out bool right);

        hover = null; hoverClick = null;
        if (current == null && cam != null)
        {
            var ray = cam.ScreenPointToRay(mouse);
            var hits = Physics.RaycastAll(ray, cam.farClipPlane);
            System.Array.Sort(hits, (a, b) => a.distance.CompareTo(b.distance));
            foreach (var h in hits)
            {
                var click = h.collider.GetComponent<ILobbyClickable>();
                if (click != null) { hoverClick = click; break; }
                var vt = h.collider.GetComponentInParent<ViewTarget>();
                if (vt != null) { hover = vt; break; }
            }
        }

        if (left && hoverClick != null) hoverClick.Click();
        else if (left && hover != null) GoTo(hover);
        else if (right && current != null && !CaptureKeys) GoHome();

        if (t < 1f)
        {
            t = Mathf.Min(1f, t + Time.deltaTime / Mathf.Max(0.01f, moveTime));
            float e = t * t * (3f - 2f * t);   // ease in and out
            transform.SetPositionAndRotation(Vector3.Lerp(fromPos, toPos, e), Quaternion.Slerp(fromRot, toRot, e));
        }
    }

    void GoTo(ViewTarget target)
    {
        var b = target.Bounds;
        var rot = Quaternion.Euler(target.pitch, 0f, 0f);
        float halfV = cam.fieldOfView * 0.5f * Mathf.Deg2Rad;
        float halfH = Mathf.Atan(Mathf.Tan(halfV) * cam.aspect);
        float dist = Mathf.Max(b.extents.y / Mathf.Tan(halfV), b.extents.x / Mathf.Tan(halfH)) * target.padding + b.extents.z;
        Begin(b.center - rot * Vector3.forward * dist, rot);
        current = target;
        CurrentLabel = target.label;
    }

    void GoHome()
    {
        Begin(homePos, homeRot);
        current = null;
        CurrentLabel = null;
    }

    void Begin(Vector3 pos, Quaternion rot)
    {
        fromPos = transform.position; fromRot = transform.rotation;
        toPos = pos; toRot = rot; t = 0f;
    }

    void OnGUI()
    {
        var style = new GUIStyle(GUI.skin.label) { fontSize = 15 };
        style.normal.textColor = new Color(1f, 1f, 1f, 0.85f);
        if (current != null && !CaptureKeys && GUI.Button(new Rect(14, 40, 90, 30), "Back")) GoHome();
        string msg = current != null ? "Right click, Esc or scroll out to go back"
                   : hoverClick != null ? hoverClick.Hint
                   : hover != null ? hover.label
                   : "Click the tank or the computer to take a closer look";
        GUI.Label(new Rect(14, 10, 800, 26), msg, style);
    }
}