using UnityEngine;
using UnityEditor;
using SplashEdit.RuntimeCode;

namespace SplashEdit.EditorCode
{
    /// <summary>
    /// Custom inspector for PSXSceneExporter.
    /// When the component is selected and fog is enabled, activates a Unity scene-view
    /// fog preview that approximates the PS1 linear fog distances.
    ///
    /// Fog distance mapping:
    ///   fogFarSZ  = 8000 / FogDensity          (GTE SZ units)
    ///   fogNearSZ = fogFarSZ / 3
    ///   SZ is 20.12 fixed-point: SZ = (unityCoord / GTEScaling) * 4096
    ///   => unityDist = SZ * GTEScaling / 4096
    ///   => Unity fog near = (8000 / (FogDensity * 3)) * GTEScaling / 4096
    ///   => Unity fog far  = (8000 / FogDensity) * GTEScaling / 4096
    /// </summary>
    [CustomEditor(typeof(PSXSceneExporter))]
    public class PSXSceneExporterEditor : UnityEditor.Editor
    {
        // Saved RenderSettings state so we can restore it on deselect.
        private bool _savedFog;
        private Color _savedFogColor;
        private FogMode _savedFogMode;
        private float _savedFogStart;
        private float _savedFogEnd;

        private bool _previewActive = false;

        private void OnEnable()
        {
            SaveAndApplyFogPreview();
            // Re-apply whenever the scene is repainted (handles inspector value changes).
            EditorApplication.update += OnEditorUpdate;
        }

        private void OnDisable()
        {
            EditorApplication.update -= OnEditorUpdate;
            RestoreFog();
        }

        private void OnEditorUpdate()
        {
            // Keep the preview in sync when the user tweaks values in the inspector.
            if (_previewActive)
                ApplyFogPreview();
        }

        private void SaveAndApplyFogPreview()
        {
            _savedFog = RenderSettings.fog;
            _savedFogColor = RenderSettings.fogColor;
            _savedFogMode = RenderSettings.fogMode;
            _savedFogStart = RenderSettings.fogStartDistance;
            _savedFogEnd = RenderSettings.fogEndDistance;

            _previewActive = true;
            ApplyFogPreview();
        }

        private void ApplyFogPreview()
        {
            var exporter = (PSXSceneExporter)target;
            if (exporter == null) return;

            if (!exporter.FogEnabled)
            {
                // Fog disabled on the component - turn off the preview.
                RenderSettings.fog = false;
                return;
            }

            float gteScale = exporter.GTEScaling;
            int density = Mathf.Clamp(exporter.FogDensity, 1, 10);

            // fogFarSZ in GTE SZ units (20.12 fp); convert to Unity world-space.
            // SZ = (unityDist / GTEScaling) * 4096, so unityDist = SZ * GTEScaling / 4096
            float fogFarSZ = 8000f / density;
            float fogNearSZ = fogFarSZ / 3f;

            float fogFarUnity = fogFarSZ * gteScale / 4096f;
            float fogNearUnity = fogNearSZ * gteScale / 4096f;

            RenderSettings.fog = true;
            RenderSettings.fogColor = exporter.FogColor;
            RenderSettings.fogMode = FogMode.Linear;
            RenderSettings.fogStartDistance = fogNearUnity;
            RenderSettings.fogEndDistance = fogFarUnity;
        }

        private void RestoreFog()
        {
            if (!_previewActive) return;
            _previewActive = false;

            RenderSettings.fog = _savedFog;
            RenderSettings.fogColor = _savedFogColor;
            RenderSettings.fogMode = _savedFogMode;
            RenderSettings.fogStartDistance = _savedFogStart;
            RenderSettings.fogEndDistance = _savedFogEnd;
        }

        public override void OnInspectorGUI()
        {
            serializedObject.Update();

            DrawDefaultInspector();

            // Show computed fog distances when fog is enabled, so the user
            // can see exactly what range the preview represents.
            var exporter = (PSXSceneExporter)target;
            if (exporter.FogEnabled)
            {
                EditorGUILayout.Space(4);
                EditorGUILayout.BeginVertical(EditorStyles.helpBox);
                GUILayout.Label("Fog Preview (active in Scene view)", EditorStyles.boldLabel);

                float gteScale = exporter.GTEScaling;
                int density = Mathf.Clamp(exporter.FogDensity, 1, 10);
                float fogFarUnity = (8000f / density) * gteScale / 4096f;
                float fogNearUnity = fogFarUnity / 3f;

                EditorGUILayout.LabelField("Near distance", $"{fogNearUnity:F1} Unity units");
                EditorGUILayout.LabelField("Far distance",  $"{fogFarUnity:F1} Unity units");
                EditorGUILayout.LabelField("(PS1 SZ range)", $"{8000f / (density * 3f):F0} - {8000f / density:F0} GTE units");
                EditorGUILayout.EndVertical();

                // Keep preview applied as values may have changed.
                ApplyFogPreview();
            }
            else
            {
                // Make sure preview is off when fog is disabled.
                RenderSettings.fog = false;
            }

            serializedObject.ApplyModifiedProperties();
        }
    }
}