using System.Collections.Generic;
using UnityEngine;

namespace Game.WorldGen
{
    public enum IslandShape { Radial, Square }

    /// <summary>
    /// All parameters for one world. Stored as an asset so you can version several
    /// presets (test island, final island, flat playground, ...) side by side.
    /// </summary>
    [CreateAssetMenu(fileName = "WorldGenSettings", menuName = "Game/World Gen Settings")]
    public class WorldGenSettings : ScriptableObject
    {
        [Header("Output")]
        [Tooltip("Name of the root GameObject that will hold all terrain tiles.")]
        public string worldRootName = "GeneratedWorld";
        [Tooltip("Project folder where TerrainData + shared material assets are saved.")]
        public string outputFolder = "Assets/GAME/World/Generated";

        [Header("World layout")]
        public int seed = 12345;
        [Tooltip("World edge length in meters (square). 6000 = 6 km like ARK: The Island.")]
        public float worldSizeMeters = 6000f;
        [Tooltip("Tiles per side. 6 -> 36 tiles of 1 km.")]
        [Range(1, 16)] public int tilesPerSide = 6;
        [Tooltip("Heightmap resolution per tile. Must be 2^n + 1 (513 / 1025 / 2049 / 4097).")]
        public int heightmapResolution = 1025;
        [Tooltip("Max terrain height in meters (the terrain's Y size).")]
        public float maxHeightMeters = 1000f;
        [Tooltip("Reference sea level as a height fraction. Used for the water plane + splat rules.")]
        [Range(0f, 1f)] public float seaLevel01 = 0.30f;

        [Header("Base terrain noise")]
        [Tooltip("Approx size of the largest land features, in meters.")]
        public float baseFeatureSizeMeters = 1500f;
        [Range(1, 10)] public int baseOctaves = 6;
        [Range(1.5f, 3f)] public float lacunarity = 2f;
        [Range(0.2f, 0.8f)] public float gain = 0.5f;
        [Tooltip("Remaps the raw [0,1] base height -> lets you flatten lowlands or sharpen peaks.")]
        public AnimationCurve heightCurve = AnimationCurve.Linear(0, 0, 1, 1);

        [Header("Domain warp (organic, less grid-like coastlines)")]
        public bool domainWarp = true;
        [Range(0f, 1f)] public float warpStrength = 0.35f;

        [Header("Procedural mountains (ridged)")]
        [Range(0f, 1f), Tooltip("How strongly ridged mountains rise above the base.")]
        public float mountainAmplitude = 0.55f;
        public float mountainFeatureSizeMeters = 2200f;
        [Range(1, 8)] public int mountainOctaves = 5;
        [Tooltip("Size of the regions where mountains are allowed to appear.")]
        public float mountainMaskFeatureSizeMeters = 3500f;
        [Range(0f, 1f), Tooltip("Higher = mountains confined to fewer, tighter ranges.")]
        public float mountainThreshold = 0.55f;

        [Header("Island falloff")]
        public bool island = true;
        public IslandShape islandShape = IslandShape.Radial;
        [Tooltip("Maps normalised distance-from-center (0..1) to a height multiplier (1 center -> 0 edge).")]
        public AnimationCurve falloffCurve = new AnimationCurve(
            new Keyframe(0f, 1f), new Keyframe(0.55f, 1f), new Keyframe(1f, 0f));

        [Header("Hand-placed features")]
        public List<TerrainFeature> features = new List<TerrainFeature>();

        [Header("Auto texturing by height (optional)")]
        [Tooltip("Enable height/slope based auto texturing at bake (and via the Apply button).")]
        public bool autoTexture = false;
        [Tooltip("Alphamap (splatmap) resolution per tile. Higher = smoother blends but more VRAM.")]
        public int alphamapResolution = 1024;
        [Tooltip("Height/slope bands, painted bottom-to-top. Heights are in world meters.")]
        public List<SplatRule> splatRules = new List<SplatRule>();

        [Header("Detail / grass painting")]
        [Tooltip("Grid resolution for painted details (grass meshes). 0 = details disabled. " +
                 "1024 over a 1 km tile ≈ 1 detail cell/m. Must be a multiple of 'per patch'.")]
        public int detailResolution = 1024;
        [Tooltip("Detail cells per patch. detailResolution / this = number of patches per axis.")]
        [Range(8, 128)] public int detailResolutionPerPatch = 32;

        [Header("Terrain quality")]
        [Range(1f, 50f)] public float heightmapPixelError = 5f;
        public float basemapDistance = 1000f;
        public bool drawInstanced = true;

        void Reset()
        {
            heightCurve = AnimationCurve.Linear(0, 0, 1, 1);
            falloffCurve = new AnimationCurve(
                new Keyframe(0f, 1f), new Keyframe(0.55f, 1f), new Keyframe(1f, 0f));
        }

        /// <summary>Validates / repairs values; returns false with a reason if unusable.</summary>
        public bool Validate(out string error)
        {
            error = null;
            if (tilesPerSide < 1) { error = "tilesPerSide must be >= 1."; return false; }
            if (worldSizeMeters <= 0f) { error = "worldSizeMeters must be > 0."; return false; }
            if (!IsPowerOfTwoPlusOne(heightmapResolution))
            {
                error = $"heightmapResolution ({heightmapResolution}) must be 2^n + 1 (e.g. 513, 1025, 2049, 4097).";
                return false;
            }
            if (string.IsNullOrWhiteSpace(outputFolder) || !outputFolder.StartsWith("Assets"))
            {
                error = "outputFolder must be a project path starting with 'Assets'.";
                return false;
            }
            return true;
        }

        public static bool IsPowerOfTwoPlusOne(int v)
        {
            int n = v - 1;
            return n >= 32 && (n & (n - 1)) == 0;
        }
    }
}