import {mat4Identity, mat4RotateX, mat4RotateY, mat4Translate} from "./math.js";

const MISSING_MODEL_JSON = {
    "textures": {"missing": ":missing"},
    "elements": [
        {
            "from": [0, 0, 0],
            "to": [16, 16, 16],
            "faces": {
                "down": {"texture": "#missing"},
                "up": {"texture": "#missing"},
                "north": {"texture": "#missing"},
                "south": {"texture": "#missing"},
                "west": {"texture": "#missing"},
                "east": {"texture": "#missing"}
            }
        }
    ]
};

export class ModelHandler {
    async process(cache, id, url) {
        if (id === ':missing') return new BlockModel(MISSING_MODEL_JSON);

        try {
            const res = await fetch(url + '.json');
            if (!res.ok) throw new Error(`HTTP ${res.status}`);
            const json = await res.json();

            if (json.parent) {
                const parent = await cache.getAsync(json.parent, 'models');
                json.textures = {...parent.textures, ...json.textures};
                if (!json.elements && parent.elements) {
                    json.elements = parent.elements;
                }
            }
            return new BlockModel(json);
        } catch (e) {
            console.warn(`Model missing/broken (${id}), falling back to :missing`);
            return new BlockModel(MISSING_MODEL_JSON);
        }
    }

    getFallback(id) {
        return new BlockModel(MISSING_MODEL_JSON);
    }
}

const CUBOID_FACES = {
    down: {n: [0, -1, 0], c: [[0, 0, 0], [1, 0, 0], [1, 0, 1], [0, 0, 1]]},
    up: {n: [0, 1, 0], c: [[0, 1, 1], [1, 1, 1], [1, 1, 0], [0, 1, 0]]},
    north: {n: [0, 0, -1], c: [[1, 0, 0], [0, 0, 0], [0, 1, 0], [1, 1, 0]]},
    south: {n: [0, 0, 1], c: [[0, 0, 1], [1, 0, 1], [1, 1, 1], [0, 1, 1]]},
    west: {n: [-1, 0, 0], c: [[0, 0, 0], [0, 0, 1], [0, 1, 1], [0, 1, 0]]},
    east: {n: [1, 0, 0], c: [[1, 0, 1], [1, 0, 0], [1, 1, 0], [1, 1, 1]]}
};

export class BlockModel {
    constructor(json) {
        this.elements = json.elements || [];
        this.textures = json.textures || {};

        this._geometryCache = new Map();
    }

    resolveTexture(ref) {
        if (!ref) return ':missing';

        let val = ref;
        if (ref[0] === '#') {
            let key = ref.slice(1);
            val = this.textures[key];
            while (typeof val === 'string' && val[0] === '#') {
                key = val.slice(1);
                val = this.textures[key];
            }
            if (val && typeof val === 'object' && val.sprite) val = val.sprite;
        }

        if (typeof val === 'string') {
            return val.includes(':') ? val : `minecraft:${val}`;
        }

        return ':missing';
    }

    calculateDefaultUV(faceName, from, to) {
        switch (faceName) {
            case 'up':
                return [from[0], from[2], to[0], to[2]];
            case 'down':
                return [from[0], 16 - to[2], to[0], 16 - from[2]];
            case 'north':
                return [16 - to[0], 16 - to[1], 16 - from[0], 16 - from[1]];
            case 'south':
                return [from[0], 16 - to[1], to[0], 16 - from[1]];
            case 'west':
                return [from[2], 16 - to[1], to[2], 16 - from[1]];
            case 'east':
                return [16 - to[2], 16 - to[1], 16 - from[2], 16 - from[1]];
            default:
                return [0, 0, 16, 16];
        }
    }

    buildGeometry(uvmap, variant = {}) {
        const cacheKey = `${variant.x || 0},${variant.y || 0},${!!variant.uvlock}`;

        if (this._geometryCache.has(cacheKey)) {
            return this._geometryCache.get(cacheKey);
        }

        const pos = [], norm = [], uv = [], tint = [], shade = [], idx = [];
        let vOffset = 0;

        const blockMatrix = mat4Identity(new Float32Array(16));
        mat4Translate(blockMatrix, blockMatrix, [0.5, 0.5, 0.5]);
        if (variant.x) mat4RotateX(blockMatrix, blockMatrix, -variant.x * Math.PI / 180);
        if (variant.y) mat4RotateY(blockMatrix, blockMatrix, -variant.y * Math.PI / 180);
        mat4Translate(blockMatrix, blockMatrix, [-0.5, -0.5, -0.5]);

        for (const el of this.elements) {
            const [fx, fy, fz] = el.from.map(x => x / 16);
            const [tx, ty, tz] = el.to.map(x => x / 16);
            const size = [tx - fx, ty - fy, tz - fz];
            const elementShade = el.shade === false ? 0.0 : 1.0;

            for (const [name, face] of Object.entries(el.faces || {})) {
                const tmpl = CUBOID_FACES[name];

                const texPath = this.resolveTexture(face.texture);
                const a = texPath ? uvmap.get(texPath) : null;
                if (!a) continue;

                const rawUV = face.uv || this.calculateDefaultUV(name, el.from, el.to);
                let u1 = rawUV[0] / 16, v1 = rawUV[1] / 16;
                let u2 = rawUV[2] / 16, v2 = rawUV[3] / 16;

                let texRot = face.rotation || 0;
                if (variant.uvlock && (name === 'up' || name === 'down') && variant.y) {
                    texRot = (texRot - variant.y + 360) % 360;
                }

                const au1 = a.u + u1 * a.du, au2 = a.u + u2 * a.du;
                const av1 = a.v + v1 * a.dv, av2 = a.v + v2 * a.dv;

                let faceUVs;
                if (texRot === 90) faceUVs = [au2, av2, au2, av1, au1, av1, au1, av2];
                else if (texRot === 180) faceUVs = [au2, av1, au1, av1, au1, av2, au2, av2];
                else if (texRot === 270) faceUVs = [au1, av1, au1, av2, au2, av2, au2, av1];
                else faceUVs = [au1, av2, au2, av2, au2, av1, au1, av1];

                const tintable = face.tintindex !== undefined ? 1.0 : 0.0;

                for (let i = 0; i < 4; i++) {
                    const [cx, cy, cz] = tmpl.c[i];
                    let vx = fx + cx * size[0], vy = fy + cy * size[1], vz = fz + cz * size[2];

                    let wx = blockMatrix[0] * vx + blockMatrix[4] * vy + blockMatrix[8] * vz + blockMatrix[12];
                    let wy = blockMatrix[1] * vx + blockMatrix[5] * vy + blockMatrix[9] * vz + blockMatrix[13];
                    let wz = blockMatrix[2] * vx + blockMatrix[6] * vy + blockMatrix[10] * vz + blockMatrix[14];
                    pos.push(wx, wy, wz);

                    let nx = blockMatrix[0] * tmpl.n[0] + blockMatrix[4] * tmpl.n[1] + blockMatrix[8] * tmpl.n[2];
                    let ny = blockMatrix[1] * tmpl.n[0] + blockMatrix[5] * tmpl.n[1] + blockMatrix[9] * tmpl.n[2];
                    let nz = blockMatrix[2] * tmpl.n[0] + blockMatrix[6] * tmpl.n[1] + blockMatrix[10] * tmpl.n[2];
                    norm.push(nx, ny, nz);

                    tint.push(tintable);
                    shade.push(elementShade);
                }

                uv.push(...faceUVs);
                idx.push(vOffset, vOffset + 1, vOffset + 2, vOffset, vOffset + 2, vOffset + 3);
                vOffset += 4;
            }
        }

        const bakedGeometry = {
            positions: new Float32Array(pos),
            normals: new Float32Array(norm),
            uvs: new Float32Array(uv),
            tints: new Float32Array(tint),
            shades: new Float32Array(shade),
            indices: new Uint16Array(idx)
        };

        this._geometryCache.set(cacheKey, bakedGeometry);
        return bakedGeometry;
    }
}