// DFF (RenderWare Clump) reader.
//
// Layout:  Clump -> FrameList -> GeometryList -> Geometry* -> MaterialList
//                -> Atomic*   (pairs a geometry with a frame)
//
// Only the parts a viewer needs are read: transforms, vertex data, triangles
// and material/texture names. Skinning, collision and 2dfx are skipped.

import { RW, Chunk, Reader, versionString } from './stream.js';

const FLAG_TRISTRIP = 0x0001;
const FLAG_TEXTURED = 0x0004;
const FLAG_PRELIT = 0x0008;
const FLAG_NORMALS = 0x0010;
const FLAG_TEXTURED2 = 0x0080;
const FLAG_NATIVE = 0x01000000;

function parseFrameList(chunk) {
  const r = chunk.structReader();
  const count = r.i32();
  const frames = [];
  for (let i = 0; i < count; i++) {
    // 3x3 basis (right, up, at) then position - already column major for three.js.
    const m = r.f32Array(12);
    const parent = r.i32();
    r.u32(); // matrix flags, unused
    frames.push({
      parent,
      name: '',
      matrix: [m[0], m[1], m[2], 0, m[3], m[4], m[5], 0, m[6], m[7], m[8], 0, m[9], m[10], m[11], 1],
    });
  }
  // Each frame's extension follows the struct, in the same order.
  let i = 0;
  for (const ext of chunk.findAll(RW.EXTENSION)) {
    if (i >= frames.length) break;
    const nameChunk = ext.find(RW.FRAME_NAME);
    if (nameChunk) frames[i].name = nameChunk.reader().fixedString(nameChunk.size);
    i++;
  }
  return frames;
}

function parseTexture(chunk) {
  const r = chunk.structReader();
  r.u16(); // filter mode
  r.u16(); // uv addressing
  const strings = chunk.findAll(RW.STRING);
  const read = (c) => (c ? c.reader().fixedString(c.size) : '');
  return { name: read(strings[0]), mask: read(strings[1]) };
}

function parseMaterial(chunk) {
  const r = chunk.structReader();
  r.i32(); // flags
  const color = [r.u8() / 255, r.u8() / 255, r.u8() / 255, r.u8() / 255];
  r.i32(); // unused
  const isTextured = r.i32();
  let ambient = 1, specular = 1, diffuse = 1;
  if (chunk.version > 0x30400) {
    ambient = r.f32();
    specular = r.f32();
    diffuse = r.f32();
  }
  const texChunk = chunk.find(RW.TEXTURE);
  const texture = texChunk ? parseTexture(texChunk) : null;
  return { color, isTextured: !!isTextured, ambient, specular, diffuse, texture };
}

function parseMaterialList(chunk) {
  const r = chunk.structReader();
  const count = r.i32();
  const refs = [];
  for (let i = 0; i < count; i++) refs.push(r.i32());

  const chunks = chunk.findAll(RW.MATERIAL);
  const materials = [];
  let next = 0;
  for (let i = 0; i < count; i++) {
    // -1 means "a new material follows", anything else reuses an earlier one.
    if (refs[i] >= 0 && materials[refs[i]]) materials.push(materials[refs[i]]);
    else if (next < chunks.length) materials.push(parseMaterial(chunks[next++]));
    else materials.push(parseMaterial(chunks[chunks.length - 1]));
  }
  return materials;
}

function parseGeometry(chunk) {
  const r = chunk.structReader();
  const format = r.u32();
  const numTriangles = r.i32();
  const numVertices = r.i32();
  const numMorphTargets = r.i32();
  if (chunk.version < 0x34000) {
    r.f32(); r.f32(); r.f32(); // surface properties moved into the material later
  }

  if (format & FLAG_NATIVE) {
    throw new Error('native (PS2/Xbox) geometry is not supported - use a PC dff');
  }

  let uvSets = (format & 0x00ff0000) >> 16;
  if (!uvSets) uvSets = format & FLAG_TEXTURED2 ? 2 : format & FLAG_TEXTURED ? 1 : 0;

  let colors = null;
  if (format & FLAG_PRELIT) {
    colors = new Float32Array(numVertices * 3);
    for (let i = 0; i < numVertices; i++) {
      colors[i * 3] = r.u8() / 255;
      colors[i * 3 + 1] = r.u8() / 255;
      colors[i * 3 + 2] = r.u8() / 255;
      r.u8(); // prelit alpha, unused
    }
  }

  let uvs = null;
  for (let set = 0; set < uvSets; set++) {
    const data = r.f32Array(numVertices * 2);
    if (set === 0) uvs = data;
  }

  // Stored as (b, a, materialId, c) - the second vertex comes first and the
  // material index sits between the vertices.
  const tris = new Uint16Array(numTriangles * 3);
  const triMaterial = new Uint16Array(numTriangles);
  for (let i = 0; i < numTriangles; i++) {
    const b = r.u16();
    const a = r.u16();
    triMaterial[i] = r.u16();
    const c = r.u16();
    tris[i * 3] = a;
    tris[i * 3 + 1] = b;
    tris[i * 3 + 2] = c;
  }

  let positions = null;
  let normals = null;
  for (let i = 0; i < numMorphTargets; i++) {
    r.f32Array(4); // bounding sphere
    const hasVertices = r.u32();
    const hasNormals = r.u32();
    const verts = hasVertices ? r.f32Array(numVertices * 3) : null;
    const norms = hasNormals ? r.f32Array(numVertices * 3) : null;
    if (i === 0) {
      positions = verts;
      normals = norms;
    }
  }
  if (!positions) throw new Error('geometry has no vertex positions');

  const matList = chunk.find(RW.MATLIST);
  const materials = matList ? parseMaterialList(matList) : [];

  // A skinned geometry stores its vertices in bind pose rather than in its
  // frame's local space, so the viewer must not apply the frame transform.
  const extension = chunk.find(RW.EXTENSION);
  const skinned = !!(extension && extension.find(RW.SKIN));

  // One draw group per material, so each group can get its own texture.
  const order = [...Array(numTriangles).keys()].sort((x, y) => triMaterial[x] - triMaterial[y]);
  let indices = new Uint32Array(numTriangles * 3);
  let groups = [];
  let current = null;
  order.forEach((tri, slot) => {
    indices[slot * 3] = tris[tri * 3];
    indices[slot * 3 + 1] = tris[tri * 3 + 1];
    indices[slot * 3 + 2] = tris[tri * 3 + 2];
    const material = triMaterial[tri];
    if (!current || current.material !== material) {
      current = { start: slot * 3, count: 0, material };
      groups.push(current);
    }
    current.count += 3;
  });

  // Many GTA:SA exporters leave the per-triangle material index at zero and put
  // the real split in the BINMESH extension instead. The struct then yields a
  // single group and the whole model renders with material 0's texture, so
  // prefer BINMESH whenever it describes more submeshes than the struct did.
  const binMesh = extension && extension.find(RW.BINMESH);
  if (binMesh) {
    const split = parseBinMesh(binMesh, numVertices);
    if (split && split.groups.length > groups.length) {
      indices = split.indices;
      groups = split.groups;
    }
  }

  return {
    numVertices,
    positions,
    normals,
    uvs,
    colors,
    indices,
    groups,
    materials,
    skinned,
    tristrip: !!(format & FLAG_TRISTRIP),
  };
}

// The BINMESH extension holds the render-ready index lists, one submesh per
// material. flags bit 0 means the indices are tristrips rather than triangle
// lists; degenerate triangles are the standard way strips stitch together, so
// they are dropped rather than emitted as zero area faces.
function parseBinMesh(chunk, numVertices) {
  const r = chunk.reader();
  if (r.remaining < 12) return null;
  const strip = r.u32() & 1;
  const numMeshes = r.u32();
  r.u32(); // total index count, recomputed below
  const out = [];
  const groups = [];
  for (let i = 0; i < numMeshes; i++) {
    if (r.remaining < 8) return null;
    const count = r.u32();
    const material = r.u32();
    if (r.remaining < count * 4) return null;
    const list = new Uint32Array(count);
    for (let k = 0; k < count; k++) list[k] = r.u32();

    const start = out.length;
    if (strip) {
      for (let k = 0; k + 2 < count; k++) {
        const a = list[k], b = list[k + (k & 1 ? 2 : 1)], c = list[k + (k & 1 ? 1 : 2)];
        if (a === b || b === c || a === c) continue; // strip stitch
        out.push(a, b, c);
      }
    } else {
      for (let k = 0; k + 2 < count; k += 3) out.push(list[k], list[k + 1], list[k + 2]);
    }
    if (out.length > start) groups.push({ start, count: out.length - start, material });
  }
  if (!groups.length) return null;
  for (const index of out) {
    if (index >= numVertices) return null; // not indices we can trust
  }
  return { indices: Uint32Array.from(out), groups };
}

export function parseDFF(buffer) {
  const view = new DataView(buffer);
  let clump = new Chunk(view, 0);
  if (clump.type !== RW.CLUMP) {
    // Some files carry a UV animation dictionary or similar before the clump.
    clump = null;
    for (let offset = 0; offset + 12 <= view.byteLength; ) {
      const c = new Chunk(view, offset);
      if (c.type === RW.CLUMP) { clump = c; break; }
      if (c.size <= 0) break;
      offset += 12 + c.size;
    }
    if (!clump) throw new Error('no clump chunk found - this is not a dff');
  }

  const r = clump.structReader();
  const numAtomics = r.i32();
  if (clump.version > 0x33000) {
    r.i32(); // lights
    r.i32(); // cameras
  }

  const frameList = clump.find(RW.FRAMELIST);
  const frames = frameList ? parseFrameList(frameList) : [];

  const geometryList = clump.find(RW.GEOMETRYLIST);
  const geometries = [];
  const errors = [];
  if (geometryList) {
    geometryList.findAll(RW.GEOMETRY).forEach((geo, i) => {
      try {
        geometries.push(parseGeometry(geo));
      } catch (err) {
        errors.push(`geometry ${i}: ${err.message}`);
        geometries.push(null);
      }
    });
  }

  const atomics = clump.findAll(RW.ATOMIC).map((atomic) => {
    const a = atomic.structReader();
    return { frame: a.i32(), geometry: a.i32(), flags: a.u32() };
  });

  return {
    version: clump.version,
    versionText: versionString(clump.version),
    numAtomics,
    frames,
    geometries,
    atomics,
    errors,
  };
}