# Copyright (c) 2026 Dominic Masters
#
# This software is released under the MIT License.
# https://opensource.org/licenses/MIT

"""
Generates DCF + companion DMF files from raw chunk JSON files, or upgrades
legacy DCF files (version 1 or 2) to version 3.

JSON input (assetsraw/chunks/chunk_X_Y_Z.json):
  {
    "tiles": [
      { "pos": [x, y, z], "type": <tile_shape_int>, "tile": <uv_tile_int> }
    ],
    "meshes": [
      { "file": "house_5_3.dmf", "pos": [x, y, z] }
    ]
  }

  Tiles absent from the array default to TILE_SHAPE_NULL.
  Mesh files are located by searching under assets/meshes/ and referenced by
  path from the assets root in the DCF.

  Output DCF is derived automatically:
    assetsraw/chunks/chunk_X_Y_Z.json -> assets/chunks/X_Y_Z.dcf

Version 3 DCF format (after 8-byte header + tiles):
  uint8_t  meshCount
  for each mesh:
    null-terminated string  (relative asset path to .dmf)
    float32[3]              (x, y, z offset)

DMF format:
  Bytes 0-3:  DMF\\x00
  Bytes 4-7:  uint32_t version = 1 (little-endian)
  Bytes 8-11: uint32_t vertCount  (little-endian)
  Bytes 12+:  meshvertex_t vertices[vertCount]
              Each vertex: uv[2] + pos[3] = 5 x float32 LE = 20 bytes

Usage:
  python3 -m tools.asset.chunk              # process all assetsraw/chunks/*.json
  python3 -m tools.asset.chunk <file.json>  # process one JSON file
  python3 -m tools.asset.chunk <file.dcf>   # upgrade legacy DCF in-place
"""

import json
import os
import struct
import sys

_HERE        = os.path.dirname(os.path.abspath(__file__))
PROJECT_ROOT = os.path.normpath(os.path.join(_HERE, '..', '..', '..'))
ASSETSRAW_DIR = os.path.join(PROJECT_ROOT, 'assetsraw')
ASSETS_DIR    = os.path.join(PROJECT_ROOT, 'assets')

CHUNK_WIDTH      = 16
CHUNK_HEIGHT     = 16
CHUNK_DEPTH      = 32
CHUNK_TILE_COUNT = CHUNK_WIDTH * CHUNK_HEIGHT * CHUNK_DEPTH  # 8192

CHUNK_MESH_COUNT_MAX = 10
CHUNK_MESH_NAME_MAX  = 64

TILE_SIZE   = 4
VERTEX_SIZE = 20

TILE_SHAPE_NULL   = 0
TILE_SHAPE_GROUND = 1

FILE_MAGIC  = b'DCF'
DMF_MAGIC   = b'DMF\x00'
VERSION_OUT = 3
DMF_VERSION = 1


# ---------------------------------------------------------------------------
# Helpers
# ---------------------------------------------------------------------------

def tile_index(x, y, z):
    return x + y * CHUNK_WIDTH + z * CHUNK_WIDTH * CHUNK_HEIGHT


def find_mesh(filename):
    """Search ASSETS_DIR/meshes/ recursively for filename.
    Returns the path relative to ASSETS_DIR (forward slashes), or None."""
    meshes_root = os.path.join(ASSETS_DIR, 'meshes')
    for dirpath, _, filenames in os.walk(meshes_root):
        if filename in filenames:
            rel = os.path.relpath(
                os.path.join(dirpath, filename), ASSETS_DIR
            )
            return rel.replace('\\', '/')
    return None


def derive_dcf_path(json_path):
    """assetsraw/chunks/chunk_X_Y_Z.json -> assets/chunks/X_Y_Z.dcf"""
    base = os.path.splitext(os.path.basename(json_path))[0]
    if base.startswith('chunk_'):
        base = base[len('chunk_'):]
    rel_dir = os.path.relpath(os.path.dirname(os.path.abspath(json_path)), ASSETSRAW_DIR)
    return os.path.join(ASSETS_DIR, rel_dir, base + '.dcf')


def write_dmf(path, vertex_bytes):
    vert_count = len(vertex_bytes) // VERTEX_SIZE
    buf = bytearray()
    buf += DMF_MAGIC
    buf += struct.pack('<I', DMF_VERSION)
    buf += struct.pack('<I', vert_count)
    buf += vertex_bytes
    with open(path, 'wb') as f:
        f.write(buf)
    print(f'  Wrote DMF {path}: {vert_count} vertices, {len(buf)} bytes')


def write_v3(dcf_path, tiles, mesh_names, mesh_offsets=None):
    """Write a v3 DCF referencing the given DMF asset paths."""
    mesh_count = len(mesh_names)
    if mesh_offsets is None:
        mesh_offsets = [(0.0, 0.0, 0.0)] * mesh_count

    buf = bytearray()
    buf += FILE_MAGIC
    buf += b'\x00'
    buf += struct.pack('<I', VERSION_OUT)
    buf += tiles
    buf += struct.pack('<B', mesh_count)
    for name, offset in zip(mesh_names, mesh_offsets):
        encoded = name.encode('ascii')
        if len(encoded) >= CHUNK_MESH_NAME_MAX:
            raise ValueError(
                f"Mesh name too long (>= {CHUNK_MESH_NAME_MAX}): {name}"
            )
        buf += encoded + b'\x00'
        buf += struct.pack('<3f', offset[0], offset[1], offset[2])
    with open(dcf_path, 'wb') as f:
        f.write(buf)
    print(
        f'  Wrote DCF {dcf_path}: '
        f'version {VERSION_OUT}, {mesh_count} mesh(es), {len(buf)} bytes'
    )


# ---------------------------------------------------------------------------
# JSON -> DCF + DMF
# ---------------------------------------------------------------------------

def build_terrain_verts(tiles_bytes):
    """Generate top-face quads for every TILE_SHAPE_GROUND tile."""
    buf = bytearray()
    for z in range(CHUNK_DEPTH):
        for y in range(CHUNK_HEIGHT):
            for x in range(CHUNK_WIDTH):
                idx = tile_index(x, y, z)
                tile_type = struct.unpack_from(
                    '<I', tiles_bytes, idx * TILE_SIZE
                )[0]
                if tile_type != TILE_SHAPE_GROUND:
                    continue
                fx, fy, fz = float(x), float(y), float(z)
                uv_u0 = x / CHUNK_WIDTH
                uv_u1 = (x + 1) / CHUNK_WIDTH
                uv_v0 = y / CHUNK_HEIGHT
                uv_v1 = (y + 1) / CHUNK_HEIGHT
                for v in [
                    (uv_u0, uv_v0, fx,   fy,   fz),
                    (uv_u1, uv_v0, fx+1, fy,   fz),
                    (uv_u1, uv_v1, fx+1, fy+1, fz),
                    (uv_u0, uv_v0, fx,   fy,   fz),
                    (uv_u1, uv_v1, fx+1, fy+1, fz),
                    (uv_u0, uv_v1, fx,   fy+1, fz),
                ]:
                    buf += struct.pack('<5f', *v)
    return bytes(buf)


def from_json(json_path, dcf_path):
    with open(json_path) as f:
        data = json.load(f)

    tiles = bytearray(CHUNK_TILE_COUNT * TILE_SIZE)
    for tile in data.get('tiles', []):
        pos = tile['pos']
        x, y, z = int(pos[0]), int(pos[1]), int(pos[2])
        struct.pack_into(
            '<I', tiles, tile_index(x, y, z) * TILE_SIZE, int(tile['type'])
        )

    terrain_verts = build_terrain_verts(tiles)
    mesh_names = []
    mesh_offsets = []

    # Terrain mesh (only written if non-empty)
    dcf_base = os.path.splitext(os.path.basename(dcf_path))[0]
    terrain_dir = os.path.join(ASSETS_DIR, 'meshes', 'chunks')
    os.makedirs(terrain_dir, exist_ok=True)
    if terrain_verts:
        dmf_name = f'chunk_{dcf_base}_0.dmf'
        write_dmf(os.path.join(terrain_dir, dmf_name), terrain_verts)
        mesh_names.append(f'meshes/chunks/{dmf_name}')
        mesh_offsets.append((0.0, 0.0, 0.0))

    # External mesh references
    for mesh in data.get('meshes', []):
        filename = mesh['file']
        pos = mesh.get('pos', [0, 0, 0])
        rel = find_mesh(filename)
        if rel is None:
            raise ValueError(f"Mesh not found under assets/meshes/: {filename}")
        mesh_names.append(rel)
        mesh_offsets.append((float(pos[0]), float(pos[1]), float(pos[2])))
        print(f'  Resolved {filename} -> {rel}')

    write_v3(dcf_path, bytes(tiles), mesh_names, mesh_offsets)


def process_json(json_path):
    dcf_path = derive_dcf_path(json_path)
    os.makedirs(os.path.dirname(dcf_path), exist_ok=True)
    print(f"{json_path} -> {dcf_path}")
    from_json(json_path, dcf_path)


# ---------------------------------------------------------------------------
# Legacy DCF (v1/v2) -> v3
# ---------------------------------------------------------------------------

def read_legacy_dcf(path):
    with open(path, 'rb') as f:
        data = f.read()
    if data[:3] != FILE_MAGIC:
        raise ValueError(f"{path}: not a DCF file")
    version = struct.unpack_from('<I', data, 4)[0]
    if version not in (1, 2):
        raise ValueError(f"{path}: expected version 1 or 2, got {version}")

    offset = 8
    tiles_size = CHUNK_TILE_COUNT * TILE_SIZE
    tiles = data[offset:offset + tiles_size]
    offset += tiles_size

    meshes = []
    if version == 1:
        vert_count = struct.unpack_from('<I', data, offset)[0]
        offset += 4
        verts = data[offset:offset + vert_count * VERTEX_SIZE]
        if len(verts) != vert_count * VERTEX_SIZE:
            raise ValueError(f"{path}: truncated vertex data")
        if vert_count > 0:
            meshes.append(verts)
    else:
        mesh_count = data[offset]
        offset += 1
        for _ in range(mesh_count):
            vert_count = struct.unpack_from('<I', data, offset)[0]
            offset += 4
            verts = data[offset:offset + vert_count * VERTEX_SIZE]
            if len(verts) != vert_count * VERTEX_SIZE:
                raise ValueError(f"{path}: truncated vertex data")
            offset += vert_count * VERTEX_SIZE
            if vert_count > 0:
                meshes.append(verts)
    return tiles, meshes


def upgrade_dcf(path):
    print(f"Upgrading legacy DCF {path} ...")
    tiles, meshes = read_legacy_dcf(path)
    print(
        f"  tiles={CHUNK_TILE_COUNT}, meshes={len(meshes)}, "
        f"total_verts={sum(len(m) // VERTEX_SIZE for m in meshes)}"
    )
    base = os.path.splitext(os.path.basename(path))[0]
    terrain_dir = os.path.join(ASSETS_DIR, 'meshes', 'chunks')
    os.makedirs(terrain_dir, exist_ok=True)
    mesh_names = []
    for idx, verts in enumerate(meshes):
        dmf_name = f'chunk_{base}_{idx}.dmf'
        write_dmf(os.path.join(terrain_dir, dmf_name), verts)
        mesh_names.append(f'meshes/chunks/{dmf_name}')
    write_v3(path, tiles, mesh_names)


# ---------------------------------------------------------------------------
# Entry point
# ---------------------------------------------------------------------------

def main():
    args = sys.argv[1:]

    if not args:
        chunks_dir = os.path.join(ASSETSRAW_DIR, 'chunks')
        if not os.path.isdir(chunks_dir):
            print(f"No directory found: {chunks_dir}")
            sys.exit(1)
        json_files = sorted(
            os.path.join(chunks_dir, f)
            for f in os.listdir(chunks_dir)
            if f.endswith('.json')
        )
        if not json_files:
            print(f"No JSON files found in {chunks_dir}")
            sys.exit(0)
        for p in json_files:
            process_json(p)
        return

    src = args[0]
    if os.path.splitext(src)[1].lower() == '.json':
        process_json(src)
    else:
        upgrade_dcf(src)


if __name__ == '__main__':
    main()