import struct
import numpy as np
from PIL import Image, ImageDraw
import os
import zipfile
import xml.etree.ElementTree as ET


def parse_stl_file(file_path: str):
    """Parse an STL file (binary or ASCII) and return mesh data + metadata."""
    with open(file_path, 'rb') as f:
        header = f.read(80)

    is_binary = False
    if not header.startswith(b'solid'):
        is_binary = True
    else:
        with open(file_path, 'rb') as f:
            f.read(80)
            tri_count_bytes = f.read(4)
            if len(tri_count_bytes) == 4:
                tri_count = struct.unpack('<I', tri_count_bytes)[0]
                file_size = os.path.getsize(file_path)
                expected = 80 + 4 + tri_count * 50
                if file_size == expected:
                    is_binary = True

    if is_binary:
        return _parse_binary(file_path)
    else:
        return _parse_ascii(file_path)


def _parse_binary(file_path: str):
    with open(file_path, 'rb') as f:
        f.read(80)
        tri_count = struct.unpack('<I', f.read(4))[0]
        vertices = []
        for _ in range(tri_count):
            f.read(12)  # normal
            v1 = struct.unpack('<3f', f.read(12))
            v2 = struct.unpack('<3f', f.read(12))
            v3 = struct.unpack('<3f', f.read(12))
            f.read(2)
            vertices.extend([v1, v2, v3])
    vertices = np.array(vertices, dtype=np.float32)
    return _compute_metadata(vertices, tri_count)


def _parse_ascii(file_path: str):
    vertices = []
    with open(file_path, 'r', encoding='utf-8', errors='ignore') as f:
        for line in f:
            line = line.strip().lower()
            if line.startswith('vertex'):
                parts = line.split()
                if len(parts) >= 4:
                    v = [float(parts[1]), float(parts[2]), float(parts[3])]
                    vertices.append(v)
    vertices = np.array(vertices, dtype=np.float32)
    tri_count = len(vertices) // 3
    return _compute_metadata(vertices, tri_count)


def _compute_metadata(vertices: np.ndarray, tri_count: int):
    if len(vertices) == 0:
        return {
            'vertices': vertices,
            'faces': 0,
            'width': 0.0,
            'height': 0.0,
            'depth': 0.0,
        }
    min_v = vertices.min(axis=0)
    max_v = vertices.max(axis=0)
    dims = max_v - min_v
    return {
        'vertices': vertices,
        'faces': tri_count,
        'width': float(dims[0]),
        'height': float(dims[1]),
        'depth': float(dims[2]),
    }


def parse_3mf_file(file_path: str):
    """Parse a 3MF file (zip with XML) and return mesh data + metadata."""
    vertices = []
    tri_count = 0
    try:
        with zipfile.ZipFile(file_path, 'r') as zf:
            model_path = None
            for name in zf.namelist():
                if name.endswith('3dmodel.model') or name.endswith('.model'):
                    model_path = name
                    break
            if not model_path:
                raise ValueError("No 3D model found in 3MF archive")

            with zf.open(model_path) as mf:
                tree = ET.parse(mf)
                root = tree.getroot()

            # Find namespace
            ns = {'m': root.tag.split('}')[0].strip('{') if '}' in root.tag else ''}
            if ns['m']:
                ns = {'m': ns['m']}
                mesh = root.find('.//m:mesh', ns)
            else:
                mesh = root.find('.//mesh')

            if mesh is None:
                raise ValueError("No mesh found in 3MF model")

            verts_elem = mesh.find('m:vertices', ns) if ns else mesh.find('vertices')
            if verts_elem is not None:
                tag = 'm:vertex' if ns else 'vertex'
                for v in verts_elem.findall(tag, ns) if ns else verts_elem.findall(tag):
                    x = float(v.get('x', 0))
                    y = float(v.get('y', 0))
                    z = float(v.get('z', 0))
                    vertices.append([x, y, z])

            tris_elem = mesh.find('m:triangles', ns) if ns else mesh.find('triangles')
            if tris_elem is not None:
                tag = 'm:triangle' if ns else 'triangle'
                tri_verts = []
                for t in tris_elem.findall(tag, ns) if ns else tris_elem.findall(tag):
                    v1 = int(t.get('v1', 0))
                    v2 = int(t.get('v2', 0))
                    v3 = int(t.get('v3', 0))
                    tri_verts.extend([vertices[v1], vertices[v2], vertices[v3]])
                vertices = tri_verts
                tri_count = len(tris_verts) // 3
            else:
                vertices = []

    except Exception as e:
        raise ValueError(f"Failed to parse 3MF: {str(e)}")

    vertices = np.array(vertices, dtype=np.float32)
    return _compute_metadata(vertices, tri_count)


def parse_model_file(file_path: str):
    """Auto-detect format and parse."""
    lower = file_path.lower()
    if lower.endswith('.stl'):
        return parse_stl_file(file_path)
    elif lower.endswith('.3mf'):
        return parse_3mf_file(file_path)
    else:
        raise ValueError("Unsupported file format. Only STL and 3MF are supported.")


def generate_thumbnail(vertices: np.ndarray, output_path: str, size: int = 256):
    """Generate a simple orthographic thumbnail from vertices."""
    if len(vertices) == 0:
        img = Image.new('RGB', (size, size), color=(30, 30, 30))
        img.save(output_path)
        return

    min_v = vertices.min(axis=0)
    max_v = vertices.max(axis=0)
    dims = max_v - min_v
    scale = max(dims[0], dims[1])
    if scale == 0:
        scale = 1.0

    margin = 20
    img_size = size - 2 * margin

    img = Image.new('RGB', (size, size), color=(30, 30, 30))
    draw = ImageDraw.Draw(img)

    for i in range(0, len(vertices), 3):
        tri = vertices[i:i+3]
        pts = []
        for v in tri:
            x = margin + int(((v[0] - min_v[0]) / scale) * img_size)
            y = margin + int(((1.0 - (v[1] - min_v[1]) / scale)) * img_size)
            pts.append((x, y))
        if len(pts) == 3:
            z_avg = sum(v[2] for v in tri) / 3.0
            z_norm = (z_avg - min_v[2]) / (dims[2] if dims[2] > 0 else 1)
            brightness = int(80 + z_norm * 120)
            color = (brightness, brightness, int(brightness * 1.1))
            draw.polygon(pts, fill=color, outline=(50, 50, 60))

    fmt = 'WEBP' if output_path.lower().endswith('.webp') else 'PNG'
    img.save(output_path, fmt)


def generate_generic_thumbnail(output_path: str, size: int = 256, label: str = "3D"):
    """Generate a generic thumbnail for unsupported previews."""
    img = Image.new('RGB', (size, size), color=(30, 30, 30))
    draw = ImageDraw.Draw(img)
    draw.rectangle([40, 40, size-40, size-40], outline=(6, 182, 212), width=3)
    try:
        from PIL import ImageFont
        font = ImageFont.truetype("/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf", 36)
    except:
        font = ImageFont.load_default()
    bbox = draw.textbbox((0,0), label, font=font)
    text_w = bbox[2] - bbox[0]
    text_h = bbox[3] - bbox[1]
    draw.text(((size - text_w) // 2, (size - text_h) // 2), label, fill=(6, 182, 212), font=font)
    img.save(output_path, 'PNG')