"""3D model conversion processor with LOD support."""

import logging
from pathlib import Path
from typing import Any

import numpy as np
import trimesh

from ..config import settings

logger = logging.getLogger(__name__)

# LOD configuration: level -> face ratio (for non-STEP files)
LOD_LEVELS = {
    0: 1.0,    # LOD0: 100% faces (original)
    1: 0.5,    # LOD1: 50% faces
    2: 0.25,   # LOD2: 25% faces
}

# LOD tessellation parameters for STEP files (cascadio)
# Higher values = coarser mesh = fewer triangles
LOD_TESSELLATION = {
    0: {'tol_linear': 0.01, 'tol_angular': 0.5},   # High quality (default)
    1: {'tol_linear': 0.1,  'tol_angular': 1.0},   # Medium quality
    2: {'tol_linear': 0.5,  'tol_angular': 2.0},   # Low quality (for preview)
}


def convert_to_glb(input_path: Path, output_path: Path, file_type: str) -> dict[str, Any]:
    """
    Convert a 3D model to GLB format with LOD support.

    Supports: STEP, STL, OBJ, and other formats via trimesh/cascadio.

    Returns metadata about the converted model including LOD file paths.
    """
    file_type = file_type.lower()

    # Ensure output directory exists
    output_path.parent.mkdir(parents=True, exist_ok=True)

    if file_type in ('step', 'stp'):
        return _convert_step(input_path, output_path)
    else:
        return _convert_with_trimesh(input_path, output_path, file_type)


def convert_to_glb_with_lod(input_path: Path, output_dir: Path, file_type: str, model_id: str) -> dict[str, Any]:
    """
    Convert a 3D model to GLB format with multiple LOD levels.

    For STEP files: Generate each LOD directly from source with different tessellation precision.
    For other files: Generate LOD0 then simplify for other levels.

    Args:
        input_path: Path to input file
        output_dir: Directory to save LOD files
        file_type: File extension (step, stl, obj, etc.)
        model_id: Unique model identifier for file naming

    Returns:
        Metadata including LOD file paths and statistics
    """
    file_type = file_type.lower()
    output_dir.mkdir(parents=True, exist_ok=True)

    lod_files = {}

    # STEP files: Generate each LOD with different tessellation precision
    if file_type in ('step', 'stp'):
        return _convert_step_with_lod(input_path, output_dir, model_id)

    # Non-STEP files: Use post-processing simplification
    return _convert_other_with_lod(input_path, output_dir, file_type, model_id)


def _convert_step_with_lod(input_path: Path, output_dir: Path, model_id: str) -> dict[str, Any]:
    """
    Convert STEP file to GLB with multiple LOD levels using different tessellation precision.

    This is more effective than post-processing simplification because it controls
    mesh generation at the source.
    """
    lod_files = {}
    metadata = None

    for level, params in LOD_TESSELLATION.items():
        lod_path = output_dir / f"{model_id}_lod{level}.glb"

        try:
            level_metadata = _convert_step(
                input_path,
                lod_path,
                tol_linear=params['tol_linear'],
                tol_angular=params['tol_angular'],
            )

            lod_files[f'lod{level}'] = str(lod_path.name)
            faces = level_metadata.get('faces', 0)
            logger.info(f"Generated LOD{level} with {faces:,} faces (tol_linear={params['tol_linear']})")

            # Use LOD0 metadata as the primary metadata
            if level == 0:
                metadata = level_metadata

        except Exception as e:
            logger.error(f"Failed to generate LOD{level}: {e}")
            # Fall back to LOD0 if available
            if 'lod0' in lod_files:
                lod_files[f'lod{level}'] = lod_files['lod0']

    # If LOD0 failed, raise error
    if metadata is None:
        raise RuntimeError("Failed to convert STEP file")

    # Add LOD info to metadata
    metadata['lod_files'] = lod_files
    metadata['lod_levels'] = len(set(lod_files.values()))

    return metadata


def _convert_other_with_lod(input_path: Path, output_dir: Path, file_type: str, model_id: str) -> dict[str, Any]:
    """
    Convert non-STEP files to GLB with LOD using post-processing simplification.
    """
    # LOD0 path (original quality)
    lod0_path = output_dir / f"{model_id}_lod0.glb"

    # Convert to LOD0
    metadata = _convert_with_trimesh(input_path, lod0_path, file_type)

    lod_files = {
        'lod0': str(lod0_path.name),
    }

    # Get face count for LOD generation decision
    total_faces = metadata.get('faces', 0)

    # Only generate LODs if model has enough faces
    if total_faces > 1000:
        try:
            # Generate LOD1 and LOD2 using mesh simplification
            for level in [1, 2]:
                lod_path = output_dir / f"{model_id}_lod{level}.glb"
                ratio = LOD_LEVELS[level]

                # Reload mesh fresh for each LOD level
                mesh = trimesh.load(str(lod0_path))

                simplified = _simplify_mesh(mesh, ratio)
                if simplified is not None:
                    simplified.export(str(lod_path), file_type='glb')
                    lod_files[f'lod{level}'] = str(lod_path.name)
                    logger.info(f"Generated LOD{level} with {ratio*100:.0f}% faces: {lod_path.name}")
                else:
                    logger.warning(f"Failed to generate LOD{level}, using LOD0")
                    lod_files[f'lod{level}'] = lod_files['lod0']

        except Exception as e:
            logger.warning(f"LOD generation failed: {e}, using LOD0 for all levels")
            lod_files['lod1'] = lod_files['lod0']
            lod_files['lod2'] = lod_files['lod0']
    else:
        # Small model, use LOD0 for all levels
        logger.info(f"Model has {total_faces} faces, skipping LOD generation")
        lod_files['lod1'] = lod_files['lod0']
        lod_files['lod2'] = lod_files['lod0']

    # Add LOD info to metadata
    metadata['lod_files'] = lod_files
    metadata['lod_levels'] = len(set(lod_files.values()))

    return metadata


def _simplify_mesh(mesh: trimesh.Trimesh | trimesh.Scene, ratio: float) -> trimesh.Trimesh | trimesh.Scene | None:
    """
    Simplify a mesh or scene to the target face ratio.

    Args:
        mesh: Trimesh mesh or scene
        ratio: Target ratio of faces (0.0 - 1.0)

    Returns:
        Simplified mesh/scene or None if failed
    """
    # Minimum reduction required (at least 10% reduction for fast_simplification to work)
    MIN_REDUCTION_RATIO = 0.9

    try:
        if isinstance(mesh, trimesh.Scene):
            # Simplify each geometry in the scene
            simplified_geometries = {}
            for name, geom in mesh.geometry.items():
                # Skip small geometries and non-mesh objects
                if not hasattr(geom, 'faces') or len(geom.faces) < 100:
                    simplified_geometries[name] = geom
                    continue

                original_faces = len(geom.faces)
                target_faces = max(int(original_faces * ratio), 4)

                # Only simplify if we're reducing by at least 10%
                # (fast_simplification requires reduction > 0)
                if target_faces < original_faces * MIN_REDUCTION_RATIO:
                    try:
                        simplified = geom.simplify_quadric_decimation(target_faces)
                        simplified_geometries[name] = simplified
                    except Exception as e:
                        logger.warning(f"Failed to simplify geometry {name}: {e}")
                        simplified_geometries[name] = geom
                else:
                    # Reduction too small, skip simplification
                    simplified_geometries[name] = geom

            # Create new scene with simplified geometries
            new_scene = trimesh.Scene()
            for name, geom in simplified_geometries.items():
                try:
                    # Get original transform if exists
                    node_name = None
                    if hasattr(mesh.graph, 'nodes_geometry'):
                        for item in mesh.graph.nodes_geometry:
                            # Handle both tuple formats: (node, geom_name) or (node, geom_name, ...)
                            if len(item) >= 2 and item[1] == name:
                                node_name = item[0]
                                break

                    if node_name:
                        transform = mesh.graph.get(node_name)[0]
                        new_scene.add_geometry(geom, node_name=node_name, geom_name=name, transform=transform)
                    else:
                        new_scene.add_geometry(geom, geom_name=name)
                except Exception as e:
                    # If transform lookup fails, just add geometry without transform
                    logger.debug(f"Could not get transform for {name}: {e}")
                    new_scene.add_geometry(geom, geom_name=name)

            return new_scene

        elif hasattr(mesh, 'faces') and len(mesh.faces) >= 100:
            # Single mesh simplification
            original_faces = len(mesh.faces)
            target_faces = max(int(original_faces * ratio), 4)

            # Only simplify if we're reducing by at least 10%
            if target_faces < original_faces * MIN_REDUCTION_RATIO:
                return mesh.simplify_quadric_decimation(target_faces)

        return mesh

    except Exception as e:
        logger.error(f"Mesh simplification failed: {e}")
        return None


def _convert_step(
    input_path: Path,
    output_path: Path,
    tol_linear: float = 0.01,
    tol_angular: float = 0.5,
) -> dict[str, Any]:
    """Convert STEP file using cascadio with configurable tessellation precision.

    Args:
        input_path: Path to STEP file
        output_path: Path to save GLB file
        tol_linear: Linear deflection tolerance (higher = coarser mesh)
        tol_angular: Angular deflection tolerance in radians (higher = coarser mesh)

    Returns:
        Metadata about the converted model
    """
    try:
        import cascadio

        logger.info(f"Converting STEP file with cascadio: {input_path}")
        logger.info(f"Tessellation params: tol_linear={tol_linear}, tol_angular={tol_angular}")

        cascadio.step_to_glb(
            str(input_path),
            str(output_path),
            tol_linear=tol_linear,
            tol_angular=tol_angular,
        )

        # Load the result to get metadata
        mesh = trimesh.load(str(output_path))
        return _extract_metadata(mesh)

    except ImportError:
        logger.error("cascadio not installed, cannot convert STEP files")
        raise RuntimeError("STEP conversion requires cascadio package")
    except Exception as e:
        logger.error(f"STEP conversion failed: {e}")
        raise


def _convert_with_trimesh(input_path: Path, output_path: Path, file_type: str) -> dict[str, Any]:
    """Convert STL, OBJ, and other formats using trimesh."""
    logger.info(f"Converting {file_type.upper()} file with trimesh: {input_path}")

    try:
        # Load the mesh
        mesh = trimesh.load(str(input_path))

        # Export to GLB
        mesh.export(str(output_path), file_type='glb')

        return _extract_metadata(mesh)

    except Exception as e:
        logger.error(f"Trimesh conversion failed: {e}")
        raise


def _extract_metadata(mesh: trimesh.Trimesh | trimesh.Scene) -> dict[str, Any]:
    """Extract metadata from a trimesh object."""
    metadata: dict[str, Any] = {}

    try:
        if isinstance(mesh, trimesh.Scene):
            # Scene with multiple meshes
            metadata['type'] = 'scene'
            metadata['parts_count'] = len(mesh.geometry)

            # Aggregate stats
            total_vertices = 0
            total_faces = 0

            for name, geom in mesh.geometry.items():
                if hasattr(geom, 'vertices'):
                    total_vertices += len(geom.vertices)
                if hasattr(geom, 'faces'):
                    total_faces += len(geom.faces)

            metadata['vertices'] = total_vertices
            metadata['faces'] = total_faces

            # Bounding box
            if hasattr(mesh, 'bounds') and mesh.bounds is not None:
                bounds = mesh.bounds
                metadata['bounding_box'] = {
                    'min': {'x': float(bounds[0][0]), 'y': float(bounds[0][1]), 'z': float(bounds[0][2])},
                    'max': {'x': float(bounds[1][0]), 'y': float(bounds[1][1]), 'z': float(bounds[1][2])},
                }

            # Parts info
            parts = []
            for name, geom in mesh.geometry.items():
                part_info = {'name': name}

                if hasattr(geom, 'bounds') and geom.bounds is not None:
                    part_bounds = geom.bounds
                    part_info['bounding_box'] = {
                        'min': {'x': float(part_bounds[0][0]), 'y': float(part_bounds[0][1]), 'z': float(part_bounds[0][2])},
                        'max': {'x': float(part_bounds[1][0]), 'y': float(part_bounds[1][1]), 'z': float(part_bounds[1][2])},
                    }
                    part_info['center_point'] = {
                        'x': float((part_bounds[0][0] + part_bounds[1][0]) / 2),
                        'y': float((part_bounds[0][1] + part_bounds[1][1]) / 2),
                        'z': float((part_bounds[0][2] + part_bounds[1][2]) / 2),
                    }

                parts.append(part_info)

            metadata['parts'] = parts

        else:
            # Single mesh
            metadata['type'] = 'mesh'
            metadata['parts_count'] = 1

            if hasattr(mesh, 'vertices'):
                metadata['vertices'] = len(mesh.vertices)
            if hasattr(mesh, 'faces'):
                metadata['faces'] = len(mesh.faces)

            if hasattr(mesh, 'bounds') and mesh.bounds is not None:
                bounds = mesh.bounds
                metadata['bounding_box'] = {
                    'min': {'x': float(bounds[0][0]), 'y': float(bounds[0][1]), 'z': float(bounds[0][2])},
                    'max': {'x': float(bounds[1][0]), 'y': float(bounds[1][1]), 'z': float(bounds[1][2])},
                }

    except Exception as e:
        logger.warning(f"Error extracting metadata: {e}")

    return metadata