"""
Polar Mirror Graph for GNN Training
====================================

This module creates a fixed polar grid graph structure for the mirror optical surface.
The key insight is that the mirror has a fixed topology (circular annulus), so we can
use a fixed graph structure regardless of FEA mesh variations.

Why Polar Grid?
1. Matches mirror geometry (annulus)
2. Same approach as extract_zernike_surface.py
3. Enables mesh-independent training
4. Edge structure respects radial/angular physics

Grid Structure:
    - n_radial points from r_inner to r_outer
    - n_angular points from 0 to 2π (not including 2π to avoid duplicate)
    - Total nodes = n_radial × n_angular
    - Edges connect radial neighbors and angular neighbors (wrap-around)

Usage:
    from optimization_engine.gnn.polar_graph import PolarMirrorGraph

    graph = PolarMirrorGraph(r_inner=100, r_outer=650, n_radial=50, n_angular=60)

    # Interpolate FEA results to fixed grid
    z_disp_grid = graph.interpolate_from_mesh(fea_coords, fea_z_disp)

    # Get PyTorch Geometric data
    data = graph.to_pyg_data(z_disp_grid, design_vars)
"""

import numpy as np
from pathlib import Path
from typing import Dict, Any, Optional, Tuple, List
import json

try:
    import torch
    HAS_TORCH = True
except ImportError:
    HAS_TORCH = False

try:
    from scipy.interpolate import RBFInterpolator, LinearNDInterpolator, CloughTocher2DInterpolator
    from scipy.spatial import Delaunay
    HAS_SCIPY = True
except ImportError:
    HAS_SCIPY = False


class PolarMirrorGraph:
    """
    Fixed polar grid graph for mirror optical surface.

    This creates a mesh-independent graph structure that can be used for GNN training
    regardless of the underlying FEA mesh. FEA results are interpolated to this fixed grid.

    Attributes:
        n_nodes: Total number of nodes (n_radial × n_angular)
        r: Radial coordinates [n_nodes]
        theta: Angular coordinates [n_nodes]
        x: Cartesian X coordinates [n_nodes]
        y: Cartesian Y coordinates [n_nodes]
        edge_index: Graph edges [2, n_edges]
        edge_attr: Edge features [n_edges, 4] - (dr, dtheta, distance, angle)
    """

    def __init__(
        self,
        r_inner: float = 100.0,
        r_outer: float = 650.0,
        n_radial: int = 50,
        n_angular: int = 60
    ):
        """
        Initialize polar grid graph.

        Args:
            r_inner: Inner radius (central hole), mm
            r_outer: Outer radius, mm
            n_radial: Number of radial samples
            n_angular: Number of angular samples
        """
        self.r_inner = r_inner
        self.r_outer = r_outer
        self.n_radial = n_radial
        self.n_angular = n_angular
        self.n_nodes = n_radial * n_angular

        # Create polar grid coordinates
        r_1d = np.linspace(r_inner, r_outer, n_radial)
        theta_1d = np.linspace(0, 2 * np.pi, n_angular, endpoint=False)

        # Meshgrid: theta varies fast (angular index), r varies slow (radial index)
        # Shape after flatten: [n_angular * n_radial] with angular varying fastest
        Theta, R = np.meshgrid(theta_1d, r_1d)  # R shape: [n_radial, n_angular]

        # Flatten: radial index varies slowest
        self.r = R.flatten().astype(np.float32)
        self.theta = Theta.flatten().astype(np.float32)
        self.x = (self.r * np.cos(self.theta)).astype(np.float32)
        self.y = (self.r * np.sin(self.theta)).astype(np.float32)

        # Build graph edges
        self.edge_index, self.edge_attr = self._build_polar_edges()

        # Precompute normalization factors
        self._r_mean = (r_inner + r_outer) / 2
        self._r_std = (r_outer - r_inner) / 2

    def _node_index(self, i_r: int, i_theta: int) -> int:
        """Convert (radial_index, angular_index) to flat node index."""
        # Angular wraps around
        i_theta = i_theta % self.n_angular
        return i_r * self.n_angular + i_theta

    def _build_polar_edges(self) -> Tuple[np.ndarray, np.ndarray]:
        """
        Create graph edges respecting polar topology.

        Edge types:
        1. Radial edges: Connect adjacent radial rings
        2. Angular edges: Connect adjacent angular positions (with wrap-around)
        3. Diagonal edges: Connect diagonal neighbors for better message passing

        Returns:
            edge_index: [2, n_edges] array of (source, target) pairs
            edge_attr: [n_edges, 4] array of (dr, dtheta, distance, angle)
        """
        edges = []
        edge_features = []

        for i_r in range(self.n_radial):
            for i_theta in range(self.n_angular):
                node = self._node_index(i_r, i_theta)

                # Radial neighbor (outward)
                if i_r < self.n_radial - 1:
                    neighbor = self._node_index(i_r + 1, i_theta)
                    edges.append([node, neighbor])
                    edges.append([neighbor, node])  # Bidirectional

                    # Edge features: (dr, dtheta, distance, relative_angle)
                    dr = self.r[neighbor] - self.r[node]
                    dtheta = 0.0
                    dist = abs(dr)
                    angle = 0.0  # Radial direction
                    edge_features.append([dr, dtheta, dist, angle])
                    edge_features.append([-dr, dtheta, dist, np.pi])  # Reverse

                # Angular neighbor (counterclockwise, with wrap-around)
                neighbor = self._node_index(i_r, i_theta + 1)
                edges.append([node, neighbor])
                edges.append([neighbor, node])  # Bidirectional

                # Edge features for angular edge
                dr = 0.0
                dtheta = 2 * np.pi / self.n_angular
                # Arc length at this radius
                dist = self.r[node] * dtheta
                angle = np.pi / 2  # Tangential direction
                edge_features.append([dr, dtheta, dist, angle])
                edge_features.append([dr, -dtheta, dist, -np.pi / 2])  # Reverse

                # Diagonal neighbor (outward + counterclockwise) for better connectivity
                if i_r < self.n_radial - 1:
                    neighbor = self._node_index(i_r + 1, i_theta + 1)
                    edges.append([node, neighbor])
                    edges.append([neighbor, node])

                    dr = self.r[neighbor] - self.r[node]
                    dtheta = 2 * np.pi / self.n_angular
                    dx = self.x[neighbor] - self.x[node]
                    dy = self.y[neighbor] - self.y[node]
                    dist = np.sqrt(dx**2 + dy**2)
                    angle = np.arctan2(dy, dx)
                    edge_features.append([dr, dtheta, dist, angle])
                    edge_features.append([-dr, -dtheta, dist, angle + np.pi])

        edge_index = np.array(edges, dtype=np.int64).T  # [2, n_edges]
        edge_attr = np.array(edge_features, dtype=np.float32)  # [n_edges, 4]

        return edge_index, edge_attr

    def get_node_features(self, normalized: bool = True) -> np.ndarray:
        """
        Get node features for GNN input.

        Features: (r, theta, x, y) - polar and Cartesian coordinates

        Args:
            normalized: If True, normalize features to ~[-1, 1] range

        Returns:
            Node features [n_nodes, 4]
        """
        if normalized:
            r_norm = (self.r - self._r_mean) / self._r_std
            theta_norm = self.theta / np.pi - 1  # [0, 2π] → [-1, 1]
            x_norm = self.x / self.r_outer
            y_norm = self.y / self.r_outer
            return np.column_stack([r_norm, theta_norm, x_norm, y_norm]).astype(np.float32)
        else:
            return np.column_stack([self.r, self.theta, self.x, self.y]).astype(np.float32)

    def get_edge_features(self, normalized: bool = True) -> np.ndarray:
        """
        Get edge features for GNN input.

        Features: (dr, dtheta, distance, angle)

        Args:
            normalized: If True, normalize features

        Returns:
            Edge features [n_edges, 4]
        """
        if normalized:
            edge_attr = self.edge_attr.copy()
            edge_attr[:, 0] /= self._r_std  # dr
            edge_attr[:, 1] /= np.pi  # dtheta
            edge_attr[:, 2] /= self.r_outer  # distance
            edge_attr[:, 3] /= np.pi  # angle
            return edge_attr
        else:
            return self.edge_attr

    def interpolate_from_mesh(
        self,
        mesh_coords: np.ndarray,
        mesh_values: np.ndarray,
        method: str = 'rbf'
    ) -> np.ndarray:
        """
        Interpolate FEA results from mesh nodes to fixed polar grid.

        Args:
            mesh_coords: FEA node coordinates [n_fea_nodes, 2] or [n_fea_nodes, 3] (X, Y, [Z])
            mesh_values: Values to interpolate [n_fea_nodes] or [n_fea_nodes, n_features]
            method: Interpolation method ('rbf', 'linear', 'clough_tocher')

        Returns:
            Interpolated values on polar grid [n_nodes] or [n_nodes, n_features]
        """
        if not HAS_SCIPY:
            raise ImportError("scipy required for interpolation: pip install scipy")

        # Use only X, Y coordinates
        xy = mesh_coords[:, :2] if mesh_coords.shape[1] > 2 else mesh_coords

        # Handle multi-dimensional values
        values_1d = mesh_values.ndim == 1
        if values_1d:
            mesh_values = mesh_values.reshape(-1, 1)

        # Target coordinates
        target_xy = np.column_stack([self.x, self.y])

        result = np.zeros((self.n_nodes, mesh_values.shape[1]), dtype=np.float32)

        for i in range(mesh_values.shape[1]):
            vals = mesh_values[:, i]

            if method == 'rbf':
                # RBF interpolation - smooth, handles scattered data well
                interp = RBFInterpolator(
                    xy, vals,
                    kernel='thin_plate_spline',
                    smoothing=0.0
                )
                result[:, i] = interp(target_xy)

            elif method == 'linear':
                # Linear interpolation via Delaunay triangulation
                interp = LinearNDInterpolator(xy, vals, fill_value=np.nan)
                result[:, i] = interp(target_xy)

                # Handle NaN (points outside convex hull) with nearest neighbor
                nan_mask = np.isnan(result[:, i])
                if nan_mask.any():
                    from scipy.spatial import cKDTree
                    tree = cKDTree(xy)
                    _, idx = tree.query(target_xy[nan_mask])
                    result[nan_mask, i] = vals[idx]

            elif method == 'clough_tocher':
                # Clough-Tocher (C1 smooth) interpolation
                interp = CloughTocher2DInterpolator(xy, vals, fill_value=np.nan)
                result[:, i] = interp(target_xy)

                # Handle NaN
                nan_mask = np.isnan(result[:, i])
                if nan_mask.any():
                    from scipy.spatial import cKDTree
                    tree = cKDTree(xy)
                    _, idx = tree.query(target_xy[nan_mask])
                    result[nan_mask, i] = vals[idx]
            else:
                raise ValueError(f"Unknown interpolation method: {method}")

        return result[:, 0] if values_1d else result

    def interpolate_field_data(
        self,
        field_data: Dict[str, Any],
        subcases: List[int] = [1, 2, 3, 4],
        method: str = 'linear'  # Changed from 'rbf' - much faster
    ) -> Dict[str, np.ndarray]:
        """
        Interpolate field data from extract_displacement_field() to polar grid.

        Args:
            field_data: Output from extract_displacement_field()
            subcases: List of subcases to interpolate
            method: Interpolation method

        Returns:
            Dictionary with:
                - z_displacement: [n_nodes, n_subcases] array
                - original_n_nodes: Number of FEA nodes
        """
        mesh_coords = field_data['node_coords']
        z_disp_dict = field_data['z_displacement']

        # Stack subcases
        z_disp_list = []
        for sc in subcases:
            if sc in z_disp_dict:
                z_disp_list.append(z_disp_dict[sc])
            else:
                raise KeyError(f"Subcase {sc} not found in field_data")

        # [n_fea_nodes, n_subcases]
        z_disp_mesh = np.column_stack(z_disp_list)

        # Interpolate to polar grid
        z_disp_grid = self.interpolate_from_mesh(mesh_coords, z_disp_mesh, method=method)

        return {
            'z_displacement': z_disp_grid,  # [n_nodes, n_subcases]
            'original_n_nodes': len(mesh_coords),
        }

    def to_pyg_data(
        self,
        z_displacement: np.ndarray,
        design_vars: np.ndarray,
        objectives: Optional[Dict[str, float]] = None
    ):
        """
        Convert to PyTorch Geometric Data object.

        Args:
            z_displacement: [n_nodes, n_subcases] displacement field
            design_vars: [n_design_vars] design parameters
            objectives: Optional dict of objective values (ground truth)

        Returns:
            torch_geometric.data.Data object
        """
        if not HAS_TORCH:
            raise ImportError("PyTorch required: pip install torch")

        try:
            from torch_geometric.data import Data
        except ImportError:
            raise ImportError("PyTorch Geometric required: pip install torch-geometric")

        # Node features: (r, theta, x, y)
        node_features = torch.tensor(self.get_node_features(normalized=True), dtype=torch.float32)

        # Edge index and features
        edge_index = torch.tensor(self.edge_index, dtype=torch.long)
        edge_attr = torch.tensor(self.get_edge_features(normalized=True), dtype=torch.float32)

        # Target: Z-displacement field
        y = torch.tensor(z_displacement, dtype=torch.float32)

        # Design variables (global feature)
        design = torch.tensor(design_vars, dtype=torch.float32)

        data = Data(
            x=node_features,
            edge_index=edge_index,
            edge_attr=edge_attr,
            y=y,
            design=design,
        )

        # Add objectives if provided
        if objectives:
            for key, value in objectives.items():
                setattr(data, key, torch.tensor([value], dtype=torch.float32))

        return data

    def save(self, path: Path) -> None:
        """Save graph structure to JSON file."""
        path = Path(path)

        data = {
            'r_inner': self.r_inner,
            'r_outer': self.r_outer,
            'n_radial': self.n_radial,
            'n_angular': self.n_angular,
            'n_nodes': self.n_nodes,
            'n_edges': self.edge_index.shape[1],
        }

        with open(path, 'w') as f:
            json.dump(data, f, indent=2)

        # Save arrays separately for efficiency
        np.savez_compressed(
            path.with_suffix('.npz'),
            r=self.r,
            theta=self.theta,
            x=self.x,
            y=self.y,
            edge_index=self.edge_index,
            edge_attr=self.edge_attr,
        )

    @classmethod
    def load(cls, path: Path) -> 'PolarMirrorGraph':
        """Load graph structure from file."""
        path = Path(path)

        with open(path, 'r') as f:
            data = json.load(f)

        return cls(
            r_inner=data['r_inner'],
            r_outer=data['r_outer'],
            n_radial=data['n_radial'],
            n_angular=data['n_angular'],
        )

    def __repr__(self) -> str:
        return (
            f"PolarMirrorGraph("
            f"r=[{self.r_inner}, {self.r_outer}]mm, "
            f"grid={self.n_radial}×{self.n_angular}, "
            f"nodes={self.n_nodes}, "
            f"edges={self.edge_index.shape[1]})"
        )


# =============================================================================
# Convenience functions
# =============================================================================

def create_mirror_dataset(
    study_dir: Path,
    polar_graph: Optional[PolarMirrorGraph] = None,
    subcases: List[int] = [1, 2, 3, 4],
    verbose: bool = True
) -> List[Dict[str, Any]]:
    """
    Create GNN dataset from a study's gnn_data folder.

    Args:
        study_dir: Path to study directory
        polar_graph: PolarMirrorGraph instance (created if None)
        subcases: Subcases to include
        verbose: Print progress

    Returns:
        List of data dictionaries, each containing:
            - z_displacement: [n_nodes, n_subcases]
            - design_vars: [n_vars]
            - trial_number: int
            - original_n_nodes: int
    """
    from optimization_engine.gnn.extract_displacement_field import load_field

    study_dir = Path(study_dir)
    gnn_data_dir = study_dir / "gnn_data"

    if not gnn_data_dir.exists():
        raise FileNotFoundError(f"No gnn_data folder in {study_dir}")

    # Load index
    index_path = gnn_data_dir / "dataset_index.json"
    with open(index_path, 'r') as f:
        index = json.load(f)

    if polar_graph is None:
        polar_graph = PolarMirrorGraph()

    dataset = []

    for trial_num, trial_info in index['trials'].items():
        if trial_info.get('status') != 'success':
            continue

        trial_dir = study_dir / trial_info['trial_dir']

        # Find field file
        field_path = None
        for ext in ['.h5', '.npz']:
            candidate = trial_dir / f"displacement_field{ext}"
            if candidate.exists():
                field_path = candidate
                break

        if field_path is None:
            if verbose:
                print(f"[WARN] No field file for trial {trial_num}")
            continue

        try:
            # Load field data
            field_data = load_field(field_path)

            # Interpolate to polar grid
            interp_result = polar_graph.interpolate_field_data(field_data, subcases=subcases)

            # Get design parameters
            params = trial_info.get('params', {})
            design_vars = np.array(list(params.values()), dtype=np.float32) if params else np.array([])

            dataset.append({
                'z_displacement': interp_result['z_displacement'],
                'design_vars': design_vars,
                'design_names': list(params.keys()) if params else [],
                'trial_number': int(trial_num),
                'original_n_nodes': interp_result['original_n_nodes'],
            })

            if verbose:
                print(f"[OK] Trial {trial_num}: {interp_result['original_n_nodes']} → {polar_graph.n_nodes} nodes")

        except Exception as e:
            if verbose:
                print(f"[ERR] Trial {trial_num}: {e}")

    return dataset


# =============================================================================
# CLI
# =============================================================================

if __name__ == '__main__':
    import argparse

    parser = argparse.ArgumentParser(description='Test PolarMirrorGraph')
    parser.add_argument('--test', action='store_true', help='Run basic tests')
    parser.add_argument('--study', type=Path, help='Create dataset from study')

    args = parser.parse_args()

    if args.test:
        print("="*60)
        print("TESTING PolarMirrorGraph")
        print("="*60)

        # Create graph
        graph = PolarMirrorGraph(r_inner=100, r_outer=650, n_radial=50, n_angular=60)
        print(f"\n{graph}")

        # Check node features
        node_feat = graph.get_node_features(normalized=True)
        print(f"\nNode features shape: {node_feat.shape}")
        print(f"  r range: [{node_feat[:, 0].min():.2f}, {node_feat[:, 0].max():.2f}]")
        print(f"  theta range: [{node_feat[:, 1].min():.2f}, {node_feat[:, 1].max():.2f}]")

        # Check edge features
        edge_feat = graph.get_edge_features(normalized=True)
        print(f"\nEdge features shape: {edge_feat.shape}")
        print(f"  dr range: [{edge_feat[:, 0].min():.2f}, {edge_feat[:, 0].max():.2f}]")
        print(f"  distance range: [{edge_feat[:, 2].min():.2f}, {edge_feat[:, 2].max():.2f}]")

        # Test interpolation with synthetic data
        print("\n--- Testing Interpolation ---")

        # Create fake mesh data (random points in annulus)
        np.random.seed(42)
        n_mesh = 5000
        r_mesh = np.random.uniform(100, 650, n_mesh)
        theta_mesh = np.random.uniform(0, 2*np.pi, n_mesh)
        x_mesh = r_mesh * np.cos(theta_mesh)
        y_mesh = r_mesh * np.sin(theta_mesh)
        mesh_coords = np.column_stack([x_mesh, y_mesh])

        # Synthetic displacement: smooth function
        mesh_values = 0.001 * (r_mesh / 650) ** 2 * np.cos(2 * theta_mesh)

        # Interpolate
        grid_values = graph.interpolate_from_mesh(mesh_coords, mesh_values, method='rbf')
        print(f"Interpolated {n_mesh} mesh nodes → {len(grid_values)} grid nodes")
        print(f"  Input range: [{mesh_values.min():.6f}, {mesh_values.max():.6f}]")
        print(f"  Output range: [{grid_values.min():.6f}, {grid_values.max():.6f}]")

        print("\n✓ All tests passed!")

    elif args.study:
        # Create dataset from study
        print(f"Creating dataset from: {args.study}")

        graph = PolarMirrorGraph()
        dataset = create_mirror_dataset(args.study, polar_graph=graph)

        print(f"\nDataset: {len(dataset)} samples")
        if dataset:
            print(f"  Z-displacement shape: {dataset[0]['z_displacement'].shape}")
            print(f"  Design vars: {len(dataset[0]['design_vars'])} variables")

    else:
        # Default: just show info
        graph = PolarMirrorGraph()
        print(graph)
        print(f"\nNode features: {graph.get_node_features().shape}")
        print(f"Edge index: {graph.edge_index.shape}")
        print(f"Edge features: {graph.edge_attr.shape}")