"""
Effect processing backends.

Provides abstraction over different rendering backends:
- numpy: CPU-based, works everywhere, ~3-5 fps
- glsl: GPU-based, requires OpenGL, 30+ fps (future)
"""

import numpy as np
from abc import ABC, abstractmethod
from typing import List, Dict, Any, Optional
from pathlib import Path


class Backend(ABC):
    """Abstract base class for effect processing backends."""

    @abstractmethod
    def process_frame(
        self,
        frames: List[np.ndarray],
        effects_per_frame: List[List[Dict]],
        compositor_config: Dict,
        t: float,
        analysis_data: Dict,
    ) -> np.ndarray:
        """
        Process multiple input frames through effects and composite.

        Args:
            frames: List of input frames (one per source)
            effects_per_frame: List of effect chains (one per source)
            compositor_config: How to blend the layers
            t: Current time in seconds
            analysis_data: Analysis data for binding resolution

        Returns:
            Composited output frame
        """
        pass

    @abstractmethod
    def load_effect(self, effect_path: Path) -> Any:
        """Load an effect definition."""
        pass


class NumpyBackend(Backend):
    """
    CPU-based effect processing using NumPy.

    Uses existing sexp_effects interpreter for effect execution.
    Works on any system, but limited to ~3-5 fps for complex effects.
    """

    def __init__(self, recipe_dir: Path = None, minimal_primitives: bool = True):
        self.recipe_dir = recipe_dir or Path(".")
        self.minimal_primitives = minimal_primitives
        self._interpreter = None
        self._loaded_effects = {}

    def _get_interpreter(self):
        """Lazy-load the sexp interpreter."""
        if self._interpreter is None:
            from sexp_effects import get_interpreter
            self._interpreter = get_interpreter(minimal_primitives=self.minimal_primitives)
        return self._interpreter

    def load_effect(self, effect_path: Path) -> Any:
        """Load an effect from sexp file."""
        effect_key = str(effect_path)
        if effect_key not in self._loaded_effects:
            interp = self._get_interpreter()
            interp.load_effect(str(effect_path))
            self._loaded_effects[effect_key] = effect_path.stem
        return self._loaded_effects[effect_key]

    def _resolve_binding(self, value: Any, t: float, analysis_data: Dict) -> Any:
        """Resolve a parameter binding to its value at time t."""
        if not isinstance(value, dict):
            return value

        if "_binding" in value or "_bind" in value:
            source = value.get("source") or value.get("_bind")
            feature = value.get("feature", "values")
            range_map = value.get("range")

            track = analysis_data.get(source, {})
            times = track.get("times", [])
            values = track.get("values", [])

            if not times or not values:
                return 0.0

            # Find value at time t (linear interpolation)
            if t <= times[0]:
                val = values[0]
            elif t >= times[-1]:
                val = values[-1]
            else:
                # Binary search for bracket
                for i in range(len(times) - 1):
                    if times[i] <= t <= times[i + 1]:
                        alpha = (t - times[i]) / (times[i + 1] - times[i])
                        val = values[i] * (1 - alpha) + values[i + 1] * alpha
                        break
                else:
                    val = values[-1]

            # Apply range mapping
            if range_map and len(range_map) == 2:
                val = range_map[0] + val * (range_map[1] - range_map[0])

            return val

        return value

    def _apply_effect(
        self,
        frame: np.ndarray,
        effect_name: str,
        params: Dict,
        t: float,
        analysis_data: Dict,
    ) -> np.ndarray:
        """Apply a single effect to a frame."""
        # Resolve bindings in params
        resolved_params = {"_time": t}
        for key, value in params.items():
            if key in ("effect", "effect_path", "cid", "analysis_refs"):
                continue
            resolved_params[key] = self._resolve_binding(value, t, analysis_data)

        # Try fast native effects first
        result = self._apply_native_effect(frame, effect_name, resolved_params)
        if result is not None:
            return result

        # Fall back to sexp interpreter for complex effects
        interp = self._get_interpreter()
        if effect_name in interp.effects:
            result, _ = interp.run_effect(effect_name, frame, resolved_params, {})
            return result

        # Unknown effect - pass through
        return frame

    def _apply_native_effect(
        self,
        frame: np.ndarray,
        effect_name: str,
        params: Dict,
    ) -> Optional[np.ndarray]:
        """Fast native numpy effects for real-time streaming."""
        import cv2

        if effect_name == "zoom":
            amount = float(params.get("amount", 1.0))
            if abs(amount - 1.0) < 0.01:
                return frame
            h, w = frame.shape[:2]
            # Crop center and resize
            new_w, new_h = int(w / amount), int(h / amount)
            x1, y1 = (w - new_w) // 2, (h - new_h) // 2
            cropped = frame[y1:y1+new_h, x1:x1+new_w]
            return cv2.resize(cropped, (w, h))

        elif effect_name == "rotate":
            angle = float(params.get("angle", 0))
            if abs(angle) < 0.5:
                return frame
            h, w = frame.shape[:2]
            center = (w // 2, h // 2)
            matrix = cv2.getRotationMatrix2D(center, angle, 1.0)
            return cv2.warpAffine(frame, matrix, (w, h))

        elif effect_name == "brightness":
            amount = float(params.get("amount", 1.0))
            return np.clip(frame * amount, 0, 255).astype(np.uint8)

        elif effect_name == "invert":
            amount = float(params.get("amount", 1.0))
            if amount < 0.5:
                return frame
            return 255 - frame

        # Not a native effect
        return None

    def process_frame(
        self,
        frames: List[np.ndarray],
        effects_per_frame: List[List[Dict]],
        compositor_config: Dict,
        t: float,
        analysis_data: Dict,
    ) -> np.ndarray:
        """
        Process frames through effects and composite.
        """
        if not frames:
            return np.zeros((720, 1280, 3), dtype=np.uint8)

        processed = []

        # Apply effects to each input frame
        for i, (frame, effects) in enumerate(zip(frames, effects_per_frame)):
            result = frame.copy()
            for effect_config in effects:
                effect_name = effect_config.get("effect", "")
                if effect_name:
                    result = self._apply_effect(
                        result, effect_name, effect_config, t, analysis_data
                    )
            processed.append(result)

        # Composite layers
        if len(processed) == 1:
            return processed[0]

        return self._composite(processed, compositor_config, t, analysis_data)

    def _composite(
        self,
        frames: List[np.ndarray],
        config: Dict,
        t: float,
        analysis_data: Dict,
    ) -> np.ndarray:
        """Composite multiple frames into one."""
        mode = config.get("mode", "alpha")
        weights = config.get("weights", [1.0 / len(frames)] * len(frames))

        # Resolve weight bindings
        resolved_weights = []
        for w in weights:
            resolved_weights.append(self._resolve_binding(w, t, analysis_data))

        # Normalize weights
        total = sum(resolved_weights)
        if total > 0:
            resolved_weights = [w / total for w in resolved_weights]
        else:
            resolved_weights = [1.0 / len(frames)] * len(frames)

        # Resize frames to match first frame
        target_h, target_w = frames[0].shape[:2]
        resized = []
        for frame in frames:
            if frame.shape[:2] != (target_h, target_w):
                import cv2
                frame = cv2.resize(frame, (target_w, target_h))
            resized.append(frame.astype(np.float32))

        # Weighted blend
        result = np.zeros_like(resized[0])
        for frame, weight in zip(resized, resolved_weights):
            result += frame * weight

        return np.clip(result, 0, 255).astype(np.uint8)


class GLSLBackend(Backend):
    """
    GPU-based effect processing using OpenGL/GLSL.

    Requires GPU with OpenGL 3.3+ support (or Mesa software renderer).
    Achieves 30+ fps real-time processing.

    TODO: Implement when ready for GPU acceleration.
    """

    def __init__(self):
        raise NotImplementedError(
            "GLSL backend not yet implemented. Use NumpyBackend for now."
        )

    def load_effect(self, effect_path: Path) -> Any:
        pass

    def process_frame(
        self,
        frames: List[np.ndarray],
        effects_per_frame: List[List[Dict]],
        compositor_config: Dict,
        t: float,
        analysis_data: Dict,
    ) -> np.ndarray:
        pass


def get_backend(name: str = "numpy", **kwargs) -> Backend:
    """
    Get a backend by name.

    Args:
        name: "numpy" or "glsl"
        **kwargs: Backend-specific options

    Returns:
        Backend instance
    """
    if name == "numpy":
        return NumpyBackend(**kwargs)
    elif name == "glsl":
        return GLSLBackend(**kwargs)
    else:
        raise ValueError(f"Unknown backend: {name}")