"""Key frame selection utilities."""

from __future__ import annotations

import logging
from dataclasses import dataclass, field
from datetime import datetime
from pathlib import Path
from typing import Any, Iterable, Mapping

import cv2
import numpy as np

from .config import WorkerSettings
from .pipeline import run_stream3r_inference
from .runtime import WorkerRuntime


logger = logging.getLogger(__name__)


@dataclass(slots=True)
class FrameRecord:
    index: int
    frame_id: str
    path: Path
    source: str | None = None
    timestamp: str | None = None
    metadata: dict[str, Any] = field(default_factory=dict)


@dataclass(slots=True)
class KeyframeSelectionResult:
    indices: list[int]
    diagnostics: list[dict[str, Any]]
    top_k: int


def pose_confidence(predictions: Mapping[str, np.ndarray]) -> np.ndarray | None:
    if "world_points_conf" in predictions:
        return np.asarray(predictions["world_points_conf"], dtype=np.float32)
    if "depth_conf" in predictions:
        return np.asarray(predictions["depth_conf"], dtype=np.float32)
    return None


def _camera_poses(extrinsic: np.ndarray) -> tuple[np.ndarray, np.ndarray]:
    matrices = np.asarray(extrinsic, dtype=np.float64)
    if matrices.ndim != 3 or matrices.shape[1:] != (3, 4):
        raise ValueError("Extrinsic array must have shape (N, 3, 4)")
    count = matrices.shape[0]
    rotations = np.empty((count, 3, 3), dtype=np.float64)
    translations = np.empty((count, 3), dtype=np.float64)
    for idx in range(count):
        mat = np.eye(4, dtype=np.float64)
        mat[:3, :4] = matrices[idx]
        cam_to_world = np.linalg.inv(mat)
        rotations[idx] = cam_to_world[:3, :3]
        translations[idx] = cam_to_world[:3, 3]
    return rotations, translations


def _compute_motion_deltas(rotations: np.ndarray, translations: np.ndarray, rot_weight: float) -> np.ndarray:
    count = rotations.shape[0]
    deltas = np.zeros(count, dtype=np.float64)
    if count <= 1:
        return deltas
    for idx in range(1, count):
        delta_t = np.linalg.norm(translations[idx] - translations[idx - 1])
        rel = rotations[idx - 1].T @ rotations[idx]
        trace = np.clip((np.trace(rel) - 1.0) / 2.0, -1.0, 1.0)
        delta_r = float(np.arccos(trace))
        deltas[idx] = delta_t + rot_weight * delta_r
    return deltas


def _hash_quantized_voxels(coords: np.ndarray) -> np.ndarray:
    coords = coords.astype(np.int64, copy=False)
    primes = np.array([73856093, 19349663, 83492791], dtype=np.int64)
    return coords @ primes


def _frame_voxel_sets(
    world_points: np.ndarray,
    confidence: np.ndarray,
    *,
    threshold: float,
    voxel_size: float,
    max_points: int,
) -> tuple[list[set[int]], int]:
    rng = np.random.default_rng(42)
    frames = world_points.shape[0]
    voxel_sets: list[set[int]] = []
    global_union: set[int] = set()
    if voxel_size <= 0.0:
        return [set() for _ in range(frames)], 0
    for idx in range(frames):
        conf_frame = confidence[idx]
        mask = conf_frame >= threshold
        if not np.any(mask):
            voxel_sets.append(set())
            continue
        points = world_points[idx][mask]
        if points.shape[0] > max_points:
            sample_idx = rng.choice(points.shape[0], max_points, replace=False)
            points = points[sample_idx]
        quantized = np.floor(points / voxel_size).astype(np.int64, copy=False)
        hashes = np.unique(_hash_quantized_voxels(quantized))
        voxel_set = set(int(v) for v in hashes.tolist())
        voxel_sets.append(voxel_set)
        global_union.update(voxel_set)
    return voxel_sets, len(global_union)


def _select_motion_indices(
    motion_deltas: np.ndarray,
    *,
    threshold: float,
    min_gap: int,
    max_gap: int,
) -> tuple[list[int], dict[int, dict[str, float]]]:
    total_frames = motion_deltas.shape[0]
    if total_frames == 0:
        return [], {}
    selected = [0]
    diagnostics: dict[int, dict[str, float]] = {0: {"motion_delta": 0.0, "cum_motion": 0.0}}
    cumulative = 0.0
    gap = 0
    for idx in range(1, total_frames):
        delta = float(motion_deltas[idx])
        cumulative += delta
        gap += 1
        if gap < max(1, min_gap):
            continue
        should_select = cumulative >= threshold
        if max_gap > 0 and gap >= max_gap:
            should_select = True
        if should_select:
            selected.append(idx)
            diagnostics[idx] = {"motion_delta": delta, "cum_motion": cumulative}
            cumulative = 0.0
            gap = 0
    if selected[-1] != total_frames - 1:
        selected.append(total_frames - 1)
        diagnostics.setdefault(total_frames - 1, {"motion_delta": float(motion_deltas[-1]), "cum_motion": cumulative})
    return selected, diagnostics


def select_keyframes_motion_coverage(
    frame_records: list[FrameRecord],
    predictions: Mapping[str, np.ndarray],
    settings: WorkerSettings,
    requested_top_k: int,
) -> KeyframeSelectionResult | None:
    extrinsic = np.asarray(predictions.get("extrinsic"))
    if extrinsic.size == 0:
        return None
    rotations, translations = _camera_poses(extrinsic)
    motion_deltas = _compute_motion_deltas(rotations, translations, settings.keyframe_rotation_weight)
    motion_indices, motion_diag = _select_motion_indices(
        motion_deltas,
        threshold=settings.keyframe_motion_threshold,
        min_gap=max(1, settings.keyframe_min_gap_frames),
        max_gap=max(0, settings.keyframe_max_gap_frames),
    )

    total_frames = len(frame_records)
    confidence = pose_confidence(predictions)
    world_points = predictions.get("world_points")
    if world_points is None:
        world_points = predictions.get("world_points_from_depth")

    voxel_sets: list[set[int]] = [set() for _ in range(total_frames)]
    total_voxels = 0
    mean_conf = np.zeros(total_frames, dtype=np.float32)
    if confidence is not None:
        mean_conf = confidence.reshape(confidence.shape[0], -1).mean(axis=1)

    if confidence is not None and world_points is not None:
        voxel_sets, total_voxels = _frame_voxel_sets(
            np.asarray(world_points),
            np.asarray(confidence),
            threshold=settings.keyframe_coverage_confidence,
            voxel_size=settings.keyframe_coverage_voxel_size,
            max_points=max(1000, settings.keyframe_coverage_max_points),
        )

    total_voxels = max(total_voxels, 1)
    top_k = requested_top_k if requested_top_k > 0 else settings.keyframe_default_top_k
    top_k = max(min(top_k, total_frames), len(motion_indices))

    selected_set: set[int] = set(motion_indices)
    diagnostics: dict[int, dict[str, Any]] = {}
    covered: set[int] = set()

    for idx in motion_indices:
        gain_count = len(voxel_sets[idx] - covered) if voxel_sets[idx] else 0
        gain_ratio = gain_count / total_voxels
        covered.update(voxel_sets[idx])
        diagnostics[idx] = {
            "frame_id": frame_records[idx].frame_id,
            "frame_index": frame_records[idx].index,
            "reason": "motion",
            "motion_delta": float(motion_deltas[idx]),
            "cum_motion": float(motion_diag.get(idx, {}).get("cum_motion", 0.0)),
            "coverage_gain_ratio": float(gain_ratio),
            "coverage_gain_count": int(gain_count),
            "mean_confidence": float(mean_conf[idx]) if confidence is not None else None,
        }

    if len(selected_set) < top_k and total_voxels > 0:
        min_gain_ratio = settings.keyframe_min_gain_ratio
        remaining = [i for i in range(total_frames) if i not in selected_set and voxel_sets[i]]
        while remaining and len(selected_set) < top_k:
            best_idx = -1
            best_gain = -1
            best_ratio = -1.0
            for idx in remaining:
                gain = len(voxel_sets[idx] - covered)
                if gain <= 0:
                    continue
                ratio = gain / total_voxels
                if ratio > best_ratio or (np.isclose(ratio, best_ratio) and gain > best_gain):
                    best_idx = idx
                    best_gain = gain
                    best_ratio = ratio
            if best_idx == -1 or best_ratio < min_gain_ratio:
                break
            selected_set.add(best_idx)
            covered.update(voxel_sets[best_idx])
            diagnostics[best_idx] = {
                "frame_id": frame_records[best_idx].frame_id,
                "frame_index": frame_records[best_idx].index,
                "reason": "coverage",
                "motion_delta": float(motion_deltas[best_idx]),
                "cum_motion": float(motion_diag.get(best_idx, {}).get("cum_motion", 0.0)),
                "coverage_gain_ratio": float(best_ratio),
                "coverage_gain_count": int(best_gain),
                "mean_confidence": float(mean_conf[best_idx]) if confidence is not None else None,
            }
            remaining.remove(best_idx)

    if requested_top_k > 0 and len(selected_set) > requested_top_k:
        coverage_candidates = [idx for idx in selected_set if diagnostics[idx]["reason"] == "coverage"]
        coverage_candidates.sort(key=lambda idx: diagnostics[idx].get("coverage_gain_ratio", 0.0))
        while len(selected_set) > requested_top_k and coverage_candidates:
            drop_idx = coverage_candidates.pop(0)
            selected_set.remove(drop_idx)
            diagnostics.pop(drop_idx, None)

    final_indices = sorted(selected_set)
    final_diags = [diagnostics[idx] for idx in final_indices]
    return KeyframeSelectionResult(indices=final_indices, diagnostics=final_diags, top_k=len(final_indices))


def run_keyframe_prepass(
    *,
    runtime: WorkerRuntime,
    payload: Mapping[str, Any],
    frame_records: list[FrameRecord],
    mode: str,
    streaming: bool,
    window_size: int | None,
) -> KeyframeSelectionResult | None:
    if len(frame_records) <= 1:
        return None

    settings = runtime.settings
    top_k_payload = int(payload.get("prepass_top_k") or payload.get("top_k_frames") or payload.get("top_k") or 0)

    try:
        inference = run_stream3r_inference(
            runtime=runtime,
            image_paths=[record.path for record in frame_records],
            mode=mode,
            streaming=streaming,
            cache_output_path=None,
            progress_cb=None,
            window_size=window_size if streaming and mode == "window" else None,
        )
    except Exception:
        logger.exception("Keyframe pre-pass inference failed")
        return None

    try:
        return select_keyframes_motion_coverage(
            frame_records,
            inference.predictions,
            settings,
            requested_top_k=top_k_payload,
        )
    finally:
        del inference


def extract_video_frames(
    video_path: Path,
    output_dir: Path,
    *,
    target_fps: float | None = None,
    max_frames: int | None = None,
) -> tuple[list[FrameRecord], float]:
    if not video_path.exists():
        raise FileNotFoundError(f"Video file not found: {video_path}")

    output_dir.mkdir(parents=True, exist_ok=True)
    cap = cv2.VideoCapture(str(video_path))
    if not cap.isOpened():
        raise RuntimeError(f"Failed to open video: {video_path}")

    native_fps = cap.get(cv2.CAP_PROP_FPS)
    if not native_fps or native_fps <= 0:
        native_fps = 30.0
    frame_interval = 1
    if target_fps and target_fps > 0:
        frame_interval = max(1, int(round(native_fps / target_fps)))

    frame_records: list[FrameRecord] = []
    total_frames = int(cap.get(cv2.CAP_PROP_FRAME_COUNT) or 0)
    frame_idx = 0
    extracted = 0
    success, frame = cap.read()
    while success:
        if frame_idx % frame_interval == 0:
            frame_id = f"frame_{extracted:06d}"
            frame_path = output_dir / f"{frame_id}.jpg"
            if not cv2.imwrite(str(frame_path), frame):
                cap.release()
                raise RuntimeError(f"Failed to write frame: {frame_path}")
            timestamp_s = frame_idx / native_fps
            frame_records.append(
                FrameRecord(
                    index=extracted,
                    frame_id=frame_id,
                    path=frame_path,
                    metadata={"frame_number": frame_idx, "timestamp_s": timestamp_s},
                )
            )
            extracted += 1
            if max_frames and extracted >= max_frames:
                break
        frame_idx += 1
        success, frame = cap.read()

    cap.release()
    if not frame_records:
        raise RuntimeError("No frames extracted from video")

    return frame_records, native_fps


def linear_sample_indices(total: int, desired: int) -> list[int]:
    if desired <= 0 or total <= desired:
        return list(range(total))
    step = total / desired
    return [min(total - 1, int(round(i * step))) for i in range(desired)]


def build_keyframe_uploads(
    runtime: WorkerRuntime,
    scene_id: str,
    selected_records: Iterable[FrameRecord],
    diagnostics: list[dict[str, Any]],
    *,
    subdir: str,
) -> tuple[list[dict[str, Any]], list[dict[str, Any]]]:
    diag_by_index = {entry.get("frame_index"): entry for entry in diagnostics}
    storage_entries: list[dict[str, Any]] = []
    media_entries: list[dict[str, Any]] = []

    for record in selected_records:
        diag = diag_by_index.get(record.index, {})
        filename = f"{record.frame_id}.jpg"
        key = runtime.storage.build_key(scene_id, subdir, filename)
        uri = runtime.storage.upload_file(record.path, key, content_type="image/jpeg")
        storage_entries.append(
            {
                "frame_id": record.frame_id,
                "frame_index": record.index,
                "url": uri,
                "storage_key": key,
                "diagnostics": diag,
            }
        )

        media_entries.append(
            {
                "media_type": "image",
                "file": key,
                "captured_at": _diagnostic_captured_at(record, diag),
            }
        )

    return storage_entries, media_entries


def _diagnostic_captured_at(record: FrameRecord, diag: Mapping[str, Any]) -> str | None:
    if record.timestamp:
        return record.timestamp
    ts = diag.get("timestamp") or record.metadata.get("timestamp")
    if isinstance(ts, str):
        return ts
    if isinstance(ts, (int, float)):
        return datetime.utcfromtimestamp(float(ts)).isoformat() + "Z"
    timestamp_s = record.metadata.get("timestamp_s")
    if isinstance(timestamp_s, (int, float)):
        return datetime.utcfromtimestamp(float(timestamp_s)).isoformat() + "Z"
    return None