from __future__ import annotations

from pathlib import Path
from typing import Any

from .frames import seconds_to_timecode
from .manifest import read_jsonl, write_manifest
from .timeline import derive_time_from_reference


def build_clip_records(
    frame_records: list[dict[str, Any]],
    clip_config: dict[str, Any],
) -> list[dict[str, Any]]:
    sampled_frames = [
        record for record in frame_records if record.get("status") == "sampled"
    ]
    by_video: dict[str, list[dict[str, Any]]] = {}
    for frame in sampled_frames:
        by_video.setdefault(str(frame["video_id"]), []).append(frame)

    clips = []
    for video_id, frames in sorted(by_video.items()):
        clips.extend(_build_video_clips(video_id, frames, clip_config))
    return clips


def build_clip_records_from_manifest(
    frame_manifest_path: str | Path,
    clip_manifest_path: str | Path,
    clip_config: dict[str, Any],
) -> list[dict[str, Any]]:
    clips = build_clip_records(read_jsonl(frame_manifest_path), clip_config)
    write_manifest(clip_manifest_path, clips)
    return clips


def _build_video_clips(
    video_id: str,
    frames: list[dict[str, Any]],
    clip_config: dict[str, Any],
) -> list[dict[str, Any]]:
    sorted_frames = sorted(frames, key=lambda frame: float(frame["offset_seconds"]))
    if not sorted_frames:
        return []

    length_seconds = float(clip_config.get("length_seconds", 10))
    stride_seconds = float(clip_config.get("stride_seconds", length_seconds))
    frames_per_clip = int(clip_config.get("frames_per_clip", 8))
    min_frames_per_clip = int(clip_config.get("min_frames_per_clip", 4))
    max_offset = max(float(frame["offset_seconds"]) for frame in sorted_frames)
    timeline_end = _estimated_timeline_end(sorted_frames)

    clips = []
    clip_index = 1
    start = 0.0
    while start <= max_offset:
        end = min(start + length_seconds, timeline_end)
        in_window = [
            frame
            for frame in sorted_frames
            if start <= float(frame["offset_seconds"]) < end
        ]
        if len(in_window) >= min_frames_per_clip:
            selected_frames = _uniform_sample(in_window, frames_per_clip)
            start_beijing_time, end_beijing_time = _clip_beijing_time_range(
                in_window,
                start,
                end,
            )
            clip = {
                "video_id": video_id,
                "clip_id": f"{video_id}_c{clip_index:06d}",
                "clip_start_seconds": round(start, 6),
                "clip_end_seconds": round(end, 6),
                "clip_start_timecode": seconds_to_timecode(start),
                "clip_end_timecode": seconds_to_timecode(end),
                "frame_times": [_frame_time(frame) for frame in selected_frames],
                "status": "pending",
                "retry_count": 0,
                "last_error": None,
            }
            if start_beijing_time is not None:
                clip["clip_start_beijing_time"] = start_beijing_time
            if end_beijing_time is not None:
                clip["clip_end_beijing_time"] = end_beijing_time
            clips.append(clip)
            clip_index += 1
        start += stride_seconds
    return clips


def _estimated_timeline_end(frames: list[dict[str, Any]]) -> float:
    offsets = [float(frame["offset_seconds"]) for frame in frames]
    if len(offsets) < 2:
        return offsets[-1]
    intervals = [
        current - previous
        for previous, current in zip(offsets, offsets[1:])
        if current > previous
    ]
    if not intervals:
        return offsets[-1]
    return offsets[-1] + min(intervals)


def _uniform_sample(
    frames: list[dict[str, Any]],
    frames_per_clip: int,
) -> list[dict[str, Any]]:
    if len(frames) <= frames_per_clip:
        return frames
    if frames_per_clip <= 1:
        return [frames[0]]
    last_index = len(frames) - 1
    indexes = [
        round(position * last_index / (frames_per_clip - 1))
        for position in range(frames_per_clip)
    ]
    return [frames[index] for index in indexes]


def _frame_time(frame: dict[str, Any]) -> dict[str, Any]:
    record = {
        "frame_id": frame.get("frame_id"),
        "frame_path": frame.get("frame_path"),
        "offset_seconds": frame.get("offset_seconds"),
        "timecode": frame.get("timecode"),
        "pts_time": frame.get("pts_time"),
    }
    if frame.get("beijing_time") is not None:
        record["beijing_time"] = frame.get("beijing_time")
    return record


def _clip_beijing_time_range(
    frames: list[dict[str, Any]],
    start: float,
    end: float,
) -> tuple[str | None, str | None]:
    for frame in frames:
        reference_time = frame.get("beijing_time")
        if not reference_time:
            continue
        reference_offset = frame.get("offset_seconds")
        return (
            derive_time_from_reference(
                str(reference_time),
                reference_offset_seconds=reference_offset,
                target_offset_seconds=start,
            ),
            derive_time_from_reference(
                str(reference_time),
                reference_offset_seconds=reference_offset,
                target_offset_seconds=end,
            ),
        )
    return None, None