app/operations/trim.py

from __future__ import annotations

from collections.abc import Sequence
from pathlib import Path
from typing import Any

from app.core.exceptions import InputError
from app.models.media import InputMedia, OperationResult
from app.operations.common import audio_codec, execute, output_path, require_inputs, video_codecs
from app.services.ffmpeg_service import FFmpegService


def _times(params: dict[str, Any]) -> tuple[float, float | None]:
    try:
        start = float(params.get("start", 0))
        duration = float(params["duration"]) if params.get("duration") is not None else None
        if duration is None and params.get("end") is not None:
            duration = float(params["end"]) - start
    except (TypeError, ValueError) as exc:
        raise InputError("start, end, and duration must be numbers") from exc
    if start < 0 or (duration is not None and duration <= 0):
        raise InputError("start must be non-negative and duration/end must follow start")
    return start, duration


async def trim_video(
    ffmpeg: FFmpegService, inputs: Sequence[InputMedia], params: dict[str, Any], output_dir: Path
) -> OperationResult:
    require_inputs(inputs)
    start, duration = _times(params)
    output = output_path(output_dir, "trimmed", "mp4")
    args: list[str | Path] = ["-ss", str(start), "-i", inputs[0].temp_path]
    if duration is not None:
        args += ["-t", str(duration)]
    args += [*video_codecs("mp4"), output]
    return await execute(ffmpeg, args, output, "video.trim", {"start": start, "duration": duration})


async def trim_audio(
    ffmpeg: FFmpegService, inputs: Sequence[InputMedia], params: dict[str, Any], output_dir: Path
) -> OperationResult:
    require_inputs(inputs)
    start, duration = _times(params)
    output = output_path(output_dir, "trimmed", "mp3")
    args: list[str | Path] = ["-ss", str(start), "-i", inputs[0].temp_path]
    if duration is not None:
        args += ["-t", str(duration)]
    args += [*audio_codec("mp3"), output]
    return await execute(ffmpeg, args, output, "audio.trim", {"start": start, "duration": duration})