"""
视频合成服务
"""
import os
import subprocess
import json
import shlex
from pathlib import Path
from loguru import logger
from typing import Optional

class VideoService:
    def __init__(self):
        pass

    def _run_ffmpeg(self, cmd: list) -> bool:
        cmd_str = ' '.join(shlex.quote(str(c)) for c in cmd)
        logger.debug(f"FFmpeg CMD: {cmd_str}")
        try:
            # Synchronous call for BackgroundTasks compatibility
            result = subprocess.run(
                cmd,
                shell=False,
                capture_output=True,
                text=True,
                encoding='utf-8',
            )
            if result.returncode != 0:
                logger.error(f"FFmpeg Error: {result.stderr}")
                return False
            return True
        except Exception as e:
            logger.error(f"FFmpeg Exception: {e}")
            return False

    def _get_duration(self, file_path: str) -> float:
        # Synchronous call for BackgroundTasks compatibility
        # 使用参数列表形式避免 shell=True 的命令注入风险
        cmd = [
            'ffprobe', '-v', 'error',
            '-show_entries', 'format=duration',
            '-of', 'default=noprint_wrappers=1:nokey=1',
            file_path
        ]
        try:
            result = subprocess.run(
                cmd,
                capture_output=True,
                text=True,
            )
            return float(result.stdout.strip())
        except Exception:
            return 0.0

    def mix_audio(
        self,
        voice_path: str,
        bgm_path: str,
        output_path: str,
        bgm_volume: float = 0.2
    ) -> str:
        """混合人声与背景音乐"""
        Path(output_path).parent.mkdir(parents=True, exist_ok=True)

        volume = max(0.0, min(float(bgm_volume), 1.0))
        filter_complex = (
            f"[0:a]volume=1.0[a0];"
            f"[1:a]volume={volume}[a1];"
            f"[a0][a1]amix=inputs=2:duration=first:dropout_transition=2:normalize=0[aout]"
        )

        cmd = [
            "ffmpeg", "-y",
            "-i", voice_path,
            "-stream_loop", "-1", "-i", bgm_path,
            "-filter_complex", filter_complex,
            "-map", "[aout]",
            "-c:a", "pcm_s16le",
            "-shortest",
            output_path,
        ]

        if self._run_ffmpeg(cmd):
            return output_path
        raise RuntimeError("FFmpeg audio mix failed")

    async def compose(
        self,
        video_path: str,
        audio_path: str,
        output_path: str,
        subtitle_path: Optional[str] = None
    ) -> str:
        """合成视频"""
        # Ensure output dir
        Path(output_path).parent.mkdir(parents=True, exist_ok=True)
        
        video_duration = self._get_duration(video_path)
        audio_duration = self._get_duration(audio_path)
        
        # Audio loop if needed
        loop_count = 1
        if audio_duration > video_duration and video_duration > 0:
            loop_count = int(audio_duration / video_duration) + 1
            
        cmd = ["ffmpeg", "-y"]
        
        # Input video (stream_loop must be before -i)
        if loop_count > 1:
            cmd.extend(["-stream_loop", str(loop_count)])
        cmd.extend(["-i", video_path])
        
        # Input audio
        cmd.extend(["-i", audio_path])
        
        # Filter complex
        filter_complex = []
        
        # Subtitles (skip for now to mimic previous state or implement basic)
        # Previous state: subtitles disabled due to font issues
        # if subtitle_path: ...
        
        # Audio map with high quality encoding
        cmd.extend([
            "-c:v", "libx264",
            "-preset", "slow",      # 慢速预设，更好的压缩效率
            "-crf", "18",           # 高质量（与 LatentSync 一致）
            "-c:a", "aac",
            "-b:a", "192k",         # 音频比特率
            "-shortest"
        ])
        # Use audio from input 1
        cmd.extend(["-map", "0:v", "-map", "1:a"])
        
        cmd.append(output_path)
        
        if self._run_ffmpeg(cmd):
            return output_path
        else:
            raise RuntimeError("FFmpeg composition failed")