import os
import pathlib
import subprocess
from typing import Union

import matplotlib
import matplotlib.pyplot as plt


class Week1:
    def __init__(self):
        # 避免覆盖内置名 list
        self.qualities = [2, 7, 12, 17, 22, 27, 31]

    def _ffmpeg_path(self) -> pathlib.Path:
        """
        返回项目 bin 目录下 ffmpeg 的可执行路径。
        Week1/Week1.py 位于项目的 Week1 目录内，bin 与 Week1 处于同级。
        """
        here = pathlib.Path(__file__).resolve()
        project_root = here.parent.parent  # <project_root>/Week1/Week1.py -> <project_root>
        bin_dir = project_root / "bin"
        exe_name = "ffmpeg.exe" if os.name == "nt" else "ffmpeg"
        ffmpeg = bin_dir / exe_name
        if not ffmpeg.exists():
            raise FileNotFoundError(f"未找到 ffmpeg 可执行文件: {ffmpeg}")
        return ffmpeg

    def compress(self, image_src: Union[str, pathlib.Path]):
        """
        使用不同 q:v 质量参数将 PNG 转为 JPEG。
        输出文件与输入文件位于同目录，命名为 <原名>_<q>.jpg
        """
        image_path = pathlib.Path(image_src).resolve()
        if not image_path.exists():
            raise FileNotFoundError(f"输入图像不存在: {image_path}")

        ffmpeg = self._ffmpeg_path()
        stem = image_path.stem
        parent = image_path.parent

        for q in self.qualities:
            out_path = parent / f"{stem}_{q}.jpg"
            # -y 覆盖已存在文件；参数以列表方式传入
            cmd = [
                str(ffmpeg),
                "-y",
                "-i", str(image_path),
                "-q:v", str(q),
                str(out_path),
            ]
            # 失败时抛异常，便于定位问题
            subprocess.run(cmd, check=True)

    def render(self, image_src: Union[str, pathlib.Path]):
        """
        读取生成的 JPEG 文件大小，并绘制质量(q) vs 文件大小(bytes) 的折线图。
        """
        image_path = pathlib.Path(image_src).resolve()
        stem = image_path.stem
        parent = image_path.parent

        sizes = []
        qualities = []
        for q in self.qualities:
            jpg_path = parent / f"{stem}_{q}.jpg"
            if not jpg_path.exists():
                # 若缺失，给出清晰异常，提示先运行 compress
                raise FileNotFoundError(f"缺少压缩输出文件，请先运行 compress: {jpg_path}")
            qualities.append(q)
            sizes.append(os.path.getsize(jpg_path)/8)

        # 使用 pyplot 正确保存图像
        plt.figure(figsize=(6, 4))
        plt.plot(qualities, sizes, marker="o")
        plt.xlabel("JPEG quality (q:v)")
        plt.ylabel("File size (Kbytes)")
        plt.title("Quality vs File Size")
        plt.grid(True)

        project_root = pathlib.Path(__file__).resolve().parent.parent
        out_png = project_root / "data" / "render.png"
        out_png.parent.mkdir(parents=True, exist_ok=True)
        plt.tight_layout()
        plt.savefig(str(out_png))
        plt.close()