from __future__ import annotations

import io
from dataclasses import dataclass
from typing import Optional


@dataclass(frozen=True)
class CaptureResult:
    image_bytes: bytes
    # 截图区域在“屏幕坐标系”中的位置（left, top, width, height）
    region: tuple[int, int, int, int]
    # 截图图片像素坐标 -> 屏幕坐标 的缩放系数
    scale_x: float
    scale_y: float


def capture_screen(region: Optional[tuple[int, int, int, int]] = None, *, prefer_mss: bool = True) -> CaptureResult:
    """
    截取屏幕（全屏或局部），返回 PNG bytes + region + 像素到屏幕坐标的缩放。

    - region: (left, top, width, height) 使用屏幕坐标
    - scale_x/scale_y: 用于处理高 DPI 下 mss 取到的物理像素与 pyautogui 屏幕坐标不一致的问题
    """
    if prefer_mss:
        try:
            return _capture_with_mss(region)
        except Exception:
            # 回退到 pyautogui（更贴近“屏幕坐标系”）
            return _capture_with_pyautogui(region)
    return _capture_with_pyautogui(region)


def _capture_with_pyautogui(region: Optional[tuple[int, int, int, int]]) -> CaptureResult:
    import pyautogui

    img = pyautogui.screenshot(region=region)  # type: ignore[arg-type]
    buf = io.BytesIO()
    img.save(buf, format="PNG")

    if region is None:
        w, h = img.size
        region2 = (0, 0, int(w), int(h))
    else:
        region2 = (int(region[0]), int(region[1]), int(region[2]), int(region[3]))

    return CaptureResult(image_bytes=buf.getvalue(), region=region2, scale_x=1.0, scale_y=1.0)


def _capture_with_mss(region: Optional[tuple[int, int, int, int]]) -> CaptureResult:
    import mss
    import mss.tools
    import pyautogui

    with mss.mss() as sct:
        if region is None:
            mon = sct.monitors[1]  # 主屏
            left, top, width, height = int(mon["left"]), int(mon["top"]), int(mon["width"]), int(mon["height"])
        else:
            left, top, width, height = (int(region[0]), int(region[1]), int(region[2]), int(region[3]))

        shot = sct.grab({"left": left, "top": top, "width": width, "height": height})
        png_bytes = mss.tools.to_png(shot.rgb, shot.size)

        # DPI 缩放处理：mss 的像素尺寸可能与 pyautogui 的屏幕坐标尺寸不同
        screen_w, screen_h = pyautogui.size()
        mon = sct.monitors[1]
        mon_w, mon_h = int(mon["width"]), int(mon["height"])
        # 若 mss 返回的是物理像素，mon_w/mon_h 往往大于 pyautogui.size()
        scale_x = float(screen_w) / float(mon_w) if mon_w else 1.0
        scale_y = float(screen_h) / float(mon_h) if mon_h else 1.0

        return CaptureResult(
            image_bytes=png_bytes,
            region=(left, top, width, height),
            scale_x=scale_x,
            scale_y=scale_y,
        )