// RDP 远程桌面弹窗 — 纯函数（视口计算 + 位图绘制 + 二进制帧解析）
import type { KeyboardEvent } from "react";
import type {
  KeyModifierState,
  RdpFrame,
  RdpRawFrame,
} from "./types";
import {
  RDP_BINARY_HEADER,
  RDP_DEFAULT_HEIGHT,
  RDP_DEFAULT_WIDTH,
  RDP_HEADER_HEIGHT,
  RDP_MAX_HEIGHT,
  RDP_MAX_WIDTH,
  RDP_MIN_HEIGHT,
  RDP_MIN_WIDTH,
} from "./types";

/** 将分辨率约束到 [min, max] 且为偶数（RDP 协议要求偶数宽高）。 */
export function clampRdpSize(value: number, min: number, max: number) {
  const clamped = Math.max(min, Math.min(max, value));
  return clamped % 2 === 0 ? clamped : clamped - 1;
}

/** 根据窗口大小 + 全屏状态计算远程桌面最佳分辨率。 */
export function calcRdpViewport(fullscreen: boolean) {
  if (!fullscreen) {
    // 13 寸屏默认保留外层操作空间，最大化时再提升远端分辨率。 // Logan.Li
    return {
      width: Math.min(
        RDP_DEFAULT_WIDTH,
        clampRdpSize(
          Math.floor(window.innerWidth * 0.78),
          RDP_MIN_WIDTH,
          RDP_DEFAULT_WIDTH,
        ),
      ),
      height: Math.min(
        RDP_DEFAULT_HEIGHT,
        clampRdpSize(
          Math.floor(window.innerHeight - 180),
          RDP_MIN_HEIGHT,
          RDP_DEFAULT_HEIGHT,
        ),
      ),
    };
  }
  const maxWidth = window.innerWidth;
  const maxHeight = window.innerHeight - RDP_HEADER_HEIGHT;
  return {
    width: clampRdpSize(Math.floor(maxWidth), RDP_MIN_WIDTH, RDP_MAX_WIDTH),
    height: clampRdpSize(
      Math.floor(maxHeight),
      RDP_MIN_HEIGHT,
      RDP_MAX_HEIGHT,
    ),
  };
}

/** 将 dataURL/bitmap 绘制到 canvas 上下文（先试 createImageBitmap，失败回退 Image.onload）。 */
export async function paintBitmap(
  ctx: CanvasRenderingContext2D,
  frame: RdpFrame,
): Promise<void> {
  const dx = frame.x || 0;
  const dy = frame.y || 0;
  const dw = frame.width || 0;
  const dh = frame.height || 0;
  try {
    if ("createImageBitmap" in window && frame.image) {
      const blob = await fetch(frame.image).then((resp) => resp.blob());
      const bitmap = await createImageBitmap(blob);
      ctx.drawImage(bitmap, dx, dy, dw || bitmap.width, dh || bitmap.height);
      bitmap.close();
      return;
    }
  } catch {
    // dataURL 在个别浏览器上可能解码失败，回退到 Image.onload 路径 // Logan.Li
  }

  await new Promise<void>((resolve, reject) => {
    const img = new Image();
    img.onload = () => {
      ctx.drawImage(img, dx, dy, dw || img.width, dh || img.height);
      resolve();
    };
    img.onerror = () => reject(new Error("bitmap decode failed"));
    img.src = frame.image || "";
  });
}

/** 解析 RDP 二进制帧（magic=RDPR，4 字节 + x/y/width/height 各 4 字节 + RGBA 像素）。 */
export async function parseRawFrame(
  data: Blob | ArrayBuffer,
): Promise<RdpRawFrame | null> {
  const buffer = data instanceof Blob ? await data.arrayBuffer() : data;
  if (buffer.byteLength < RDP_BINARY_HEADER) return null;
  const view = new DataView(buffer);
  const magic =
    String.fromCharCode(view.getUint8(0)) +
    String.fromCharCode(view.getUint8(1)) +
    String.fromCharCode(view.getUint8(2)) +
    String.fromCharCode(view.getUint8(3));
  if (magic !== "RDPR") return null;
  const x = view.getUint32(4, true);
  const y = view.getUint32(8, true);
  const width = view.getUint32(12, true);
  const height = view.getUint32(16, true);
  const bytes = width * height * 4;
  if (width <= 0 || height <= 0 || buffer.byteLength < RDP_BINARY_HEADER + bytes)
    return null;
  return {
    x,
    y,
    width,
    height,
    rgba: new Uint8ClampedArray(buffer, RDP_BINARY_HEADER, bytes),
  };
}

/** 从 keydown/keyup 事件提取修饰键状态（keyup 经常丢失 ctrlKey/metaKey，用 ref 补全）。 */
export function readModifiers(
  e: KeyboardEvent<HTMLElement>,
  fallback: KeyModifierState,
): KeyModifierState {
  // keyup 事件经常丢失 ctrlKey/metaKey，使用本地状态保证组合键释放也能发到远端。 // Logan.Li
  return {
    ctrl: fallback.ctrl || e.ctrlKey,
    alt: fallback.alt || e.altKey,
    shift: fallback.shift || e.shiftKey,
    meta: fallback.meta || e.metaKey,
  };
}