/**
 * 行内短代码解析（纯函数）：
 * ==高亮== / [kbd]Ctrl[/kbd] / [color=前景( bg=背景)]文字[/color] / [bg=背景]文字[/bg]
 * 颜色值白名单（#hex 或 CSS 颜色名），非法值整段按普通文本回退，防 CSS 注入。
 */

export type InlineShortcodeSegment =
  | { type: "text"; value: string }
  | { type: "mark"; value: string }
  | { type: "kbd"; value: string }
  | { type: "color"; value: string; fg?: string; bg?: string };

export const COLOR_VALUE_RE = /^(#[0-9a-fA-F]{3,8}|[a-zA-Z]{1,32})$/;

export function isValidColorValue(v: string): boolean {
  return COLOR_VALUE_RE.test(v);
}

/**
 * 扫描顺序：[kbd] → [color] → [bg] → ==…==。
 * 标签内容不含 [ 与换行，避免嵌套歧义；未闭合标记保持字面。
 * 无任何短代码命中时返回 null（调用方保留原节点）。
 */
const SCAN_RE =
  /\[kbd\]([^\[\]\n]+)\[\/kbd\]|\[color=([^\]\s\[]+)(?:\s+bg=([^\]\s\[]+))?\]([^\[\]\n]+)\[\/color\]|\[bg=([^\]\s\[]+)\]([^\[\]\n]+)\[\/bg\]|==([^=\n]+)==/gi;

export function splitInlineShortcodes(
  text: string
): InlineShortcodeSegment[] | null {
  if (!text) return null;
  const re = new RegExp(SCAN_RE.source, "gi");
  const out: InlineShortcodeSegment[] = [];
  let last = 0;
  let changed = false;
  let m: RegExpExecArray | null;
  while ((m = re.exec(text))) {
    const [full, kbd, colorFg, colorBg, colorBody, bgVal, bgBody, markBody] = m;
    const before = text.slice(last, m.index);
    if (before) out.push({ type: "text", value: before });
    last = m.index + full.length;

    if (kbd !== undefined) {
      out.push({ type: "kbd", value: kbd });
      changed = true;
      continue;
    }
    if (colorFg !== undefined) {
      if (!isValidColorValue(colorFg) || (colorBg !== undefined && !isValidColorValue(colorBg))) {
        out.push({ type: "text", value: full });
        continue;
      }
      out.push(
        colorBg
          ? { type: "color", value: colorBody, fg: colorFg, bg: colorBg }
          : { type: "color", value: colorBody, fg: colorFg }
      );
      changed = true;
      continue;
    }
    if (bgVal !== undefined) {
      if (!isValidColorValue(bgVal)) {
        out.push({ type: "text", value: full });
        continue;
      }
      out.push({ type: "color", value: bgBody, bg: bgVal });
      changed = true;
      continue;
    }
    out.push({ type: "mark", value: markBody });
    changed = true;
  }
  const rest = text.slice(last);
  if (rest) out.push({ type: "text", value: rest });
  return changed ? out : null;
}