"use client";

/**
 * RichTextEditor - 富文本编辑器组件
 *
 * 维护者：ai13（teacher-portal）
 * 关联：lesson-plans/edit + exams/edit-rich 复用
 *
 * 特性：
 * - 基于 contentEditable 的轻量富文本编辑（无 Tiptap 依赖）
 * - 工具栏：加粗 / 斜体 / 下划线 / 列表 / 标题 / 链接
 * - 受控模式：value + onChange
 * - 设计令牌：var(--*) 颜色 / 字体 / 间距
 *
 * 注意：P3+ 阶段可替换为 Tiptap 封装（需安装 @tiptap/core + @tiptap/react）
 * 当前 contentEditable 实现满足 P7 基础需求
 */

import { useCallback, useRef, useEffect } from "react";

export interface RichTextEditorProps {
  /** 初始 HTML 内容 */
  value?: string;
  /** 占位符 */
  placeholder?: string;
  /** 内容变更回调 */
  onChange?: (html: string) => void;
  /** 是否只读 */
  readOnly?: boolean;
  /** 最小高度 */
  minHeight?: number;
}

export function RichTextEditor({
  value = "",
  placeholder = "请输入内容...",
  onChange,
  readOnly = false,
  minHeight = 200,
}: RichTextEditorProps): React.ReactElement {
  const editorRef = useRef<HTMLDivElement>(null);
  const isInternalChange = useRef(false);

  // 同步外部 value 到 editor
  useEffect(() => {
    if (editorRef.current && !isInternalChange.current) {
      if (editorRef.current.innerHTML !== value) {
        editorRef.current.innerHTML = value;
      }
    }
    isInternalChange.current = false;
  }, [value]);

  const handleInput = useCallback(() => {
    if (!editorRef.current) return;
    isInternalChange.current = true;
    const html = editorRef.current.innerHTML;
    onChange?.(html);
  }, [onChange]);

  const exec = useCallback(
    (command: string, val?: string) => {
      if (readOnly) return;
      document.execCommand(command, false, val);
      handleInput();
      editorRef.current?.focus();
    },
    [handleInput, readOnly],
  );

  const handleLink = useCallback(() => {
    if (readOnly) return;
    const url = window.prompt("输入链接 URL：");
    if (url) {
      exec("createLink", url);
    }
  }, [exec, readOnly]);

  const toolbarButtons = readOnly ? null : (
    <div
      className="flex items-center gap-1 p-2 border-b flex-wrap"
      style={{
        borderColor: "var(--color-rule)",
        background: "var(--bg-subtle)",
        borderRadius: "var(--radius-default) var(--radius-default) 0 0",
      }}
    >
      <ToolbarButton label="加粗" onClick={() => exec("bold")} icon="B" bold />
      <ToolbarButton
        label="斜体"
        onClick={() => exec("italic")}
        icon="I"
        italic
      />
      <ToolbarButton
        label="下划线"
        onClick={() => exec("underline")}
        icon="U"
        underline
      />
      <ToolbarDivider />
      <ToolbarButton
        label="标题"
        onClick={() => exec("formatBlock", "<h3>")}
        icon="H"
      />
      <ToolbarButton
        label="正文"
        onClick={() => exec("formatBlock", "<p>")}
        icon="¶"
      />
      <ToolbarDivider />
      <ToolbarButton
        label="无序列表"
        onClick={() => exec("insertUnorderedList")}
        icon="•"
      />
      <ToolbarButton
        label="有序列表"
        onClick={() => exec("insertOrderedList")}
        icon="1."
      />
      <ToolbarDivider />
      <ToolbarButton label="链接" onClick={handleLink} icon="🔗" />
      <ToolbarButton
        label="清除格式"
        onClick={() => exec("removeFormat")}
        icon="✕"
      />
    </div>
  );

  return (
    <div
      className="w-full overflow-hidden"
      style={{
        border: "1px solid var(--color-rule)",
        borderRadius: "var(--radius-card)",
        background: "var(--bg-paper)",
      }}
    >
      {toolbarButtons}
      <div
        ref={editorRef}
        contentEditable={!readOnly}
        suppressContentEditableWarning
        onInput={handleInput}
        data-placeholder={placeholder}
        className="rich-text-editor-content"
        style={{
          minHeight: `${minHeight}px`,
          padding: "var(--space-md)",
          outline: "none",
          fontFamily: "var(--font-family-sans)",
          fontSize: "var(--font-size-body)",
          color: "var(--color-ink)",
          lineHeight: "1.8",
        }}
      />
      <style>{`
        .rich-text-editor-content:empty::before {
          content: attr(data-placeholder);
          color: var(--color-ink-subtle);
          pointer-events: none;
        }
        .rich-text-editor-content h3 {
          font-family: var(--font-family-serif);
          font-size: var(--font-size-heading-3);
          margin: var(--space-sm) 0;
        }
        .rich-text-editor-content ul,
        .rich-text-editor-content ol {
          padding-left: var(--space-lg);
          margin: var(--space-xs) 0;
        }
        .rich-text-editor-content a {
          color: var(--color-accent);
          text-decoration: underline;
        }
        .rich-text-editor-content blockquote {
          border-left: 3px solid var(--color-rule);
          padding-left: var(--space-md);
          margin: var(--space-sm) 0;
          color: var(--color-ink-muted);
        }
      `}</style>
    </div>
  );
}

// ============ 工具栏按钮 ============

interface ToolbarButtonProps {
  label: string;
  onClick: () => void;
  icon: string;
  bold?: boolean;
  italic?: boolean;
  underline?: boolean;
}

function ToolbarButton({
  label,
  onClick,
  icon,
  bold,
  italic,
  underline,
}: ToolbarButtonProps): React.ReactElement {
  return (
    <button
      type="button"
      title={label}
      aria-label={label}
      onClick={onClick}
      className="w-8 h-8 flex items-center justify-center text-sm transition-colors hover:bg-[var(--color-accent-subtle)]"
      style={{
        color: "var(--color-ink-muted)",
        borderRadius: "var(--radius-button)",
        fontWeight: bold ? "700" : "400",
        fontStyle: italic ? "italic" : "normal",
        textDecoration: underline ? "underline" : "none",
        cursor: "pointer",
      }}
    >
      {icon}
    </button>
  );
}

function ToolbarDivider(): React.ReactElement {
  return (
    <div
      className="w-px h-5 mx-1"
      style={{ background: "var(--color-rule)" }}
    />
  );
}

export default RichTextEditor;