feat: 添加文章大纲解析与状态管理核心逻辑及单元测试

src/lib/editor/outline.svelte.ts

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+import type { OutlineHeading } from './outline';
+
+// Each editing page owns its state; never share article content across SSR requests.
+export class EditorOutline {
+	headings = $state.raw<OutlineHeading[]>([]);
+	active = $state(-1);
+	navigate: (heading: OutlineHeading) => void = () => {};
+}

src/lib/editor/outline.test.ts

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+import { describe, expect, it } from 'vitest';
+import { activeHeadingAt, extractOutline } from './outline';
+
+describe('editor outline', () => {
+	it('recognizes all heading levels and Setext headings with exact source positions', () => {
+		const source =
+			'# 一\n\n## 二 ##\n\n### 三\n\n#### 四\n\n##### 五\n\n###### 六\n\n下划线标题\n====\n';
+		const headings = extractOutline(source);
+		expect(headings.map(({ level, text }) => [level, text])).toEqual([
+			[1, '一'],
+			[2, '二'],
+			[3, '三'],
+			[4, '四'],
+			[5, '五'],
+			[6, '六'],
+			[1, '下划线标题']
+		]);
+		expect(headings.at(-1)?.from).toBe(source.indexOf('下划线标题'));
+	});
+	it('ignores fenced and indented code, HTML blocks and escaped heading markers', () => {
+		const source =
+			'```md\n# 假标题\n```\n\n~~~\n## 假标题\n~~~\n\n    # 代码\n\n\\# 普通文本\n\n<div>\n# HTML 内文本\n</div>\n\n## 真标题\n';
+		expect(extractOutline(source).map((heading) => heading.text)).toEqual(['真标题']);
+	});
+	it('keeps duplicate headings distinct and includes headings inside quotes and lists', () => {
+		const source = '## 重复\n\n> ### 引用\n\n- #### 列表\n\n## 重复\n';
+		const headings = extractOutline(source);
+		expect(headings.map((heading) => heading.text)).toEqual(['重复', '引用', '列表', '重复']);
+		expect(headings[3].from).toBe(source.lastIndexOf('## 重复'));
+	});
+	it('shows plain labels for formatted headings and handles empty headings', () => {
+		expect(
+			extractOutline('## **粗体** [链接](https://example.com) `code`\n\n#\n').map((h) => h.text)
+		).toEqual(['粗体 链接 code', '未命名标题']);
+	});
+	it('includes offscreen headings and refreshes offsets after insertion or deletion', () => {
+		const source = '正文\n\n'.repeat(4000) + '## 结尾\n';
+		expect(extractOutline(source)[0].from).toBe(source.indexOf('##'));
+		expect(extractOutline('前言\n\n' + source)[0].from).toBe(source.indexOf('##') + 4);
+		expect(extractOutline(source.replace('## 结尾', '结尾'))).toEqual([]);
+	});
+	it('finds the enclosing section for cursor or viewport positions', () => {
+		const headings = extractOutline('前言\n\n## 第一节\n内容\n\n## 第二节\n内容');
+		expect(activeHeadingAt(headings, 0)).toBe(-1);
+		expect(activeHeadingAt(headings, headings[0].from)).toBe(0);
+		expect(activeHeadingAt(headings, headings[1].from - 1)).toBe(0);
+		expect(activeHeadingAt(headings, 100)).toBe(1);
+		expect(activeHeadingAt([], 100)).toBe(-1);
+	});
+});

src/lib/editor/outline.ts

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+import { markdownLanguage } from '@codemirror/lang-markdown';
+import { Lexer, type Token } from 'marked';
+
+export type OutlineHeading = { from: number; level: number; text: string };
+
+function plainText(tokens: Token[]): string {
+	return tokens
+		.map((token) => {
+			if (token.type === 'html') return '';
+			if ('tokens' in token && token.tokens) return plainText(token.tokens);
+			return 'text' in token ? token.text : token.raw;
+		})
+		.join('');
+}
+
+/** Parse the whole document, including headings beyond CodeMirror's rendered viewport. */
+export function extractOutline(source: string): OutlineHeading[] {
+	const headings: OutlineHeading[] = [];
+	markdownLanguage.parser.parse(source).iterate({
+		enter(node) {
+			const match = /^(?:ATX|Setext)Heading([1-6])$/.exec(node.name);
+			if (!match) return;
+			let start = node.from;
+			let raw = '';
+			for (let child = node.node.firstChild; child; child = child.nextSibling) {
+				if (child.name === 'HeaderMark') {
+					raw += source.slice(start, child.from);
+					start = child.to;
+				}
+			}
+			raw += source.slice(start, node.to);
+			headings.push({
+				from: node.from,
+				level: Number(match[1]),
+				text: plainText(Lexer.lexInline(raw.trim())).trim() || '未命名标题'
+			});
+			return false;
+		}
+	});
+	return headings;
+}
+
+export function activeHeadingAt(headings: OutlineHeading[], position: number): number {
+	let active = -1;
+	for (let i = 0; i < headings.length && headings[i].from <= position; i++) active = i;
+	return active;
+}