feat: 预览区划选文字浮窗「添加到对话」（md 预览 + 兜底 code 查看器）

tests/selection-payload.spec.ts

@@ -0,0 +1,94 @@
+/**
+ * Pure payload logic for the viewer selection popup ("add to
+ * conversation"): the fence header (relative path + line span), the
+ * over-limit plain-line fallback, and the best-effort reverse-search that
+ * maps a preview selection back to source lines.
+ */
+import { describe, expect, it } from 'vitest'
+import {
+  SELECTION_LIMIT,
+  buildSelectionInsert,
+  headerOf,
+  linesOfSelection,
+} from '../src/client/selection-payload.ts'
+
+describe('headerOf', () => {
+  it('projects the path relative to the session cwd', () => {
+    expect(headerOf('/p/docs/plan.md', '/p', { start: 12, end: 12 })).toBe('docs/plan.md:12')
+  })
+
+  it('falls back to the absolute path when the cwd is unknown', () => {
+    expect(headerOf('/p/docs/plan.md', undefined, { start: 3, end: 3 })).toBe('/p/docs/plan.md:3')
+  })
+
+  it('keeps the absolute path for files outside the cwd', () => {
+    expect(headerOf('/other/x.md', '/p', { start: 1, end: 1 })).toBe('/other/x.md:1')
+  })
+
+  it('writes a single line number for single-line selections', () => {
+    expect(headerOf('/p/a.md', '/p', { start: 5, end: 5 })).toBe('a.md:5')
+  })
+
+  it('writes the start-end range for multi-line selections', () => {
+    expect(headerOf('/p/a.md', '/p', { start: 5, end: 9 })).toBe('a.md:5-9')
+  })
+
+  it('omits the line suffix entirely when the lines are unknown', () => {
+    expect(headerOf('/p/a.md', '/p', undefined)).toBe('a.md')
+  })
+})
+
+describe('buildSelectionInsert', () => {
+  it('wraps a small selection in a fenced block with the path:line info line', () => {
+    expect(buildSelectionInsert('/p/a.ts', '/p', { start: 2, end: 4 }, 'const x = 1')).toBe(
+      '```a.ts:2-4\nconst x = 1\n```',
+    )
+  })
+
+  it('accepts a selection exactly at the limit (fenced)', () => {
+    const text = 'x'.repeat(SELECTION_LIMIT)
+    expect(buildSelectionInsert('/p/a.ts', '/p', { start: 1, end: 1 }, text)).toBe(
+      `\`\`\`a.ts:1\n${text}\n\`\`\``,
+    )
+  })
+
+  it('drops the content past the limit: one plain path line, no fence', () => {
+    const text = 'x'.repeat(SELECTION_LIMIT + 1)
+    expect(buildSelectionInsert('/p/a.ts', '/p', { start: 7, end: 7 }, text)).toBe('a.ts:7')
+  })
+
+  it('keeps the plain-line form when past the limit without line numbers', () => {
+    const text = 'x'.repeat(SELECTION_LIMIT + 1)
+    expect(buildSelectionInsert('/p/a.ts', '/p', undefined, text)).toBe('a.ts')
+  })
+})
+
+describe('linesOfSelection', () => {
+  const source = 'alpha\nbeta\ngamma alpha\ndelta\n'
+
+  it('maps a unique hit to its source line span', () => {
+    expect(linesOfSelection(source, 'beta')).toEqual({ start: 2, end: 2 })
+    expect(linesOfSelection(source, 'gamma alpha')).toEqual({ start: 3, end: 3 })
+  })
+
+  it('spans the end line when the selection crosses line breaks', () => {
+    expect(linesOfSelection(source, 'beta\ngamma')).toEqual({ start: 2, end: 3 })
+  })
+
+  it('returns null when the text is missing from the source', () => {
+    expect(linesOfSelection(source, 'nope')).toBeNull()
+  })
+
+  it('returns null on an ambiguous (multi-hit) match', () => {
+    expect(linesOfSelection(source, 'alpha')).toBeNull()
+  })
+
+  it('strips a single trailing newline before searching (DOM block selections)', () => {
+    expect(linesOfSelection(source, 'delta\n')).toEqual({ start: 4, end: 4 })
+  })
+
+  it('returns null for an empty selection', () => {
+    expect(linesOfSelection(source, '')).toBeNull()
+    expect(linesOfSelection(source, '\n')).toBeNull()
+  })
+})