chore: import upstream snapshot with attribution

apps/sim/lib/copilot/tools/server/files/file-preview.test.ts

@@ -0,0 +1,79 @@
+/**
+ * @vitest-environment node
+ */
+import { describe, expect, it } from 'vitest'
+import { buildFilePreviewText } from '@/lib/copilot/tools/server/files/file-preview'
+
+describe('buildFilePreviewText', () => {
+  it('returns the full streamed content for update previews', () => {
+    expect(
+      buildFilePreviewText({
+        operation: 'update',
+        streamedContent: '',
+      })
+    ).toBe('')
+
+    expect(
+      buildFilePreviewText({
+        operation: 'update',
+        streamedContent: 'updated body',
+      })
+    ).toBe('updated body')
+  })
+
+  it('builds append previews from the existing file content', () => {
+    expect(
+      buildFilePreviewText({
+        operation: 'append',
+        existingContent: 'line one',
+        streamedContent: 'line two',
+      })
+    ).toBe('line one\nline two')
+  })
+
+  it('applies anchored replace_between previews', () => {
+    expect(
+      buildFilePreviewText({
+        operation: 'patch',
+        existingContent: ['# Title', 'before', 'after', 'footer'].join('\n'),
+        streamedContent: 'replacement',
+        edit: {
+          strategy: 'anchored',
+          mode: 'replace_between',
+          before_anchor: '# Title',
+          after_anchor: 'after',
+        },
+      })
+    ).toBe(['# Title', 'replacement', 'after', 'footer'].join('\n'))
+  })
+
+  it('applies delete_between previews without streamed replacement text', () => {
+    expect(
+      buildFilePreviewText({
+        operation: 'patch',
+        existingContent: ['keep', 'start', 'remove me', 'end', 'keep too'].join('\n'),
+        streamedContent: '',
+        edit: {
+          strategy: 'anchored',
+          mode: 'delete_between',
+          start_anchor: 'start',
+          end_anchor: 'end',
+        },
+      })
+    ).toBe(['keep', 'end', 'keep too'].join('\n'))
+  })
+
+  it('applies search_replace previews', () => {
+    expect(
+      buildFilePreviewText({
+        operation: 'patch',
+        existingContent: 'hello world',
+        streamedContent: 'sim',
+        edit: {
+          strategy: 'search_replace',
+          search: 'world',
+        },
+      })
+    ).toBe('hello sim')
+  })
+})