chore: import upstream snapshot with attribution

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

@@ -0,0 +1,193 @@
+import { createLogger } from '@sim/logger'
+import { toError } from '@sim/utils/errors'
+import {
+  fetchWorkspaceFileBuffer,
+  getWorkspaceFile,
+} from '@/lib/uploads/contexts/workspace/workspace-file-manager'
+
+const logger = createLogger('CopilotFilePreview')
+
+type FilePreviewEdit = {
+  strategy?: string
+  search?: string
+  replaceAll?: boolean
+  mode?: string
+  occurrence?: number
+  before_anchor?: string
+  after_anchor?: string
+  anchor?: string
+  start_anchor?: string
+  end_anchor?: string
+}
+
+interface BuildFilePreviewTextOptions {
+  operation: 'create' | 'append' | 'update' | 'patch'
+  streamedContent: string
+  existingContent?: string
+  edit?: Record<string, unknown>
+}
+
+function findAnchorIndex(lines: string[], anchor: string, occurrence = 1, afterIndex = -1): number {
+  const trimmed = anchor.trim()
+  let count = 0
+  for (let i = afterIndex + 1; i < lines.length; i++) {
+    if (lines[i].trim() === trimmed) {
+      count++
+      if (count === occurrence) return i
+    }
+  }
+  return -1
+}
+
+function extractPatchPreview(
+  streamedContent: string,
+  existingContent: string,
+  edit?: Record<string, unknown>
+): string | undefined {
+  const strategy = typeof edit?.strategy === 'string' ? edit.strategy : undefined
+  const lines = existingContent.split('\n')
+  const occurrence =
+    typeof edit?.occurrence === 'number' && Number.isFinite(edit.occurrence) ? edit.occurrence : 1
+
+  if (strategy === 'search_replace') {
+    const search = typeof edit?.search === 'string' ? edit.search : ''
+    if (!search) return undefined
+    if (edit?.replaceAll === true) {
+      return existingContent.split(search).join(streamedContent)
+    }
+    const firstIdx = existingContent.indexOf(search)
+    if (firstIdx === -1) return undefined
+    return (
+      existingContent.slice(0, firstIdx) +
+      streamedContent +
+      existingContent.slice(firstIdx + search.length)
+    )
+  }
+
+  const mode = typeof edit?.mode === 'string' ? edit.mode : undefined
+  if (!mode) return undefined
+
+  if (mode === 'replace_between') {
+    const beforeAnchor = typeof edit?.before_anchor === 'string' ? edit.before_anchor : undefined
+    const afterAnchor = typeof edit?.after_anchor === 'string' ? edit.after_anchor : undefined
+    if (!beforeAnchor || !afterAnchor) return undefined
+
+    const beforeIdx = findAnchorIndex(lines, beforeAnchor, occurrence)
+    const afterIdx = findAnchorIndex(lines, afterAnchor, occurrence, beforeIdx)
+    if (beforeIdx === -1 || afterIdx === -1 || afterIdx <= beforeIdx) return undefined
+
+    const spliced = [
+      ...lines.slice(0, beforeIdx + 1),
+      ...(streamedContent.length > 0 ? streamedContent.split('\n') : []),
+      ...lines.slice(afterIdx),
+    ]
+    return spliced.join('\n')
+  }
+
+  if (mode === 'insert_after') {
+    const anchor = typeof edit?.anchor === 'string' ? edit.anchor : undefined
+    if (!anchor) return undefined
+
+    const anchorIdx = findAnchorIndex(lines, anchor, occurrence)
+    if (anchorIdx === -1) return undefined
+
+    const spliced = [
+      ...lines.slice(0, anchorIdx + 1),
+      ...(streamedContent.length > 0 ? streamedContent.split('\n') : []),
+      ...lines.slice(anchorIdx + 1),
+    ]
+    return spliced.join('\n')
+  }
+
+  if (mode === 'delete_between') {
+    const startAnchor = typeof edit?.start_anchor === 'string' ? edit.start_anchor : undefined
+    const endAnchor = typeof edit?.end_anchor === 'string' ? edit.end_anchor : undefined
+    if (!startAnchor || !endAnchor) return undefined
+
+    const startIdx = findAnchorIndex(lines, startAnchor, occurrence)
+    const endIdx = findAnchorIndex(lines, endAnchor, occurrence, startIdx)
+    if (startIdx === -1 || endIdx === -1 || endIdx <= startIdx) return undefined
+
+    const spliced = [...lines.slice(0, startIdx), ...lines.slice(endIdx)]
+    return spliced.join('\n')
+  }
+
+  return undefined
+}
+
+function shouldApplyPatchPreview(streamedContent: string, edit?: Record<string, unknown>): boolean {
+  const strategy = typeof edit?.strategy === 'string' ? edit.strategy : undefined
+  const mode = typeof edit?.mode === 'string' ? edit.mode : undefined
+
+  if (strategy === 'anchored' && mode === 'delete_between') {
+    return true
+  }
+
+  return streamedContent.length > 0
+}
+
+function buildAppendPreview(existingContent: string, incomingContent: string): string {
+  if (incomingContent.length === 0) return existingContent
+  if (existingContent.length === 0) return incomingContent
+  return `${existingContent}\n${incomingContent}`
+}
+
+/**
+ * Reads the current UTF-8 text of a workspace file for streaming previews.
+ *
+ * Preview runs in the SSE loop on `workspace_file` **call** events, which are
+ * processed **before** the async tool executor persists {@link storeFileIntent}.
+ * Loading the base here avoids a race where `edit_content` `args_delta` arrives
+ * before Redis holds `existingContent`, which would make append previews look like
+ * full-file replacement until the intent landed.
+ */
+export async function loadWorkspaceFileTextForPreview(
+  workspaceId: string,
+  fileId: string
+): Promise<string | undefined> {
+  try {
+    const record = await getWorkspaceFile(workspaceId, fileId)
+    if (!record) return undefined
+    const buffer = await fetchWorkspaceFileBuffer(record)
+    return buffer.toString('utf-8')
+  } catch (error) {
+    logger.warn('Failed to load workspace file text for preview', {
+      workspaceId,
+      fileId,
+      error: toError(error).message,
+    })
+    return undefined
+  }
+}
+
+export function buildFilePreviewText({
+  operation,
+  streamedContent,
+  existingContent,
+  edit,
+}: BuildFilePreviewTextOptions): string | undefined {
+  if (operation === 'update') {
+    return streamedContent
+  }
+
+  if (operation === 'create') {
+    return streamedContent
+  }
+
+  if (operation === 'append') {
+    if (existingContent !== undefined) {
+      return buildAppendPreview(existingContent, streamedContent)
+    }
+    return streamedContent
+  }
+
+  if (existingContent === undefined) {
+    return undefined
+  }
+
+  if (!shouldApplyPatchPreview(streamedContent, edit)) {
+    return undefined
+  }
+
+  return extractPatchPreview(streamedContent, existingContent, edit)
+}