Initial commit: restructure to flat layout with ui/ and web/ at root

ui/src/lib/contextFileOpenGuard.ts

@@ -0,0 +1,66 @@
+import type { FilesAPI } from '@/lib/api/types';
+import { MAX_OPEN_FILE_LINES, countLinesWithLimit } from '@/lib/fileOpenLimits';
+
+export type ContextFileOpenFailureReason = 'too-large' | 'missing' | 'unreadable';
+
+export type ContextFileOpenValidationResult =
+  | { ok: true }
+  | { ok: false; reason: ContextFileOpenFailureReason };
+
+const classifyReadError = (error: unknown): ContextFileOpenFailureReason => {
+  const message = error instanceof Error ? error.message : String(error ?? '');
+  const normalized = message.toLowerCase();
+
+  if (
+    normalized.includes('file not found')
+    || normalized.includes('not found')
+    || normalized.includes('enoent')
+    || normalized.includes('no such file')
+    || normalized.includes('does not exist')
+  ) {
+    return 'missing';
+  }
+
+  return 'unreadable';
+};
+
+const readFileContent = async (files: FilesAPI, path: string): Promise<string> => {
+  if (files.readFile) {
+    const result = await files.readFile(path);
+    return result.content ?? '';
+  }
+
+  const response = await fetch(`/api/fs/read?path=${encodeURIComponent(path)}`);
+  if (!response.ok) {
+    const errorPayload = await response.json().catch(() => ({ error: response.statusText }));
+    throw new Error((errorPayload as { error?: string }).error || 'Failed to read file');
+  }
+
+  return response.text();
+};
+
+export const validateContextFileOpen = async (files: FilesAPI, path: string): Promise<ContextFileOpenValidationResult> => {
+  try {
+    const content = await readFileContent(files, path);
+    const lineCount = countLinesWithLimit(content, MAX_OPEN_FILE_LINES);
+    if (lineCount > MAX_OPEN_FILE_LINES) {
+      return { ok: false, reason: 'too-large' };
+    }
+
+    return { ok: true };
+  } catch (error) {
+    return { ok: false, reason: classifyReadError(error) };
+  }
+};
+
+export const getContextFileOpenFailureMessage = (reason: ContextFileOpenFailureReason): string => {
+  if (reason === 'too-large') {
+    return `File is too large to open (>${MAX_OPEN_FILE_LINES.toLocaleString()} lines)`;
+  }
+
+  if (reason === 'missing') {
+    return 'File not found';
+  }
+
+  return 'Failed to open file';
+};