// edit-guards-imports — detects dropped imports in edited files.
// Ported from opencode-morph-fast-apply (MIT).

export interface ImportCheckResult {
  ok: boolean;
  missingImports: string[];
  reason?: string;
}

const IMPORT_PATTERNS = [
  /^import\s+(?:\{[^}]*\}|\*\s+as\s+\w+|\w+)\s+from\s+['"][^'"]+['"]\s*;?$/m,
  /^import\s+['"][^'"]+['"]\s*;?$/m,
  /^export\s+.*\s+from\s+['"][^'"]+['"]\s*;?$/m,
  /^require\s*\(\s*['"][^'"]+['"]\s*\)\s*;?$/m,
  /^import\s+type\s+\{[^}]*\}\s+from\s+['"][^'"]+['"]\s*;?$/m,
];

function extractImportLines(content: string): string[] {
  return content.split('\n').filter((line) =>
    IMPORT_PATTERNS.some((p) => p.test(line.trim())),
  );
}

export function checkDroppedImports(
  original: string,
  updated: string,
  filePath: string,
): ImportCheckResult {
  const originalImports = extractImportLines(original);
  const updatedImports = extractImportLines(updated);

  if (originalImports.length === 0) {
    return { ok: true, missingImports: [] };
  }

  const missing = originalImports.filter((imp) => !updatedImports.includes(imp));

  if (missing.length > 0 && originalImports.length > 0) {
    return {
      ok: false,
      missingImports: missing,
      reason: `Edit would drop ${missing.length} import(s) from ${filePath}`,
    };
  }

  return { ok: true, missingImports: [] };
}