// src/utils/fileManifest.ts
//
// Utility for building a lightweight [Conversation Files] context block
// from a file manifest. Injected into the compaction windowed view so the
// LLM retains awareness of ALL conversation files, even when old messages
// (with full file content) are behind the summary.

import type { FileManifestEntry } from '@/types/graph';

/**
 * Prefix marker for the file manifest block.
 * Used to detect and deduplicate manifest messages across turns.
 */
export const FILE_MANIFEST_PREFIX = '[Conversation Files]';

/**
 * Builds a compact text block listing all files in the conversation.
 * Each entry costs ~10-15 tokens, so 10 files ≈ 100-150 tokens total.
 *
 * The block includes retrieval hints so the LLM knows how to fetch
 * full content on demand (via file_search or content_tool).
 *
 * @param manifest - Array of file metadata entries
 * @returns Formatted text block, or empty string if manifest is empty/undefined
 */
export function buildFileManifestBlock(
  manifest: FileManifestEntry[] | undefined
): string {
  if (!manifest || manifest.length === 0) {
    return '';
  }

  const lines = manifest.map((entry) => {
    const parts: string[] = [`- ${entry.filename}`];
    if (entry.contentId) {
      parts.push(`(content_id: ${entry.contentId})`);
    }
    if (entry.source) {
      parts.push(`[${entry.source}]`);
    }
    return parts.join(' ');
  });

  return [
    FILE_MANIFEST_PREFIX,
    'The following files have been shared in this conversation.',
    'Use file_search or content_tool read (with content_id) to retrieve full content when needed.',
    '',
    ...lines,
  ].join('\n');
}