/**
 * Citation decoration — Phase 2.
 *
 * Ported from upstream `extensions/memory-core/src/tools.citations.ts`.
 * Decorates memory_search hits with `[path#L{start}-L{end}]` markers so
 * the model can attribute claims back to specific memory files when it
 * uses them in its answer.
 *
 * Since our backend stores files as single rows (not line-chunked), we
 * compute line ranges from the returned content block on the fly:
 *   - `startLine` = 1 (line 1 of the file)
 *   - `endLine`   = total number of lines in the block
 * This matches upstream's output format exactly while keeping the pg
 * schema chunk-free.
 */

export type MemoryCitationsMode = 'on' | 'off' | 'auto';

export const DEFAULT_CITATIONS_MODE: MemoryCitationsMode = 'auto';

export function resolveMemoryCitationsMode(
  raw: string | undefined | null
): MemoryCitationsMode {
  if (raw === 'on' || raw === 'off' || raw === 'auto') return raw;
  return DEFAULT_CITATIONS_MODE;
}

export interface CitationCandidate {
  path: string;
  content: string;
  startLine?: number;
  endLine?: number;
  citation?: string;
}

function countLines(text: string): number {
  if (!text) return 1;
  return Math.max(1, text.split('\n').length);
}

function formatCitation(
  path: string,
  startLine: number,
  endLine: number
): string {
  if (startLine === endLine) return `${path}#L${startLine}`;
  return `${path}#L${startLine}-L${endLine}`;
}

/**
 * Decorate each hit with a citation marker. Mirrors upstream's behavior:
 * appends `\n\nSource: <citation>` to the content and sets `citation`.
 * When `include=false`, clears any existing citation field.
 */
export function decorateCitations<T extends CitationCandidate>(
  hits: T[],
  include: boolean
): T[] {
  if (!include) return hits.map((h) => ({ ...h, citation: undefined }));
  return hits.map((h) => {
    const start = Math.max(1, Math.floor(h.startLine ?? 1));
    const end = Math.max(start, Math.floor(h.endLine ?? countLines(h.content)));
    const citation = formatCitation(h.path, start, end);
    const content = `${(h.content ?? '').trimEnd()}\n\nSource: ${citation}`;
    return { ...h, citation, content, startLine: start, endLine: end };
  });
}

/**
 * Whether citations should be emitted for this call.
 *
 * Upstream keys `auto` off the session type (direct/group/channel). In
 * Phase 1 we only have direct chat, so `auto` => `on`. Callers that
 * later distinguish session types can pass `mode` explicitly.
 */
export function shouldIncludeCitations(mode: MemoryCitationsMode): boolean {
  if (mode === 'on') return true;
  if (mode === 'off') return false;
  return true;
}