import { createHash } from 'node:crypto';
import { createReadStream } from 'node:fs';
import { stat } from 'node:fs/promises';
import { resolve } from 'node:path';
import { VclawError } from './errors.js';

interface ReferencePacket { sceneIndex: number; references: Array<{ path?: string }> }
export interface FilmReferenceEvidence { sceneIndex: number; path: string; status: 'hashed' | 'missing' | 'remote-unverified'; sha256?: string }
/** Only local reference bytes are measured. Remote handles retain explicit unverified status. */
export async function captureFilmReferenceEvidence(projectDir: string, packets: ReferencePacket[]): Promise<FilmReferenceEvidence[]> {
  const evidence: FilmReferenceEvidence[] = [];
  for (const packet of packets) for (const ref of packet.references) {
    if (!ref.path) continue;
    const base = { sceneIndex: packet.sceneIndex, path: ref.path };
    if (/^[a-z][a-z0-9+.-]*:\/\//i.test(ref.path)) { evidence.push({ ...base, status: 'remote-unverified' }); continue; }
    const path = resolve(projectDir, ref.path);
    try {
      if (!(await stat(path)).isFile()) throw new Error(`Reference is not a regular file: ${ref.path}`);
      const hash = createHash('sha256');
      for await (const chunk of createReadStream(path)) hash.update(chunk);
      evidence.push({ ...base, status: 'hashed', sha256: hash.digest('hex') });
    } catch (error) {
      if ((error as NodeJS.ErrnoException).code !== 'ENOENT') throw error;
      evidence.push({ ...base, status: 'missing' });
    }
  }
  return evidence;
}
export async function assertFilmReferenceEvidence(projectDir: string, packets: ReferencePacket[], previous: FilmReferenceEvidence[] | undefined): Promise<void> {
  const current = await captureFilmReferenceEvidence(projectDir, packets);
  if (!previous) throw new VclawError('invalid_flag_value', 'Reference evidence is missing: rebuild filmmaking-prompts before generation.', { code: 'film-reference-evidence-missing' });
  const changed = current.filter((entry, index) => JSON.stringify(entry) !== JSON.stringify(previous[index]));
  const removed = previous.slice(current.length);
  if (changed.length || removed.length) {
    const scenes = [...new Set([...changed, ...removed].map(entry => entry.sceneIndex))];
    throw new VclawError('invalid_flag_value', `Reference bytes or attachments changed for scenes ${scenes.join(', ')}: inspect references and rebuild filmmaking-prompts.`, { code: 'film-reference-stale', scenes });
  }
}