/**
 * uat-report/screenshot-embeds.ts — IO: collect failure screenshots as base64
 * data URIs so the report is a single transmissible document.
 *
 * Deliberately NOT pure (statSync/readFileSync) — the pure renderer receives the
 * resulting map through the model and never touches the disk. Policy:
 *   - only TRUE failures embed (executed, determinate, !ok, screenshot set) —
 *     indeterminates and passes keep their relative links, saving budget;
 *   - a per-image cap and a total budget bound the report size; over-cap shots
 *     fall back to the relative link with an explicit note (never silent);
 *   - artifact order ⇒ deterministic selection under the total budget.
 *
 * Map keys are the artifact's POSIX rel paths VERBATIM (`screenshots/{role}/…`,
 * `screenshotRelPath` builds with forward slashes) — `path.join` is used for
 * READING only, so Windows separators never leak into the keys.
 */
import { readFileSync, statSync } from 'node:fs';
import { join } from 'node:path';
import { humanBytes, type UiRunFile } from '../lib/run-results.js';
import type { ScreenshotEmbed } from './build-model.js';

export const PER_IMAGE_CAP_BYTES = 300 * 1024;
export const TOTAL_CAP_BYTES = 8 * 1024 * 1024;

export interface EmbedCaps {
  perImage: number;
  total: number;
}

export function collectScreenshotEmbeds(
  runDirAbs: string,
  uiFile: UiRunFile | null,
  caps: EmbedCaps = { perImage: PER_IMAGE_CAP_BYTES, total: TOTAL_CAP_BYTES },
): Record<string, ScreenshotEmbed> {
  const embeds: Record<string, ScreenshotEmbed> = {};
  if (!uiFile) return embeds;
  let budget = caps.total;
  for (const r of uiFile.results) {
    if (!r.screenshot || !r.executed || r.ok || r.actual === 'indeterminate') continue;
    if (r.screenshot in embeds) continue; // one entry per file
    const abs = join(runDirAbs, r.screenshot);
    let size: number;
    try {
      size = statSync(abs).size;
    } catch {
      continue; // missing file → no entry, the renderer falls back to the link
    }
    if (size > caps.perImage) {
      embeds[r.screenshot] = { note: `not embedded (${humanBytes(size)} > ${humanBytes(caps.perImage)} cap)` };
      continue;
    }
    if (size > budget) {
      embeds[r.screenshot] = { note: 'embed budget reached — linked instead' };
      continue;
    }
    try {
      const buf = readFileSync(abs);
      embeds[r.screenshot] = { dataUri: `data:image/png;base64,${buf.toString('base64')}` };
      budget -= size;
    } catch {
      // unreadable → no entry, link fallback
    }
  }
  return embeds;
}