// lib/headers.js
// headers(cfg) injection + per-role / layout-mode suppression (ARCHITECTURE.md 7.6)
//
// Grounding (real Saltcorn source under packages/):
//   - server/wrapper.js:137 -- a header is emitted only when `h.only_if(req) === true`
//     (strict equality), so every predicate here returns an explicit boolean.
//   - saltcorn-data/db/state.ts:1122-1135 -- only `script` URLs are de-duped; `css`
//     headers are not, so distinct per-role ?v/&theme/&role links coexist.
const { CSS_ROUTE } = require("./constants");
const {
  getActiveThemeId,
  getActiveByRole,
  activeHashHint,
  isLayoutMode,
  requestRendersViaThemeBuilder,
} = require("./cfgReaders");

function headers(cfg) {
  const def = getActiveThemeId(cfg);
  const byRole = getActiveByRole(cfg);
  const list = [];
  if (!def) return list;

  // ONE header; only_if decides per-request whether this role gets the overlay.
  list.push({
    css: `${CSS_ROUTE}?v=${activeHashHint(cfg)}`,
    only_if: (req) => {
      const role = req.user?.role_id ?? 100;
      // LAYOUT MODE: suppress ONLY for requests that actually render via theme-builder.
      // Detected by replicating getLayout's fallback precedence (cfgReaders), NOT by reading
      // getLayout().pluginName -- the last-installed fallback omits pluginName, so an uncovered
      // role would otherwise be double-themed (overlay + wrap()). (folded review fix)
      if (isLayoutMode(cfg) && requestRendersViaThemeBuilder(req)) return false;
      // role with an explicit override gets its own header below, not this one
      return byRole[role] === undefined || byRole[role] === def;
    },
  });

  // per-role overlays for explicit overrides (Phase 1)
  for (const [roleStr, tid] of Object.entries(byRole)) {
    if (tid === def) continue;
    const role = Number(roleStr);
    list.push({
      css: `${CSS_ROUTE}?v=${activeHashHint(cfg)}&theme=${encodeURIComponent(tid)}&role=${role}`,
      only_if: (req) => {
        if (isLayoutMode(cfg) && requestRendersViaThemeBuilder(req)) return false;
        return (req.user?.role_id ?? 100) === role;     // MUST strictly return true (wrapper.js:137)
      },
    });
  }
  return list;
}

module.exports = { headers };