/**
 * Publish-mode policy — read + write + enumerate.
 *
 * Three modes, named after what they do rather than numbered:
 *   `append`       Any valid listing goes in; readers see the signed scan report
 *                  and their trust lists decide (the launch default).
 *   `scan-first`   Infected uploads are rejected before they land. Clean ones
 *                  publish immediately. Already the current /api/upload shape,
 *                  so this mode is the default behaviour today.
 *   `review`       Clean listings sit in a human-review queue before browse
 *                  shows them. Not yet enforced — the toggle persists, the
 *                  queue logic lands in a later milestone.
 *
 * Global mode is the fallback; a per-category override is read when a listing's
 * category has one set. The admin UI exposes both.
 */

import { getSetting, setSetting } from './db.js';
import { logAudit } from './audit.js';

export const MODES = ['append', 'scan-first', 'review'];
const DEFAULT_MODE = 'append';
const GLOBAL_KEY = 'publish_mode_global';
const perCatKey = (slug) => `publish_mode_${slug}`;

export function globalMode() {
  const v = getSetting(GLOBAL_KEY, DEFAULT_MODE);
  return MODES.includes(v) ? v : DEFAULT_MODE;
}

export function categoryMode(slug) {
  const v = getSetting(perCatKey(slug), null);
  if (v && MODES.includes(v)) return { mode: v, source: 'category' };
  return { mode: globalMode(), source: 'global' };
}

export function allModes(categories) {
  const g = globalMode();
  const out = { global: g, categories: {} };
  for (const slug of categories) {
    const v = getSetting(perCatKey(slug), null);
    out.categories[slug] = v && MODES.includes(v) ? v : null; // null = inherits global
  }
  return out;
}

/**
 * Set a mode (global or per-category). `category=null` sets the global default;
 * a slug sets that category. Writing an empty value for a category clears the
 * override and the category falls back to the global default.
 */
export function setMode({ category, value, actor }) {
  const key = category ? perCatKey(category) : GLOBAL_KEY;
  const now = new Date().toISOString();

  if (!value) {
    // Clearing: delete the row by writing a sentinel and relying on the admin
    // page to show "inherits global". Simpler: just set the global default
    // string so getSetting returns the default. For an override we need an
    // actual delete — add it as a direct exec since it's one path.
    deleteSetting(key, actor, now, category);
    return;
  }

  if (!MODES.includes(value)) {
    throw new Error(`unknown mode: ${value}`);
  }

  const prev = getSetting(key, category ? null : DEFAULT_MODE);
  setSetting(key, value, actor, now);
  logAudit({
    actor,
    action: 'set_mode',
    target: category || 'global',
    details: { before: prev, after: value },
  });
}

/* The one-off path for clearing a per-category override. */
function deleteSetting(key, actor, now, category) {
  // We don't ship a dedicated delete-setting helper — this is the only caller.
  // Importing the raw db just for this would be a dependency inversion; use
  // the public API: write a reserved sentinel, then the resolver ignores it.
  // Easier: just set it to the empty string and have the reader fall through.
  const prev = getSetting(key, null);
  setSetting(key, '', actor, now);
  logAudit({
    actor,
    action: 'clear_mode',
    target: category || 'global',
    details: { before: prev, after: null },
  });
}