<?php
/**
 * Background resolver + cache for alternate idHAL forms.
 *
 * Problem: a member's WP `identifiant_hal` stores ONE idHAL form, but HAL may
 * tag their publications under other valid forms of the same person. Matching
 * on the single stored form silently drops those links.
 *
 * Fix: resolve every member's full set of valid idHAL forms (via HAL ref/author)
 * and cache them in usermeta `_hal_id_forms`. Matching then uses the cached
 * forms — with ZERO network calls in the UI / import path.
 *
 * All resolution happens in the background via WP-Cron, in small batches, so the
 * admin interface and the import flow stay as fast as before.
 */

if (!defined('ABSPATH')) {
    exit;
}

class Thalim_HAL_Forms_Cache {

    const META_FORMS   = '_hal_id_forms';      // usermeta: JSON array of forms
    const META_SOURCE  = '_hal_id_forms_src';  // usermeta: the identifiant_hal the cache was built from
    const CRON_HOOK    = 'thalim_hal_refresh_forms';
    const BATCH_SIZE   = 15;                    // members resolved per cron tick

    /** Wire the background hooks. Called once at plugins_loaded. */
    public static function init() {
        add_action(self::CRON_HOOK, [__CLASS__, 'run_batch']);

        // Ensure the recurring event exists (hourly).
        if (!wp_next_scheduled(self::CRON_HOOK)) {
            wp_schedule_event(time() + 60, 'hourly', self::CRON_HOOK);
        }

        // When a profile's identifiant_hal changes, invalidate its cache so the
        // next background tick re-resolves it (no synchronous API call here).
        add_action('updated_user_meta', [__CLASS__, 'on_user_meta_change'], 10, 4);
        add_action('added_user_meta',   [__CLASS__, 'on_user_meta_change'], 10, 4);
    }

    /** Remove the scheduled event (plugin deactivation). */
    public static function clear_schedule() {
        $ts = wp_next_scheduled(self::CRON_HOOK);
        if ($ts) wp_unschedule_event($ts, self::CRON_HOOK);
    }

    /** Invalidate a user's cache when their identifiant_hal is edited. */
    public static function on_user_meta_change($meta_id, $user_id, $meta_key, $_meta_value) {
        if ($meta_key === 'identifiant_hal') {
            delete_user_meta($user_id, self::META_SOURCE); // marks the cache stale
        }
    }

    /**
     * Read cached alternate forms for a user's identifiant_hal.
     * Always returns at least the stored form itself (graceful degradation:
     * behaves exactly like the old code until the background job has run).
     *
     * @return string[] lowercased idHAL forms.
     */
    public static function forms_for_user($user_id, $identifiant_hal) {
        $base = strtolower(trim((string) $identifiant_hal));
        if ($base === '') return [];

        $src = get_user_meta($user_id, self::META_SOURCE, true);
        if ($src === $base) {
            $cached = json_decode((string) get_user_meta($user_id, self::META_FORMS, true), true);
            if (is_array($cached) && $cached) {
                $cached[] = $base;
                return array_values(array_unique(array_map('strtolower', $cached)));
            }
        }
        // Not resolved yet (or stale) -> fall back to the single stored form.
        return [$base];
    }

    /**
     * Cron worker: resolve forms for a batch of members whose cache is missing
     * or stale. Runs in the background; safe to be interrupted (idempotent).
     */
    public static function run_batch() {
        $users = get_users([
            'meta_key'     => 'identifiant_hal',
            'meta_compare' => 'EXISTS',
            'fields'       => ['ID'],
            'number'       => 500,
        ]);

        // Select those needing (re)resolution: stored form != cached source.
        $todo = [];
        foreach ($users as $u) {
            $idhal = strtolower(trim((string) get_user_meta($u->ID, 'identifiant_hal', true)));
            if ($idhal === '') continue;
            $src = get_user_meta($u->ID, self::META_SOURCE, true);
            if ($src !== $idhal) {
                $todo[$idhal][] = (int) $u->ID; // group users sharing a slug
            }
            if (count($todo) >= self::BATCH_SIZE) break;
        }
        if (empty($todo)) return;

        $api = new Thalim_HAL_API();
        $expanded = $api->expand_hal_id_forms(array_keys($todo));

        foreach ($todo as $idhal => $user_ids) {
            $forms = $expanded[$idhal] ?? [$idhal];
            foreach ($user_ids as $uid) {
                update_user_meta($uid, self::META_FORMS, wp_json_encode(array_values($forms)));
                update_user_meta($uid, self::META_SOURCE, $idhal);
            }
        }
    }
}