<?php
namespace Zadex\Forms\Integrations;

defined('ABSPATH') || exit;

use WP_Error;
use Zadex\Forms\Fields;
use Zadex\Forms\Shortcodes;
use Zadex\Forms\Submission;

/**
 * Base class of the email-marketing actions (Mailchimp, ActiveCampaign, GetResponse, ConvertKit, MailerLite,
 * Drip). The Form widget settings of provider `<id>` use the prefix `<id>_`:
 *
 *   <id>_list             list / audience / campaign / form / group id (select loaded from
 *                         GET zadex/v1/forms/integrations/<id>/lists, see ListsController)
 *   <id>_email_field      field id holding the email ('' = the first email field)
 *   <id>_name_field       field id of the (first) name   <id>_last_name_field  field id of the last name
 *   <id>_fields           repeater {key, value}: provider custom / merge fields, value with shortcodes
 *   <id>_tags             comma separated tags (names; ConvertKit: tag ids)
 *   <id>_double_optin     Mailchimp only: new contacts get "pending" (confirmation email)
 *   <id>_required         a failure makes the visitor see the form's error message
 *
 * Every HTTP call goes through `Http` (`wp_remote_request`). Errors are logged (`Log`) and returned as
 * `WP_Error`, which the action registry reports through `zadex/forms/action_failed`; visitors never see
 * provider messages.
 */
abstract class EmailProvider
{
    abstract public function id(): string;

    abstract public function label(): string;

    /** Whether the credentials needed by this provider are saved. */
    abstract public function configured(): bool;

    /** Whether the provider needs a list / audience to subscribe to. */
    public function needs_list(): bool
    {
        return true;
    }

    /**
     * Lists / audiences for the editor select.
     *
     * @return array<int, array{value: string, label: string}>|WP_Error
     */
    abstract public function lists();

    /**
     * Adds or updates the contact.
     *
     * @param array{email: string, first_name: string, last_name: string, name: string, fields: array<string, string>, tags: array<int, string>, list: string, double_optin: bool} $contact
     * @return true|WP_Error
     */
    abstract public function subscribe(array $contact);

    /** Action handler registered in the Actions registry. @return null|WP_Error */
    public function handle(Submission $s, array $settings)
    {
        $contact = $this->contact($s, $settings);
        if ($contact instanceof WP_Error) {
            Log::error($this->id(), $contact->get_error_message(), ['form' => $s->form_id]);
            return $contact;
        }
        if (!$this->configured()) {
            $error = new WP_Error('zadex_integration_not_configured', $this->label() . ': the API key is not set (Zadex > Settings > Integrations).');
            Log::error($this->id(), $error->get_error_message(), ['form' => $s->form_id]);
            return $error;
        }
        if ($this->needs_list() && $contact['list'] === '') {
            $error = new WP_Error('zadex_integration_no_list', $this->label() . ': no list selected in the form settings.');
            Log::error($this->id(), $error->get_error_message(), ['form' => $s->form_id]);
            return $error;
        }
        $result = $this->subscribe($contact);
        if ($result instanceof WP_Error) {
            Log::error($this->id(), $result->get_error_message(), ['form' => $s->form_id, 'submission' => $s->id]);
            return $result;
        }
        return null;
    }

    /**
     * Contact data from the submission and the form settings.
     *
     * @return array{email: string, first_name: string, last_name: string, name: string, fields: array<string, string>, tags: array<int, string>, list: string, double_optin: bool}|WP_Error
     */
    public function contact(Submission $s, array $settings)
    {
        $p = $this->id() . '_';
        $get = static fn(string $k): string => isset($settings[$p . $k]) && is_scalar($settings[$p . $k]) ? trim((string) $settings[$p . $k]) : '';
        $email_field = Fields::sanitize_id($get('email_field'));
        $email = $email_field !== '' ? $s->text($email_field) : $s->first_email();
        $email = sanitize_email($email);
        if ($email === '' || !is_email($email)) {
            return new WP_Error('zadex_integration_no_email', $this->label() . ': the submission has no valid email address.');
        }
        $name_field = Fields::sanitize_id($get('name_field'));
        $last_field = Fields::sanitize_id($get('last_name_field'));
        $first = $name_field !== '' ? sanitize_text_field($s->text($name_field)) : '';
        $last = $last_field !== '' ? sanitize_text_field($s->text($last_field)) : '';
        $fields = [];
        foreach (is_array($settings[$p . 'fields'] ?? null) ? $settings[$p . 'fields'] : [] as $row) {
            if (!is_array($row)) {
                continue;
            }
            $key = isset($row['key']) && is_scalar($row['key']) ? preg_replace('/[^A-Za-z0-9_\-.]/', '', (string) $row['key']) : '';
            $value = isset($row['value']) && is_scalar($row['value']) ? (string) $row['value'] : '';
            if ($key !== '' && $key !== null) {
                $fields[$key] = Shortcodes::render($value, $s, 'plain');
            }
        }
        return [
            'email'        => $email,
            'first_name'   => $first,
            'last_name'    => $last,
            'name'         => trim($first . ' ' . $last),
            'fields'       => $fields,
            'tags'         => self::tags(Shortcodes::render($get('tags'), $s, 'header')),
            'list'         => $get('list'),
            'double_optin' => !empty($settings[$p . 'double_optin']),
        ];
    }

    /** @return array<int, string> */
    public static function tags(string $raw): array
    {
        $tags = array_map(static fn(string $t): string => sanitize_text_field($t), explode(',', $raw));
        return array_values(array_unique(array_filter($tags, static fn(string $t): bool => $t !== '')));
    }

    /**
     * Maps a provider list response into select options.
     *
     * @param mixed $items
     * @return array<int, array{value: string, label: string}>
     */
    protected static function options($items, string $id_key, string $name_key): array
    {
        $out = [];
        foreach (is_array($items) ? $items : [] as $item) {
            if (is_array($item) && isset($item[$id_key]) && is_scalar($item[$id_key])) {
                $label = isset($item[$name_key]) && is_scalar($item[$name_key]) ? wp_strip_all_tags((string) $item[$name_key]) : '';
                $out[] = ['value' => (string) $item[$id_key], 'label' => $label !== '' ? $label : (string) $item[$id_key]];
            }
        }
        return $out;
    }

    protected static function basic(string $user, string $password): string
    {
        // HTTP Basic authentication header required by the provider API (not obfuscation).
        return 'Basic ' . base64_encode($user . ':' . $password);
    }
}