/* core builder */
function scg_build_for_post($post_id) {
    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) return false;
    if (wp_is_post_revision($post_id)) return false;
    if (get_post_type($post_id) !== 'post') return false;

    $title = get_the_title($post_id);
    $post_link = get_permalink($post_id);

    $intros_text = get_option(SCG_OPT_INTROS, '');
    $outros_text = get_option(SCG_OPT_OUTROS, '');
    $intros = scg_split_units($intros_text);
    $outros = scg_split_units($outros_text);

    if (empty($intros)) $intros = array('<p>{BOLD_TITLE}</p>');
    if (empty($outros)) $outros = array('<p>{BOLD_TITLE}</p>');

    $intro_idx = intval(get_option(SCG_OPT_INTRO_IDX, -1));
    $outro_idx = intval(get_option(SCG_OPT_OUTRO_IDX, -1));
    $next_intro = ($intro_idx + 1) % count($intros);
    $next_outro = ($outro_idx + 1) % count($outros);
    update_option(SCG_OPT_INTRO_IDX, $next_intro);
    update_option(SCG_OPT_OUTRO_IDX, $next_outro);

    $intro_tpl = $intros[$next_intro];
    $outro_tpl = $outros[$next_outro];

    // split keywords for sections
    $keywords = scg_get_keywords();
    $intro_kws = array_slice($keywords, 0, 3);
    $pros_kws = array_slice($keywords, 3, 3);
    $cons_kws = array_slice($keywords, 6, 3);
    $faq_kws = array_slice($keywords, 9, 3);
    $outro_kws = array_slice($keywords, 12, 2); // remaining keywords for outro

    // apply placeholders in intro
    $intro_html = $intro_tpl;
    foreach ($intro_kws as $i => $kw) {
        $intro_html = str_replace('{A_KW' . $i . '}', '<a href="' . esc_url($post_link) . '" rel="dofollow"><strong>' . esc_html($title . ' ' . $kw) . '</strong></a>', $intro_html);
    }
    $intro_html = str_replace('{BOLD_TITLE}', '<a href="' . esc_url($post_link) . '" rel="dofollow"><strong>' . esc_html($title) . '</strong></a>', $intro_html);

    // Pros
    $pros_html = "<h2><strong>Pros of {$title}</strong></h2>
    <ul>
        <li><strong>{$title}</strong> provides an extremely user-friendly interface that allows seamless navigation and effortless management of multiple tasks daily. Additionally, <strong>{$title} {$pros_kws[0]}</strong> is included for convenience.</li>
        <li>Performance remains consistent, ensuring smooth operations and access to functionalities across platforms. Moreover, updates improve security and reliability through <strong>{$title} {$pros_kws[1]}</strong>.</li>
        <li>The app is compatible with various devices, offering reliable results whether on phones or tablets. Integration options include <strong>{$title} {$pros_kws[2]}</strong>.</li>
        <li>Frequent updates introduce new features without disruption. Furthermore, usability is enhanced continuously.</li>
        <li>Seamless integration with other apps facilitates workflow, multitasking, and collaboration efficiently.</li>
    </ul>";

    // Cons
    $cons_html = "<h3><strong>Cons of {$title}</strong></h3>
    <ul>
        <li>Occasional ads appear but do not significantly disrupt experience. Nevertheless, core functionality remains fully accessible.</li>
        <li>An active internet connection is required for advanced features. Some options include <strong>{$title} {$cons_kws[0]}</strong>.</li>
        <li>Storage may increase over time due to updates and cached data. Additionally, periodic cleanup is recommended (<strong>{$title} {$cons_kws[1]}</strong>).</li>
        <li>Minor bugs may appear, but updates ensure stability (<strong>{$title} {$cons_kws[2]}</strong>).</li>
        <li>Optional in-app purchases enhance features but are not required to enjoy core functionality.</li>
    </ul>";

    // FAQ
    $faq_tpl = "<h4><strong>FAQs about {BOLD_TITLE}</strong></h4>
        <h5>What is {BOLD_TITLE}?</h5><p>{BOLD_TITLE} simplifies digital tasks and offers powerful tools. {A_KW0}</p>
        <h5>Is {BOLD_TITLE} free?</h5><p>Basic features are free; premium upgrades available. {A_KW1}</p>
        <h5>How to install?</h5><p>Install via official stores. {A_KW2}</p>
        <h5>Is it safe?</h5><p>Regular updates and verified sources ensure safety.</p>";

    $faq_html = $faq_tpl;
    foreach ($faq_kws as $i => $kw) {
        $faq_html = str_replace('{A_KW' . $i . '}', '<a href="' . esc_url($post_link) . '" rel="dofollow"><strong>' . esc_html($title . ' ' . $kw) . '</strong></a>', $faq_html);
    }
    $faq_html = str_replace('{BOLD_TITLE}', '<a href="' . esc_url($post_link) . '" rel="dofollow"><strong>' . esc_html($title) . '</strong></a>', $faq_html);

    // Outro
    $outro_html_final = $outro_tpl;
    foreach ($outro_kws as $i => $kw) {
        $outro_html_final = str_replace('{A_KW' . $i . '}', '<a href="' . esc_url($post_link) . '" rel="dofollow"><strong>' . esc_html($title . ' ' . $kw) . '</strong></a>', $outro_html_final);
    }
    $outro_html_final = str_replace('{BOLD_TITLE}', '<a href="' . esc_url($post_link) . '" rel="dofollow"><strong>' . esc_html($title) . '</strong></a>', $outro_html_final);

    // Download section remains unchanged
    $download_section = "<h4><strong>How to Download and Install {$title}</strong></h4>
    <p>Easy installation on Android and iOS devices ensures quick access to advanced features. Furthermore, users can follow step-by-step instructions seamlessly.</p>
    <ol>
        <li>Open Google Play or App Store.</li>
        <li>Search for {$title} official application.</li>
        <li>Tap Install or Get.</li>
        <li>Open the app and start using immediately.</li>
    </ol>
    <p>📱 <strong>Download from Google Play:</strong> <a href='https://play.google.com/store/apps' target='_blank' rel='dofollow'>Google Play Store</a><br>
    🍏 <strong>Download from App Store:</strong> <a href='https://apps.apple.com/' target='_blank' rel='dofollow'>App Store</a></p>";

    $final = $intro_html . $pros_html . $cons_html . $faq_html . $download_section . $outro_html_final;

    // Update post content safely
    remove_action('save_post', 'scg_on_save');
    wp_update_post(array('ID' => $post_id, 'post_content' => $final));
    add_action('save_post', 'scg_on_save');

    return true;
}