function fetch_nepse_data() {
    // Try transient first
    $cached = get_transient( 'nepse_market_summary_cache' );
    if ( false !== $cached ) {
        return $cached;
    }

    $api_url = 'https://nepseapi.surajrimal.dev';
    $args = array(
        'timeout'   => 20,
        'sslverify' => true,
        'headers'   => array(
            'Accept' => 'application/json, text/json, application/*+json, */*'
        ),
    );

    $response = wp_remote_get( $api_url, $args );

    // WP error
    if ( is_wp_error( $response ) ) {
        $err_msg = 'Error fetching NEPSE data: ' . $response->get_error_message();
        // cache short to avoid hammering endpoint
        set_transient( 'nepse_market_summary_cache', '<p>' . esc_html( $err_msg ) . '</p>', 5 * MINUTE_IN_SECONDS );
        if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) error_log( $err_msg );
        return '<p>' . esc_html( $err_msg ) . '</p>';
    }

    $code = wp_remote_retrieve_response_code( $response );
    $body = wp_remote_retrieve_body( $response );
    $headers = wp_remote_retrieve_headers( $response );
    $content_type = isset( $headers['content-type'] ) ? $headers['content-type'] : ( isset( $headers['Content-Type'] ) ? $headers['Content-Type'] : '' );

    // non-200
    if ( $code < 200 || $code >= 300 ) {
        $msg = sprintf( 'NEPSE API returned HTTP %d.', intval( $code ) );
        // Save raw body for debugging (short-lived)
        set_transient( 'nepse_market_summary_raw', $body, 5 * MINUTE_IN_SECONDS );
        set_transient( 'nepse_market_summary_cache', '<p>' . esc_html( $msg ) . ' Please try again shortly.</p>', 5 * MINUTE_IN_SECONDS );
        if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
            error_log( $msg . ' Content-Type: ' . $content_type . ' Body (first 500 chars): ' . substr( $body, 0, 500 ) );
        }
        return '<p>' . esc_html( $msg ) . ' Please try again shortly.</p>';
    }

    // Attempt to decode JSON directly
    $data = json_decode( $body, true );

    if ( json_last_error() !== JSON_ERROR_NONE ) {
        // Try to extract the first JSON object or array inside the body (handles HTML-wrapped JSON)
        $json_found = null;

        // A recursive pattern to capture the first {...} or [...] block (PCRE recursion)
        if ( preg_match('/(\{(?:[^{}]|(?R))*\}|\[(?:[^\[\]]|(?R))*\])/', $body, $m) ) {
            $candidate = $m[0];
            $tmp = json_decode( $candidate, true );
            if ( json_last_error() === JSON_ERROR_NONE ) {
                $json_found = $tmp;
            }
        }

        if ( $json_found === null ) {
            // final fallback: strip html tags and try decode
            $stripped = html_entity_decode( strip_tags( $body ), ENT_QUOTES | ENT_HTML5 );
            $tmp2 = json_decode( $stripped, true );
            if ( json_last_error() === JSON_ERROR_NONE ) {
                $json_found = $tmp2;
            }
        }

        if ( $json_found === null ) {
            // Save raw body for debugging (short-lived)
            set_transient( 'nepse_market_summary_raw', $body, 10 * MINUTE_IN_SECONDS );

            $err = 'Error decoding NEPSE data. Invalid format.';
            if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
                error_log( $err . ' JSON error: ' . json_last_error_msg() . ' Response code: ' . $code . ' Content-Type: ' . $content_type );
                error_log( 'Response body (first 1000 chars): ' . substr( $body, 0, 1000 ) );
            }

            $display = '<p>' . esc_html( $err ) . '</p>';
            $display .= '<p><em>Raw response saved to transient "nepse_market_summary_raw" for debugging (short-lived).</em></p>';
            set_transient( 'nepse_market_summary_cache', $display, 5 * MINUTE_IN_SECONDS );
            return $display;
        } else {
            $data = $json_found;
        }
    }

    // Flexible parsing for many possible shapes
    $index   = $data['index'] ?? $data['nepse']['index'] ?? $data['market']['index'] ?? null;
    $current = $data['currentValue'] ?? $data['nepse']['currentValue'] ?? $data['market']['currentValue'] ?? $data['value'] ?? null;
    $point   = $data['pointChange'] ?? $data['nepse']['pointChange'] ?? $data['market']['pointChange'] ?? $data['change'] ?? null;
    $perc    = $data['percChange'] ?? $data['nepse']['percChange'] ?? $data['market']['percChange'] ?? $data['percent'] ?? null;

    if ( $index === null || $current === null ) {
        // Save raw body for later inspection
        set_transient( 'nepse_market_summary_raw', $body, 10 * MINUTE_IN_SECONDS );

        $output = '<p>Missing expected NEPSE fields in API response.</p>';
        if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
            $output .= '<pre>' . esc_html( print_r( array(
                'http_code' => $code,
                'content_type' => $content_type,
                'parsed_json_keys' => is_array( $data ) ? array_keys( $data ) : 'not array',
            ), true ) ) . '</pre>';
            error_log( 'NEPSE missing fields. Response keys: ' . ( is_array( $data ) ? implode( ',', array_keys( $data ) ) : 'not array' ) );
        }
        set_transient( 'nepse_market_summary_cache', $output, 5 * MINUTE_IN_SECONDS );
        return $output;
    }

    // Build output
    $output  = '<h3>NEPSE Market Summary</h3>';
    $output .= '<table border="1" cellpadding="5" cellspacing="0">';
    $output .= '<tr><th>Index</th><th>Value</th><th>Change</th><th>Percentage</th></tr>';
    $output .= '<tr>';
    $output .= '<td>' . esc_html( $index ) . '</td>';
    $output .= '<td>' . esc_html( number_format( (float) $current, 2 ) ) . '</td>';
    $output .= '<td>' . esc_html( is_null( $point ) ? '-' : number_format( (float) $point, 2 ) ) . '</td>';
    $output .= '<td>' . esc_html( is_null( $perc ) ? '-' : number_format( (float) $perc, 2 ) . '%' ) . '</td>';
    $output .= '</tr>';
    $output .= '</table>';
    $output .= '<p><em>Data is typically delayed and for informational purposes only.</em></p>';

    // Cache for 10 minutes
    set_transient( 'nepse_market_summary_cache', $output, 10 * MINUTE_IN_SECONDS );
    return $output;
}