<?php
/**
 * Small bounded PDF renderer for opt-in AI traffic analytics attachments.
 *
 * No Composer dependency, external service, raw request logs, temporary public
 * URL or font download. Built only when an enabled report is mailed from
 * admin/cron; the ordinary front end never loads this class.
 */
if ( ! defined( 'ABSPATH' ) ) { exit; }

final class AI_O_Optimiser_Email_Report_PDF {
    /** Render a real, self-contained PDF 1.4 document from the safe mail summary. */
    public static function render( $summary, $frequency, $host ) {
        $summary = substr( (string) $summary, 0, 24000 );
        $rows = array();
        foreach ( preg_split( '/\r\n|\r|\n/', $summary ) as $raw ) {
            $raw = self::ascii( trim( (string) $raw ) );
            if ( '' === $raw ) {
                $rows[] = '';
                continue;
            }
            foreach ( explode( "\n", wordwrap( $raw, 85, "\n", true ) ) as $part ) {
                $rows[] = $part;
            }
        }
        $rows = array_slice( $rows, 0, 180 );
        $pages = array_chunk( $rows, 31 );
        if ( ! $pages ) { $pages = array( array() ); }
        $objects = array();
        $objects[1] = '<< /Type /Catalog /Pages 2 0 R >>';
        $kids = array();
        foreach ( $pages as $n => $_ ) { $kids[] = ( 5 + $n * 2 ) . ' 0 R'; }
        $objects[2] = '<< /Type /Pages /Kids [' . implode( ' ', $kids ) . '] /Count ' . count( $pages ) . ' >>';
        $objects[3] = '<< /Type /Font /Subtype /Type1 /BaseFont /Helvetica >>';
        $objects[4] = '<< /Type /Font /Subtype /Type1 /BaseFont /Helvetica-Bold >>';
        foreach ( $pages as $n => $page_rows ) {
            $page_id = 5 + $n * 2;
            $stream_id = $page_id + 1;
            $stream = self::page_stream( $page_rows, $frequency, $host, $n + 1, count( $pages ) );
            $objects[ $page_id ] = '<< /Type /Page /Parent 2 0 R /MediaBox [0 0 595 842] /Resources << /Font << /F1 3 0 R /F2 4 0 R >> >> /Contents ' . $stream_id . ' 0 R >>';
            $objects[ $stream_id ] = '<< /Length ' . strlen( $stream ) . " >>\nstream\n" . $stream . "\nendstream";
        }
        ksort( $objects, SORT_NUMERIC );
        $pdf = "%PDF-1.4\n%\xE2\xE3\xCF\xD3\n";
        $offsets = array( 0 );
        foreach ( $objects as $id => $object ) {
            $offsets[ $id ] = strlen( $pdf );
            $pdf .= $id . " 0 obj\n" . $object . "\nendobj\n";
        }
        $xref = strlen( $pdf );
        $pdf .= "xref\n0 " . ( count( $objects ) + 1 ) . "\n0000000000 65535 f \n";
        foreach ( $objects as $id => $_ ) {
            $pdf .= sprintf( '%010d 00000 n ', $offsets[ $id ] ) . "\n";
        }
        $pdf .= "trailer\n<< /Size " . ( count( $objects ) + 1 ) . " /Root 1 0 R >>\nstartxref\n" . $xref . "\n%%EOF\n";
        return $pdf;
    }

    private static function page_stream( array $lines, $frequency, $host, $page, $pages ) {
        $title = strtoupper( self::ascii( $frequency ) ) . ' ACTIVITY REPORT';
        $site = self::ascii( $host );
        $out = array(
            '0.035 0.42 0.46 rg 0 742 595 100 re f',
            '1 1 1 rg',
            self::text( 42, 794, 19, 'F2', 'AI-O  /  ' . $title ),
            self::text( 42, 765, 10, 'F1', $site ),
            '0.86 0.92 0.94 RG 42 726 m 553 726 l S',
        );
        $y = 705;
        foreach ( $lines as $line ) {
            if ( '' === $line ) {
                $y -= 10;
                continue;
            }
            $heading = in_array( $line, array( 'AI bot / fetch requests', 'Top AI bots / fetchers (requests, last seen UTC)', 'Most-fetched pages (bot requests)', 'AI referral sources (visits)', 'Guidance files (requests)' ), true );
            $out[] = $heading ? '0.035 0.42 0.46 rg' : '0.17 0.23 0.27 rg';
            $out[] = self::text( 44, $y, $heading ? 12 : 10, $heading ? 'F2' : 'F1', $line );
            $y -= $heading ? 23 : 16;
        }
        $out[] = '0.75 0.79 0.82 RG 42 62 m 553 62 l S';
        $out[] = '0.33 0.39 0.42 rg';
        $out[] = self::text( 44, 43, 9, 'F1', 'Observed AI requests and referrals - not unique users or guaranteed citations.' );
        $out[] = self::text( 487, 43, 9, 'F1', $page . ' / ' . $pages );
        return implode( "\n", $out ) . "\n";
    }

    private static function text( $x, $y, $size, $font, $value ) {
        $safe = str_replace( array( '\\', '(', ')' ), array( '\\\\', '\\(', '\\)' ), (string) $value );
        return sprintf( 'BT /%s %d Tf 1 0 0 1 %d %d Tm (%s) Tj ET', $font, $size, $x, $y, $safe );
    }

    private static function ascii( $value ) {
        $value = strtr( (string) $value, array(
            '—' => '-', '–' => '-', '→' => '>', '’' => "'", '“' => '"', '”' => '"', '•' => '-',
        ) );
        if ( function_exists( 'iconv' ) ) {
            $converted = @iconv( 'UTF-8', 'ASCII//TRANSLIT//IGNORE', $value );
            if ( false !== $converted ) { $value = $converted; }
        }
        return (string) preg_replace( '/[^\x20-\x7e]/', '', $value );
    }
}