Incremental revisions

<?php

declare(strict_types=1);

use PDF\Document\DocumentInformation;
use PDF\Document\Fonts\StandardFont;
use PDF\Document\Fonts\Type1Font;
use PDF\Document\Information\Title;
use PDF\Document\ResourceDictionary;
use PDF\Document\Resources\Font;
use PDF\FileStructure;
use PDF\Syntax\ContentStreamsResources\ContentStreams;
use PDF\Syntax\ContentStreamsResources\Operators\BeginTextObject;
use PDF\Syntax\ContentStreamsResources\Operators\EndTextObject;
use PDF\Syntax\ContentStreamsResources\Operators\MoveTextPosition;
use PDF\Syntax\ContentStreamsResources\Operators\SetTextFontAndSize;
use PDF\Syntax\ContentStreamsResources\Operators\ShowText;
use PDF\Syntax\DataStructure\Rectangle;
use PDF\Syntax\DataStructure\TextString;
use PDF\Syntax\DocumentStructure\DocumentCatalog;
use PDF\Syntax\DocumentStructure\PageTree\PageObject;
use PDF\Syntax\DocumentStructure\PageTree\PageTreeNode;
use PDF\Syntax\FileStructure\CrossReferenceFormat;
use PDF\Syntax\FileStructure\FileBody;
use PDF\Syntax\FileStructure\FileHeader;
use PDF\Syntax\FileStructure\IncrementalUpdate;
use PDF\Syntax\Object\ArrayType;
use PDF\Syntax\Object\DictionaryObject\Entry;
use PDF\Syntax\Object\DictionaryType;
use PDF\Syntax\Object\IndirectObject;
use PDF\Syntax\Object\IndirectReference;
use PDF\Syntax\Object\NameType;
use PDF\Syntax\Object\NumericType;
use PDF\Syntax\Object\StreamObject;
use PDF\Syntax\Object\StringObject\HexadecimalString;
use PDF\Syntax\Object\StringObject\LiteralString;

require dirname(__DIR__) . '/vendor/autoload.php';

// Tutorial 11: all three stream versions remain in the file's bytes.
// Readers follow the latest xref and display only revision 2 content.
$font = new Type1Font(StandardFont::Helvetica);
$resources = new ResourceDictionary(new Font(new DictionaryType(
    new Entry(new NameType('F1'), new IndirectReference($font)),
)));
$initialContents = new StreamObject(new ContentStreams(
    new BeginTextObject(),
    new SetTextFontAndSize(new NameType('F1'), new NumericType(20)),
    new MoveTextPosition(new NumericType(64), new NumericType(700)),
    new ShowText(new LiteralString('Revision 0 : document initial.')),
    new EndTextObject(),
));
$page = new PageObject(
    new Rectangle(new NumericType(0), new NumericType(0), new NumericType(612), new NumericType(792)),
    $resources,
    $initialContents,
);
$catalog = new DocumentCatalog((new PageTreeNode())->addKid($page));
$information = new DocumentInformation(new Title(new TextString('Document initial')));
$initial = (new FileStructure(
    new FileHeader('1.7'),
    new FileBody($catalog),
    trailerEntries: new DictionaryType(
        new Entry(new NameType('Info'), new IndirectReference($information)),
        new Entry(new NameType('ID'), new ArrayType(
            new HexadecimalString('incremental-example-original'),
            new HexadecimalString('incremental-example-revision-0'),
        )),
    ),
    crossReferenceFormat: CrossReferenceFormat::Stream,
))->toRevision();

// The identifier belongs to the snapshot, not a global counter.
// It is preserved: replacing a live object does not change its generation.
$contentIdentifier = $initial->binding($initialContents)->identifier;
$revision = $initial;
foreach ([1, 2] as $number) {
    $contents = new StreamObject(new ContentStreams(
        new BeginTextObject(),
        new SetTextFontAndSize(new NameType('F1'), new NumericType(22)),
        new MoveTextPosition(new NumericType(64), new NumericType(700)),
        new ShowText(new LiteralString('Revision ' . $number . ' : contenu mis a jour.')),
        new EndTextObject(),
        new BeginTextObject(),
        new SetTextFontAndSize(new NameType('F1'), new NumericType(12)),
        new MoveTextPosition(new NumericType(64), new NumericType(646)),
        new ShowText(new LiteralString('La police, la page et le catalogue restent les objets initiaux.')),
        new EndTextObject(),
        new BeginTextObject(),
        new SetTextFontAndSize(new NameType('F1'), new NumericType(12)),
        new MoveTextPosition(new NumericType(64), new NumericType(614)),
        new ShowText(new LiteralString('Les anciens octets sont conserves ; Prev relie les trois xref.')),
        new EndTextObject(),
    ));
    // FileBody explicitly selects the stream to replace. A historical
    // reference alone would not republish any already recorded object.
    $updatedInformation = new DocumentInformation(new Title(new TextString('Révision incrémentale ' . $number)));
    $revision = (new IncrementalUpdate(
        $revision,
        new FileBody(new IndirectObject($contents, $contentIdentifier)),
        trailerEntries: new DictionaryType(new Entry(new NameType('Info'), new IndirectReference($updatedInformation))),
    ))->toRevision();
}

// The first ID stays identical; the writer renews the second each time.
// Initial-revision bytes always form the PDF's exact prefix.
if (!str_starts_with($revision->bytes, $initial->bytes)) {
    throw new LogicException('The initial revision must remain byte-for-byte intact.');
}
$path = $argv[1] ?? __DIR__ . '/incremental-update.pdf';
$revision->writeTo($path);
echo $path . PHP_EOL;