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| 1 | <?php |
| 2 | |
| 3 | namespace Wikimedia\Purtle; |
| 4 | |
| 5 | use Closure; |
| 6 | use InvalidArgumentException; |
| 7 | use LogicException; |
| 8 | |
| 9 | /** |
| 10 | * Base class for RdfWriter implementations. |
| 11 | * |
| 12 | * Subclasses have to implement at least the writeXXX() methods to generate the desired output |
| 13 | * for the respective RDF constructs. Subclasses may override the startXXX() and finishXXX() |
| 14 | * methods to generate structural output, and override expandXXX() to transform identifiers. |
| 15 | * |
| 16 | * @license GPL-2.0-or-later |
| 17 | * @author Daniel Kinzler |
| 18 | */ |
| 19 | abstract class RdfWriterBase implements RdfWriter { |
| 20 | |
| 21 | /** |
| 22 | * @var array An array of strings, RdfWriters, or closures. |
| 23 | */ |
| 24 | private $buffer = []; |
| 25 | |
| 26 | /** |
| 27 | * @var RdfWriter[] sub-writers. |
| 28 | */ |
| 29 | private $subs = []; |
| 30 | |
| 31 | protected const STATE_START = 0; |
| 32 | protected const STATE_DOCUMENT = 5; |
| 33 | protected const STATE_SUBJECT = 10; |
| 34 | protected const STATE_PREDICATE = 11; |
| 35 | protected const STATE_OBJECT = 12; |
| 36 | protected const STATE_FINISH = 666; |
| 37 | |
| 38 | /** |
| 39 | * @var int the current state |
| 40 | */ |
| 41 | private $state = self::STATE_START; |
| 42 | |
| 43 | /** |
| 44 | * Shorthands that can be used in place of IRIs, e.g. ("a" to mean rdf:type). |
| 45 | * |
| 46 | * @var string[][] a map of shorthand names to [ $base, $local ] pairs. |
| 47 | * @todo Handle "a" as a special case directly. Use for custom "variables" like %currentValue |
| 48 | * instead. |
| 49 | */ |
| 50 | private $shorthands = []; |
| 51 | |
| 52 | /** |
| 53 | * @var string[] a map of prefixes to base IRIs |
| 54 | */ |
| 55 | protected $prefixes = []; |
| 56 | |
| 57 | /** |
| 58 | * @var array pair to store the current subject. |
| 59 | * Holds the $base and $local parameters passed to about(). |
| 60 | */ |
| 61 | protected $currentSubject = [ null, null ]; |
| 62 | |
| 63 | /** |
| 64 | * @var array pair to store the current predicate. |
| 65 | * Holds the $base and $local parameters passed to say(). |
| 66 | */ |
| 67 | protected $currentPredicate = [ null, null ]; |
| 68 | |
| 69 | /** |
| 70 | * @var BNodeLabeler |
| 71 | */ |
| 72 | private $labeler; |
| 73 | |
| 74 | /** |
| 75 | * Role ID for writers that will generate a full RDF document. |
| 76 | */ |
| 77 | public const DOCUMENT_ROLE = 'document'; |
| 78 | public const SUBDOCUMENT_ROLE = 'sub'; |
| 79 | |
| 80 | /** |
| 81 | * @var string The writer's role, see the XXX_ROLE constants. |
| 82 | */ |
| 83 | protected $role; |
| 84 | |
| 85 | /** |
| 86 | * Are prefixed locked against modification? |
| 87 | * @var bool |
| 88 | */ |
| 89 | private $prefixesLocked = false; |
| 90 | |
| 91 | /** |
| 92 | * @param string $role The writer's role, use the XXX_ROLE constants. |
| 93 | * @param BNodeLabeler|null $labeler |
| 94 | * |
| 95 | * @throws InvalidArgumentException |
| 96 | */ |
| 97 | public function __construct( $role, ?BNodeLabeler $labeler = null ) { |
| 98 | if ( !is_string( $role ) ) { |
| 99 | throw new InvalidArgumentException( '$role must be a string' ); |
| 100 | } |
| 101 | |
| 102 | $this->role = $role; |
| 103 | $this->labeler = $labeler ?: new BNodeLabeler(); |
| 104 | |
| 105 | $this->registerShorthand( 'a', 'rdf', 'type' ); |
| 106 | |
| 107 | $this->prefix( 'rdf', 'http://www.w3.org/1999/02/22-rdf-syntax-ns#' ); |
| 108 | $this->prefix( 'xsd', 'http://www.w3.org/2001/XMLSchema#' ); |
| 109 | } |
| 110 | |
| 111 | /** |
| 112 | * @param string $role |
| 113 | * @param BNodeLabeler $labeler |
| 114 | * |
| 115 | * @return RdfWriterBase |
| 116 | */ |
| 117 | abstract protected function newSubWriter( $role, BNodeLabeler $labeler ); |
| 118 | |
| 119 | /** |
| 120 | * Registers a shorthand that can be used instead of a qname, |
| 121 | * like 'a' can be used instead of 'rdf:type'. |
| 122 | * |
| 123 | * @param string $shorthand |
| 124 | * @param string $prefix |
| 125 | * @param string $local |
| 126 | */ |
| 127 | protected function registerShorthand( $shorthand, $prefix, $local ) { |
| 128 | $this->shorthands[$shorthand] = [ $prefix, $local ]; |
| 129 | } |
| 130 | |
| 131 | /** |
| 132 | * Registers a prefix |
| 133 | * |
| 134 | * @param string $prefix |
| 135 | * @param string $iri The base IRI |
| 136 | * |
| 137 | * @throws LogicException |
| 138 | */ |
| 139 | public function prefix( $prefix, $iri ) { |
| 140 | if ( $this->prefixesLocked ) { |
| 141 | throw new LogicException( 'Prefixes can not be added after start()' ); |
| 142 | } |
| 143 | |
| 144 | $this->prefixes[$prefix] = $iri; |
| 145 | } |
| 146 | |
| 147 | /** |
| 148 | * Determines whether $shorthand can be used as a shorthand. |
| 149 | * |
| 150 | * @param string $shorthand |
| 151 | * |
| 152 | * @return bool |
| 153 | */ |
| 154 | protected function isShorthand( $shorthand ) { |
| 155 | return isset( $this->shorthands[$shorthand] ); |
| 156 | } |
| 157 | |
| 158 | /** |
| 159 | * Determines whether $shorthand can legally be used as a prefix. |
| 160 | * |
| 161 | * @param string $prefix |
| 162 | * |
| 163 | * @return bool |
| 164 | */ |
| 165 | protected function isPrefix( $prefix ) { |
| 166 | return isset( $this->prefixes[$prefix] ); |
| 167 | } |
| 168 | |
| 169 | /** |
| 170 | * Returns the prefix map. |
| 171 | * |
| 172 | * @return string[] An associative array mapping prefixes to base IRIs. |
| 173 | */ |
| 174 | public function getPrefixes() { |
| 175 | return $this->prefixes; |
| 176 | } |
| 177 | |
| 178 | /** |
| 179 | * @param string|null $languageCode |
| 180 | * |
| 181 | * @return bool |
| 182 | */ |
| 183 | protected function isValidLanguageCode( $languageCode ) { |
| 184 | // preg_match is somewhat (12%) slower than strspn but more readable |
| 185 | return $languageCode !== null && preg_match( '/^[\da-z-]{2,}$/i', $languageCode ); |
| 186 | } |
| 187 | |
| 188 | /** |
| 189 | * @return RdfWriter |
| 190 | */ |
| 191 | final public function sub() { |
| 192 | $writer = $this->newSubWriter( self::SUBDOCUMENT_ROLE, $this->labeler ); |
| 193 | $writer->state = self::STATE_DOCUMENT; |
| 194 | |
| 195 | // share registered prefixes |
| 196 | $writer->prefixes =& $this->prefixes; |
| 197 | |
| 198 | $this->subs[] = $writer; |
| 199 | return $writer; |
| 200 | } |
| 201 | |
| 202 | /** |
| 203 | * @return string A string corresponding to one of the the XXX_ROLE constants. |
| 204 | */ |
| 205 | final public function getRole() { |
| 206 | return $this->role; |
| 207 | } |
| 208 | |
| 209 | /** |
| 210 | * Appends string to the output buffer. |
| 211 | * @param string $w |
| 212 | */ |
| 213 | final protected function write( $w ) { |
| 214 | $this->buffer[] = $w; |
| 215 | } |
| 216 | |
| 217 | /** |
| 218 | * If $base is a shorthand, $base and $local are updated to hold whatever qname |
| 219 | * the shorthand was associated with. |
| 220 | * |
| 221 | * Otherwise, $base and $local remain unchanged. |
| 222 | * |
| 223 | * @param string &$base |
| 224 | * @param string|null &$local |
| 225 | */ |
| 226 | protected function expandShorthand( &$base, &$local ) { |
| 227 | if ( $local === null && isset( $this->shorthands[$base] ) ) { |
| 228 | [ $base, $local ] = $this->shorthands[$base]; |
| 229 | } |
| 230 | } |
| 231 | |
| 232 | /** |
| 233 | * If $base is a registered prefix, $base will be replaced by the base IRI associated with |
| 234 | * that prefix, with $local appended. $local will be set to null. |
| 235 | * |
| 236 | * Otherwise, $base and $local remain unchanged. |
| 237 | * |
| 238 | * @param string &$base |
| 239 | * @param string|null &$local |
| 240 | * |
| 241 | * @throws LogicException |
| 242 | */ |
| 243 | protected function expandQName( &$base, &$local ) { |
| 244 | if ( $local !== null && $base !== '_' ) { |
| 245 | if ( isset( $this->prefixes[$base] ) ) { |
| 246 | $base = $this->prefixes[$base] . $local; // XXX: can we avoid this concat? |
| 247 | $local = null; |
| 248 | } else { |
| 249 | throw new LogicException( 'Unknown prefix: ' . $base ); |
| 250 | } |
| 251 | } |
| 252 | } |
| 253 | |
| 254 | /** |
| 255 | * @see RdfWriter::blank() |
| 256 | * |
| 257 | * @param string|null $label node label; will be generated if not given. |
| 258 | * |
| 259 | * @return string |
| 260 | */ |
| 261 | final public function blank( $label = null ) { |
| 262 | return $this->labeler->getLabel( $label ); |
| 263 | } |
| 264 | |
| 265 | /** |
| 266 | * @see RdfWriter::start() |
| 267 | */ |
| 268 | final public function start() { |
| 269 | $this->state( self::STATE_DOCUMENT ); |
| 270 | $this->prefixesLocked = true; |
| 271 | } |
| 272 | |
| 273 | /** |
| 274 | * @see RdfWriter::finish() |
| 275 | */ |
| 276 | final public function finish() { |
| 277 | // close all unclosed states |
| 278 | $this->state( self::STATE_DOCUMENT ); |
| 279 | |
| 280 | // ...then insert output of sub-writers into the buffer, |
| 281 | // so it gets placed before the footer... |
| 282 | $this->drainSubs(); |
| 283 | |
| 284 | // and then finalize |
| 285 | $this->state( self::STATE_FINISH ); |
| 286 | |
| 287 | // Detaches all subs. |
| 288 | $this->subs = []; |
| 289 | } |
| 290 | |
| 291 | /** |
| 292 | * @see RdfWriter::drain() |
| 293 | * |
| 294 | * @return string RDF |
| 295 | */ |
| 296 | final public function drain() { |
| 297 | // we can drain after finish, but finish state is sticky |
| 298 | if ( $this->state !== self::STATE_FINISH ) { |
| 299 | $this->state( self::STATE_DOCUMENT ); |
| 300 | } |
| 301 | |
| 302 | $this->drainSubs(); |
| 303 | $this->flattenBuffer(); |
| 304 | |
| 305 | $rdf = implode( '', $this->buffer ); |
| 306 | $this->buffer = []; |
| 307 | |
| 308 | return $rdf; |
| 309 | } |
| 310 | |
| 311 | /** |
| 312 | * Calls drain() an any RdfWriter instances in $this->buffer, and replaces them |
| 313 | * in $this->buffer with the string returned by the drain() call. Any closures |
| 314 | * present in the $this->buffer will be called, and replaced by their return value. |
| 315 | */ |
| 316 | private function flattenBuffer() { |
| 317 | foreach ( $this->buffer as &$b ) { |
| 318 | if ( $b instanceof Closure ) { |
| 319 | $b = $b(); |
| 320 | } |
| 321 | if ( $b instanceof RdfWriter ) { |
| 322 | $b = $b->drain(); |
| 323 | } |
| 324 | } |
| 325 | } |
| 326 | |
| 327 | /** |
| 328 | * Drains all subwriters, and appends their output to this writer's buffer. |
| 329 | * Subwriters remain usable. |
| 330 | */ |
| 331 | private function drainSubs() { |
| 332 | foreach ( $this->subs as $sub ) { |
| 333 | $rdf = $sub->drain(); |
| 334 | $this->write( $rdf ); |
| 335 | } |
| 336 | } |
| 337 | |
| 338 | /** |
| 339 | * @see RdfWriter::about() |
| 340 | * |
| 341 | * @param string $base A QName prefix if $local is given, or an IRI if $local is null. |
| 342 | * @param string|null $local A QName suffix, or null if $base is an IRI. |
| 343 | * |
| 344 | * @return RdfWriter $this |
| 345 | */ |
| 346 | final public function about( $base, $local = null ) { |
| 347 | $this->expandSubject( $base, $local ); |
| 348 | |
| 349 | if ( $this->state === self::STATE_OBJECT |
| 350 | && $base === $this->currentSubject[0] |
| 351 | && $local === $this->currentSubject[1] |
| 352 | ) { |
| 353 | return $this; // redundant about() call |
| 354 | } |
| 355 | |
| 356 | $this->state( self::STATE_SUBJECT ); |
| 357 | |
| 358 | $this->currentSubject[0] = $base; |
| 359 | $this->currentSubject[1] = $local; |
| 360 | $this->currentPredicate[0] = null; |
| 361 | $this->currentPredicate[1] = null; |
| 362 | |
| 363 | $this->writeSubject( $base, $local ); |
| 364 | return $this; |
| 365 | } |
| 366 | |
| 367 | /** |
| 368 | * @see RdfWriter::a() |
| 369 | * Shorthand for say( 'a' )->is( $type ). |
| 370 | * |
| 371 | * @param string $typeBase The data type's QName prefix if $typeLocal is given, |
| 372 | * or an IRI or shorthand if $typeLocal is null. |
| 373 | * @param string|null $typeLocal The data type's QName suffix, |
| 374 | * or null if $typeBase is an IRI or shorthand. |
| 375 | * |
| 376 | * @return RdfWriter $this |
| 377 | */ |
| 378 | final public function a( $typeBase, $typeLocal = null ) { |
| 379 | return $this->say( 'a' )->is( $typeBase, $typeLocal ); |
| 380 | } |
| 381 | |
| 382 | /** |
| 383 | * @see RdfWriter::say() |
| 384 | * |
| 385 | * @param string $base A QName prefix. |
| 386 | * @param string|null $local A QName suffix. |
| 387 | * |
| 388 | * @return RdfWriter $this |
| 389 | */ |
| 390 | final public function say( $base, $local = null ) { |
| 391 | $this->expandPredicate( $base, $local ); |
| 392 | |
| 393 | if ( $this->state === self::STATE_OBJECT |
| 394 | && $base === $this->currentPredicate[0] |
| 395 | && $local === $this->currentPredicate[1] |
| 396 | ) { |
| 397 | return $this; // redundant about() call |
| 398 | } |
| 399 | |
| 400 | $this->state( self::STATE_PREDICATE ); |
| 401 | |
| 402 | $this->currentPredicate[0] = $base; |
| 403 | $this->currentPredicate[1] = $local; |
| 404 | |
| 405 | $this->writePredicate( $base, $local ); |
| 406 | return $this; |
| 407 | } |
| 408 | |
| 409 | /** |
| 410 | * @see RdfWriter::is() |
| 411 | * |
| 412 | * @param string $base A QName prefix if $local is given, or an IRI if $local is null. |
| 413 | * @param string|null $local A QName suffix, or null if $base is an IRI. |
| 414 | * |
| 415 | * @return RdfWriter $this |
| 416 | */ |
| 417 | final public function is( $base, $local = null ) { |
| 418 | $this->state( self::STATE_OBJECT ); |
| 419 | |
| 420 | $this->expandResource( $base, $local ); |
| 421 | $this->writeResource( $base, $local ); |
| 422 | return $this; |
| 423 | } |
| 424 | |
| 425 | /** |
| 426 | * @see RdfWriter::text() |
| 427 | * |
| 428 | * @param string $text the text to be placed in the output |
| 429 | * @param string|null $language the language the text is in |
| 430 | * |
| 431 | * @return $this |
| 432 | */ |
| 433 | final public function text( $text, $language = null ) { |
| 434 | $this->state( self::STATE_OBJECT ); |
| 435 | |
| 436 | $this->writeText( $text, $language ); |
| 437 | return $this; |
| 438 | } |
| 439 | |
| 440 | /** |
| 441 | * @see RdfWriter::value() |
| 442 | * |
| 443 | * @param string $value the value encoded as a string |
| 444 | * @param string|null $typeBase The data type's QName prefix if $typeLocal is given, |
| 445 | * or an IRI or shorthand if $typeLocal is null. |
| 446 | * @param string|null $typeLocal The data type's QName suffix, |
| 447 | * or null if $typeBase is an IRI or shorthand. |
| 448 | * |
| 449 | * @return $this |
| 450 | */ |
| 451 | final public function value( $value, $typeBase = null, $typeLocal = null ) { |
| 452 | $this->state( self::STATE_OBJECT ); |
| 453 | |
| 454 | if ( $typeBase === null && !is_string( $value ) ) { |
| 455 | $vtype = gettype( $value ); |
| 456 | switch ( $vtype ) { |
| 457 | case 'integer': |
| 458 | $typeBase = 'xsd'; |
| 459 | $typeLocal = 'integer'; |
| 460 | $value = "$value"; |
| 461 | break; |
| 462 | |
| 463 | case 'double': |
| 464 | $typeBase = 'xsd'; |
| 465 | $typeLocal = 'double'; |
| 466 | $value = "$value"; |
| 467 | break; |
| 468 | |
| 469 | case 'boolean': |
| 470 | $typeBase = 'xsd'; |
| 471 | $typeLocal = 'boolean'; |
| 472 | $value = $value ? 'true' : 'false'; |
| 473 | break; |
| 474 | } |
| 475 | } |
| 476 | |
| 477 | $this->expandType( $typeBase, $typeLocal ); |
| 478 | |
| 479 | $this->writeValue( $value, $typeBase, $typeLocal ); |
| 480 | return $this; |
| 481 | } |
| 482 | |
| 483 | /** |
| 484 | * State transition table |
| 485 | * First state is "from", second is "to" |
| 486 | * @var array |
| 487 | */ |
| 488 | protected $transitionTable = [ |
| 489 | self::STATE_START => [ |
| 490 | self::STATE_DOCUMENT => true, |
| 491 | ], |
| 492 | self::STATE_DOCUMENT => [ |
| 493 | self::STATE_DOCUMENT => true, |
| 494 | self::STATE_SUBJECT => true, |
| 495 | self::STATE_FINISH => true, |
| 496 | ], |
| 497 | self::STATE_SUBJECT => [ |
| 498 | self::STATE_PREDICATE => true, |
| 499 | ], |
| 500 | self::STATE_PREDICATE => [ |
| 501 | self::STATE_OBJECT => true, |
| 502 | ], |
| 503 | self::STATE_OBJECT => [ |
| 504 | self::STATE_DOCUMENT => true, |
| 505 | self::STATE_SUBJECT => true, |
| 506 | self::STATE_PREDICATE => true, |
| 507 | self::STATE_OBJECT => true, |
| 508 | ], |
| 509 | ]; |
| 510 | |
| 511 | /** |
| 512 | * Perform a state transition. Writer states roughly correspond to states in a naive |
| 513 | * regular parser for the respective syntax. State transitions may generate output, |
| 514 | * particularly of structural elements which correspond to terminals in a respective |
| 515 | * parser. |
| 516 | * |
| 517 | * @param int $newState one of the self::STATE_... constants |
| 518 | * |
| 519 | * @throws LogicException |
| 520 | */ |
| 521 | final protected function state( $newState ) { |
| 522 | if ( !isset( $this->transitionTable[$this->state][$newState] ) ) { |
| 523 | throw new LogicException( 'Bad transition: ' . $this->state . ' -> ' . $newState ); |
| 524 | } |
| 525 | |
| 526 | $action = $this->transitionTable[$this->state][$newState]; |
| 527 | if ( $action !== true ) { |
| 528 | if ( is_string( $action ) ) { |
| 529 | $this->write( $action ); |
| 530 | } else { |
| 531 | $action(); |
| 532 | } |
| 533 | } |
| 534 | |
| 535 | $this->state = $newState; |
| 536 | } |
| 537 | |
| 538 | /** |
| 539 | * Must be implemented to generate output that starts a statement (or set of statements) |
| 540 | * about a subject. Depending on the requirements of the output format, the implementation |
| 541 | * may be empty. |
| 542 | * |
| 543 | * @note $base and $local are given as passed to about() and processed by expandSubject(). |
| 544 | * |
| 545 | * @param string $base |
| 546 | * @param string|null $local |
| 547 | */ |
| 548 | abstract protected function writeSubject( $base, $local = null ); |
| 549 | |
| 550 | /** |
| 551 | * Must be implemented to generate output that represents the association of a predicate |
| 552 | * with a subject that was previously defined by a call to writeSubject(). |
| 553 | * |
| 554 | * @note $base and $local are given as passed to say() and processed by expandPredicate(). |
| 555 | * |
| 556 | * @param string $base |
| 557 | * @param string|null $local |
| 558 | */ |
| 559 | abstract protected function writePredicate( $base, $local = null ); |
| 560 | |
| 561 | /** |
| 562 | * Must be implemented to generate output that represents a resource used as the object |
| 563 | * of a statement. |
| 564 | * |
| 565 | * @note $base and $local are given as passed to is() and processed by expandObject(). |
| 566 | * |
| 567 | * @param string $base |
| 568 | * @param string|null $local |
| 569 | */ |
| 570 | abstract protected function writeResource( $base, $local = null ); |
| 571 | |
| 572 | /** |
| 573 | * Must be implemented to generate output that represents a text used as the object |
| 574 | * of a statement. |
| 575 | * |
| 576 | * @param string $text the text to be placed in the output |
| 577 | * @param string|null $language the language the text is in |
| 578 | */ |
| 579 | abstract protected function writeText( $text, $language ); |
| 580 | |
| 581 | /** |
| 582 | * Must be implemented to generate output that represents a (typed) literal used as the object |
| 583 | * of a statement. |
| 584 | * |
| 585 | * @note $typeBase and $typeLocal are given as passed to value() and processed by expandType(). |
| 586 | * |
| 587 | * @param string $value the value encoded as a string |
| 588 | * @param string|null $typeBase |
| 589 | * @param string|null $typeLocal |
| 590 | */ |
| 591 | abstract protected function writeValue( $value, $typeBase, $typeLocal = null ); |
| 592 | |
| 593 | /** |
| 594 | * Perform any expansion (shorthand to qname, qname to IRI) desired |
| 595 | * for subject identifiers. |
| 596 | * |
| 597 | * @param string &$base |
| 598 | * @param string|null &$local |
| 599 | */ |
| 600 | protected function expandSubject( &$base, &$local ) { |
| 601 | } |
| 602 | |
| 603 | /** |
| 604 | * Perform any expansion (shorthand to qname, qname to IRI) desired |
| 605 | * for predicate identifiers. |
| 606 | * |
| 607 | * @param string &$base |
| 608 | * @param string|null &$local |
| 609 | */ |
| 610 | protected function expandPredicate( &$base, &$local ) { |
| 611 | } |
| 612 | |
| 613 | /** |
| 614 | * Perform any expansion (shorthand to qname, qname to IRI) desired |
| 615 | * for resource identifiers. |
| 616 | * |
| 617 | * @param string &$base |
| 618 | * @param string|null &$local |
| 619 | */ |
| 620 | protected function expandResource( &$base, &$local ) { |
| 621 | } |
| 622 | |
| 623 | /** |
| 624 | * Perform any expansion (shorthand to qname, qname to IRI) desired |
| 625 | * for type identifiers. |
| 626 | * |
| 627 | * @param string|null &$base |
| 628 | * @param string|null &$local |
| 629 | */ |
| 630 | protected function expandType( &$base, &$local ) { |
| 631 | } |
| 632 | |
| 633 | } |