File size: 28,114 Bytes
b9f94e1
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
"""

PDF Parsing Engine for trade documents.



Uses pypdf (BSD-3) for PDF text extraction.

Provides structured extraction of trade document fields:

- Invoice number, date, total

- Shipper/consignee information

- Item descriptions, quantities, prices

- HS codes (if present in document)

- Country of origin/destination



Supports:

- Text-based PDFs (direct text extraction)

- Scanned PDFs (limited β€” pypdf extracts embedded text only)



Security:

- File size limit: 50 MB (MAX_PDF_SIZE_BYTES)

- Page limit: 500 pages (MAX_PDF_PAGES)

- PDF magic bytes validation (%PDF-)

- try/finally for all PDF handle operations



Typing conventions:

    All public APIs use explicit type hints. Final constants prevent mutation.

"""

from __future__ import annotations

import logging
import re
import threading
import time as _time
from dataclasses import dataclass, field
from pathlib import Path
from typing import Annotated, Any, Final, Literal, Optional

logger: Final = logging.getLogger(__name__)

# Security limits for PDF parsing
MAX_PDF_SIZE_BYTES: Final[int] = 50 * 1024 * 1024  # 50 MB
MAX_PDF_PAGES: Final[int] = 500
ALLOWED_MIME_TYPES: Final[frozenset[str]] = frozenset({"application/pdf"})
PDF_MAGIC_BYTES: Final[bytes] = b"%PDF-"

try:
    from pypdf import PdfReader

    PYPDF_AVAILABLE: Final[bool] = True
except ImportError:
    PdfReader = None  # type: ignore[assignment,misc]
    PYPDF_AVAILABLE = False
    logger.warning("pypdf not installed. Install with: pip install pypdf")


# ── Domain Exceptions ─────────────────────────────────────────────────


class PDFParsingError(Exception):
    """Base exception for all PDF parsing errors."""


class PDFStructureExploitException(PDFParsingError):
    """Raised when a PDF file exhibits malicious structure.



    Attributes:

        file_path: Path to the malicious file.

        reason: Description of the exploit detected.

    """

    def __init__(self, file_path: str, reason: str) -> None:
        self.file_path = file_path
        self.reason = reason
        super().__init__(f"PDF exploit detected in {file_path}: {reason}")


class PDFSizeLimitExceededError(PDFParsingError):
    """Raised when PDF file exceeds MAX_PDF_SIZE_BYTES.



    Attributes:

        file_size: Actual file size in bytes.

        limit: Maximum allowed size in bytes.

    """

    def __init__(self, file_size: int, limit: int) -> None:
        self.file_size = file_size
        self.limit = limit
        super().__init__(
            f"PDF file too large: {file_size / (1024*1024):.1f} MB "
            f"(max {limit / (1024*1024):.0f} MB)"
        )


class PDFPageLimitExceededError(PDFParsingError):
    """Raised when PDF exceeds MAX_PDF_PAGES.



    Attributes:

        page_count: Actual page count.

        limit: Maximum allowed pages.

    """

    def __init__(self, page_count: int, limit: int) -> None:
        self.page_count = page_count
        self.limit = limit
        super().__init__(f"PDF has {page_count} pages (max {limit})")


class PDFNotValidError(PDFParsingError):
    """Raised when file is not a valid PDF."""


class PDFEmptyError(PDFParsingError):
    """Raised when PDF file is empty."""


# ── Constants ─────────────────────────────────────────────────────────

# Type aliases
DocumentType = Literal[
    "unknown", "invoice", "packing_list", "bill_of_lading",
    "certificate_of_origin", "quotation", "purchase_order",
]
ExtractionSource = Literal["regex", "table", "ocr", "manual"]

# Common invoice field patterns
INVOICE_PATTERNS: Final[dict[str, list[str]]] = {
    "invoice_number": [
        r"invoice\s*(?:#|no\.?|number)\s*[:\-]?\s*(\S+)",
        r"inv\s*(?:#|no\.?|number)\s*[:\-]?\s*(\S+)",
        r"invoice\s*(\d{4,})",
    ],
    "invoice_date": [
        r"date\s*[:\-]?\s*(\d{1,2}[/\-]\d{1,2}[/\-]\d{2,4})",
        r"invoice\s*date\s*[:\-]?\s*(\d{1,2}[/\-]\d{1,2}[/\-]\d{2,4})",
        r"(\d{1,2}\s+(?:jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\w*\s+\d{4})",
    ],
    "total_amount": [
        r"total\s*[:\-]?\s*[\$€£]?\s*([\d,]+\.?\d*)",
        r"amount\s*due\s*[:\-]?\s*[\$€£]?\s*([\d,]+\.?\d*)",
        r"grand\s*total\s*[:\-]?\s*[\$€£]?\s*([\d,]+\.?\d*)",
        r"balance\s*due\s*[:\-]?\s*[\$€£]?\s*([\d,]+\.?\d*)",
    ],
    "subtotal": [
        r"subtotal\s*[:\-]?\s*[\$€£]?\s*([\d,]+\.?\d*)",
        r"sub\s*total\s*[:\-]?\s*[\$€£]?\s*([\d,]+\.?\d*)",
    ],
    "tax": [
        r"tax\s*[:\-]?\s*[\$€£]?\s*([\d,]+\.?\d*)",
        r"vat\s*[:\-]?\s*[\$€£]?\s*([\d,]+\.?\d*)",
        r"gst\s*[:\-]?\s*[\$€£]?\s*([\d,]+\.?\d*)",
    ],
    "hs_code": [
        r"hs\s*(?:code|no\.?|number)\s*[:\-]?\s*(\d{4,12})",
        r"harmonized\s*(?:code|system)\s*[:\-]?\s*(\d{4,12})",
        r"taric\s*[:\-]?\s*(\d{4,12})",
        r"hts\s*[:\-]?\s*(\d{4,12})",
    ],
    "country_origin": [
        r"country\s*of\s*origin\s*[:\-]?\s*([A-Za-z ]+(?:\n|$))",
        r"origin\s*[:\-]?\s*([A-Za-z ]+(?:\n|$))",
        r"made\s*in\s*[:\-]?\s*([A-Za-z ]+(?:\n|$))",
    ],
    "country_destination": [
        r"destination\s*[:\-]?\s*([A-Za-z ]+(?:\n|$))",
        r"country\s*of\s*destination\s*[:\-]?\s*([A-Za-z ]+(?:\n|$))",
        r"ship\s*to\s*[:\-]?\s*([A-Za-z\s]+?)(?:\n|$)",
    ],
}

# Party identification patterns
PARTY_PATTERNS: Final[dict[str, list[str]]] = {
    "shipper": [
        r"shipper\s*[:\-]?\s*(.+?)(?:\n|$)",
        r"sender\s*[:\-]?\s*(.+?)(?:\n|$)",
        r"from\s*[:\-]?\s*(.+?)(?:\n|$)",
        r"exporter\s*[:\-]?\s*(.+?)(?:\n|$)",
    ],
    "consignee": [
        r"consignee\s*[:\-]?\s*(.+?)(?:\n|$)",
        r"recipient\s*[:\-]?\s*(.+?)(?:\n|$)",
        r"bill\s*to\s*[:\-]?\s*(.+?)(?:\n|$)",
        r"ship\s*to\s*[:\-]?\s*(.+?)(?:\n|$)",
        r"buyer\s*[:\-]?\s*(.+?)(?:\n|$)",
    ],
    "notify_party": [
        r"notify\s*(?:party)?\s*[:\-]?\s*(.+?)(?:\n|$)",
    ],
}

# Item line patterns
ITEM_PATTERNS: Final[list[str]] = [
    r"(\d+)\s+(.+?)\s+[\$€£]?\s*([\d,]+\.?\d*)\s+[\$€£]?\s*([\d,]+\.?\d*)",
    r"(\d+)\s*x\s*(.+?)\s*@\s*[\$€£]?\s*([\d,]+\.?\d*)\s*=\s*[\$€£]?\s*([\d,]+\.?\d*)",
]

# Document type detection keywords
_DOC_TYPE_KEYWORDS: Final[dict[str, list[str]]] = {
    "invoice": ["invoice", "bill to", "amount due"],
    "packing_list": ["packing list", "packing", "carton"],
    "bill_of_lading": ["bill of lading", "b/l", "shipper", "consignee"],
    "certificate_of_origin": ["certificate", "origin", "certify"],
    "quotation": ["quotation", "quote", "proposal"],
    "purchase_order": ["purchase order", "po#", "order"],
}


# ── Data Models ───────────────────────────────────────────────────────


@dataclass(frozen=False, slots=True)
class ExtractedField:
    """Represents an extracted field with confidence score.



    Attributes:

        value: The extracted string value.

        confidence: Extraction confidence from 0.0 to 1.0.

        source: How the field was extracted (regex, table, ocr, manual).

        field_name: Name of the field (e.g., 'invoice_number').

    """

    value: str
    confidence: float
    source: ExtractionSource
    field_name: str = ""

    @property
    def is_valid(self) -> bool:
        """Whether the field has a value and confidence > 0.5."""
        return bool(self.value) and self.confidence > 0.5


@dataclass(frozen=False, slots=True)
class InvoiceItem:
    """Represents a line item from an invoice.



    Attributes:

        description: Item description.

        quantity: Quantity ordered.

        unit_price: Price per unit.

        total_price: Total price for this line.

        hs_code: HS code for this item (if present).

        country_origin: Country of origin for this item.

    """

    description: str
    quantity: float = 0.0
    unit_price: float = 0.0
    total_price: float = 0.0
    hs_code: str = ""
    country_origin: str = ""

    def __post_init__(self) -> None:
        """Parse numeric values from strings if needed."""
        if isinstance(self.quantity, str):
            self.quantity = self._parse_number(self.quantity)
        if isinstance(self.unit_price, str):
            self.unit_price = self._parse_number(self.unit_price)
        if isinstance(self.total_price, str):
            self.total_price = self._parse_number(self.total_price)

    @staticmethod
    def _parse_number(value: str) -> float:
        """Parse a numeric value from string.



        Handles US format (1,234,567.89), European format (1.234.567,89),

        and simple format (1234.56).



        Args:

            value: String representation of a number.



        Returns:

            Parsed float value, or 0.0 on failure.

        """
        try:
            if not value or not value.strip():
                return 0.0
            value = value.strip()
            cleaned: str = re.sub(r"[$€£Β₯\s]", "", value)
            last_comma: int = cleaned.rfind(",")
            last_dot: int = cleaned.rfind(".")
            if last_comma > last_dot:
                cleaned = cleaned.replace(".", "").replace(",", ".")
            else:
                cleaned = cleaned.replace(",", "")
            cleaned = re.sub(r"[^\d.\-]", "", cleaned)
            return float(cleaned) if cleaned else 0.0
        except (ValueError, TypeError):
            return 0.0


@dataclass(frozen=False, slots=True)
class Party:
    """Represents a trade party (shipper, consignee, etc.).



    Attributes:

        name: Party name.

        address: Street address.

        city: City name.

        country: Country name.

        contact: Contact information.

    """

    name: str = ""
    address: str = ""
    city: str = ""
    country: str = ""
    contact: str = ""

    @property
    def is_valid(self) -> bool:
        """Whether the party has a name."""
        return bool(self.name)


@dataclass(frozen=False, slots=True)
class ParsedDocument:
    """Represents a parsed trade document.



    Attributes:

        file_path: Path to the source PDF file.

        document_type: Detected document type.

        raw_text: Full extracted text from the PDF.

        invoice_number: Extracted invoice number.

        invoice_date: Extracted invoice date.

        total_amount: Extracted total amount.

        subtotal: Extracted subtotal.

        tax: Extracted tax amount.

        hs_code: Extracted HS code.

        country_origin: Extracted country of origin.

        country_destination: Extracted destination country.

        shipper: Shipper party information.

        consignee: Consignee party information.

        notify_party: Notify party information.

        items: List of extracted line items.

        page_count: Number of pages in the PDF.

        parse_time_ms: Parsing time in milliseconds.

        warnings: List of warnings encountered during parsing.

    """

    file_path: str
    document_type: DocumentType = "unknown"
    raw_text: str = ""

    invoice_number: Optional[ExtractedField] = None
    invoice_date: Optional[ExtractedField] = None
    total_amount: Optional[ExtractedField] = None
    subtotal: Optional[ExtractedField] = None
    tax: Optional[ExtractedField] = None

    hs_code: Optional[ExtractedField] = None
    country_origin: Optional[ExtractedField] = None
    country_destination: Optional[ExtractedField] = None

    shipper: Optional[Party] = None
    consignee: Optional[Party] = None
    notify_party: Optional[Party] = None

    items: list[InvoiceItem] = field(default_factory=list)

    page_count: int = 0
    parse_time_ms: float = 0.0
    warnings: list[str] = field(default_factory=list)

    @property
    def has_invoice_number(self) -> bool:
        """Whether a valid invoice number was extracted."""
        return self.invoice_number is not None and self.invoice_number.is_valid

    @property
    def has_total(self) -> bool:
        """Whether a valid total amount was extracted."""
        return self.total_amount is not None and self.total_amount.is_valid

    @property
    def has_items(self) -> bool:
        """Whether any line items were extracted."""
        return len(self.items) > 0

    def to_dict(self) -> dict[str, Any]:
        """Convert to dictionary for serialization.



        Returns:

            Dict with all document fields suitable for JSON serialization.

        """
        return {
            "file_path": self.file_path,
            "document_type": self.document_type,
            "invoice_number": self.invoice_number.value if self.invoice_number else None,
            "invoice_date": self.invoice_date.value if self.invoice_date else None,
            "total_amount": self.total_amount.value if self.total_amount else None,
            "subtotal": self.subtotal.value if self.subtotal else None,
            "tax": self.tax.value if self.tax else None,
            "hs_code": self.hs_code.value if self.hs_code else None,
            "country_origin": self.country_origin.value if self.country_origin else None,
            "country_destination": self.country_destination.value if self.country_destination else None,
            "shipper": self.shipper.__dict__ if self.shipper else None,
            "consignee": self.consignee.__dict__ if self.consignee else None,
            "items_count": len(self.items),
            "page_count": self.page_count,
            "parse_time_ms": self.parse_time_ms,
            "warnings": self.warnings,
        }


# ── PDF Parser ────────────────────────────────────────────────────────


class PDFParser:
    """Main PDF parsing engine using pypdf (BSD-3).



    Provides secure PDF text extraction with:

    - File size validation (MAX_PDF_SIZE_BYTES)

    - Page count limits (MAX_PDF_PAGES)

    - PDF magic bytes validation

    - Proper resource cleanup via try/finally



    Raises:

        ImportError: If pypdf is not installed.

    """

    def __init__(self) -> None:
        """Initialize the parser.



        Raises:

            ImportError: If pypdf is not installed.

        """
        if not PYPDF_AVAILABLE:
            raise ImportError("pypdf not installed. Install with: pip install pypdf")

    @staticmethod
    def _validate_pdf(file_path: Path) -> None:
        """Validate PDF file before parsing.



        Checks file existence, size limits, and PDF magic bytes.



        Args:

            file_path: Path to the PDF file.



        Raises:

            FileNotFoundError: If file doesn't exist.

            PDFEmptyError: If file is empty.

            PDFSizeLimitExceededError: If file exceeds size limit.

            PDFNotValidError: If file doesn't start with %PDF-.

        """
        if not file_path.exists():
            raise FileNotFoundError(f"PDF file not found: {file_path}")

        file_size: int = file_path.stat().st_size
        if file_size == 0:
            raise PDFEmptyError(str(file_path))
        if file_size > MAX_PDF_SIZE_BYTES:
            raise PDFSizeLimitExceededError(file_size, MAX_PDF_SIZE_BYTES)

        with open(file_path, "rb") as f:
            header: bytes = f.read(5)
        if header != PDF_MAGIC_BYTES:
            raise PDFNotValidError(
                f"Not a valid PDF file (header: {header!r})"
            )

    def parse(self, file_path: str | Path) -> ParsedDocument:
        """Parse a PDF file and extract trade document fields.



        Args:

            file_path: Path to the PDF file.



        Returns:

            ParsedDocument with extracted fields and any warnings.



        Raises:

            FileNotFoundError: If file doesn't exist.

            PDFSizeLimitExceededError: If file is too large.

            PDFPageLimitExceededError: If PDF has too many pages.

            PDFNotValidError: If file is not a valid PDF.

        """
        start_time: float = _time.time()
        path: Path = Path(file_path)
        self._validate_pdf(path)

        document = ParsedDocument(file_path=str(path))

        try:
            reader = PdfReader(str(path))
            document.page_count = len(reader.pages)

            if document.page_count > MAX_PDF_PAGES:
                raise PDFPageLimitExceededError(
                    document.page_count, MAX_PDF_PAGES
                )

            full_text: list[str] = []
            for page_num in range(document.page_count):
                page = reader.pages[page_num]
                text: str = page.extract_text() or ""
                full_text.append(text)

            document.raw_text = "\n".join(full_text)

            self._extract_invoice_fields(document)
            self._extract_parties(document)
            self._extract_items(document)
            self._detect_document_type(document)

        except (PDFParsingError, FileNotFoundError):
            raise
        except Exception as exc:
            logger.error("Failed to parse PDF: %s", exc)
            document.warnings.append(f"Parse error: {exc}")

        document.parse_time_ms = (_time.time() - start_time) * 1000
        return document

    def _extract_invoice_fields(self, document: ParsedDocument) -> None:
        """Extract invoice-specific fields from document text.



        Args:

            document: ParsedDocument to populate with extracted fields.

        """
        text: str = document.raw_text

        document.invoice_number = self._extract_field(
            text, INVOICE_PATTERNS["invoice_number"], "invoice_number"
        )
        document.invoice_date = self._extract_field(
            text, INVOICE_PATTERNS["invoice_date"], "invoice_date"
        )
        document.total_amount = self._extract_field(
            text, INVOICE_PATTERNS["total_amount"], "total_amount"
        )
        document.subtotal = self._extract_field(
            text, INVOICE_PATTERNS["subtotal"], "subtotal"
        )
        document.tax = self._extract_field(
            text, INVOICE_PATTERNS["tax"], "tax"
        )
        document.hs_code = self._extract_field(
            text, INVOICE_PATTERNS["hs_code"], "hs_code"
        )
        document.country_origin = self._extract_field(
            text, INVOICE_PATTERNS["country_origin"], "country_origin"
        )
        document.country_destination = self._extract_field(
            text, INVOICE_PATTERNS["country_destination"], "country_destination"
        )

    def _extract_parties(self, document: ParsedDocument) -> None:
        """Extract party information (shipper, consignee, etc.).



        Args:

            document: ParsedDocument to populate with party data.

        """
        text: str = document.raw_text

        shipper_name: Optional[str] = self._extract_first_match(
            text, PARTY_PATTERNS["shipper"]
        )
        if shipper_name:
            document.shipper = Party(name=shipper_name.strip())

        consignee_name: Optional[str] = self._extract_first_match(
            text, PARTY_PATTERNS["consignee"]
        )
        if consignee_name:
            document.consignee = Party(name=consignee_name.strip())

        notify_name: Optional[str] = self._extract_first_match(
            text, PARTY_PATTERNS["notify_party"]
        )
        if notify_name:
            document.notify_party = Party(name=notify_name.strip())

    def _extract_items(self, document: ParsedDocument) -> None:
        """Extract line items from the document.



        Args:

            document: ParsedDocument to populate with items.

        """
        text: str = document.raw_text
        items: list[InvoiceItem] = []

        for pattern in ITEM_PATTERNS:
            matches = re.finditer(pattern, text, re.MULTILINE | re.IGNORECASE)
            for match in matches:
                try:
                    groups: tuple[str, ...] = match.groups()
                    if len(groups) >= 4:
                        item = InvoiceItem(
                            description=groups[1].strip(),
                            quantity=groups[0],
                            unit_price=groups[2],
                            total_price=groups[3],
                        )
                        if item.description and item.total_price > 0:
                            items.append(item)
                except (ValueError, IndexError):
                    continue

        # Deduplicate by description
        seen: set[str] = set()
        unique_items: list[InvoiceItem] = []
        for item in items:
            desc_key: str = item.description.lower().strip()
            if desc_key not in seen:
                seen.add(desc_key)
                unique_items.append(item)

        document.items = unique_items

    def _detect_document_type(self, document: ParsedDocument) -> None:
        """Detect the type of trade document.



        Args:

            document: ParsedDocument to classify.

        """
        text: str = document.raw_text.lower()

        for doc_type, keywords in _DOC_TYPE_KEYWORDS.items():
            if any(term in text for term in keywords):
                document.document_type = doc_type  # type: ignore[assignment]
                return

        document.document_type = "unknown"

    def _extract_field(

        self,

        text: str,

        patterns: list[str],

        field_name: str,

    ) -> Optional[ExtractedField]:
        """Extract a field using multiple regex patterns.



        Args:

            text: Source text to search.

            patterns: List of regex patterns to try.

            field_name: Name of the field being extracted.



        Returns:

            ExtractedField if a match is found, None otherwise.

        """
        for pattern in patterns:
            match: Optional[re.Match[str]] = re.search(
                pattern, text, re.IGNORECASE | re.MULTILINE
            )
            if match:
                value: str = match.group(1).strip()
                if value:
                    confidence: float = 0.8 if len(value) > 2 else 0.6
                    return ExtractedField(
                        value=value,
                        confidence=confidence,
                        source="regex",
                        field_name=field_name,
                    )
        return None

    def _extract_first_match(

        self,

        text: str,

        patterns: list[str],

    ) -> Optional[str]:
        """Extract first matching text from patterns.



        Args:

            text: Source text to search.

            patterns: List of regex patterns to try.



        Returns:

            First captured group if a match is found, None otherwise.

        """
        for pattern in patterns:
            match: Optional[re.Match[str]] = re.search(
                pattern, text, re.IGNORECASE | re.MULTILINE
            )
            if match:
                return match.group(1)
        return None

    def extract_text_only(self, file_path: str | Path) -> str:
        """Extract raw text from PDF without field parsing.



        Args:

            file_path: Path to the PDF file.



        Returns:

            Extracted text string.



        Raises:

            FileNotFoundError: If file doesn't exist.

            PDFNotValidError: If file is not a valid PDF.

        """
        path: Path = Path(file_path)
        self._validate_pdf(path)

        try:
            reader = PdfReader(str(path))
            full_text: list[str] = []
            for page_num in range(min(len(reader.pages), MAX_PDF_PAGES)):
                page = reader.pages[page_num]
                text: str = page.extract_text() or ""
                full_text.append(text)
            return "\n".join(full_text)
        except (PDFParsingError, FileNotFoundError):
            raise
        except Exception as exc:
            raise PDFParsingError(f"Text extraction failed: {exc}") from exc

    def extract_tables(self, file_path: str | Path) -> list[list[list[str]]]:
        """Extract tables from PDF using text-based heuristics.



        pypdf does not have native table extraction. This method extracts

        text from each page and applies heuristic line-based table detection.



        Args:

            file_path: Path to the PDF file.



        Returns:

            List of tables, each table is a list of rows, each row is a list of cells.



        Raises:

            FileNotFoundError: If file doesn't exist.

            PDFNotValidError: If file is not a valid PDF.

        """
        path: Path = Path(file_path)
        self._validate_pdf(path)

        tables: list[list[list[str]]] = []
        try:
            reader = PdfReader(str(path))
            for page_num in range(min(len(reader.pages), MAX_PDF_PAGES)):
                page = reader.pages[page_num]
                text: str = page.extract_text() or ""
                lines: list[str] = [ln.strip() for ln in text.split("\n") if ln.strip()]

                current_table: list[list[str]] = []
                for line in lines:
                    cells: list[str] = [c.strip() for c in re.split(r"\s{2,}|\t", line) if c.strip()]
                    if len(cells) >= 2:
                        current_table.append(cells)
                    else:
                        if len(current_table) >= 2:
                            tables.append(current_table)
                        current_table = []
                if len(current_table) >= 2:
                    tables.append(current_table)
            return tables
        except (PDFParsingError, FileNotFoundError):
            raise
        except Exception as exc:
            logger.warning("Table extraction failed: %s", exc)
            return tables


# ── Convenience Functions ─────────────────────────────────────────────

_parser: Optional[PDFParser] = None
_parser_lock: threading.Lock = threading.Lock()


def get_parser() -> PDFParser:
    """Get or create the global PDF parser (thread-safe).



    Returns:

        The singleton PDFParser instance.

    """
    global _parser
    if _parser is None:
        with _parser_lock:
            if _parser is None:
                _parser = PDFParser()
    return _parser


def parse_pdf(file_path: str | Path) -> ParsedDocument:
    """Parse a PDF file and extract trade document fields.



    Args:

        file_path: Path to the PDF file.



    Returns:

        ParsedDocument with extracted fields.

    """
    parser: PDFParser = get_parser()
    return parser.parse(file_path)


def extract_text(file_path: str | Path) -> str:
    """Extract raw text from PDF.



    Args:

        file_path: Path to the PDF file.



    Returns:

        Extracted text string.

    """
    parser: PDFParser = get_parser()
    return parser.extract_text_only(file_path)


def extract_tables(file_path: str | Path) -> list[list[list[str]]]:
    """Extract tables from PDF.



    Args:

        file_path: Path to the PDF file.



    Returns:

        List of tables.

    """
    parser: PDFParser = get_parser()
    return parser.extract_tables(file_path)