unstructured-io--unstructured/test_unstructured/partition/pdf_image/test_pdfminer_processing.py

import os
import tempfile
from unittest.mock import Mock, patch

import numpy as np
import pytest
from pdfminer.layout import LAParams, LTChar, LTContainer
from PIL import Image
from unstructured_inference.constants import IsExtracted
from unstructured_inference.constants import Source as InferenceSource
from unstructured_inference.inference.elements import (
    EmbeddedTextRegion,
    Rectangle,
    TextRegion,
    TextRegions,
)
from unstructured_inference.inference.layout import DocumentLayout, LayoutElement, PageLayout
from unstructured_inference.inference.layoutelement import LayoutElements

from test_unstructured.unit_utils import example_doc_path
from unstructured.partition.auto import partition
from unstructured.partition.pdf_image.pdfminer_processing import (
    _deduplicate_ltchars,
    _rotate_bboxes,
    _validate_bbox,
    aggregate_embedded_text_by_block,
    bboxes1_is_almost_subregion_of_bboxes2,
    boxes_self_iou,
    clean_pdfminer_inner_elements,
    get_widget_text_from_annots,
    process_file_with_pdfminer,
    remove_duplicate_elements,
    text_is_embedded,
)
from unstructured.partition.utils.constants import Source

# A set of elements with pdfminer elements inside tables
deletable_elements_inside_table = [
    LayoutElement(
        bbox=Rectangle(0, 0, 100, 100),
        text="Table with inner elements",
        type="Table",
    ),
    LayoutElement(bbox=Rectangle(50, 50, 70, 70), text="text1", source=Source.PDFMINER),
    LayoutElement(bbox=Rectangle(70, 70, 80, 80), text="text2", source=Source.PDFMINER),
]

# A set of elements without pdfminer elements inside
# tables (no elements with source=Source.PDFMINER)
no_deletable_elements_inside_table = [
    LayoutElement(
        bbox=Rectangle(0, 0, 100, 100),
        text="Table with inner elements",
        type="Table",
        source=InferenceSource.YOLOX,
    ),
    LayoutElement(bbox=Rectangle(50, 50, 70, 70), text="text1", source=InferenceSource.YOLOX),
    LayoutElement(bbox=Rectangle(70, 70, 80, 80), text="text2", source=InferenceSource.YOLOX),
]
# A set of elements with pdfminer elements inside tables and other
# elements with source=Source.PDFMINER
# Note: there is some elements with source=Source.PDFMINER are not inside tables
mix_elements_inside_table = [
    LayoutElement(
        bbox=Rectangle(0, 0, 100, 100),
        text="Table1 with inner elements",
        type="Table",
        source=InferenceSource.YOLOX,
    ),
    LayoutElement(bbox=Rectangle(50, 50, 70, 70), text="Inside table1"),
    LayoutElement(bbox=Rectangle(70, 70, 80, 80), text="Inside table1", source=Source.PDFMINER),
    LayoutElement(
        bbox=Rectangle(150, 150, 170, 170),
        text="Outside tables",
        source=Source.PDFMINER,
    ),
    LayoutElement(
        bbox=Rectangle(180, 180, 200, 200),
        text="Outside tables",
        source=Source.PDFMINER,
    ),
    LayoutElement(
        bbox=Rectangle(0, 500, 100, 700),
        text="Table2 with inner elements",
        type="Table",
        source=InferenceSource.YOLOX,
    ),
    LayoutElement(bbox=Rectangle(0, 510, 50, 600), text="Inside table2", source=Source.PDFMINER),
    LayoutElement(bbox=Rectangle(0, 550, 70, 650), text="Inside table2", source=Source.PDFMINER),
]


def test_rotate_bboxes_matches_pil_rotation_directions():
    """_rotate_bboxes mirrors PIL.Image.rotate(angle, expand=True) (counter-clockwise)."""
    W, H = 100.0, 200.0  # portrait display-frame canvas
    coords = np.array([[10.0, 20.0, 30.0, 60.0]])

    # 0 / 360 are no-ops
    assert np.array_equal(_rotate_bboxes(coords, 0, W, H), coords)
    assert np.array_equal(_rotate_bboxes(coords, 360, W, H), coords)

    # 90 CCW (expand): x' = y, y' = W - x
    r90 = _rotate_bboxes(coords, 90, W, H)
    assert np.allclose(r90, [[20.0, W - 30.0, 60.0, W - 10.0]])
    # 180
    r180 = _rotate_bboxes(coords, 180, W, H)
    assert np.allclose(r180, [[W - 30.0, H - 60.0, W - 10.0, H - 20.0]])
    # 270 CCW
    assert np.allclose(_rotate_bboxes(coords, 270, W, H), [[H - 60.0, 10.0, H - 20.0, 30.0]])

    # rotating 90 then 270 (about the post-rotation H x W canvas) restores the original box
    assert np.allclose(_rotate_bboxes(r90, 270, H, W), coords)

    # outputs remain valid bboxes (x1 < x2, y1 < y2)
    for angle in (90, 180, 270):
        r = _rotate_bboxes(coords, angle, W, H)
        assert r[0, 0] < r[0, 2]
        assert r[0, 1] < r[0, 3]


@pytest.mark.parametrize(
    ("bbox", "is_valid"),
    [
        ([0, 1, 0, 1], False),
        ([0, 1, 1, 2], True),
        ([0, 1, 1, None], False),
        ([0, 1, 1, np.nan], False),
        ([0, 1, -1, 0], False),
        ([0, 1, -1, 2], False),
    ],
)
def test_valid_bbox(bbox, is_valid):
    assert _validate_bbox(bbox) is is_valid


@pytest.mark.parametrize(
    ("elements", "length_extra_info", "expected_document_length"),
    [
        (deletable_elements_inside_table, 1, 1),
        (no_deletable_elements_inside_table, 0, 3),
        (mix_elements_inside_table, 2, 5),
    ],
)
def test_clean_pdfminer_inner_elements(elements, length_extra_info, expected_document_length):
    # create a sample document with pdfminer elements inside tables
    page = PageLayout(number=1, image=Image.new("1", (1, 1)))
    page.elements_array = LayoutElements.from_list(elements)
    document_with_table = DocumentLayout(pages=[page])
    document = document_with_table

    # call the function to clean the pdfminer inner elements
    cleaned_doc = clean_pdfminer_inner_elements(document)

    # check that the pdfminer elements were stored in the extra_info dictionary
    assert len(cleaned_doc.pages[0].elements_array) == expected_document_length


elements_with_duplicate_images = [
    LayoutElement(
        bbox=Rectangle(0, 0, 100, 100),
        text="Image1",
        type="Image",
        source=Source.PDFMINER,
    ),
    LayoutElement(
        bbox=Rectangle(10, 10, 110, 110), text="Image1", type="Image", source=Source.PDFMINER
    ),
    LayoutElement(bbox=Rectangle(150, 150, 170, 170), text="Title1", type="Title"),
]

elements_without_duplicate_images = [
    LayoutElement(
        bbox=Rectangle(0, 0, 100, 100),
        text="Sample image",
        type="Image",
        source=Source.PDFMINER,
    ),
    LayoutElement(
        bbox=Rectangle(10, 10, 110, 110),
        text="Sample image with similar bbox",
        type="Image",
        source=Source.PDFMINER,
    ),
    LayoutElement(
        bbox=Rectangle(200, 200, 250, 250),
        text="Sample image",
        type="Image",
        source=Source.PDFMINER,
    ),
    LayoutElement(bbox=Rectangle(150, 150, 170, 170), text="Title1", type="Title"),
]


def test_aggregate_by_block():
    expected = "Inside region1 Inside region2"
    embedded_regions = TextRegions.from_list(
        [
            TextRegion.from_coords(0, 0, 300, 20, "Inside region1"),
            TextRegion.from_coords(0, 20, 300, 80, None),
            TextRegion.from_coords(0, 80, 200, 300, "Inside region2"),
            TextRegion.from_coords(250, 250, 350, 350, "Outside region"),
        ]
    )
    embedded_regions.is_extracted_array = np.array([IsExtracted.TRUE] * 4)
    target_region = TextRegions.from_list([TextRegion.from_coords(0, 0, 300, 300)])

    text, extracted = aggregate_embedded_text_by_block(target_region, embedded_regions)
    assert text == expected
    assert extracted.value == "true"


def test_aggregate_only_partially_fill_target():
    expected = "Inside region1"
    embedded_regions = TextRegions.from_list(
        [
            TextRegion.from_coords(0, 0, 20, 20, "Inside region1"),
        ]
    )
    embedded_regions.is_extracted_array = np.array([IsExtracted.TRUE])
    target_region = TextRegions.from_list([TextRegion.from_coords(0, 0, 300, 300)])

    text, extracted = aggregate_embedded_text_by_block(target_region, embedded_regions)
    assert text == expected
    assert extracted.value == "partial"


def test_aggregate_not_filling_target():
    embedded_regions = TextRegions.from_list(
        [
            TextRegion.from_coords(300, 0, 400, 20, "outside"),
        ]
    )
    embedded_regions.is_extracted_array = np.array([IsExtracted.TRUE])
    target_region = TextRegions.from_list([TextRegion.from_coords(0, 0, 300, 300)])

    text, extracted = aggregate_embedded_text_by_block(target_region, embedded_regions)
    assert text == ""
    assert extracted.value == "false"


@pytest.mark.parametrize(
    ("coords1", "coords2", "expected"),
    [
        (
            [[0, 0, 10, 10], [10, 0, 20, 10], [10, 10, 20, 20]],
            [[0, 0, 10, 10], [0, 0, 12, 12]],
            [[True, True], [False, False], [False, False]],
        ),
        (
            [[0, 0, 10, 10], [10, 0, 20, 10], [10, 10, 20, 20]],
            [[0, 0, 10, 10], [10, 10, 22, 22], [0, 0, 5, 5]],
            [[True, False, False], [False, False, False], [False, True, False]],
        ),
        (
            [[0, 0, 10, 10], [10, 10, 10, 10]],
            [[0, 0, 10, 10], [10, 10, 22, 22], [0, 0, 5, 5]],
            [[True, False, False], [True, True, False]],
        ),
    ],
)
def test_bboxes1_is_almost_subregion_of_bboxes2(coords1, coords2, expected):
    bboxes1 = [Rectangle(*row) for row in coords1]
    bboxes2 = [Rectangle(*row) for row in coords2]
    np.testing.assert_array_equal(
        bboxes1_is_almost_subregion_of_bboxes2(bboxes1, bboxes2), expected
    )


@pytest.mark.parametrize(
    ("coords", "threshold", "expected"),
    [
        (
            [[0, 0, 10, 10], [2, 2, 12, 12], [10, 10, 20, 20]],
            0.5,
            [[True, True, False], [True, True, False], [False, False, True]],
        ),
        (
            [[0, 0, 10, 10], [2, 2, 12, 12], [10, 10, 20, 20]],
            0.9,
            [[True, False, False], [False, True, False], [False, False, True]],
        ),
        (
            [[0, 0, 10, 10], [10, 10, 10, 10]],
            0.5,
            [[True, False], [False, True]],
        ),
    ],
)
def test_boxes_self_iou(coords, threshold, expected):
    bboxes = [Rectangle(*row) for row in coords]
    np.testing.assert_array_equal(boxes_self_iou(bboxes, threshold), expected)


def test_remove_duplicate_elements():
    sample_elements = TextRegions.from_list(
        [
            EmbeddedTextRegion(bbox=Rectangle(0, 0, 10, 10), text="Text 1"),
            EmbeddedTextRegion(bbox=Rectangle(0, 0, 10, 10), text="Text 2"),
            EmbeddedTextRegion(bbox=Rectangle(20, 20, 30, 30), text="Text 3"),
        ]
    )

    result = remove_duplicate_elements(sample_elements)

    # Check that duplicates were removed and only 2 unique elements remain
    assert len(result) == 2
    assert result.texts.tolist() == ["Text 2", "Text 3"]
    assert result.element_coords.tolist() == [[0, 0, 10, 10], [20, 20, 30, 30]]


def test_remove_duplicate_elements_dense_page_is_not_decimated():
    """Pages with more than ~2000 elements are chunked internally; the dedup mask for each
    chunk must be offset by the chunk's global index. Otherwise rows in later chunks match
    themselves and are wrongly dropped, decimating dense pages."""
    # 2500 unique, non-overlapping boxes on a 50x50 grid (zero IoU between any two)
    unique = [
        EmbeddedTextRegion(
            bbox=Rectangle((i % 50) * 20, (i // 50) * 20, (i % 50) * 20 + 10, (i // 50) * 20 + 10),
            text=f"Text {i}",
        )
        for i in range(2500)
    ]
    # one exact duplicate of the first box, appended last so the pair spans two chunks
    duplicate = EmbeddedTextRegion(bbox=Rectangle(0, 0, 10, 10), text="Text 0 dup")
    sample_elements = TextRegions.from_list([*unique, duplicate])

    result = remove_duplicate_elements(sample_elements)

    # only the single cross-chunk duplicate pair collapses; every unique box is kept
    assert len(result) == 2500
    # the later element of the duplicate pair is the one retained
    assert "Text 0 dup" in result.texts.tolist()
    assert "Text 0" not in result.texts.tolist()


def test_process_file_with_pdfminer():
    layout, links = process_file_with_pdfminer(example_doc_path("pdf/layout-parser-paper-fast.pdf"))
    assert len(layout)
    assert "LayoutParser: A Unified Toolkit for Deep\n" in layout[0].texts
    assert links[0][0]["url"] == "https://layout-parser.github.io"


def test_process_file_with_pdfminer_is_extracted_array():
    layout, _ = process_file_with_pdfminer(example_doc_path("pdf/layout-parser-paper-fast.pdf"))
    # first page contains rotated text that are considered low fidelity, i.e., is_extracted=partial
    assert layout[0].is_extracted_array[0] is None
    assert all(is_extracted is IsExtracted.TRUE for is_extracted in layout[1].is_extracted_array)


def test_process_file_hidden_ocr_text():
    """Test processing a PDF that contains hidden OCR text layer."""
    layout, _ = process_file_with_pdfminer(example_doc_path("pdf/pdf-with-ocr-text.pdf"))
    assert all(is_extracted is None for is_extracted in layout[0].is_extracted_array[:-1])
    assert layout[0].is_extracted_array[-1] == IsExtracted.TRUE


def test_process_file_recovers_figure_overlay_text():
    """Text inside a Form XObject (LTFigure overlay) is recovered, not dropped.

    Regression test: such text is real, embedded text held as loose LTChars that pdfminer does not
    group into LTTextLine objects, so extract_text_objects (LTTextLine only) used to drop it. The
    fixture has "Printed Name:" in the main content stream and "Jane Doe" inside a form XObject.
    """
    layout, _ = process_file_with_pdfminer(example_doc_path("pdf/figure-overlay-text.pdf"))
    texts = " ".join(str(t) for page in layout for t in page.texts if t)
    assert "Printed Name:" in texts  # main content stream
    assert "Jane Doe" in texts  # figure-overlay text (dropped before the fix)


# A synthetic AcroForm: filled text fields whose values live only in widget annotations
# (the page content stream is empty), plus one empty field that must be skipped.
SYNTHETIC_FORM_FIELDS = [
    ("name", "Jane Doe", (40, 700, 300, 720)),
    ("date of birth", "1990-01-01", (40, 650, 300, 670)),
    ("address", "123 Main Street", (40, 600, 300, 620)),
    ("phone", "", (40, 550, 300, 570)),  # empty -> should be skipped
]


def _build_synthetic_form_pdf(path: str) -> None:
    """Write a 1-page PDF whose only text lives in AcroForm text-field (/Tx) widgets.

    The page content stream is empty, so pdfminer's normal text pass yields nothing; the
    values are reachable only through the widget annotations in ``page.annots``.
    """
    from pypdf import PdfWriter
    from pypdf.generic import (
        ArrayObject,
        DictionaryObject,
        NameObject,
        NumberObject,
        TextStringObject,
    )

    writer = PdfWriter()
    writer.add_blank_page(width=612, height=792)
    page = writer.pages[0]

    refs = []
    for field_name, value, rect in SYNTHETIC_FORM_FIELDS:
        widget = DictionaryObject()
        widget[NameObject("/Type")] = NameObject("/Annot")
        widget[NameObject("/Subtype")] = NameObject("/Widget")
        widget[NameObject("/FT")] = NameObject("/Tx")
        widget[NameObject("/T")] = TextStringObject(field_name)
        widget[NameObject("/V")] = TextStringObject(value)
        widget[NameObject("/Rect")] = ArrayObject([NumberObject(c) for c in rect])
        refs.append(writer._add_object(widget))

    page[NameObject("/Annots")] = ArrayObject(refs)
    acro_form = DictionaryObject()
    acro_form[NameObject("/Fields")] = ArrayObject(refs)
    writer._root_object[NameObject("/AcroForm")] = writer._add_object(acro_form)

    with open(path, "wb") as f:
        writer.write(f)


def test_get_widget_text_from_annots_extracts_filled_text_fields():
    """The widget helper recovers filled /Tx field values and skips empty ones."""
    from pdfminer.pdfpage import PDFPage

    with tempfile.TemporaryDirectory() as tmp_dir:
        pdf_path = os.path.join(tmp_dir, "form.pdf")
        _build_synthetic_form_pdf(pdf_path)
        with open(pdf_path, "rb") as fp:
            page = next(PDFPage.get_pages(fp))
            widgets = get_widget_text_from_annots(page.annots, height=792)

    texts = [w["text"] for w in widgets]
    assert texts == ["Jane Doe", "1990-01-01", "123 Main Street"]  # empty "phone" skipped
    # Every widget carries a valid bounding box.
    assert all(_validate_bbox(w["bbox"]) for w in widgets)


def test_get_widget_text_from_annots_decodes_utf16_text_without_bom():
    from pdfminer.psparser import PSLiteral

    widgets = get_widget_text_from_annots(
        [
            {
                "Subtype": PSLiteral("Widget"),
                "FT": PSLiteral("Tx"),
                "V": b"\xfe\xff\x00J\x00a\x00n\x00e",
                "Rect": (10, 80, 90, 95),
            }
        ],
        height=100,
    )

    assert widgets == [{"text": "Jane", "bbox": (10.0, 5.0, 90.0, 20.0)}]


def test_get_widget_text_from_annots_decodes_choice_field_value_arrays():
    from pdfminer.psparser import PSLiteral

    widgets = get_widget_text_from_annots(
        [
            {
                "Subtype": PSLiteral("Widget"),
                "FT": PSLiteral("Ch"),
                "V": [PSLiteral("ChoiceA"), b"\xfe\xff\x00C\x00h\x00o\x00i\x00c\x00e\x00B"],
                "Rect": (10, 70, 90, 95),
            }
        ],
        height=100,
    )

    assert widgets == [{"text": "ChoiceA\nChoiceB", "bbox": (10.0, 5.0, 90.0, 30.0)}]


def test_get_widget_text_from_annots_inherits_field_type_and_value_from_parent():
    """FT/V absent on the widget are inherited by walking up the /Parent chain.

    The intermediate parent is a direct dict (the case PDFObjRef-only traversal missed) and
    the root parent carries the inherited /FT, exercising multi-level inheritance.
    """
    from pdfminer.psparser import PSLiteral

    root_parent = {"FT": PSLiteral("Tx")}  # field type lives at the top of the hierarchy
    mid_parent = {"V": b"\xfe\xff\x00J\x00a\x00n\x00e", "Parent": root_parent}  # value mid-chain

    widgets = get_widget_text_from_annots(
        [
            {
                "Subtype": PSLiteral("Widget"),
                "Parent": mid_parent,  # neither FT nor V on the widget itself
                "Rect": (10, 80, 90, 95),
            }
        ],
        height=100,
    )

    assert widgets == [{"text": "Jane", "bbox": (10.0, 5.0, 90.0, 20.0)}]


def test_process_file_with_pdfminer_recovers_form_field_text():
    """The extracted (hi_res) layer includes AcroForm field values as text regions."""
    with tempfile.TemporaryDirectory() as tmp_dir:
        pdf_path = os.path.join(tmp_dir, "form.pdf")
        _build_synthetic_form_pdf(pdf_path)
        layout, _ = process_file_with_pdfminer(pdf_path)

    texts = [str(t) for t in layout[0].texts if t]
    assert "Jane Doe" in texts
    assert "1990-01-01" in texts
    assert "123 Main Street" in texts
    # Widget-sourced regions are marked as extracted text.
    assert IsExtracted.TRUE in list(layout[0].is_extracted_array)


def test_partition_pdf_fast_recovers_form_field_text():
    """End-to-end: the fast strategy emits elements for filled form fields."""
    from unstructured.partition.pdf import partition_pdf

    with tempfile.TemporaryDirectory() as tmp_dir:
        pdf_path = os.path.join(tmp_dir, "form.pdf")
        _build_synthetic_form_pdf(pdf_path)
        elements = partition_pdf(filename=pdf_path, strategy="fast")

    blob = "\n".join(el.text for el in elements)
    assert "Jane Doe" in blob
    assert "1990-01-01" in blob
    assert "123 Main Street" in blob


@patch("unstructured.partition.pdf_image.pdfminer_utils.LAParams", return_value=LAParams())
def test_laprams_are_passed_from_partition_to_pdfminer(pdfminer_mock):
    partition(
        filename=example_doc_path("pdf/layout-parser-paper-fast.pdf"),
        pdfminer_line_margin=1.123,
        pdfminer_char_margin=None,
        pdfminer_line_overlap=0.0123,
        pdfminer_word_margin=3.21,
    )
    assert pdfminer_mock.call_args.kwargs == {
        "line_margin": 1.123,
        "line_overlap": 0.0123,
        "word_margin": 3.21,
    }


def create_mock_ltchar(text, invisible=False, rotated=False):
    """Create a mock LTChar object"""

    graphicstate = Mock()
    matrix = (1, 0.5, 0, 1, 0, 0) if rotated else (1, 0, 0, 1, 0, 0)

    char = LTChar(
        matrix=matrix,  # transformation matrix
        font=Mock(),  # you'd need to mock PDFFont
        fontsize=12,
        scaling=1,
        rise=0,
        text=text,
        textwidth=10,
        textdisp=(0, 1),
        ncs=Mock(),
        graphicstate=graphicstate,
    )
    if invisible:
        char.rendermode = 3
    else:
        char.rendermode = 0

    return char


def create_mock_ltcontainer(chars):
    """Create a mock LTContainer with LTChar objects"""
    container = LTContainer(bbox=(0, 0, 1, 1))

    # The container should be iterable
    container.extend(chars)

    return container


# Now you can use it in tests
def test_text_is_embedded():
    chars = [
        create_mock_ltchar("H"),
        create_mock_ltchar("e"),
        create_mock_ltchar("l"),
        create_mock_ltchar("l", rotated=True),
        create_mock_ltchar("o", invisible=True),
    ]

    container = create_mock_ltcontainer(chars)

    assert text_is_embedded(container, threshold=0.5)
    assert not text_is_embedded(container, threshold=0.3)


# -- Tests for _deduplicate_ltchars (fake bold fix) --


def _create_positioned_ltchar(text: str, x0: float, y0: float) -> LTChar:
    """Create an LTChar with a specific position for deduplication testing."""
    graphicstate = Mock()
    # Matrix format: (a, b, c, d, e, f) where e=x, f=y for translation
    matrix = (1, 0, 0, 1, x0, y0)

    char = LTChar(
        matrix=matrix,
        font=Mock(),
        fontsize=12,
        scaling=1,
        rise=0,
        text=text,
        textwidth=10,
        textdisp=(0, 1),
        ncs=Mock(),
        graphicstate=graphicstate,
    )
    return char


class TestDeduplicateLtchars:
    """Tests for _deduplicate_ltchars function."""

    def test_empty_list_returns_empty(self):
        """Empty character list should return empty list."""
        result = _deduplicate_ltchars([], threshold=3.0)
        assert result == []

    def test_threshold_zero_disables_deduplication(self):
        """Threshold of 0 should disable deduplication and return original list."""
        chars = [
            _create_positioned_ltchar("A", 10.0, 20.0),
            _create_positioned_ltchar("A", 10.5, 20.0),  # Would be duplicate
        ]
        result = _deduplicate_ltchars(chars, threshold=0)
        assert len(result) == 2

    def test_fake_bold_duplicates_removed(self):
        """Fake bold (double-rendered) characters should be deduplicated."""
        # Simulate "AB" rendered as "AABB" with fake bold
        chars = [
            _create_positioned_ltchar("A", 10.0, 20.0),
            _create_positioned_ltchar("A", 10.5, 20.0),  # Duplicate - close position
            _create_positioned_ltchar("B", 25.0, 20.0),
            _create_positioned_ltchar("B", 25.5, 20.0),  # Duplicate - close position
        ]
        result = _deduplicate_ltchars(chars, threshold=3.0)
        assert len(result) == 2
        assert result[0].get_text() == "A"
        assert result[1].get_text() == "B"

    def test_legitimate_repeated_chars_preserved(self):
        """Legitimate repeated characters at different positions should be preserved."""
        # "AA" where both A's are at legitimately different positions
        chars = [
            _create_positioned_ltchar("A", 10.0, 20.0),
            _create_positioned_ltchar("A", 25.0, 20.0),  # Far enough - not duplicate
        ]
        result = _deduplicate_ltchars(chars, threshold=3.0)
        assert len(result) == 2

    def test_single_char_returns_single(self):
        """Single character should return single character."""
        chars = [_create_positioned_ltchar("X", 10.0, 20.0)]
        result = _deduplicate_ltchars(chars, threshold=3.0)
        assert len(result) == 1
        assert result[0].get_text() == "X"

    def test_mixed_duplicates_and_normal(self):
        """Mix of duplicated and normal characters should be handled correctly."""
        # "HELLO" where only H and L are fake-bold
        chars = [
            _create_positioned_ltchar("H", 10.0, 20.0),
            _create_positioned_ltchar("H", 10.5, 20.0),  # Duplicate
            _create_positioned_ltchar("E", 20.0, 20.0),  # Normal
            _create_positioned_ltchar("L", 30.0, 20.0),
            _create_positioned_ltchar("L", 30.5, 20.0),  # Duplicate
            _create_positioned_ltchar("L", 40.0, 20.0),  # Second L (normal, different position)
            _create_positioned_ltchar("O", 50.0, 20.0),  # Normal
        ]
        result = _deduplicate_ltchars(chars, threshold=3.0)
        assert len(result) == 5
        text = "".join(c.get_text() for c in result)
        assert text == "HELLO"