Skip to content

DocHandler

dcmspec.doc_handler.DocHandler

Base class for DICOM document handlers.

Handles DICOM documents in various formats (e.g., XHTML, PDF). Subclasses must implement the load_document method to handle reading/parsing input files. The base class provides a generic download method for both text and binary files.

Progress Reporting: The observer pattern is used for progress reporting. Subclasses may extend the Progress class and use the progress_observer to report additional information (e.g., status, errors, or other context) beyond percent complete, enabling future extensibility for richer progress tracking.

Source code in src/dcmspec/doc_handler.py 
 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
class DocHandler:
    """Base class for DICOM document handlers.

    Handles DICOM documents in various formats (e.g., XHTML, PDF).
    Subclasses must implement the `load_document` method to handle
    reading/parsing input files. The base class provides a generic
    download method for both text and binary files.

    Progress Reporting:
    The observer pattern is used for progress reporting. Subclasses may extend
    the Progress class and use the progress_observer to report additional information
    (e.g., status, errors, or other context) beyond percent complete, enabling future
    extensibility for richer progress tracking.
    """

    def __init__(self, config: Optional[Config] = None, logger: Optional[logging.Logger] = None):
        """Initialize the document handler with an optional logger.

        Args:
            config (Optional[Config]): Config instance to use. If None, a default Config is created.
            logger (Optional[logging.Logger]): Logger instance to use. If None, a default logger is created.

        Logging:
            A logger may be passed for custom logging control. If no logger is provided,
            a default logger for this class is used. In both cases, no logging handlers
            are added by default. To see log output, logging should be configured in the
            application (e.g., with logging.basicConfig()).

        """
        if logger is not None and not isinstance(logger, logging.Logger):
            raise TypeError("logger must be an instance of logging.Logger or None")
        self.logger = logger or logging.getLogger(self.__class__.__name__)

        if config is not None and not isinstance(config, Config):
            raise TypeError("config must be an instance of Config or None")
        self.config = config or Config()

    def download(
        self,
        url: str,
        file_path: str,
        binary: bool = False,
        progress_observer: 'Optional[ProgressObserver]' = None,
        # BEGIN LEGACY SUPPORT: Remove for int progress callback deprecation
        progress_callback: 'Optional[Callable[[int], None]]' = None
        # END LEGACY SUPPORT
    ) -> str:
        """Download a file from a URL and save it to the specified path.

        Args:
            url (str): The URL to download the file from.
            file_path (str): The path to save the downloaded file.
            binary (bool): If True, save as binary. If False, save as UTF-8 text.
            progress_observer (Optional[ProgressObserver]): Optional observer to report download progress.
            progress_callback (Optional[Callable[[int], None]]): [LEGACY, Deprecated] Optional callback to
                report progress as an integer percent (0-100, or -1 if indeterminate). Use progress_observer
                instead. Will be removed in a future release.

        Returns:
            str: The file path where the document was saved.

        Raises:
            RuntimeError: If the download or save fails.

        """
        # BEGIN LEGACY SUPPORT: Remove for int progress callback deprecation
        progress_observer = handle_legacy_callback(progress_observer, progress_callback)
        # END LEGACY SUPPORT
        self.logger.info(f"Downloading document from {url} to {file_path}")
        try:
            os.makedirs(os.path.dirname(file_path), exist_ok=True)
        except OSError as e:
            self.logger.error(f"Failed to create directory for {file_path}: {e}")
            raise RuntimeError(f"Failed to create directory for {file_path}: {e}") from e
        try:
            with requests.get(url, timeout=30, stream=True, headers={"Accept-Encoding": "identity"}) as response:
                response.raise_for_status()
                total = int(response.headers.get('content-length', 0))
                chunk_size = 8192
                if binary:
                    self._download_binary(response, file_path, total, chunk_size, progress_observer)
                else:
                    self._download_text(response, file_path, total, chunk_size, progress_observer)
            self.logger.info(f"Document downloaded to {file_path}")
            return file_path
        except requests.exceptions.RequestException as e:
            self.logger.error(f"Failed to download {url}: {e}")
            raise RuntimeError(f"Failed to download {url}: {e}") from e
        except OSError as e:
            self.logger.error(f"Failed to save file {file_path}: {e}")
            raise RuntimeError(f"Failed to save file {file_path}: {e}") from e

    def _report_progress(self, downloaded, total, progress_observer, last_percent):
        """Report progress if percent changed.

        If the total file size is unknown or invalid, calls the observer with -1 to indicate
        indeterminate progress. Otherwise, calls the observer with the integer percent (0-100).
        Adds status=ProgressStatus.DOWNLOADING to all progress events.
        """
        if not progress_observer:
            return

        percent = calculate_percent(downloaded, total)
        if percent != last_percent[0]:
            progress_observer(Progress(percent, status=ProgressStatus.DOWNLOADING))
            last_percent[0] = percent

    def _download_binary(self, response, file_path, total, chunk_size, progress_observer):
        """Download and save a binary file with progress reporting.

        Streams each chunk directly to the file to avoid high memory usage.
        Reports progress using the provided observer.
        """
        downloaded = 0
        last_percent = [None]
        with open(file_path, "wb") as f:
            for chunk in response.iter_content(chunk_size=chunk_size):
                if chunk:
                    # For binary, no cleaning is needed
                    f.write(chunk)
                    downloaded += len(chunk)
                    self._report_progress(downloaded, total, progress_observer, last_percent)

    def _download_text(self, response, file_path, total, chunk_size, progress_observer):
        """Download and save a text file with progress reporting.

        Streams cleaned chunks directly to the file to avoid high memory usage.
        Reports progress using the provided observer using response.encoding if available
        for accurate byte counting.
        """
        downloaded = 0
        last_percent = [None]
        encoding = response.encoding or "utf-8"
        with open(file_path, "w", encoding="utf-8") as f:
            for chunk in response.iter_content(chunk_size=chunk_size, decode_unicode=True):
                if chunk:
                    cleaned_chunk = self.clean_text(chunk)
                    f.write(cleaned_chunk)
                    chunk_bytes = cleaned_chunk.encode(encoding)
                    downloaded += len(chunk_bytes)
                    self._report_progress(downloaded, total, progress_observer, last_percent)

    def clean_text(self, text: str) -> str:
        """Clean text content before saving.

        Subclasses can override this to perform format-specific cleaning (e.g., remove ZWSP/NBSP for XHTML).
        By default, returns the text unchanged.

        Args:
            text (str): The text content to clean.

        Returns:
            str: The cleaned text.

        """
        return text

    def load_document(
        self,
        cache_file_name: str,
        url: Optional[str] = None,
        force_download: bool = False,
        progress_observer: 'Optional[ProgressObserver]' = None,
        # BEGIN LEGACY SUPPORT: Remove for int progress callback deprecation
        progress_callback: 'Optional[Callable[[int], None]]' = None,
        # END LEGACY SUPPORT
        *args: Any,
        **kwargs: Any
    ) -> Any:
        """Implement this method to read and parse the document file, returning a parsed object.

        Subclasses should implement this method to load and parse a document file
        (e.g., XHTML, PDF, CSV) and return a format-specific parsed object.
        The exact type of the returned object depends on the subclass
        (e.g., BeautifulSoup for XHTML, pdfplumber.PDF for PDF).

        Args:
            cache_file_name (str): Path or name of the local cached file.
            url (str, optional): URL to download the file from if not cached or if force_download is True.
            force_download (bool, optional): If True, download the file even if it exists locally.
            progress_observer (Optional[ProgressObserver]): Optional observer to report download progress.
            progress_callback (Optional[Callable[[int], None]]): [LEGACY, Deprecated] Optional callback to
                report progress as an integer percent (0-100, or -1 if indeterminate). Use progress_observer
                instead. Will be removed in a future release.
            *args: Additional positional arguments for format-specific loading.
            **kwargs: Additional keyword arguments for format-specific loading.

        Returns:
            Any: The parsed document object (type depends on subclass).

        """
        # BEGIN LEGACY SUPPORT: Remove for int progress callback deprecation
        progress_observer = handle_legacy_callback(progress_observer, progress_callback)
        # END LEGACY SUPPORT
        raise NotImplementedError("Subclasses must implement load_document()")

__init__(config=None, logger=None)

Initialize the document handler with an optional logger.

PARAMETER DESCRIPTION
config

Config instance to use. If None, a default Config is created.

TYPE: Optional[Config] DEFAULT: None

logger

Logger instance to use. If None, a default logger is created.

TYPE: Optional[Logger] DEFAULT: None

Logging

A logger may be passed for custom logging control. If no logger is provided, a default logger for this class is used. In both cases, no logging handlers are added by default. To see log output, logging should be configured in the application (e.g., with logging.basicConfig()).

Source code in src/dcmspec/doc_handler.py 
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
def __init__(self, config: Optional[Config] = None, logger: Optional[logging.Logger] = None):
    """Initialize the document handler with an optional logger.

    Args:
        config (Optional[Config]): Config instance to use. If None, a default Config is created.
        logger (Optional[logging.Logger]): Logger instance to use. If None, a default logger is created.

    Logging:
        A logger may be passed for custom logging control. If no logger is provided,
        a default logger for this class is used. In both cases, no logging handlers
        are added by default. To see log output, logging should be configured in the
        application (e.g., with logging.basicConfig()).

    """
    if logger is not None and not isinstance(logger, logging.Logger):
        raise TypeError("logger must be an instance of logging.Logger or None")
    self.logger = logger or logging.getLogger(self.__class__.__name__)

    if config is not None and not isinstance(config, Config):
        raise TypeError("config must be an instance of Config or None")
    self.config = config or Config()

clean_text(text)

Clean text content before saving.

Subclasses can override this to perform format-specific cleaning (e.g., remove ZWSP/NBSP for XHTML). By default, returns the text unchanged.

PARAMETER DESCRIPTION
text

The text content to clean.

TYPE: str

RETURNS DESCRIPTION
str

The cleaned text.

TYPE: str

Source code in src/dcmspec/doc_handler.py 
162
163
164
165
166
167
168
169
170
171
172
173
174
175
def clean_text(self, text: str) -> str:
    """Clean text content before saving.

    Subclasses can override this to perform format-specific cleaning (e.g., remove ZWSP/NBSP for XHTML).
    By default, returns the text unchanged.

    Args:
        text (str): The text content to clean.

    Returns:
        str: The cleaned text.

    """
    return text

download(url, file_path, binary=False, progress_observer=None, progress_callback=None)

Download a file from a URL and save it to the specified path.

PARAMETER DESCRIPTION
url

The URL to download the file from.

TYPE: str

file_path

The path to save the downloaded file.

TYPE: str

binary

If True, save as binary. If False, save as UTF-8 text.

TYPE: bool DEFAULT: False

progress_observer

Optional observer to report download progress.

TYPE: Optional[ProgressObserver] DEFAULT: None

progress_callback

[LEGACY, Deprecated] Optional callback to report progress as an integer percent (0-100, or -1 if indeterminate). Use progress_observer instead. Will be removed in a future release.

TYPE: Optional[Callable[[int], None]] DEFAULT: None

RETURNS DESCRIPTION
str

The file path where the document was saved.

TYPE: str

RAISES DESCRIPTION
RuntimeError

If the download or save fails.
Source code in src/dcmspec/doc_handler.py 
 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
def download(
    self,
    url: str,
    file_path: str,
    binary: bool = False,
    progress_observer: 'Optional[ProgressObserver]' = None,
    # BEGIN LEGACY SUPPORT: Remove for int progress callback deprecation
    progress_callback: 'Optional[Callable[[int], None]]' = None
    # END LEGACY SUPPORT
) -> str:
    """Download a file from a URL and save it to the specified path.

    Args:
        url (str): The URL to download the file from.
        file_path (str): The path to save the downloaded file.
        binary (bool): If True, save as binary. If False, save as UTF-8 text.
        progress_observer (Optional[ProgressObserver]): Optional observer to report download progress.
        progress_callback (Optional[Callable[[int], None]]): [LEGACY, Deprecated] Optional callback to
            report progress as an integer percent (0-100, or -1 if indeterminate). Use progress_observer
            instead. Will be removed in a future release.

    Returns:
        str: The file path where the document was saved.

    Raises:
        RuntimeError: If the download or save fails.

    """
    # BEGIN LEGACY SUPPORT: Remove for int progress callback deprecation
    progress_observer = handle_legacy_callback(progress_observer, progress_callback)
    # END LEGACY SUPPORT
    self.logger.info(f"Downloading document from {url} to {file_path}")
    try:
        os.makedirs(os.path.dirname(file_path), exist_ok=True)
    except OSError as e:
        self.logger.error(f"Failed to create directory for {file_path}: {e}")
        raise RuntimeError(f"Failed to create directory for {file_path}: {e}") from e
    try:
        with requests.get(url, timeout=30, stream=True, headers={"Accept-Encoding": "identity"}) as response:
            response.raise_for_status()
            total = int(response.headers.get('content-length', 0))
            chunk_size = 8192
            if binary:
                self._download_binary(response, file_path, total, chunk_size, progress_observer)
            else:
                self._download_text(response, file_path, total, chunk_size, progress_observer)
        self.logger.info(f"Document downloaded to {file_path}")
        return file_path
    except requests.exceptions.RequestException as e:
        self.logger.error(f"Failed to download {url}: {e}")
        raise RuntimeError(f"Failed to download {url}: {e}") from e
    except OSError as e:
        self.logger.error(f"Failed to save file {file_path}: {e}")
        raise RuntimeError(f"Failed to save file {file_path}: {e}") from e

load_document(cache_file_name, url=None, force_download=False, progress_observer=None, progress_callback=None, *args, **kwargs)

Implement this method to read and parse the document file, returning a parsed object.

Subclasses should implement this method to load and parse a document file (e.g., XHTML, PDF, CSV) and return a format-specific parsed object. The exact type of the returned object depends on the subclass (e.g., BeautifulSoup for XHTML, pdfplumber.PDF for PDF).

PARAMETER DESCRIPTION
cache_file_name

Path or name of the local cached file.

TYPE: str

url

URL to download the file from if not cached or if force_download is True.

TYPE: str DEFAULT: None

force_download

If True, download the file even if it exists locally.

TYPE: bool DEFAULT: False

progress_observer

Optional observer to report download progress.

TYPE: Optional[ProgressObserver] DEFAULT: None

progress_callback

[LEGACY, Deprecated] Optional callback to report progress as an integer percent (0-100, or -1 if indeterminate). Use progress_observer instead. Will be removed in a future release.

TYPE: Optional[Callable[[int], None]] DEFAULT: None

*args

Additional positional arguments for format-specific loading.

TYPE: Any DEFAULT: ()

**kwargs

Additional keyword arguments for format-specific loading.

TYPE: Any DEFAULT: {}

RETURNS DESCRIPTION
Any

The parsed document object (type depends on subclass).

TYPE: Any

Source code in src/dcmspec/doc_handler.py 
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
def load_document(
    self,
    cache_file_name: str,
    url: Optional[str] = None,
    force_download: bool = False,
    progress_observer: 'Optional[ProgressObserver]' = None,
    # BEGIN LEGACY SUPPORT: Remove for int progress callback deprecation
    progress_callback: 'Optional[Callable[[int], None]]' = None,
    # END LEGACY SUPPORT
    *args: Any,
    **kwargs: Any
) -> Any:
    """Implement this method to read and parse the document file, returning a parsed object.

    Subclasses should implement this method to load and parse a document file
    (e.g., XHTML, PDF, CSV) and return a format-specific parsed object.
    The exact type of the returned object depends on the subclass
    (e.g., BeautifulSoup for XHTML, pdfplumber.PDF for PDF).

    Args:
        cache_file_name (str): Path or name of the local cached file.
        url (str, optional): URL to download the file from if not cached or if force_download is True.
        force_download (bool, optional): If True, download the file even if it exists locally.
        progress_observer (Optional[ProgressObserver]): Optional observer to report download progress.
        progress_callback (Optional[Callable[[int], None]]): [LEGACY, Deprecated] Optional callback to
            report progress as an integer percent (0-100, or -1 if indeterminate). Use progress_observer
            instead. Will be removed in a future release.
        *args: Additional positional arguments for format-specific loading.
        **kwargs: Additional keyword arguments for format-specific loading.

    Returns:
        Any: The parsed document object (type depends on subclass).

    """
    # BEGIN LEGACY SUPPORT: Remove for int progress callback deprecation
    progress_observer = handle_legacy_callback(progress_observer, progress_callback)
    # END LEGACY SUPPORT
    raise NotImplementedError("Subclasses must implement load_document()")