52 lines
1.7 KiB
Python
52 lines
1.7 KiB
Python
"""Serve dot diagrams inline."""
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import base64
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import logging
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import re
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import markdown
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import pydot
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logger = logging.getLogger(__name__)
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class InlinePydot(markdown.Extension):
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"""Wrap the markdown prepcoressor."""
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def extendMarkdown(self, md):
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"""Add InlinePydotPreprocessor to the Markdown instance."""
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md.preprocessors.register(InlinePydotPreprocessor(md), 'dot_block', 100)
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class InlinePydotPreprocessor(markdown.preprocessors.Preprocessor):
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"""Identify dot codeblocks and run them through pydot."""
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BLOCK_RE = re.compile(r'~~~pydot:(?P<filename>[^\s]+)\n(?P<content>.*?)~~~', re.DOTALL)
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def run(self, lines):
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"""Match and generate diagrams from dot code blocks."""
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text = '\n'.join(lines)
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for match in self.BLOCK_RE.finditer(text):
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filename = match.group(1)
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dot_string = match.group(2)
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# use pydot to turn the text into pydot
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graphs = pydot.graph_from_dot_data(dot_string)
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if not graphs:
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logger.debug("some kind of issue with parsed 'dot' %s", dot_string)
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raise ValueError("error parsing dot text!")
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# encode the image and provide as an inline image in markdown
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encoded_image = base64.b64encode(graphs[0].create_png()).decode('ascii')
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data_path = f'data:image/png;base64,{encoded_image}'
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inline_image = f''
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# replace the image in the output markdown
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text = f'{text[:match.start()]}\n{inline_image}\n{text[match.end():]}'
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return text.split('\n')
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def makeExtension(*args, **kwargs):
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"""Provide the extension to the markdown extension loader."""
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return InlinePydot(*args, **kwargs)
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