93 lines
3.6 KiB
ReStructuredText
93 lines
3.6 KiB
ReStructuredText
import2ledger code structure
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============================
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Concepts
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--------
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The main workflow of the program passes through three different types with different responsibilities.
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Entry data
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~~~~~~~~~~
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Data for an output entry is kept and passed around in a dict with the following contents:
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``date``
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A datetime.date object (if this is omitted, the ``default_date`` hook will fill in the default date from the user's configuration)
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``payee``
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A string
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``amount``
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A string or other object that can be safely converted to a decimal.Decimal
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``currency``
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A string with a three-letter code, uppercase, identifying the transaction currency
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It can optionally include additional keys for use as template variables.
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Importers
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~~~~~~~~~
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At a high level, importers read a source file, and generate data for output entries.
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Class method ``can_handle(source_file)``
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Returns true if the importer can generate entries from the given source file object, false otherwise.
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``__init__(source_file)``
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Initializes an importer to generate entries from the given source file object.
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``__iter__()``
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Returns a iterator of entry data dicts.
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Class attribute ``TEMPLATE_KEY``
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A string with the full key to load the corresponding template from the user's configuration (e.g., ``'template patreon income'``).
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Hooks
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~~~~~
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Hooks make arbitrary transformations to entry data dicts. Every entry data dict generated by an importer is run through every hook before being output.
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``__init__(config)``
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Initializes the hook with the user's configuration.
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``run(entry_data)``
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This method makes the hook's transformations to the entry data dict, if any. If this method clears the entry data dict, that entry will not be output.
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Templates
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~~~~~~~~~
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Templates receive entry data dicts and format them into final output entries.
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``__init__(template_str)``
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Initializes the template from a single string, as read from the user's configuration.
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``render(payee, amount, currency, date=None, **template_vars)``
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Returns a string with the output entry, using the given entry data. This is expected to be called as ``render(**entry_data)``; the arguments take the same types as entry data dicts.
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Loading importers and hooks
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---------------------------
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Importers and hooks are both loaded and found dynamically when the program starts. This makes it easy to extend the program: you just need to write the class following the established pattern, no registration needed.
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import2ledger finds importers by looking at all ``.py`` files in the ``importers/`` directory, skipping files whose names start with ``.`` (hidden) or ``_`` (private). It tries to import that file as a module. If it succeeds, it looks for things in the module named ``*Importer``, and adds those to the list of importers.
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Hooks follow the same pattern, searching the ``hooks/`` directory and looking for things named ``*Hook``.
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Technically this is done by ``importers.load_all()`` and ``hooks.load_all()`` functions, but most of the code to do this is in the ``util`` module.
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Main loop
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---------
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At a high level, import2ledger handles each input file this way::
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usable_importers = importers where can_handle(input_file) returns true
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for importer_class in usable_importers:
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template = built from importer_class.TEMPLATE_KEY
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input_file.seek(0)
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for entry_data in importer_class(input_file):
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for hook in all_hooks:
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hook.run(entry_data)
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if entry_data:
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template.render(**entry_data)
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Note in particular that multiple importers can handle the same input file. This helps support inputs like Patreon's earnings CSV, where completely different transactions are generated from the same source.
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