94 lines
3.6 KiB
ReStructuredText
94 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_import(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 an iterator of entry data dicts.
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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 can make arbitrary transformations to the entry data, or filter it so it isn't output.
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If this method returns ``None``, processing the entry data continues normally. Most hooks should do this, and just transform entry data in place.
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If this method returns ``False``, processing the entry data stops immediately. The entry will not appear in the program output.
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If this method returns any other value, the program replaces the entry data with the return value, and continues processing.
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Class attribute ``KIND``
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This should be one of the values of the ``hooks.HOOK_KINDS`` enum. This information determines what order hooks run in.
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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 ``dynload`` 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_import(input_file) returns true
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for importer_class in usable_importers:
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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_return = hook.run(entry_data)
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if hook_return is False:
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break
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elif hook_return is not None:
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entry_data = hook_return
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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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Running tests
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-------------
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Run ``./setup.py test`` from the source directory.
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