--- /dev/null
+# Author: John MacFarlane <jgm@berkeley.edu>
+# Copyright: (C) 2013 John MacFarlane
+# License: BSD3
+
+"""
+Functions to aid writing python scripts that process the pandoc
+AST serialized as JSON.
+"""
+
+import codecs
+import hashlib
+import io
+import json
+import os
+import sys
+
+
+# some utility-functions: make it easier to create your own filters
+
+
+def get_filename4code(module, content, ext=None):
+ """Generate filename based on content
+
+ The function ensures that the (temporary) directory exists, so that the
+ file can be written.
+
+ Example:
+ filename = get_filename4code("myfilter", code)
+ """
+ imagedir = module + "-images"
+ fn = hashlib.sha1(content.encode(sys.getfilesystemencoding())).hexdigest()
+ try:
+ os.mkdir(imagedir)
+ sys.stderr.write('Created directory ' + imagedir + '\n')
+ except OSError:
+ pass
+ if ext:
+ fn += "." + ext
+ return os.path.join(imagedir, fn)
+
+def get_value(kv, key, value = None):
+ """get value from the keyvalues (options)"""
+ res = []
+ for k, v in kv:
+ if k == key:
+ value = v
+ else:
+ res.append([k, v])
+ return value, res
+
+def get_caption(kv):
+ """get caption from the keyvalues (options)
+
+ Example:
+ if key == 'CodeBlock':
+ [[ident, classes, keyvals], code] = value
+ caption, typef, keyvals = get_caption(keyvals)
+ ...
+ return Para([Image([ident, [], keyvals], caption, [filename, typef])])
+ """
+ caption = []
+ typef = ""
+ value, res = get_value(kv, u"caption")
+ if value is not None:
+ caption = [Str(value)]
+ typef = "fig:"
+
+ return caption, typef, res
+
+
+def get_extension(format, default, **alternates):
+ """get the extension for the result, needs a default and some specialisations
+
+ Example:
+ filetype = get_extension(format, "png", html="svg", latex="eps")
+ """
+ try:
+ return alternates[format]
+ except KeyError:
+ return default
+
+# end of utilities
+
+
+def walk(x, action, format, meta):
+ """Walk a tree, applying an action to every object.
+ Returns a modified tree. An action is a function of the form
+ `action(key, value, format, meta)`, where:
+
+ * `key` is the type of the pandoc object (e.g. 'Str', 'Para') `value` is
+ * the contents of the object (e.g. a string for 'Str', a list of
+ inline elements for 'Para')
+ * `format` is the target output format (as supplied by the
+ `format` argument of `walk`)
+ * `meta` is the document's metadata
+
+ The return of an action is either:
+
+ * `None`: this means that the object should remain unchanged
+ * a pandoc object: this will replace the original object
+ * a list of pandoc objects: these will replace the original object; the
+ list is merged with the neighbors of the orignal objects (spliced into
+ the list the original object belongs to); returning an empty list deletes
+ the object
+ """
+ if isinstance(x, list):
+ array = []
+ for item in x:
+ if isinstance(item, dict) and 't' in item:
+ res = action(item['t'],
+ item['c'] if 'c' in item else None, format, meta)
+ if res is None:
+ array.append(walk(item, action, format, meta))
+ elif isinstance(res, list):
+ for z in res:
+ array.append(walk(z, action, format, meta))
+ else:
+ array.append(walk(res, action, format, meta))
+ else:
+ array.append(walk(item, action, format, meta))
+ return array
+ elif isinstance(x, dict):
+ for k in x:
+ x[k] = walk(x[k], action, format, meta)
+ return x
+ else:
+ return x
+
+def toJSONFilter(action):
+ """Like `toJSONFilters`, but takes a single action as argument.
+ """
+ toJSONFilters([action])
+
+
+def toJSONFilters(actions):
+ """Generate a JSON-to-JSON filter from stdin to stdout
+
+ The filter:
+
+ * reads a JSON-formatted pandoc document from stdin
+ * transforms it by walking the tree and performing the actions
+ * returns a new JSON-formatted pandoc document to stdout
+
+ The argument `actions` is a list of functions of the form
+ `action(key, value, format, meta)`, as described in more
+ detail under `walk`.
+
+ This function calls `applyJSONFilters`, with the `format`
+ argument provided by the first command-line argument,
+ if present. (Pandoc sets this by default when calling
+ filters.)
+ """
+ try:
+ input_stream = io.TextIOWrapper(sys.stdin.buffer, encoding='utf-8')
+ except AttributeError:
+ # Python 2 does not have sys.stdin.buffer.
+ # REF: https://stackoverflow.com/questions/2467928/python-unicodeencode
+ input_stream = codecs.getreader("utf-8")(sys.stdin)
+
+ source = input_stream.read()
+ if len(sys.argv) > 1:
+ format = sys.argv[1]
+ else:
+ format = ""
+
+ sys.stdout.write(applyJSONFilters(actions, source, format))
+
+def applyJSONFilters(actions, source, format=""):
+ """Walk through JSON structure and apply filters
+
+ This:
+
+ * reads a JSON-formatted pandoc document from a source string
+ * transforms it by walking the tree and performing the actions
+ * returns a new JSON-formatted pandoc document as a string
+
+ The `actions` argument is a list of functions (see `walk`
+ for a full description).
+
+ The argument `source` is a string encoded JSON object.
+
+ The argument `format` is a string describing the output format.
+
+ Returns a the new JSON-formatted pandoc document.
+ """
+
+ doc = json.loads(source)
+
+ if 'meta' in doc:
+ meta = doc['meta']
+ elif doc[0]: # old API
+ meta = doc[0]['unMeta']
+ else:
+ meta = {}
+ altered = doc
+ for action in actions:
+ altered = walk(altered, action, format, meta)
+
+ return json.dumps(altered)
+
+
+def stringify(x):
+ """Walks the tree x and returns concatenated string content,
+ leaving out all formatting.
+ """
+ result = []
+
+ def go(key, val, format, meta):
+ if key in ['Str', 'MetaString']:
+ result.append(val)
+ elif key == 'Code':
+ result.append(val[1])
+ elif key == 'Math':
+ result.append(val[1])
+ elif key == 'LineBreak':
+ result.append(" ")
+ elif key == 'SoftBreak':
+ result.append(" ")
+ elif key == 'Space':
+ result.append(" ")
+
+ walk(x, go, "", {})
+ return ''.join(result)
+
+
+def attributes(attrs):
+ """Returns an attribute list, constructed from the
+ dictionary attrs.
+ """
+ attrs = attrs or {}
+ ident = attrs.get("id", "")
+ classes = attrs.get("classes", [])
+ keyvals = [[x, attrs[x]] for x in attrs if (x != "classes" and x != "id")]
+ return [ident, classes, keyvals]
+
+
+def elt(eltType, numargs):
+ def fun(*args):
+ lenargs = len(args)
+ if lenargs != numargs:
+ raise ValueError(eltType + ' expects ' + str(numargs) +
+ ' arguments, but given ' + str(lenargs))
+ if numargs == 0:
+ xs = []
+ elif len(args) == 1:
+ xs = args[0]
+ else:
+ xs = list(args)
+ return {'t': eltType, 'c': xs}
+ return fun
+
+# Constructors for block elements
+
+Plain = elt('Plain', 1)
+Para = elt('Para', 1)
+CodeBlock = elt('CodeBlock', 2)
+RawBlock = elt('RawBlock', 2)
+BlockQuote = elt('BlockQuote', 1)
+OrderedList = elt('OrderedList', 2)
+BulletList = elt('BulletList', 1)
+DefinitionList = elt('DefinitionList', 1)
+Header = elt('Header', 3)
+HorizontalRule = elt('HorizontalRule', 0)
+Table = elt('Table', 5)
+Div = elt('Div', 2)
+Null = elt('Null', 0)
+
+# Constructors for inline elements
+
+Str = elt('Str', 1)
+Emph = elt('Emph', 1)
+Strong = elt('Strong', 1)
+Strikeout = elt('Strikeout', 1)
+Superscript = elt('Superscript', 1)
+Subscript = elt('Subscript', 1)
+SmallCaps = elt('SmallCaps', 1)
+Quoted = elt('Quoted', 2)
+Cite = elt('Cite', 2)
+Code = elt('Code', 2)
+Space = elt('Space', 0)
+LineBreak = elt('LineBreak', 0)
+Math = elt('Math', 2)
+RawInline = elt('RawInline', 2)
+Link = elt('Link', 3)
+Image = elt('Image', 3)
+Note = elt('Note', 1)
+SoftBreak = elt('SoftBreak', 0)
+Span = elt('Span', 2)
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