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WIP: MPD-0.21 Search/Find Expressions #52
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,128 @@ | ||
| from mopidy_mpd import exceptions | ||
|
|
||
| class peekable: | ||
| """ an iterator that can be peeked one element into the future """ | ||
| def __init__(self, it): | ||
| self._it = iter(it) | ||
| self._poked = [] | ||
| def __iter__(self): | ||
| return self | ||
| def __next__(self): | ||
| if self._poked: | ||
| return self._poked.pop() | ||
| return next(self._it) | ||
| def __bool__(self): | ||
| try: | ||
| self.peek() | ||
| return True | ||
| except StopIteration: | ||
| return False | ||
| def peek(self): | ||
| if not self._poked: | ||
| self._poked = [next(self._it)] | ||
| return self._poked[0] | ||
|
|
||
| def takewhile(it, f): | ||
| def gen(it): | ||
| while it and f(it.peek()): | ||
| yield next(it) | ||
| return ''.join(gen(it)) | ||
|
|
||
| def is_tagname(c): | ||
| return ( # A-Z, a-z or '-' or '_' | ||
| ord('A') <= ord(c) <= ord('Z') or | ||
| ord('a') <= ord(c) <= ord('z') or | ||
| c in '-_' | ||
| ) | ||
|
|
||
| def is_operator(c): | ||
| return ( # A-Z, a-z or '!' or '=' or '~' | ||
| ord('A') <= ord(c) <= ord('Z') or | ||
| ord('a') <= ord(c) <= ord('z') or | ||
| c in '!=~' | ||
| ) | ||
|
|
||
| def takeWord(it, alphabet=is_tagname): | ||
| value = takewhile(it, alphabet) | ||
| takewhile(it, str.isspace) | ||
| return value | ||
|
|
||
| def takeChar(it): | ||
| c = next(it) | ||
| takewhile(it, str.isspace) | ||
| return c | ||
|
|
||
| def takeQuoted(it): | ||
| def gen(it, quote): | ||
| while it and it.peek() != quote: | ||
| c = next(it) | ||
| if c == '\\': | ||
| c = next(it) | ||
| yield c | ||
|
|
||
| quote = next(it) | ||
| Assert(quote in '\'"', "Quoted string expected") | ||
| value = ''.join(gen(it, quote)) | ||
| Assert(next(it) == quote, "Closing quote not found") | ||
| takewhile(it, str.isspace) | ||
| return value | ||
|
|
||
|
|
||
| def Assert(p, message): | ||
| if not p: | ||
| raise exceptions.MpdArgError(message) | ||
|
|
||
| class parenthesis: | ||
| def __init__(self, it): | ||
| self.it = it | ||
| def __enter__(self): | ||
| c = takeChar(self.it) | ||
| Assert(c == '(', "'(' expected") | ||
| def __exit__(self, exc_type, exc_value, traceback): | ||
| if exc_type is None: | ||
| c = takeChar(self.it) | ||
| Assert(c == ')', "')' expected") | ||
|
|
||
| def parse_subexpression(it): | ||
| with parenthesis(it): | ||
| if it.peek() == '!': # (!EXPRESSION) | ||
| # Mopidy cannot handle '!=', so there's no point in handling this | ||
| raise exceptions.MpdArgError('non-matching not supported in Mopidy') | ||
|
|
||
| elif it.peek() == '(': # (EXPRESSION1 AND EXPRESSION2 ...) | ||
| subexpressions = [parse_subexpression(it)] | ||
| while it.peek() != ')': | ||
| Assert(takeWord(it).upper() == "AND", "'AND' expected") | ||
| subexpression = parse_subexpression(it) | ||
| subexpressions.extend(subexpression) | ||
| return subexpressions | ||
|
|
||
| else: # (TAG OP 'VALUE') or (SPECIAL 'VALUE') | ||
| filter_type = takeWord(it) | ||
| if filter_type == "": | ||
| raise exceptions.MpdArgError('Word expected') | ||
| elif filter_type in ("base", "modified-since"): | ||
| # (base 'VALUE'), (modified-since 'VALUE') | ||
| value = takeQuoted(it) | ||
| return [(filter_type, '==', value)] | ||
| else: # TAG, 'any', 'file', 'filename', 'AudioFormat' | ||
| operator = takeWord(it, is_operator).lower() | ||
| Assert( | ||
| operator not in ('!=', '!~', '!contains'), | ||
| "non-matching not supported in Mopidy" | ||
| ) | ||
| Assert( | ||
| operator in ('==', '=~', 'contains'), | ||
| 'invalid operator' | ||
| ) | ||
| value = takeQuoted(it) | ||
| return [(filter_type, operator, value)] | ||
|
|
||
| def parse_filter_expression(expression): | ||
| it = peekable(expression) | ||
| try: | ||
| expression = parse_subexpression(it) | ||
| except StopIteration: | ||
| raise Assert(False, 'incomplete filter expression') | ||
| Assert(not it, 'Unparsed garbage after expression') | ||
| return expression | ||
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The code in this file almost looks like it was copy+pasted from somewhere else, and definitely doesn't match the code style conventions of the codebase it's being inserted into.
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my implementation of
peekablewas modeled after the interface provided by more_itertools, but stripped down for the use case here. the rest of the code is original, but written outside mopidy first.for a more general take, i'm writing a 'real' comment outside the review box.