""" Helper class to create ICU rules from a configuration file. """ import io import logging import itertools from pathlib import Path import re import yaml from icu import Transliterator from nominatim.errors import UsageError import nominatim.tokenizer.icu_variants as variants LOG = logging.getLogger() def _flatten_yaml_list(content): if not content: return [] if not isinstance(content, list): raise UsageError("List expected in ICU yaml configuration.") output = [] for ele in content: if isinstance(ele, list): output.extend(_flatten_yaml_list(ele)) else: output.append(ele) return output class VariantRule: """ Saves a single variant expansion. An expansion consists of the normalized replacement term and a dicitonary of properties that describe when the expansion applies. """ def __init__(self, replacement, properties): self.replacement = replacement self.properties = properties or {} class ICURuleLoader: """ Compiler for ICU rules from a tokenizer configuration file. """ def __init__(self, configfile): self.configfile = configfile self.variants = set() if configfile.suffix == '.yaml': self._load_from_yaml() else: raise UsageError("Unknown format of tokenizer configuration.") def get_search_rules(self): """ Return the ICU rules to be used during search. The rules combine normalization and transliteration. """ # First apply the normalization rules. rules = io.StringIO() rules.write(self.normalization_rules) # Then add transliteration. rules.write(self.transliteration_rules) return rules.getvalue() def get_normalization_rules(self): """ Return rules for normalisation of a term. """ return self.normalization_rules def get_transliteration_rules(self): """ Return the rules for converting a string into its asciii representation. """ return self.transliteration_rules def get_replacement_pairs(self): """ Return the list of possible compound decompositions with application of abbreviations included. The result is a list of pairs: the first item is the sequence to replace, the second is a list of replacements. """ return self.variants def _yaml_include_representer(self, loader, node): value = loader.construct_scalar(node) if Path(value).is_absolute(): content = Path(value).read_text() else: content = (self.configfile.parent / value).read_text() return yaml.safe_load(content) def _load_from_yaml(self): yaml.add_constructor('!include', self._yaml_include_representer, Loader=yaml.SafeLoader) rules = yaml.safe_load(self.configfile.read_text()) self.normalization_rules = self._cfg_to_icu_rules(rules, 'normalization') self.transliteration_rules = self._cfg_to_icu_rules(rules, 'transliteration') self._parse_variant_list(self._get_section(rules, 'variants')) def _get_section(self, rules, section): """ Get the section named 'section' from the rules. If the section does not exist, raise a usage error with a meaningful message. """ if section not in rules: LOG.fatal("Section '%s' not found in tokenizer config '%s'.", section, str(self.configfile)) raise UsageError("Syntax error in tokenizer configuration file.") return rules[section] def _cfg_to_icu_rules(self, rules, section): """ Load an ICU ruleset from the given section. If the section is a simple string, it is interpreted as a file name and the rules are loaded verbatim from the given file. The filename is expected to be relative to the tokenizer rule file. If the section is a list then each line is assumed to be a rule. All rules are concatenated and returned. """ content = self._get_section(rules, section) if content is None: return '' return ';'.join(_flatten_yaml_list(content)) + ';' def _parse_variant_list(self, rules): self.variants.clear() if not rules: return rules = _flatten_yaml_list(rules) vmaker = _VariantMaker(self.normalization_rules) properties = [] for section in rules: # Create the property field and deduplicate against existing # instances. props = variants.ICUVariantProperties.from_rules(section) for existing in properties: if existing == props: props = existing break else: properties.append(props) for rule in (section.get('words') or []): self.variants.update(vmaker.compute(rule, props)) class _VariantMaker: """ Generater for all necessary ICUVariants from a single variant rule. All text in rules is normalized to make sure the variants match later. """ def __init__(self, norm_rules): self.norm = Transliterator.createFromRules("rule_loader_normalization", norm_rules) def compute(self, rule, props): """ Generator for all ICUVariant tuples from a single variant rule. """ parts = re.split(r'(\|)?([=-])>', rule) if len(parts) != 4: raise UsageError("Syntax error in variant rule: " + rule) decompose = parts[1] is None src_terms = [self._parse_variant_word(t) for t in parts[0].split(',')] repl_terms = (self.norm.transliterate(t.strip()) for t in parts[3].split(',')) # If the source should be kept, add a 1:1 replacement if parts[2] == '-': for src in src_terms: if src: for froms, tos in _create_variants(*src, src[0], decompose): yield variants.ICUVariant(froms, tos, props) for src, repl in itertools.product(src_terms, repl_terms): if src and repl: for froms, tos in _create_variants(*src, repl, decompose): yield variants.ICUVariant(froms, tos, props) def _parse_variant_word(self, name): name = name.strip() match = re.fullmatch(r'([~^]?)([^~$^]*)([~$]?)', name) if match is None or (match.group(1) == '~' and match.group(3) == '~'): raise UsageError("Invalid variant word descriptor '{}'".format(name)) norm_name = self.norm.transliterate(match.group(2)) if not norm_name: return None return norm_name, match.group(1), match.group(3) _FLAG_MATCH = {'^': '^ ', '$': ' ^', '': ' '} def _create_variants(src, preflag, postflag, repl, decompose): if preflag == '~': postfix = _FLAG_MATCH[postflag] # suffix decomposition src = src + postfix repl = repl + postfix yield src, repl yield ' ' + src, ' ' + repl if decompose: yield src, ' ' + repl yield ' ' + src, repl elif postflag == '~': # prefix decomposition prefix = _FLAG_MATCH[preflag] src = prefix + src repl = prefix + repl yield src, repl yield src + ' ', repl + ' ' if decompose: yield src, repl + ' ' yield src + ' ', repl else: prefix = _FLAG_MATCH[preflag] postfix = _FLAG_MATCH[postflag] yield prefix + src + postfix, prefix + repl + postfix