# Copyright (C) 2011 Google Inc. All rights reserved.
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import difflib
import logging
import re

from webkitpy.common.watchlist.amountchangedpattern import AmountChangedPattern
from webkitpy.common.watchlist.changedlinepattern import ChangedLinePattern
from webkitpy.common.watchlist.filenamepattern import FilenamePattern
from webkitpy.common.watchlist.watchlist import WatchList
from webkitpy.common.watchlist.watchlistrule import WatchListRule
from webkitpy.common.config.committers import CommitterList


_log = logging.getLogger(__name__)


class WatchListParser(object):
    _DEFINITIONS = 'DEFINITIONS'
    _CC_RULES = 'CC_RULES'
    _MESSAGE_RULES = 'MESSAGE_RULES'
    _INVALID_DEFINITION_NAME_REGEX = r'\|'

    def __init__(self, log_error=None):
        self._log_error = log_error or _log.error
        self._section_parsers = {
            self._DEFINITIONS: self._parse_definition_section,
            self._CC_RULES: self._parse_cc_rules,
            self._MESSAGE_RULES: self._parse_message_rules,
        }
        self._definition_pattern_parsers = {
            'filename': FilenamePattern,
            'in_added_lines': (lambda compiled_regex: ChangedLinePattern(compiled_regex, 0)),
            'in_deleted_lines': (lambda compiled_regex: ChangedLinePattern(compiled_regex, 1)),
            'less': (lambda compiled_regex: AmountChangedPattern(compiled_regex, 1)),
            'more': (lambda compiled_regex: AmountChangedPattern(compiled_regex, 0)),
        }

    def parse(self, watch_list_contents):
        watch_list = WatchList()

        # Change the watch list text into a dictionary.
        dictionary = self._eval_watch_list(watch_list_contents)

        # Parse the top level sections in the watch list.
        for section in dictionary:
            parser = self._section_parsers.get(section)
            if not parser:
                self._log_error(('Unknown section "%s" in watch list.'
                                + self._suggest_words(section, self._section_parsers.keys()))
                               % section)
                continue
            parser(dictionary[section], watch_list)

        self._validate(watch_list)
        return watch_list

    def _eval_watch_list(self, watch_list_contents):
        return eval(watch_list_contents, {'__builtins__': None}, None)

    def _suggest_words(self, invalid_word, valid_words):
        close_matches = difflib.get_close_matches(invalid_word, valid_words)
        if not close_matches:
            return ''
        return '\n\nPerhaps it should be %s.' % (' or '.join(close_matches))

    def _parse_definition_section(self, definition_section, watch_list):
        definitions = {}
        for name in definition_section:
            invalid_character = re.search(self._INVALID_DEFINITION_NAME_REGEX, name)
            if invalid_character:
                self._log_error('Invalid character "%s" in definition "%s".' % (invalid_character.group(0), name))
                continue

            definition = definition_section[name]
            definitions[name] = []
            for pattern_type in definition:
                pattern_parser = self._definition_pattern_parsers.get(pattern_type)
                if not pattern_parser:
                    self._log_error(('Unknown pattern type "%s" in definition "%s".'
                                     + self._suggest_words(pattern_type, self._definition_pattern_parsers.keys()))
                                    % (pattern_type, name))
                    continue

                try:
                    compiled_regex = re.compile(definition[pattern_type])
                except Exception as e:
                    self._log_error('The regex "%s" is invalid due to "%s".' % (definition[pattern_type], str(e)))
                    continue

                pattern = pattern_parser(compiled_regex)
                definitions[name].append(pattern)
            if not definitions[name]:
                self._log_error('The definition "%s" has no patterns, so it should be deleted.' % name)
                continue
        watch_list.definitions = definitions

    def _parse_rules(self, rules_section):
        rules = []
        for complex_definition in rules_section:
            instructions = rules_section[complex_definition]
            if not instructions:
                self._log_error('A rule for definition "%s" is empty, so it should be deleted.' % complex_definition)
                continue
            rules.append(WatchListRule(complex_definition, instructions))
        return rules

    def _parse_cc_rules(self, cc_section, watch_list):
        watch_list.cc_rules = self._parse_rules(cc_section)

    def _parse_message_rules(self, message_section, watch_list):
        watch_list.message_rules = self._parse_rules(message_section)

    def _validate(self, watch_list):
        cc_definitions_set = self._rule_definitions_as_set(watch_list.cc_rules)
        messages_definitions_set = self._rule_definitions_as_set(watch_list.message_rules)
        self._verify_all_definitions_are_used(watch_list, cc_definitions_set.union(messages_definitions_set))

        self._validate_definitions(cc_definitions_set, self._CC_RULES, watch_list)
        self._validate_definitions(messages_definitions_set, self._MESSAGE_RULES, watch_list)

        accounts = CommitterList()
        for cc_rule in watch_list.cc_rules:
            # Copy the instructions since we'll be remove items from the original list and
            # modifying a list while iterating through it leads to undefined behavior.
            intructions_copy = cc_rule.instructions()[:]
            for email in intructions_copy:
                if not accounts.contributor_by_email(email):
                    cc_rule.remove_instruction(email)
                    self._log_error("The email alias %s which is in the watchlist is not listed as a contributor in contributors.json" % email)
                    continue

    def _verify_all_definitions_are_used(self, watch_list, used_definitions):
        definitions_not_used = set(watch_list.definitions.keys())
        definitions_not_used.difference_update(used_definitions)
        if definitions_not_used:
            self._log_error('The following definitions are not used and should be removed: %s' % (', '.join(definitions_not_used)))

    def _validate_definitions(self, definitions, rules_section_name, watch_list):
        declared_definitions = watch_list.definitions.keys()
        definition_set = set(definitions)
        definition_set.difference_update(declared_definitions)

        if definition_set:
            suggestions = ''
            if len(definition_set) == 1:
                suggestions = self._suggest_words(set().union(definition_set).pop(), declared_definitions)
            self._log_error('In section "%s", the following definitions are not used and should be removed: %s%s' % (rules_section_name, ', '.join(definition_set), suggestions))

    def _rule_definitions_as_set(self, rules):
        definition_set = set()
        for rule in rules:
            definition_set = definition_set.union(rule.definitions_to_match)
        return definition_set