# Copyright (C) 2009 Google Inc. All rights reserved.
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"""WebKit's Python module for interacting with patches."""

import logging
import re

_log = logging.getLogger(__name__)

INDEX_PATTERN = re.compile(r'^diff --git \w/(.+) \w/(?P<FilePath>.+)')
LINES_CHANGED_PATTERN = re.compile(r"^@@ -(?P<OldStartLine>\d+)(,\d+)? \+(?P<NewStartLine>\d+)(,\d+)? @@")


_INITIAL_STATE = 1
_DECLARED_FILE_PATH = 2
_PROCESSING_CHUNK = 3


class DiffFile(object):
    """Contains the information for one file in a patch.

    The field "lines" is a list which contains tuples in this format:
       (deleted_line_number, new_line_number, line_string)
    If deleted_line_number is zero, it means this line is newly added.
    If new_line_number is zero, it means this line is deleted.
    """
    # FIXME: Tuples generally grow into classes.  We should consider
    # adding a DiffLine object.

    def added_or_modified_line_numbers(self):
        # This logic was moved from patchreader.py, but may not be
        # the right API for this object long-term.
        return [line[1] for line in self.lines if not line[0]]

    def __init__(self, filename):
        self.filename = filename
        self.lines = []

    def add_new_line(self, line_number, line):
        self.lines.append((0, line_number, line))

    def add_deleted_line(self, line_number, line):
        self.lines.append((line_number, 0, line))

    def add_unchanged_line(self, deleted_line_number, new_line_number, line):
        self.lines.append((deleted_line_number, new_line_number, line))


# If this is going to be called DiffParser, it should be a re-useable parser.
# Otherwise we should rename it to ParsedDiff or just Diff.
class DiffParser(object):
    """A parser for a patch file.

    The field "files" is a dict whose key is the filename and value is
    a DiffFile object.
    """

    def __init__(self, diff_input):
        """Parses a diff.

        Args:
          diff_input: An iterable object.
        """
        self.files = self._parse_into_diff_files(diff_input)

    # FIXME: This function is way too long and needs to be broken up.
    def _parse_into_diff_files(self, diff_input):
        files = {}
        state = _INITIAL_STATE
        current_file = None
        old_diff_line = None
        new_diff_line = None
        for line in diff_input:
            line = line.rstrip('\n')

            file_declaration = INDEX_PATTERN.match(line)
            if file_declaration:
                filename = file_declaration.group('FilePath')
                current_file = DiffFile(filename)
                files[filename] = current_file
                state = _DECLARED_FILE_PATH
                continue

            lines_changed = LINES_CHANGED_PATTERN.match(line)
            if lines_changed:
                if state != _DECLARED_FILE_PATH and state != _PROCESSING_CHUNK:
                    _log.error('Unexpected line change without file path declaration: %r', line)
                old_diff_line = int(lines_changed.group('OldStartLine'))
                new_diff_line = int(lines_changed.group('NewStartLine'))
                state = _PROCESSING_CHUNK
                continue

            if state == _PROCESSING_CHUNK:
                if line.startswith('+'):
                    current_file.add_new_line(new_diff_line, line[1:])
                    new_diff_line += 1
                elif line.startswith('-'):
                    current_file.add_deleted_line(old_diff_line, line[1:])
                    old_diff_line += 1
                elif line.startswith(' '):
                    current_file.add_unchanged_line(old_diff_line, new_diff_line, line[1:])
                    old_diff_line += 1
                    new_diff_line += 1
                elif line == '\\ No newline at end of file':
                    # Nothing to do.  We may still have some added lines.
                    pass
                else:
                    _log.error('Unexpected diff format when parsing a chunk: %r', line)
        return files