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"""WebKit's Python module for interacting with patches."""

import logging

import re

_log = logging.getLogger("webkitpy.common.checkout.diff_parser")

_regexp_compile_cache = {}

def match(pattern, string):

    """Matches the string with the pattern, caching the compiled regexp."""

    if not pattern in _regexp_compile_cache:

        _regexp_compile_cache[pattern] = re.compile(pattern)

    return _regexp_compile_cache[pattern].match(string)

def git_diff_to_svn_diff(line):

    """Converts a git formatted diff line to a svn formatted line.

    Args:

      line: A string representing a line of the diff.

    """

    conversion_patterns = (("^diff --git \w/(.+) \w/(?P<FilePath>.+)", lambda matched: "Index: " + matched.group('FilePath') + "\n"),

                           ("^new file.*", lambda matched: "\n"),

                           ("^index [0-9a-f]{7}\.\.[0-9a-f]{7} [0-9]{6}", lambda matched: "===================================================================\n"),

                           ("^--- \w/(?P<FilePath>.+)", lambda matched: "--- " + matched.group('FilePath') + "\n"),

                           ("^\+\+\+ \w/(?P<FilePath>.+)", lambda matched: "+++ " + matched.group('FilePath') + "\n"))

    for pattern, conversion in conversion_patterns:

        matched = match(pattern, line)

        if matched:

            return conversion(matched)

    return line

def get_diff_converter(first_diff_line):

    """Gets a converter function of diff lines.

    Args:

      first_diff_line: The first filename line of a diff file.

                       If this line is git formatted, we'll return a

                       converter from git to SVN.

    """

    if match(r"^diff --git \w/", first_diff_line):

        return git_diff_to_svn_diff

    return lambda input: input

_INITIAL_STATE = 1

_DECLARED_FILE_PATH = 2

_PROCESSING_CHUNK = 3

class DiffFile:

    """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.

    """

    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))

class DiffParser:

    """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.

        """

        state = _INITIAL_STATE

        self.files = {}

        current_file = None

        old_diff_line = None

        new_diff_line = None

        for line in diff_input:

            line = line.rstrip("\n")

            if state == _INITIAL_STATE:

                transform_line = get_diff_converter(line)

            line = transform_line(line)

            file_declaration = match(r"^Index: (?P<FilePath>.+)", line)

            if file_declaration:

                filename = file_declaration.group('FilePath')

                current_file = DiffFile(filename)

                self.files[filename] = current_file

                state = _DECLARED_FILE_PATH

                continue

            lines_changed = match(r"^@@ -(?P<OldStartLine>\d+)(,\d+)? \+(?P<NewStartLine>\d+)(,\d+)? @@", 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)