from difflib import SequenceMatcher


class MultiParent(object):

    def __init__(self, hunks=None):
        if hunks is not None:
            self.hunks = hunks
        else:
            self.hunks = []

    def __repr__(self):
        return "MultiParent(%r)" % self.hunks

    def __eq__(self, other):
        if self.__class__ is not other.__class__:
            return False
        return (self.hunks == other.hunks)

    @staticmethod
    def from_lines(text, parents=()):
        def compare(parent):
            return SequenceMatcher(None, parent, text).get_matching_blocks()
        parent_comparisons = [compare(p) for p in parents]
        cur_line = 0
        new_text = NewText([])
        parent_text = []
        block_iter = [iter(i) for i in parent_comparisons]
        diff = MultiParent([])
        def next_block(p):
            try:
                return block_iter[p].next()
            except StopIteration:
                return None
        cur_block = [next_block(p) for p, i in enumerate(block_iter)]
        while cur_line < len(text):
            best_match = None
            for p, block in enumerate(cur_block):
                if block is None:
                    continue
                i, j, n = block
                while j + n < cur_line:
                    block = cur_block[p] = next_block(p)
                    if block is None:
                        break
                    i, j, n = block
                if block is None:
                    continue
                if j > cur_line:
                    continue
                offset = cur_line - j
                i += offset
                j = cur_line
                n -= offset
                if n == 0:
                    continue
                if best_match is None or n > best_match.num_lines:
                    best_match = ParentText(p, i, j, n)
            if best_match is None:
                new_text.lines.append(text[cur_line])
                cur_line += 1
            else:
                if len(new_text.lines) > 0:
                    diff.hunks.append(new_text)
                    new_text = NewText([])
                diff.hunks.append(best_match)
                cur_line += best_match.num_lines
        if len(new_text.lines) > 0:
            diff.hunks.append(new_text)
        return diff

    @classmethod
    def from_texts(cls, text, parents=()):
        return cls.from_lines(text.splitlines(True),
                              [p.splitlines(True) for p in parents])

    def to_patch(self):
        for hunk in self.hunks:
            for line in hunk.to_patch():
                yield line


class NewText(object):

    def __init__(self, lines):
        self.lines = lines

    def __eq__(self, other):
        if self.__class__ is not other.__class__:
            return False
        return (other.lines == self.lines)

    def __repr__(self):
        return 'NewText(%r)' % self.lines

    def to_patch(self):
        yield 'i %d\n' % len(self.lines)
        for line in self.lines:
            yield line
        yield '\n'


class ParentText(object):

    def __init__(self, parent, parent_pos, child_pos, num_lines):
        self.parent = parent
        self.parent_pos = parent_pos
        self.child_pos = child_pos
        self.num_lines = num_lines

    def __repr__(self):
        return 'ParentText(%(parent)r, %(parent_pos)r, %(child_pos)r,'\
            ' %(num_lines)r)' % self.__dict__

    def __eq__(self, other):
        if self.__class__ != other.__class__:
            return False
        return (self.__dict__ == other.__dict__)

    def to_patch(self):
        yield 'c %(parent)d %(parent_pos)d %(child_pos)d %(num_lines)d\n'\
            % self.__dict__