"""
Tools for fusing contiguous alignment blocks together.
"""

from copy import deepcopy


def fuse_list(mafs):
    """
    Try to fuse a list of blocks by progressively fusing each adjacent pair.
    """
    last = None
    for m in mafs:
        if last is None:
            last = m
        else:
            fused = fuse(last, m)
            if fused:
                last = fused
            else:
                yield last
                last = m
    if last:
        yield last


def fuse(m1, m2):
    """
    Attempt to fuse two blocks. If they can be fused returns a new block,
    otherwise returns None.

    Example:

    >>> import bx.align.maf

    >>> block1 = bx.align.maf.from_string( '''
    ... a score=0.0
    ... s hg18.chr10 52686 44 + 135374737 GTGCTAACTTACTGCTCCACAGAAAACATCAATTCTGCTCATGC
    ... i hg18.chr10 N 0 C 0
    ... s panTro1.chrUn_random 208115356 44 - 240967748 GTGCTAACTGACTGCTCCAGAGAAAACATCAATTCTGTTCATGT
    ... ''' )

    >>> block2 = bx.align.maf.from_string( '''
    ... a score=0.0
    ... s hg18.chr10 52730 69 + 135374737 GCAGGTACAATTCATCAAGAAAGGAATTACAACTTCAGAAATGTGTTCAAAATATATCCATACTTTGAC
    ... i hg18.chr10 C 0 I 12
    ... s panTro1.chrUn_random 208115400 69 - 240967748 GCAGCTACTATTCATCAAGAAAGGGATTACAACTTCAGAAATGTGTTCAAAGTGTATCCATACTTTGAT
    ... ''' )

    >>> fused = fuse( block1, block2 )

    >>> print(fused)
    a score=0.0
    s hg18.chr10 52686 113 + 135374737 GTGCTAACTTACTGCTCCACAGAAAACATCAATTCTGCTCATGCGCAGGTACAATTCATCAAGAAAGGAATTACAACTTCAGAAATGTGTTCAAAATATATCCATACTTTGAC
    i hg18.chr10 N 0 I 12
    s panTro1.chrUn_random 208115356 113 - 240967748 GTGCTAACTGACTGCTCCAGAGAAAACATCAATTCTGTTCATGTGCAGCTACTATTCATCAAGAAAGGGATTACAACTTCAGAAATGTGTTCAAAGTGTATCCATACTTTGAT
    <BLANKLINE>
    """
    # Check if the blocks are adjacent and easily fusable
    # return none if not.
    if len(m1.components) != len(m2.components):
        return None
    for c1, c2 in zip(m1.components, m2.components):
        if c1.src != c2.src:
            return None
        if c1.strand != c2.strand:
            return None
        if c1.end != c2.start:
            return None
        if c1.empty or c2.empty:
            return None
    # Try to fuse:
    n = deepcopy(m1)
    for c1, c2 in zip(n.components, m2.components):
        c1.text += c2.text
        c1.size += c2.size
        # Propagate the synteny right
        c1.synteny_right = c2.synteny_right
    n.text_size = len(n.components[0].text)
    return n


class FusingAlignmentWriter:
    """
    Wrapper for an alignment Writer which attempts to fuse adjacent blocks
    """

    def __init__(self, maf_writer):
        self.maf_writer = maf_writer
        self.last = None

    def write(self, m):
        if not self.last:
            self.last = m
        else:
            fused = fuse(self.last, m)
            if fused:
                self.last = fused
            else:
                self.maf_writer.write(self.last)
                self.last = m

    def close(self):
        if self.last:
            self.maf_writer.write(self.last)
        self.maf_writer.close()