#!/usr/bin/env python
"""Writer for FASTA sequence format
"""

__author__ = "Jeremy Widmann"
__copyright__ = "Copyright 2007-2009, The Cogent Project"
__credits__ = ["Jeremy Widmann", "Rob Knight", "Gavin Huttley"]
__license__ = "GPL"
__version__ = "1.3"
__maintainer__ = "Jeremy Widmann"
__email__ = "jeremy.widmann@colorado.edu"
__status__ = "Production"

class _fake_seq(str):
    """a holder for string sequences that allows provision of a seq.Label
    attribute, required by fasta formatting funcs."""
    def __new__(cls, Label, Seq):
        new = str.__new__(cls, Seq)
        new.Label = Label
        return new
    
    def __getslice__(self, *args, **kwargs):
        new_seq = str.__getslice__(self, *args, **kwargs)
        return self.__new__(self.__class__,self.Label, new_seq)
    

def fasta_from_sequences(seqs, make_seqlabel = None, line_wrap = None):
    """Returns a FASTA string given a list of sequences. A sequence.Label
       attribute takes precedence over sequence.Name.
    
        - seqs can be a list of sequence objects or strings.
        - make_seqlabel: callback function that takes the seq object and returns
          a label str
        - line_wrap: a integer for maximum line width
    """
    fasta_list = []
    for i,seq in enumerate(seqs):
        # Check if it has a label, or one is to be created
        label = str(i)
        if make_seqlabel is not None:
            label = make_seqlabel(seq)
        elif hasattr(seq, 'Label') and seq.Label:
            label = seq.Label
        elif hasattr(seq, 'Name') and seq.Name:
            label = seq.Name
        
        # wrap sequence lines
        seq_str = str(seq)
        if line_wrap is not None:
            numlines,remainder = divmod(len(seq_str),line_wrap)
            if remainder:
                numlines += 1
            body = ["%s" % seq_str[j*line_wrap:(j+1)*line_wrap] \
                                        for j in range(numlines)]
        else:
            body = ["%s" % seq_str]
        
        fasta_list.append('>'+label)
        fasta_list += body
    
    return '\n'.join(fasta_list)

def fasta_from_alignment(aln, make_seqlabel = None, line_wrap = None):
    """Returns a FASTA string given an alignment.
    
        - aln can be an Alignment object or dict.
        - make_seqlabel: callback function that takes the seq object and returns
          a label str
        - line_wrap: a integer for maximum line width
    """
    # get seq output order
    try:
        order = aln.RowOrder
    except:
        order = aln.keys()
        order.sort()
    
    if hasattr(aln, 'NamedSeqs'):
        seq_dict = aln.NamedSeqs
    else:
        seq_dict = aln
    
    ordered_seqs = []
    for label in order:
        seq = seq_dict[label]
        if isinstance(seq, str):
            seq = _fake_seq(label, seq)
        ordered_seqs.append(seq)
    return fasta_from_sequences(ordered_seqs, make_seqlabel=make_seqlabel, 
                                line_wrap=line_wrap)
