#(c) 2013-2014 by Authors
#This file is a part of Ragout program.
#Released under the BSD license (see LICENSE file)

"""
This module provides some basic FASTA I/O
"""

class FastaError(Exception):
    pass

def read_fasta_dict(filename):
    """
    Reads fasta file into dictionary. Also preforms some validation
    """
    header = None
    seq = ""
    fasta_dict = {}

    try:
        with open(filename, "r") as f:
            for line in f:
                line = line.strip()
                if line.startswith(">"):
                    if header:
                        fasta_dict[header] = seq
                        seq = ""
                    header = line[1:].split(" ")[0]
                else:
                    line = line.upper()
                    if not _validate_seq(line):
                        raise FastaError("Non-ACGTN charcter in \"{0}\""
                                         .format(filename))
                    seq += line

            if header and len(seq):
                fasta_dict[header] = seq

    except IOError as e:
        raise FastaError(e)

    return fasta_dict


def write_fasta_dict(fasta_dict, filename):
    """
    Writes dictionary with fasta to file
    """
    with open(filename, "w") as f:
        for header, seq in _iter_dict(fasta_dict):
            f.write(">{0}\n".format(header))

            for i in range(0, len(seq), 60):
                f.write(seq[i:i + 60] + "\n")


def reverse_complement(string):
    res = "".join(map(_comp_sym, string[::-1]))
    return res


def _validate_seq(sequence):
    for c in sequence:
        if c not in "ACGTN":
            return False
    return True


def _iter_dict(d):
    """
    Helper fundtion to iterate through dictionary in both Python 2 and 3
    """
    iter_d = None
    try:
        iter_d = d.iteritems()
    except AttributeError:
        iter_d = d.items()
    return iter_d


COMPL = {"A" : "T", "T" : "A", "G" : "C", "C" : "G", "N" : "N"}
def _comp_sym(char):
    return COMPL[char]