#format python

"""ReverseComplement using OOP iterator
"""

import sys, string

dictDnaComp = {'A':'T', 'T':'A', 'G':'C', 'C':'G'}

class FastaRecord:
    def __init__(self, colwidth=60):
        self.title = ''
        self.sequence = ''
        self._colwidth = colwidth
 
    def __str__(self):
        s = []
        s.append('>%s' % self.title)
        i = 0
        while i < len(self.sequence):
            s.append(self.sequence[i:i+self._colwidth])
            i = i + self._colwidth
        return string.join(s, '\n')

    def cvtRevComp(self):
        newSeq = ''
        for index in range(len(self.sequence)-1, 0, -1):
            newSeq += dictDnaComp[self.sequence[index]]
        self.sequence = newSeq

class FastaParser:
    def __init__(self, filename):
        self.file = open(filename, 'r')
        self._saved = []
    
    def next(self):
        lines = []
        while(1):
            line = self.file.readline()
            if not line:
                break
            if lines and line[0]=='>':
                self.saveLine(line)
                break                            
            lines.append(line.strip())
        
        if not lines:
            return None

        record = FastaRecord()
        if lines[0][0] == '>':
            record.title = lines[0][1:]
            lines = lines[1:]
        else:
            record.title = self._saved[0][1:]
            self._saved = self._saved[1:]
        record.sequence = string.join(lines, '')
        return record

    def saveLine(self, line):
        self._saved += [line]

def main(infilename, outfilename):
    try:
        outfile = open(outfilename, 'w')
    except:
        print "Error: unable open file"
        sys.exit()
    my = FastaParser(infilename)
    while 1:
        curRecord = my.next()
        if curRecord is None: break
        curRecord.cvtRevComp()
        outfile.write(str(curRecord))


if __name__ == '__main__': 
    rfile, ofile = sys.argv[1:3]
    main(rfile, ofile)