#! /usr/bin/env python

"""Conversions to/from quoted-printable transport encoding as per RFC 1521."""

# (Dec 1991 version).

__all__ = ["encode", "decode", "encodestring", "decodestring"]

ESCAPE = '='

MAXLINESIZE = 76

HEX = '0123456789ABCDEF'

EMPTYSTRING = ''

try:

    from binascii import a2b_qp, b2a_qp

except ImportError:

    a2b_qp = None

    b2a_qp = None

def needsquoting(c, quotetabs, header):

    """Decide whether a particular character needs to be quoted.

    The 'quotetabs' flag indicates whether embedded tabs and spaces should be

    quoted.  Note that line-ending tabs and spaces are always encoded, as per

    RFC 1521.

    """

    if c in ' \t':

        return quotetabs

    # if header, we have to escape _ because _ is used to escape space

    if c == '_':

        return header

    return c == ESCAPE or not (' ' <= c <= '~')

def quote(c):

    """Quote a single character."""

    i = ord(c)

    return ESCAPE + HEX[i//16] + HEX[i%16]

def encode(input, output, quotetabs, header = 0):

    """Read 'input', apply quoted-printable encoding, and write to 'output'.

    'input' and 'output' are files with readline() and write() methods.

    The 'quotetabs' flag indicates whether embedded tabs and spaces should be

    quoted.  Note that line-ending tabs and spaces are always encoded, as per

    RFC 1521.

    The 'header' flag indicates whether we are encoding spaces as _ as per

    RFC 1522.

    """

    if b2a_qp is not None:

        data = input.read()

        odata = b2a_qp(data, quotetabs = quotetabs, header = header)

        output.write(odata)

        return

    def write(s, output=output, lineEnd='\n'):

        # RFC 1521 requires that the line ending in a space or tab must have

        # that trailing character encoded.

        if s and s[-1:] in ' \t':

            output.write(s[:-1] + quote(s[-1]) + lineEnd)

        elif s == '.':

            output.write(quote(s) + lineEnd)

        else:

            output.write(s + lineEnd)

    prevline = None

    while 1:

        line = input.readline()

        if not line:

            break

        outline = []

        # Strip off any readline induced trailing newline

        stripped = ''

        if line[-1:] == '\n':

            line = line[:-1]

            stripped = '\n'

        # Calculate the un-length-limited encoded line

        for c in line:

            if needsquoting(c, quotetabs, header):

                c = quote(c)

            if header and c == ' ':

                outline.append('_')

            else:

                outline.append(c)

        # First, write out the previous line

        if prevline is not None:

            write(prevline)

        # Now see if we need any soft line breaks because of RFC-imposed

        # length limitations.  Then do the thisline->prevline dance.

        thisline = EMPTYSTRING.join(outline)

        while len(thisline) > MAXLINESIZE:

            # Don't forget to include the soft line break `=' sign in the

            # length calculation!

            write(thisline[:MAXLINESIZE-1], lineEnd='=\n')

            thisline = thisline[MAXLINESIZE-1:]

        # Write out the current line

        prevline = thisline

    # Write out the last line, without a trailing newline

    if prevline is not None:

        write(prevline, lineEnd=stripped)

def encodestring(s, quotetabs = 0, header = 0):

    if b2a_qp is not None:

        return b2a_qp(s, quotetabs = quotetabs, header = header)

    from cStringIO import StringIO

    infp = StringIO(s)

    outfp = StringIO()

    encode(infp, outfp, quotetabs, header)

    return outfp.getvalue()

def decode(input, output, header = 0):

    """Read 'input', apply quoted-printable decoding, and write to 'output'.

    'input' and 'output' are files with readline() and write() methods.

    If 'header' is true, decode underscore as space (per RFC 1522)."""

    if a2b_qp is not None:

        data = input.read()

        odata = a2b_qp(data, header = header)

        output.write(odata)

        return

    new = ''

    while 1:

        line = input.readline()

        if not line: break

        i, n = 0, len(line)

        if n > 0 and line[n-1] == '\n':

            partial = 0; n = n-1

            # Strip trailing whitespace

            while n > 0 and line[n-1] in " \t\r":

                n = n-1

        else:

            partial = 1

        while i < n:

            c = line[i]

            if c == '_' and header:

                new = new + ' '; i = i+1

            elif c != ESCAPE:

                new = new + c; i = i+1

            elif i+1 == n and not partial:

                partial = 1; break

            elif i+1 < n and line[i+1] == ESCAPE:

                new = new + ESCAPE; i = i+2

            elif i+2 < n and ishex(line[i+1]) and ishex(line[i+2]):

                new = new + chr(unhex(line[i+1:i+3])); i = i+3

            else: # Bad escape sequence -- leave it in

                new = new + c; i = i+1

        if not partial:

            output.write(new + '\n')

            new = ''

    if new:

        output.write(new)

def decodestring(s, header = 0):

    if a2b_qp is not None:

        return a2b_qp(s, header = header)

    from cStringIO import StringIO

    infp = StringIO(s)

    outfp = StringIO()

    decode(infp, outfp, header = header)

    return outfp.getvalue()

# Other helper functions

def ishex(c):

    """Return true if the character 'c' is a hexadecimal digit."""

    return '0' <= c <= '9' or 'a' <= c <= 'f' or 'A' <= c <= 'F'

def unhex(s):

    """Get the integer value of a hexadecimal number."""

    bits = 0

    for c in s:

        if '0' <= c <= '9':

            i = ord('0')

        elif 'a' <= c <= 'f':

            i = ord('a')-10

        elif 'A' <= c <= 'F':

            i = ord('A')-10

        else:

            break

        bits = bits*16 + (ord(c) - i)

    return bits

def main():

    import sys

    import getopt

    try:

        opts, args = getopt.getopt(sys.argv[1:], 'td')

    except getopt.error, msg:

        sys.stdout = sys.stderr

        print msg

        print "usage: quopri [-t | -d] [file] ..."

        print "-t: quote tabs"

        print "-d: decode; default encode"

        sys.exit(2)

    deco = 0

    tabs = 0

    for o, a in opts:

        if o == '-t': tabs = 1

        if o == '-d': deco = 1

    if tabs and deco:

        sys.stdout = sys.stderr

        print "-t and -d are mutually exclusive"

        sys.exit(2)

    if not args: args = ['-']

    sts = 0

    for file in args:

        if file == '-':

            fp = sys.stdin

        else:

            try:

                fp = open(file)

            except IOError, msg:

                sys.stderr.write("%s: can't open (%s)\n" % (file, msg))

                sts = 1

                continue

        if deco:

            decode(fp, sys.stdout)

        else:

            encode(fp, sys.stdout, tabs)

        if fp is not sys.stdin:

            fp.close()

    if sts:

        sys.exit(sts)

if __name__ == '__main__':

    main()