#!/usr/bin/env python
#
# Electrum - lightweight Bitcoin client
# Copyright (C) 2015 Thomas Voegtlin
#
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation files
# (the "Software"), to deal in the Software without restriction,
# including without limitation the rights to use, copy, modify, merge,
# publish, distribute, sublicense, and/or sell copies of the Software,
# and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.


# This module uses code from TLSLlite
# TLSLite Author: Trevor Perrin)


import binascii


def a2b_base64(s):
    try:
        b = bytearray(binascii.a2b_base64(s))
    except Exception as e:
        raise SyntaxError("base64 error: %s" % e)
    return b


def dePem(s, name):
    """Decode a PEM string into a bytearray of its payload.

    The input must contain an appropriate PEM prefix and postfix
    based on the input name string, e.g. for name="CERTIFICATE":

    -----BEGIN CERTIFICATE-----
    MIIBXDCCAUSgAwIBAgIBADANBgkqhkiG9w0BAQUFADAPMQ0wCwYDVQQDEwRUQUNL
    ...
    KoZIhvcNAQEFBQADAwA5kw==
    -----END CERTIFICATE-----

    The first such PEM block in the input will be found, and its
    payload will be base64 decoded and returned.
    """
    prefix  = "-----BEGIN %s-----" % name
    postfix = "-----END %s-----" % name
    start = s.find(prefix)
    if start == -1:
        raise SyntaxError("Missing PEM prefix")
    end = s.find(postfix, start+len(prefix))
    if end == -1:
        raise SyntaxError("Missing PEM postfix")
    s = s[start+len("-----BEGIN %s-----" % name) : end]
    retBytes = a2b_base64(s) # May raise SyntaxError
    return retBytes

def dePemList(s, name):
    """Decode a sequence of PEM blocks into a list of bytearrays.

    The input must contain any number of PEM blocks, each with the appropriate
    PEM prefix and postfix based on the input name string, e.g. for
    name="TACK BREAK SIG".  Arbitrary text can appear between and before and
    after the PEM blocks.  For example:

    " Created by TACK.py 0.9.3 Created at 2012-02-01T00:30:10Z -----BEGIN TACK
    BREAK SIG-----
    ATKhrz5C6JHJW8BF5fLVrnQss6JnWVyEaC0p89LNhKPswvcC9/s6+vWLd9snYTUv
    YMEBdw69PUP8JB4AdqA3K6Ap0Fgd9SSTOECeAKOUAym8zcYaXUwpk0+WuPYa7Zmm
    SkbOlK4ywqt+amhWbg9txSGUwFO5tWUHT3QrnRlE/e3PeNFXLx5Bckg= -----END TACK
    BREAK SIG----- Created by TACK.py 0.9.3 Created at 2012-02-01T00:30:11Z
    -----BEGIN TACK BREAK SIG-----
    ATKhrz5C6JHJW8BF5fLVrnQss6JnWVyEaC0p89LNhKPswvcC9/s6+vWLd9snYTUv
    YMEBdw69PUP8JB4AdqA3K6BVCWfcjN36lx6JwxmZQncS6sww7DecFO/qjSePCxwM
    +kdDqX/9/183nmjx6bf0ewhPXkA0nVXsDYZaydN8rJU1GaMlnjcIYxY= -----END TACK
    BREAK SIG----- "

    All such PEM blocks will be found, decoded, and return in an ordered list
    of bytearrays, which may have zero elements if not PEM blocks are found.
     """
    bList = []
    prefix  = "-----BEGIN %s-----" % name
    postfix = "-----END %s-----" % name
    while 1:
        start = s.find(prefix)
        if start == -1:
            return bList
        end = s.find(postfix, start+len(prefix))
        if end == -1:
            raise SyntaxError("Missing PEM postfix")
        s2 = s[start+len(prefix) : end]
        retBytes = a2b_base64(s2) # May raise SyntaxError
        bList.append(retBytes)
        s = s[end+len(postfix) : ]