apb.py

#!/usr/bin/python

import base64
import os

SPEC_FILE = 'apb.yml'
DOCKERFILE = 'Dockerfile'
SPEC_LABEL = 'com.redhat.apb.spec'


def touch(fname, force):
    if os.path.exists(fname):
        os.utime(fname, None)
        if force:
            os.remove(fname)
            open(fname, 'a').close()
    else:
        open(fname, 'a').close()


def write_file(file_out, destination, force):
    touch(destination, force)
    with open(destination, 'w') as outfile:
        outfile.write(''.join(file_out))


def load_dockerfile(df_path):
    with open(df_path, 'r') as dockerfile:
        return dockerfile.readlines()


def load_spec_str(spec_path):
    with open(spec_path, 'r') as spec_file:
        return spec_file.read()


def update_dockerfile(project, dockerfile):
    spec_path = os.path.join(project, SPEC_FILE)
    dockerfile_path = os.path.join(os.path.join(project, dockerfile))

    blob = base64.b64encode(load_spec_str(spec_path))
    dockerfile_out = insert_encoded_spec(
        load_dockerfile(dockerfile_path), make_friendly(blob)
    )

    write_file(dockerfile_out, dockerfile_path, False)
    print('Finished writing dockerfile.')


def insert_encoded_spec(dockerfile, encoded_spec_lines):
    apb_spec_idx = [i for i, line in enumerate(dockerfile)
                    if SPEC_LABEL in line][0]
    if not apb_spec_idx:
        raise Exception(
            "ERROR: %s missing from dockerfile while inserting spec blob" %
            SPEC_LABEL
        )

    # Set end_spec_idx to a list of all lines ending in a quotation mark
    end_spec_idx = [i for i, line in enumerate(dockerfile)
                    if line.endswith('"\n')]

    # Find end of spec label if it already exists
    if end_spec_idx:
        for correct_end_idx in end_spec_idx:
            if correct_end_idx > apb_spec_idx:
                end_spec_idx = correct_end_idx
                del dockerfile[apb_spec_idx + 1:end_spec_idx + 1]
                break

    split_idx = apb_spec_idx + 1
    offset = apb_spec_idx + len(encoded_spec_lines) + 1

    # Insert spec label
    dockerfile[split_idx:split_idx] = encoded_spec_lines

    # Insert newline after spec label
    dockerfile.insert(offset, "\n")

    return dockerfile


def make_friendly(blob):
    line_break = 76
    count = len(blob)
    chunks = count / line_break
    mod = count % line_break

    flines = []
    for i in range(chunks):
        fmtstr = '{0}\\\n'

        # Corner cases
        if chunks == 1:
            # Exactly 76 chars, two quotes
            fmtstr = '"{0}"\n'
        elif i == 0:
            fmtstr = '"{0}\\\n'
        elif i == chunks - 1 and mod == 0:
            fmtstr = '{0}\\\n"'

        offset = i * line_break
        line = fmtstr.format(blob[offset:(offset + line_break)])
        flines.append(line)

    if mod != 0:
        # Add incomplete chunk if we've got some left over,
        # this is the usual case
        flines.append('{0}"'.format(blob[line_break * chunks:]))


    return flines


update_dockerfile('.', DOCKERFILE)