#!/usr/bin/env python

import os
import sys
import time
import requests
import tempfile
import shutil
from plumbum import local, cmd

COREOS_VERSION="250.0.0"

COREOS_ARCH="amd64-generic"
COREOS_BASE_URL="http://storage.core-os.net/coreos/{}/{}".format(COREOS_ARCH, COREOS_VERSION)
COREOS_PXE_DIGESTS="coreos_production_pxe_image.cpio.gz.DIGESTS.asc"
COREOS_PXE_KERNEL="coreos_production_pxe.vmlinuz"
COREOS_PXE_IMAGE="coreos_production_pxe_image.cpio.gz"
COREOS_PXE_IMAGE_URL = "{}/{}".format(COREOS_BASE_URL, COREOS_PXE_IMAGE)
COREOS_PXE_KERNEL_URL = "{}/{}".format(COREOS_BASE_URL, COREOS_PXE_KERNEL)
COREOS_PXE_DIGESTS_URL = "{}/{}".format(COREOS_BASE_URL, COREOS_PXE_DIGESTS)



def get_etag(cache_name):
    etag_file = "{}.etag".format(cache_name)
    if not os.path.exists(etag_file):
        return None
    with open(etag_file, 'rb') as fp:
        etag = fp.read()
    etag.strip()
    return etag

def save_etag(cache_name, etag):
    etag_file = "{}.etag".format(cache_name)
    with open(etag_file, 'w+b') as fp:
        fp.write(etag)

def cache_file(cache_name, remote_url):
    print("{} <- {}".format(cache_name, remote_url))
    etag = get_etag(cache_name)
    headers = {}
    if etag:
        headers['If-None-Match'] = etag

    start = time.time()
    r = requests.get(remote_url, headers=headers)

    if r.status_code == 304:
        print("[etag-match]")
        return

    if r.status_code != 200:
        raise RuntimeError('Failed to download {}, got HTTP {} Status Code.'.format(remote_url, r.status_code))

    with open(cache_name, 'w+b') as fp:
        fp.write(r.content)

    print("{} bytes in {} seconds".format(len(r.content), time.time() - start))
    save_etag(cache_name, r.headers['etag'])

def inject_oem(archive, oem_dir, output_file):
    d = tempfile.mkdtemp(prefix="oem-inject")
    try:
        with local.cwd(d):
            dest_oem_dir = os.path.join(d, 'usr', 'share', 'oem')
            uz = cmd.gunzip["-c", archive]
            extract = cmd.cpio["-iv"]
            chain = uz | extract
            print chain
            chain()

            shutil.copytree(oem_dir, dest_oem_dir)

            find = cmd.find['.', '-depth', '-print']
            cpio = cmd.cpio['-o', '-H', 'newc']
            gz = cmd.gzip
            chain = find | cmd.sort | cpio | gz > output_file
            print chain
            chain()
    finally:
        shutil.rmtree(d)
    return output_file

def validate_digests(digests, target, hash_type='sha1'):
    with local.cwd(os.path.dirname(digests)):
        gethashes = cmd.grep['-i', '-A1', '^# {} HASH$'.format(hash_type), digests]
        forthis = cmd.grep[os.path.basename(target)]
        viasum = local[hash_type + "sum"]['-c', '/dev/stdin']
        chain = gethashes | forthis | viasum
        print chain
        chain()

def main():
    if len(sys.argv) != 3:
        print("usage: {} [oem-directory-to-inject] [output-directory]".format(os.path.basename(__file__)))
        return

    oem_dir = os.path.abspath(os.path.expanduser(sys.argv[1]))
    output_dir = os.path.abspath(os.path.expanduser(sys.argv[2]))

    if not os.path.exists(oem_dir):
        print("Error: {} doesn't exist.".format(oem_dir))
        return

    if not os.path.exists(os.path.join(oem_dir, 'run.sh')):
        print("Error: {} is missing oem.sh".format(oem_dir))
        return

    here = os.path.abspath(os.path.dirname(__file__))

    top_cache_dir = os.path.join(os.path.dirname(here), ".image_cache")
    cache_dir = os.path.join(top_cache_dir, COREOS_ARCH, COREOS_VERSION)

    if not os.path.exists(cache_dir):
        os.makedirs(cache_dir)

    orig_cpio = os.path.join(cache_dir, COREOS_PXE_IMAGE)
    digests = os.path.join(cache_dir, COREOS_PXE_DIGESTS)
    kernel = os.path.join(cache_dir, COREOS_PXE_KERNEL)

    cache_file(digests, COREOS_PXE_DIGESTS_URL)
    gpg_verify_file(digests)
    cache_file(kernel, COREOS_PXE_KERNEL_URL)
    validate_digests(digests, kernel)
    cache_file(orig_cpio, COREOS_PXE_IMAGE_URL)
    validate_digests(digests, orig_cpio)

    if not os.path.exists(output_dir):
        os.makedirs(output_dir)

    output_kernel = os.path.join(output_dir, os.path.basename(kernel))
    output_cpio = os.path.join(output_dir, os.path.basename(orig_cpio).replace('.cpio.gz', '-oem.cpio.gz'))
    inject_oem(orig_cpio, oem_dir, output_cpio)
    shutil.copy(kernel, output_kernel)

def gpg_verify_file(ascfile):
    d = tempfile.mkdtemp(prefix="oem-gpg-validate")
    try:
        tmpring = os.path.join(d, 'tmp.gpg')
        key = os.path.join(d, 'coreos.key')
        with open(key, 'w+b') as fp:
            fp.write(gpg_key())

        i = cmd.gpg['--batch',
                '--no-default-keyring',
                '--keyring',
                tmpring,
                '--import',
                key]
        print(i)
        i()

        r = cmd.gpg['--batch',
                '--no-default-keyring',
                '--keyring',
                tmpring,
                '--verify',
                ascfile]
        print(r)
        r()

    finally:
        shutil.rmtree(d)

def gpg_key():
    GPG_LONG_ID="50E0885593D2DCB4"
    GPG_KEY="""-----BEGIN PGP PUBLIC KEY BLOCK-----
    Version: GnuPG v2.0.20 (GNU/Linux)

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    -----END PGP PUBLIC KEY BLOCK-----
    """
    return GPG_KEY

if __name__ == "__main__":
    main()