#!/usr/bin/env python3

# Yes, this is a Python program writing a Ruby program.

import argparse
import hashlib
import sys
import os

parser = argparse.ArgumentParser()
parser.add_argument("--url-base",  default = "https://brew.cryptech.is/tarballs/")
parser.add_argument("--tarball",   required = True)
parser.add_argument("--package",   required = True)
parser.add_argument("--version",   required = True)
parser.add_argument("--formula",   type = argparse.FileType("w"), nargs = "?", default = sys.stdout)
parser.add_argument("--conflicts", default = "")
args = parser.parse_args()

template = '''\
# This Homebrew forumula was automatically generated by a script.
# You might not want to edit it manually.
#
# Installation is a bit complex due to the way Homebrew handles Python
# library dependencies and due to our stuff being a mixture of Python
# and C.  It's also painfully slow, because we're not using bottles,
# due to lack of a MacOS build farm.  Sorry.
#
# Per Homebrew expectations, we install copies of external Python
# libraries ("resources") in our own private library directory, using
# Homebrew's hack to run our executable Python scripts with PYTHONPATH
# pointing to our private library directory.  Our own Python library
# code, however, is what Homebrew considers "bindings", so we install
# those where user scripts as well as our own can find them...then we
# add a symlink so that our scripts can find our bindings regardless
# of which copy of Python Homebrew decides we should use this week.
#
# We have to build our own software before installing our Python code,
# because at least one of the Python modules we install
# (cryptech.py11.attribute_map) is generated during the build.
#
# Reference for all the documented Python Homebrew voodoo:
#
# http://docs.brew.sh/Python-for-Formula-Authors.html
#
# Reference for undocumented Python Homebrew voodoo:
#
# /usr/local/Homebrew/Library/Homebrew/language/python.rb

class {classname} < Formula

  desc     "Software for working with Cryptech Alpha board HSM"
  homepage "https://cryptech.is/"
  version  "{version}"
  url      "{url}"
  sha256   "{sha256}"

  depends_on "python@3.8"

{conflicts}

  resource "pyserial" do
    url    "https://files.pythonhosted.org/packages/cc/74/11b04703ec416717b247d789103277269d567db575d2fd88f25d9767fe3d/pyserial-3.4.tar.gz"
    sha256 "6e2d401fdee0eab996cf734e67773a0143b932772ca8b42451440cfed942c627"
  end

  resource "PyYAML" do
    url    "http://pyyaml.org/download/pyyaml/PyYAML-5.3.1.tar.gz"
    sha256 "b8eac752c5e14d3eca0e6dd9199cd627518cb5ec06add0de9d32baeee6fe645d"
  end

  resource "tornado" do
    url    "https://files.pythonhosted.org/packages/source/t/tornado/tornado-4.4.3.tar.gz"
    sha256 "f267acc96d5cf3df0fd8a7bfb5a91c2eb4ec81d5962d1a7386ceb34c655634a8"
  end

  resource "pycrypto" do
    url    "https://pypi.python.org/packages/source/p/pycrypto/pycrypto-2.6.1.tar.gz"
    sha256 "f2ce1e989b272cfcb677616763e0a2e7ec659effa67a88aa92b3a65528f60a3c"
  end

  def install

    xy = Language::Python.major_minor_version "python3"

    ENV.prepend_create_path "PYTHONPATH", libexec/"vendor/lib/python#{{xy}}/site-packages"

    resources.each do |r|
      ohai "Building resource #{{r.url}}"
      r.stage do
        system "python3", *Language::Python.setup_install_args(libexec/"vendor")
      end
    end

    ohai "Building PKCS #11 code (including crypto and bignum libraries) from source, this is slow, please be patient..."
    ENV.deparallelize
    system "make", "-C", "sw/pkcs11"

    system "python3", *Language::Python.setup_install_args(prefix)
    bin.env_script_all_files(libexec/"bin", :PYTHONPATH => ENV["PYTHONPATH"])

    ln_s lib/"python#{{xy}}/site-packages/cryptech", libexec/"vendor/lib/python#{{xy}}/site-packages/cryptech"

    share.install "cryptech-alpha-firmware.tar.gz"
    lib.install   "sw/pkcs11/libcryptech-pkcs11.dylib"

  end

end
'''

with open(args.tarball, "rb") as f:
    digest = hashlib.sha256(f.read()).hexdigest()

classname = "".join(word.capitalize() for word in args.package.split("-"))

conflicts = "\n".join("  conflicts_with \"{}\", :because => \"HSM firmware and PKCS #11 library must match\"".format(conflict)
                      for conflict in args.conflicts.split())

url = os.path.join(args.url_base, os.path.basename(args.tarball))

args.formula.write(template.format(
    version   = args.version,
    url       = url,
    sha256    = digest,
    classname = classname,
    conflicts = conflicts))