apt-requirements

#!/usr/bin/env python3
import sys
import os
import subprocess
import argparse

P = argparse.ArgumentParser(description="declarative apt")
P.add_argument("path", type=str, help="Path to requirements file")
P.add_argument("--act", default=False, action='store_true',
		help="Actually do install and remove packages")

assert __name__ == "__main__"

TO_INSTALL = set()
TO_REMOVE = set()
DEB_LINES = set()
ALL_GREEN = True

def register(line):
	if line.startswith("R "):
		TO_REMOVE.add(line[2:])
	elif line.startswith("DEB "):
		DEB_LINES.add(line[4:])
	else:
		TO_INSTALL.add(line)

# Read configuration
ARGS = P.parse_args()
with open(ARGS.path) as fh:
	for line in fh:
		i = line.find("#")
		if i >= 0:
			line = line[:i]
		if not line:
			continue
		register(line.strip())

# Should update sources?
_SOURCE_PATH="/etc/apt/sources.list.d/requirements.list"
deb_lines_current = set()
if os.path.exists(_SOURCE_PATH):
	with open(_SOURCE_PATH) as fh:
		for line in fh:
			if not line.startswith("deb"):
				continue
			deb_lines_current.add(line[4:].strip())
if DEB_LINES.difference(deb_lines_current):
	if ARGS.act:
		with open(_SOURCE_PATH, "w") as fh:
			for l in sorted(DEB_LINES):
				fh.write("deb ")
				fh.write(l)
				fh.write("\n")
	else:
		print("For /etc/apt/sources.list.d/requirements.list")
		for l in sorted(DEB_LINES):
			print(l)
		print()

def error(msg):
	global ALL_GREEN
	ALL_GREEN = False
	print("Error:", msg)

both = TO_INSTALL.intersection(TO_REMOVE)
if both:
	error("remove AND install? "+" ".join(both))
	exit(1)

def precheck(pkgs, short_cmd, op):
	op = op + " "
	pkgs = " ".join(pkgs)
	cmd = "apt-get %s -s -y %s" % (short_cmd, pkgs)
	try:
		output = subprocess.check_output(cmd.split())
	except subprocess.CalledProcessError:
		error(cmd)
		return
	for line in output.decode("utf8").split("\n"):
		if line.startswith(op):
			pkg = line.split()[1]
			yield pkg

# Check removals
removals = set(precheck(TO_REMOVE, "remove", "Remv"))
for pkg in removals:
	if pkg in TO_INSTALL:
		error("Would remove '%s', which shall be installed" % pkg)

# Check installs
installs = set(precheck(TO_INSTALL, "install", "Inst"))
for pkg in installs:
	if pkg in TO_REMOVE:
		error("Would install '%s', which shall be removed" % pkg)

removals = removals.intersection(TO_REMOVE)
installs = installs.intersection(TO_INSTALL)
if ALL_GREEN:
	if (removals):
		cmd = "apt-get remove " + " ".join(removals)
		print(cmd)
		if ARGS.act:
			os.system("sudo %s -y"%cmd)
	if (installs):
		cmd = "apt-get install " + " ".join(installs)
		print(cmd)
		if ARGS.act:
			os.system("sudo %s -y "%cmd)
else:
	exit(1)