platform-init

#!/usr/bin/env python
#
# Generate the config.platform file

import glob
import re
import sys
import os
import subprocess

def kvpair(k,v):
  return k + '="{}"'.format(v)

def which(file):
    for path in os.environ["PATH"].split(os.pathsep):
        if os.path.exists(os.path.join(path, file)):
                return os.path.join(path, file)

    return None

def cabal_version(cabal):
  output = subprocess.Popen([cabal, "--version"], stdout=subprocess.PIPE).communicate()[0]
  # cabal-install version 1.22.6.0  
  m = re.match("cabal-install version (\d[.\d]*)", output)
  if m:
    return m.groups(1)[0]
  else:
    return None

def parse_version(s):
  # s must be a string of digits and '.'
  return [ int(x) for x in s.split('.') ]

def compare_versions(a,b):
  # print "compare_versions:, a:", a, "b:", b
  if (not a) and (not b):
    return 0
  if not a:
    if not b: return 0
    return compare_versions( [0], b)
  if not b:
    return compare_versions( a, [0])
  if int(a[0]) == int(b[0]):
    return compare_versions(a[1:], b[1:])
  return cmp(a[0], b[0])

def main():
  bindists = glob.glob("ghc-*.tar.xz")
  if not bindists:
    print "No GHC bindists found in the current working directory"
    sys.exit(1)
  elif len(bindists) > 1:
    print "Multiple bindists found:"
    for m in bindists:
      print "  ", m
    sys.exit(1)

  stack = which("stack")
  if not stack:
    print "unable to find stack in PATH"
    sys.exit(1)
  print "found stack at", stack

  cabal = which("cabal")
  if not cabal:
    print "unable to find cabal in PATH"
    sys.exit(1)
  print "found cabal at", stack

  # Check the cabal version
  cversion = cabal_version(cabal)
  if not cversion:
    print "unable to parse cabal version for", cabal
    sys.exit(1)

  bad_cabal = compare_versions([1,24], parse_version(cversion)) > 0
  if bad_cabal:
    cok = "NOT OK"
  else:
    cok = "OK"
  print "cabal version is", cversion, "-", cok

  if bad_cabal:
    print "\n*** WARNING - cabal >= 1.24 required"

  contents = "\n".join([ kvpair("GHC_BINDIST", bindists[0]), kvpair("STACK", stack), kvpair("CABAL", cabal) ]) + "\n"
  with open("config.platform", "w") as f:
    f.write(contents)
  print "\nCreated the file config.platform with the contents:\n"
  print contents

main()