convert-constants

#!/usr/bin/python
#

# Copyright (C) 2011, 2012 Google Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.

"""Script for converting Python constants to Haskell code fragments.

"""

import re
import types

from ganeti import compat
from ganeti import constants
from ganeti import luxi
from ganeti import qlang
from ganeti import _autoconf


#: Constant name regex
CONSTANT_RE = re.compile("^[A-Z][A-Z0-9_-]+$")

#: Private name regex
PRIVATE_RE = re.compile("^__.+__$")

#: The type of regex objects
RE_TYPE = type(CONSTANT_RE)

#: Keys which do not declare a value (manually maintained). By adding
# values here, we can make more lists use the actual names; otherwise
# we'll have (e.g.) both DEFAULT_ENABLED_HYPERVISOR and HT_XEN_PVM
# declare the same value, and thus the list of valid hypervisors will
# have strings instead of easily looked-up names.
IGNORED_DECL_NAMES = ["DEFAULT_ENABLED_HYPERVISOR"]


def NameRules(name):
  """Converts the upper-cased Python name to Haskell camelCase.

  """
  name = name.replace("-", "_")
  elems = name.split("_")
  return elems[0].lower() + "".join(e.capitalize() for e in elems[1:])


def StringValueRules(value):
  """Converts a string value from Python to Haskell.

  """
  value = value.encode("string_escape") # escapes backslashes
  value = value.replace("\"", "\\\"")
  return value


def DictKeyName(dict_name, key_name):
  """Converts a dict plus key name to a full name.

  """
  return"%s_%s" % (dict_name, str(key_name).upper())


def HaskellTypeVal(value):
  """Returns the Haskell type and value for a Python value.

  Note that this only work for 'plain' Python types.

  @returns: (string, string) or None, if we can't determine the type.

  """
  if isinstance(value, basestring):
    return ("String", "\"%s\"" % StringValueRules(value))
  elif isinstance(value, int):
    return ("Int", "%d" % value)
  elif isinstance(value, long):
    return ("Integer", "%d" % value)
  elif isinstance(value, float):
    return ("Double", "%f" % value)
  else:
    return None


def IdentifyOrigin(all_items, value):
  """Tries to identify a constant name from a constant's value.

  This uses a simple algorithm: is there a constant (and only one)
  with the same value? If so, then it returns that constants' name.

  @note: it is recommended to use this only for tuples/lists/sets, and
      not for individual (top-level) values
  @param all_items: a dictionary of name/values for the current module
  @param value: the value for which we try to find an origin

  """
  found = [name for (name, v) in all_items.items()
           if v is value and name not in IGNORED_DECL_NAMES]
  if len(found) == 1:
    return found[0]
  else:
    return None


def FormatListElems(all_items, pfx_name, ovals, tvals):
  """Formats a list's elements.

  This formats the elements as either values or, if we find all
  origins, as names.

  @param all_items: a dictionary of name/values for the current module
  @param pfx_name: the prefix name currently used
  @param ovals: the list of actual (Python) values
  @param tvals: the list of values we want to format in the Haskell form

  """
  origins = [IdentifyOrigin(all_items, v) for v in ovals]
  if compat.all(x is not None for x in origins):
    values = [NameRules(pfx_name + origin) for origin in origins]
  else:
    values = tvals
  return ", ".join(values)


def FormatDict(all_items, pfx_name, py_name, hs_name, mydict):
  """Converts a dictionary to a Haskell association list ([(k, v)]),
  if possible.

  @param all_items: a dictionary of name/values for the current module
  @param pfx_name: the prefix name currently used
  @param py_name: the Python name
  @param hs_name: the Haskell name
  @param mydict: a dictonary, unknown yet if homogenous or not

  """
  # need this for ordering
  orig_list = mydict.items()
  list_form = [(HaskellTypeVal(k), HaskellTypeVal(v)) for k, v in orig_list]
  if compat.any(v is None or k is None for k, v in list_form):
    # type not known
    return []
  all_keys = [k for k, _ in list_form]
  all_vals = [v for _, v in list_form]
  key_types = set(k[0] for k in all_keys)
  val_types = set(v[0] for v in all_vals)
  if not(len(key_types) == 1 and len(val_types) == 1):
    # multiple types
    return []
  # record the key and value Haskell types
  key_type = key_types.pop()
  val_type = val_types.pop()

  # now try to find names for the keys, instead of raw values
  key_origins = [IdentifyOrigin(all_items, k) for k, _ in orig_list]
  if compat.all(x is not None for x in key_origins):
    key_v = [NameRules(pfx_name + origin) for origin in key_origins]
  else:
    key_v = [k[1] for k in all_keys]
  # ... and for values
  val_origins = [IdentifyOrigin(all_items, v) for _, v in orig_list]
  if compat.all(x is not None for x in val_origins):
    val_v = [NameRules(pfx_name + origin) for origin in val_origins]
  else:
    val_v = [v[1] for v in all_vals]

  # finally generate the output
  kv_pairs = ["(%s, %s)" % (k, v) for k, v in zip(key_v, val_v)]
  return ["-- | Converted from Python dictionary %s" % py_name,
          "%s :: [(%s, %s)]" % (hs_name, key_type, val_type),
          "%s = [%s]" % (hs_name, ", ".join(kv_pairs)),
          ]


def ConvertVariable(prefix, name, value, all_items):
  """Converts a given variable to Haskell code.

  @param prefix: a prefix for the Haskell name (useful for module
      identification)
  @param name: the Python name
  @param value: the value
  @param all_items: a dictionary of name/value for the module being
      processed
  @return: a list of Haskell code lines

  """
  lines = []
  if prefix:
    pfx_name = prefix + "_"
    fqn = prefix + "." + name
  else:
    pfx_name = ""
    fqn = name
  hs_name = NameRules(pfx_name + name)
  hs_typeval = HaskellTypeVal(value)
  if (isinstance(value, types.ModuleType) or callable(value) or
      PRIVATE_RE.match(name)):
    # no sense in marking these, as we don't _want_ to convert them; the
    # message in the next if block is for datatypes we don't _know_
    # (yet) how to convert
    pass
  elif not CONSTANT_RE.match(name):
    lines.append("-- Skipped %s %s, not constant" % (fqn, type(value)))
  elif hs_typeval is not None:
    # this is a simple value
    (hs_type, hs_val) = hs_typeval
    lines.append("-- | Converted from Python constant %s" % fqn)
    lines.append("%s :: %s" % (hs_name, hs_type))
    lines.append("%s = %s" % (hs_name, hs_val))
  elif isinstance(value, dict):
    if value:
      lines.append("-- Following lines come from dictionary %s" % fqn)
      # try to build a real map here, if all keys have same type, and
      # all values too (i.e. we have a homogeneous dictionary)
      lines.extend(FormatDict(all_items, pfx_name, fqn, hs_name, value))
      # and now create individual names
      for k in sorted(value.keys()):
        lines.extend(ConvertVariable(prefix, DictKeyName(name, k),
                                     value[k], all_items))
  elif isinstance(value, tuple):
    tvs = [HaskellTypeVal(elem) for elem in value]
    if compat.all(e is not None for e in tvs):
      ttypes = ", ".join(e[0] for e in tvs)
      tvals = FormatListElems(all_items, pfx_name, value, [e[1] for e in tvs])
      lines.append("-- | Converted from Python tuple %s" % fqn)
      lines.append("%s :: (%s)" % (hs_name, ttypes))
      lines.append("%s = (%s)" % (hs_name, tvals))
    else:
      lines.append("-- Skipped tuple %s, cannot convert all elements" % fqn)
  elif isinstance(value, (list, set, frozenset)):
    # Lists and frozensets are handled the same in Haskell: as lists,
    # since lists are immutable and we don't need for constants the
    # high-speed of an actual Set type. However, we can only convert
    # them if they have the same type for all elements (which is a
    # normal expectation for constants, our code should be well
    # behaved); note that this is different from the tuples case,
    # where we always (for some values of always) can convert
    tvs = [HaskellTypeVal(elem) for elem in value]
    if compat.all(e is not None for e in tvs):
      ttypes, tvals = zip(*tvs)
      uniq_types = set(ttypes)
      if len(uniq_types) == 1:
        values = FormatListElems(all_items, pfx_name, value, tvals)
        lines.append("-- | Converted from Python list or set %s" % fqn)
        lines.append("%s :: [%s]" % (hs_name, uniq_types.pop()))
        lines.append("%s = [%s]" % (hs_name, values))
      else:
        lines.append("-- | Skipped list/set %s, is not homogeneous" % fqn)
    else:
      lines.append("-- | Skipped list/set %s, cannot convert all elems" % fqn)
  elif isinstance(value, RE_TYPE):
    tvs = HaskellTypeVal(value.pattern)
    assert tvs is not None
    lines.append("-- | Converted from Python RE object %s" % fqn)
    lines.append("%s :: %s" % (hs_name, tvs[0]))
    lines.append("%s = %s" % (hs_name, tvs[1]))
  else:
    lines.append("-- Skipped %s, %s not handled" % (fqn, type(value)))
  return lines


def Convert(module, prefix):
  """Converts the constants to Haskell.

  """
  lines = [""]

  all_items = dict((name, getattr(module, name)) for name in dir(module))

  for name in sorted(all_items.keys()):
    value = all_items[name]
    new_lines = ConvertVariable(prefix, name, value, all_items)
    if new_lines:
      lines.extend(new_lines)
      lines.append("")

  return "\n".join(lines)


def main():
  print Convert(constants, "")
  print Convert(luxi, "luxi")
  print Convert(qlang, "qlang")
  print Convert(_autoconf, "autoconf")


if __name__ == "__main__":
  main()