"""engine.SCons.Variables.EnumVariable

This file defines the option type for SCons allowing only specified
input-values.

Usage example:

  opts = Variables()
  opts.Add(EnumVariable('debug', 'debug output and symbols', 'no',
                      allowed_values=('yes', 'no', 'full'),
                      map={}, ignorecase=2))
  ...
  if env['debug'] == 'full':
    ...
"""

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__revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"

__all__ = ['EnumVariable',]


import SCons.Errors

def _validator(key, val, env, vals):
    if not val in vals:
        raise SCons.Errors.UserError(
            'Invalid value for option %s: %s.  Valid values are: %s' % (key, val, vals))


def EnumVariable(key, help, default, allowed_values, map={}, ignorecase=0):
    """
    The input parameters describe a option with only certain values
    allowed. They are returned with an appropriate converter and
    validator appended. The result is usable for input to
    Variables.Add().

    'key' and 'default' are the values to be passed on to Variables.Add().

    'help' will be appended by the allowed values automatically

    'allowed_values' is a list of strings, which are allowed as values
    for this option.

    The 'map'-dictionary may be used for converting the input value
    into canonical values (eg. for aliases).

    'ignorecase' defines the behaviour of the validator:

    If ignorecase == 0, the validator/converter are case-sensitive.
    If ignorecase == 1, the validator/converter are case-insensitive.
    If ignorecase == 2, the validator/converter is case-insensitive and
                        the converted value will always be lower-case.

    The 'validator' tests whether the value is in the list of allowed
    values. The 'converter' converts input values according to the
    given 'map'-dictionary (unmapped input values are returned
    unchanged). 
    """
    help = '%s (%s)' % (help, '|'.join(allowed_values))
    # define validator
    if ignorecase >= 1:
        validator = lambda key, val, env: \
                    _validator(key, val.lower(), env, allowed_values)
    else:
        validator = lambda key, val, env: \
                    _validator(key, val, env, allowed_values)
    # define converter
    if ignorecase == 2:
        converter = lambda val: map.get(val.lower(), val).lower()
    elif ignorecase == 1:
        converter = lambda val: map.get(val.lower(), val)
    else:
        converter = lambda val: map.get(val, val)
    return (key, help, default, validator, converter)

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