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"""Option type for path Variables.

This file defines an option type for SCons implementing path settings.

To be used whenever a user-specified path override should be allowed.

Arguments to PathVariable are:
  option-name  = name of this option on the command line (e.g. "prefix")
  option-help  = help string for option
  option-dflt  = default value for this option
  validator    = [optional] validator for option value.  Predefined are:
    PathAccept -- accepts any path setting; no validation
    PathIsDir  -- path must be an existing directory
    PathIsDirCreate -- path must be a dir; will create
    PathIsFile -- path must be a file
    PathExists -- path must exist (any type) [default]

  The validator is a function that is called and which should return
  True or False to indicate if the path is valid.  The arguments
  to the validator function are: (key, val, env).  The key is the
  name of the option, the val is the path specified for the option,
  and the env is the env to which the Options have been added.

Usage example::

  Examples:
      prefix=/usr/local

  opts = Variables()

  opts = Variables()
  opts.Add(PathVariable('qtdir',
                        'where the root of Qt is installed',
                        qtdir, PathIsDir))
  opts.Add(PathVariable('qt_includes',
                      'where the Qt includes are installed',
                      '$qtdir/includes', PathIsDirCreate))
  opts.Add(PathVariable('qt_libraries',
                      'where the Qt library is installed',
                      '$qtdir/lib'))
"""

__all__ = ['PathVariable',]

import os
import os.path

import SCons.Errors

class _PathVariableClass:

    @staticmethod
    def PathAccept(key, val, env):
        """Accepts any path, no checking done."""
        pass
    
    @staticmethod
    def PathIsDir(key, val, env):
        """Validator to check if Path is a directory."""
        if not os.path.isdir(val):
            if os.path.isfile(val):
                m = 'Directory path for option %s is a file: %s'
            else:
                m = 'Directory path for option %s does not exist: %s'
            raise SCons.Errors.UserError(m % (key, val))

    @staticmethod
    def PathIsDirCreate(key, val, env):
        """Validator to check if Path is a directory,
           creating it if it does not exist."""
        if os.path.isfile(val):
            m = 'Path for option %s is a file, not a directory: %s'
            raise SCons.Errors.UserError(m % (key, val))
        if not os.path.isdir(val):
            os.makedirs(val)

    @staticmethod
    def PathIsFile(key, val, env):
        """Validator to check if Path is a file"""
        if not os.path.isfile(val):
            if os.path.isdir(val):
                m = 'File path for option %s is a directory: %s'
            else:
                m = 'File path for option %s does not exist: %s'
            raise SCons.Errors.UserError(m % (key, val))

    @staticmethod
    def PathExists(key, val, env):
        """Validator to check if Path exists"""
        if not os.path.exists(val):
            m = 'Path for option %s does not exist: %s'
            raise SCons.Errors.UserError(m % (key, val))

    def __call__(self, key, help, default, validator=None):
        """
        The input parameters describe a 'path list' option, thus they
        are returned with the correct converter and validator appended. The
        result is usable for input to opts.Add() .

        The 'default' option specifies the default path to use if the
        user does not specify an override with this option.

        validator is a validator, see this file for examples
        """
        if validator is None:
            validator = self.PathExists

        if SCons.Util.is_List(key) or SCons.Util.is_Tuple(key):
            return (key, '%s ( /path/to/%s )' % (help, key[0]), default,
                    validator, None)
        else:
            return (key, '%s ( /path/to/%s )' % (help, key), default,
                    validator, None)

PathVariable = _PathVariableClass()

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