"""engine.SCons.Options

This file defines the Options class that is used to add user-friendly customizable
variables to a scons build.
"""

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__revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"

import SCons.Errors
import os.path


class Options:
    """
    Holds all the options, updates the environment with the variables,
    and renders the help text.
    """
    def __init__(self, file=None):
        """
        file - [optional] the name of the customizable file.
        """

        self.options = []
        self.file = file

    def Add(self, key, help="", default=None, validater=None, converter=None):
        """
        Add an option.

        key - the name of the variable
        help - optional help text for the options
        default - optional default value
        validater - optional function that is called to validate the option's value
        converter - optional function that is called to convert the option's value before
            putting it in the environment.
        """

        class Option:
            pass

        option = Option()
        option.key = key
        option.help = help
        option.default = default
        option.validater = validater
        option.converter = converter

        self.options.append(option)

    def Update(self, env, args):
        """
        Update an environment with the option variables.

        env - the environment to update.
        args - the dictionary to get the command line arguments from.
        """

        values = {}

        # first set the defaults:
        for option in self.options:
            if not option.default is None:
                values[option.key] = option.default

        # next set the value specified in the options file
        if self.file and os.path.exists(self.file):
            execfile(self.file, values)

        # finally set the values specified on the command line
        values.update(args)

        # put the variables in the environment:
        # (don't copy over variables that are not declared
        #  as options)
        for option in self.options:
            try:
                env[option.key] = values[option.key]
            except KeyError:
                pass

        # Call the convert functions:
        for option in self.options:
            if option.converter:
                value = env.subst('${%s}'%option.key)
                try:
                    env[option.key] = option.converter(value)
                except ValueError, x:
                    raise SCons.Errors.UserError, 'Error converting option: %s\n%s'%(option.key, x)


        # Finally validate the values:
        for option in self.options:
            if option.validater:
                option.validater(option.key, env.subst('${%s}'%option.key))


    def GenerateHelpText(self, env):
        """
        Generate the help text for the options.

        env - an environment that is used to get the current values of the options.
        """

        help_text = ""

        for option in self.options:
            help_text = help_text + '\n%s: %s\n    default: %s\n'%(option.key, option.help, option.default)
            if env.has_key(option.key):
                help_text = help_text + '    actual: %s\n'%env.subst('${%s}'%option.key)
            else:
                help_text = help_text + '    actual: None\n'

        return help_text