#
#  Copyright (C) 2017 Codethink Limited
#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU Lesser General Public
#  License as published by the Free Software Foundation; either
#  version 2 of the License, or (at your option) any later version.
#
#  This library 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
#  Lesser General Public License for more details.
#
#  You should have received a copy of the GNU Lesser General Public
#  License along with this library. If not, see <http://www.gnu.org/licenses/>.
#
#  Authors:
#        Tristan Van Berkom <tristan.vanberkom@codethink.co.uk>
#

import jinja2

from .._exceptions import LoadError, LoadErrorReason
from ..node import MappingNode, SequenceNode, _assert_symbol_name
from .optionbool import OptionBool
from .optionenum import OptionEnum
from .optionflags import OptionFlags
from .optioneltmask import OptionEltMask
from .optionarch import OptionArch
from .optionos import OptionOS


_OPTION_TYPES = {
    OptionBool.OPTION_TYPE: OptionBool,
    OptionEnum.OPTION_TYPE: OptionEnum,
    OptionFlags.OPTION_TYPE: OptionFlags,
    OptionEltMask.OPTION_TYPE: OptionEltMask,
    OptionArch.OPTION_TYPE: OptionArch,
    OptionOS.OPTION_TYPE: OptionOS,
}


class OptionPool():

    def __init__(self, element_path):
        # We hold on to the element path for the sake of OptionEltMask
        self.element_path = element_path

        #
        # Private members
        #
        self._options = {}      # The Options
        self._variables = None  # The Options resolved into typed variables

        self._environment = None
        self._init_environment()

    def __getstate__(self):
        state = self.__dict__.copy()
        # Jinja2 Environments don't appear to be serializable. It is easy
        # enough for us to reconstruct this one anyway, so no need to pickle it.
        del state['_environment']
        return state

    def __setstate__(self, state):
        self.__dict__.update(state)
        self._init_environment()

    # load()
    #
    # Loads the options described in the project.conf
    #
    # Args:
    #    node (dict): The loaded YAML options
    #
    def load(self, options):

        for option_name, option_definition in options.items():

            # Assert that the option name is a valid symbol
            _assert_symbol_name(option_name, "option name", ref_node=option_definition, allow_dashes=False)

            opt_type_name = option_definition.get_str('type')
            try:
                opt_type = _OPTION_TYPES[opt_type_name]
            except KeyError:
                p = option_definition.get_scalar('type').get_provenance()
                raise LoadError("{}: Invalid option type '{}'".format(p, opt_type_name),
                                LoadErrorReason.INVALID_DATA)

            option = opt_type(option_name, option_definition, self)
            self._options[option_name] = option

    # load_yaml_values()
    #
    # Loads the option values specified in a key/value
    # dictionary loaded from YAML
    #
    # Args:
    #    node (dict): The loaded YAML options
    #
    def load_yaml_values(self, node, *, transform=None):
        for option_name, option_value in node.items():
            try:
                option = self._options[option_name]
            except KeyError as e:
                p = option_value.get_provenance()
                raise LoadError("{}: Unknown option '{}' specified"
                                .format(p, option_name), LoadErrorReason.INVALID_DATA) from e
            option.load_value(node, transform=transform)

    # load_cli_values()
    #
    # Loads the option values specified in a list of tuples
    # collected from the command line
    #
    # Args:
    #    cli_options (list): A list of (str, str) tuples
    #    ignore_unknown (bool): Whether to silently ignore unknown options.
    #
    def load_cli_values(self, cli_options, *, ignore_unknown=False):
        for option_name, option_value in cli_options:
            try:
                option = self._options[option_name]
            except KeyError as e:
                if not ignore_unknown:
                    raise LoadError("Unknown option '{}' specified on the command line"
                                    .format(option_name), LoadErrorReason.INVALID_DATA) from e
            else:
                option.set_value(option_value)

    # resolve()
    #
    # Resolves the loaded options, this is just a step which must be
    # performed after loading all options and their values, and before
    # ever trying to evaluate an expression
    #
    def resolve(self):
        self._variables = {}
        for option_name, option in self._options.items():
            # Delegate one more method for options to
            # do some last minute validation once any
            # overrides have been performed.
            #
            option.resolve()

            self._variables[option_name] = option.value

    # export_variables()
    #
    # Exports the option values which are declared
    # to be exported, to the passed dictionary.
    #
    # Variable values are exported in string form
    #
    # Args:
    #    variables (dict): A variables dictionary
    #
    def export_variables(self, variables):
        for _, option in self._options.items():
            if option.variable:
                variables[option.variable] = option.get_value()

    # printable_variables()
    #
    # Exports all option names and string values
    # to the passed dictionary in alphabetical order.
    #
    # Args:
    #    variables (dict): A variables dictionary
    #
    def printable_variables(self, variables):
        for key in sorted(self._options):
            variables[key] = self._options[key].get_value()

    # process_node()
    #
    # Args:
    #    node (node): A YAML Loaded dictionary
    #
    def process_node(self, node):

        # A conditional will result in composition, which can
        # in turn add new conditionals to the root.
        #
        # Keep processing conditionals on the root node until
        # all directly nested conditionals are resolved.
        #
        while self._process_one_node(node):
            pass

        # Now recurse into nested dictionaries and lists
        # and process any indirectly nested conditionals.
        #
        for value in node.values():
            value_type = type(value)
            if value_type is MappingNode:
                self.process_node(value)
            elif value_type is SequenceNode:
                self._process_list(value)

    #######################################################
    #                 Private Methods                     #
    #######################################################

    # _evaluate()
    #
    # Evaluates a jinja2 style expression with the loaded options in context.
    #
    # Args:
    #    expression (str): The jinja2 style expression
    #
    # Returns:
    #    (bool): Whether the expression resolved to a truthy value or a falsy one.
    #
    # Raises:
    #    LoadError: If the expression failed to resolve for any reason
    #
    def _evaluate(self, expression):

        #
        # Variables must be resolved at this point.
        #
        try:
            template_string = "{{% if {} %}} True {{% else %}} False {{% endif %}}".format(expression)
            template = self._environment.from_string(template_string)
            context = template.new_context(self._variables, shared=True)
            result = template.root_render_func(context)
            evaluated = jinja2.utils.concat(result)
            val = evaluated.strip()

            if val == "True":
                return True
            elif val == "False":
                return False
            else:  # pragma: nocover
                raise LoadError("Failed to evaluate expression: {}".format(expression),
                                LoadErrorReason.EXPRESSION_FAILED)
        except jinja2.exceptions.TemplateError as e:
            raise LoadError("Failed to evaluate expression ({}): {}".format(expression, e),
                            LoadErrorReason.EXPRESSION_FAILED)

    # Recursion assistent for lists, in case there
    # are lists of lists.
    #
    def _process_list(self, values):
        for value in values:
            value_type = type(value)
            if value_type is MappingNode:
                self.process_node(value)
            elif value_type is SequenceNode:
                self._process_list(value)

    # Process a single conditional, resulting in composition
    # at the root level on the passed node
    #
    # Return true if a conditional was processed.
    #
    def _process_one_node(self, node):
        conditions = node.get_sequence('(?)', default=None)
        assertion = node.get_str('(!)', default=None)

        # Process assersions first, we want to abort on the first encountered
        # assertion in a given dictionary, and not lose an assertion due to
        # it being overwritten by a later assertion which might also trigger.
        if assertion is not None:
            p = node.get_scalar('(!)').get_provenance()
            raise LoadError("{}: {}".format(p, assertion.strip()), LoadErrorReason.USER_ASSERTION)

        if conditions is not None:
            del node['(?)']

            for condition in conditions:
                tuples = list(condition.items())
                if len(tuples) > 1:
                    provenance = condition.get_provenance()
                    raise LoadError("{}: Conditional statement has more than one key".format(provenance),
                                    LoadErrorReason.INVALID_DATA)

                expression, value = tuples[0]
                try:
                    apply_fragment = self._evaluate(expression)
                except LoadError as e:
                    # Prepend the provenance of the error
                    provenance = condition.get_provenance()
                    raise LoadError("{}: {}".format(provenance, e), e.reason) from e

                if type(value) is not MappingNode:  # pylint: disable=unidiomatic-typecheck
                    provenance = condition.get_provenance()
                    raise LoadError("{}: Only values of type 'dict' can be composed.".format(provenance),
                                    LoadErrorReason.ILLEGAL_COMPOSITE)

                # Apply the yaml fragment if its condition evaluates to true
                if apply_fragment:
                    value._composite(node)

            return True

        return False

    def _init_environment(self):
        # jinja2 environment, with default globals cleared out of the way
        self._environment = jinja2.Environment(undefined=jinja2.StrictUndefined)
        self._environment.globals = []