#############################################################################
# Copyright (C) 2017 - 2023  Spine Project
#
# This file is part of SpineOpt.
#
# SpineOpt 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 3 of the License, or
# (at your option) any later version.
#
# SpineOpt 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 program.  If not, see <http://www.gnu.org/licenses/>.
#############################################################################
"""
    node_voltage_angle_indices(filtering_options...)

A set of tuples for indexing the `node_voltage_angle` variable. Any filtering options can be specified
for `node`, `s`, and `t`.
"""
function node_voltage_angle_indices(
    m::Model;
    node=anything,
    stochastic_scenario=anything,
    t=anything,
    temporal_block=temporal_block(representative_periods_mapping=nothing),
)
    node_stochastic_time_indices(
        m;
        node=intersect(node, SpineOpt.node(has_voltage_angle=true)),
        stochastic_scenario=stochastic_scenario,
        t=t,
        temporal_block=temporal_block,
    )
end

"""
    add_variable_node_voltage_angle!(m::Model)

Add `node_voltage_angle` variables to model `m`.
"""
function add_variable_node_voltage_angle!(m::Model)
    add_variable!(
        m,
        :node_voltage_angle,
        node_voltage_angle_indices;
        fix_value=fix_node_voltage_angle,
        initial_value=initial_node_voltage_angle
    )
end
