utils.jl

"Helper to convert "
_missing2false(a::Union{Missing,Bool}) = ismissing(a) ? false : a

"""
    iseng(data::Dict{String,Any})

Helper function to check is data is ENGINEERING model
"""
iseng(data::Dict{String,<:Any}) = _missing2false(get(data, "data_model", missing) == ENGINEERING)
iseng(data::InfrastructureModel) = false


"""
    ismath(data::Dict{String,Any})

Helper function to check if data is MATHEMATICAL model
"""
ismath(data::Dict{String,<:Any}) = _missing2false(get(data, "data_model", missing) == MATHEMATICAL)
ismath(data::InfrastructureModel) = false


"""
    make_multiconductor!(data::Dict{String,<:Any}, conductors::Int)

**This function is not meant to be an officially supported method for creating reasonable multiconductor data sets.**

**Hacky** helper function to transform single-conductor network data, from, e.g., matpower/psse, into multi-conductor data.
"""
function make_multiconductor!(data::Dict{String,<:Any}, conductors::Int)
    @info "This function is not meant to be an officially supported method for creating reasonable multiconductor data sets"
    if ismultinetwork(data)
        for (i,nw_data) in data["nw"]
            _make_multiconductor!(nw_data, conductors)
        end
    else
         _make_multiconductor!(data, conductors)
    end
end


"Hacky helper function to transform single-conductor network data, from, e.g., matpower/psse, into multi-conductor data"
function _make_multiconductor!(data::Dict{String,<:Any}, conductors::Real)
    if haskey(data, "conductor_ids")
        @warn "skipping network that is already multiconductor"
        return
    end

    data["conductor_ids"] = collect(1:conductors)
    data["data_model"] = MATHEMATICAL
    data["settings"] = get(
        data,
        "settings",
        Dict{String,Any}(
            "sbase_default" => get(data, "baseMVA", 1e6)
        )
    )

    for (key, item) in data
        if isa(item, Dict{String,Any})
            for (item_id, item_data) in item
                if isa(item_data, Dict{String,Any})
                    item_ref_data = Dict{String,Any}()
                    for (param, value) in item_data
                        if param in _conductorless
                            item_ref_data[param] = value
                        else
                            if param in _conductor_matrix
                                item_ref_data[param] = LinearAlgebra.diagm(0=>fill(value, conductors))
                            else
                                item_ref_data[param] = fill(value, conductors)
                            end
                        end
                    end
                    item[item_id] = item_ref_data
                end
            end
        else
            #root non-dict items
        end
    end

    for (_, load) in data["load"]
        load["model"] = POWER
        load["configuration"] = WYE
    end

    for (_, gen) in data["gen"]
        gen["configuration"] = WYE
    end

    for type in ["load", "gen", "storage", "shunt"]
        if haskey(data, type)
            for (_,obj) in data[type]
                obj["connections"] = collect(1:conductors)
            end
        end
    end

    for type in ["branch", "transformer", "switch"]
        if haskey(data, type)
            for (_,obj) in data[type]
                obj["f_connections"] = collect(1:conductors)
                obj["t_connections"] = collect(1:conductors)
            end
        end
    end

    for (_,bus) in data["bus"]
        bus["terminals"] = collect(1:conductors)
        bus["grounded"] = fill(false, conductors)
    end
end


"initializes the base math object of any type, and copies any one-to-one mappings"
function _init_math_obj(obj_type::String, eng_id::Any, eng_obj::Dict{String,<:Any}, index::Int; pass_props::Vector{String}=String[])::Dict{String,Any}
    math_obj = Dict{String,Any}(
        "name" => "$eng_id",
        "source_id" => "$obj_type.$eng_id"
    )

    for key in [get(_1to1_maps, obj_type, String[]); pass_props]
        if haskey(eng_obj, key)
            if key in ["status", "dispatchable"]
                math_obj[key] = Int(eng_obj[key])
            else
                math_obj[key] = eng_obj[key]
            end
        end
    end

    math_obj["index"] = index

    return math_obj
end


"initializes the base components that are expected by powermodelsdistribution in the mathematical model"
function _init_base_components!(data_math::Dict{String,<:Any})
    for key in pmd_math_asset_types
        if !haskey(data_math, key)
            data_math[key] = Dict{String,Any}()
        end
    end
end


"function for applying a scale to a paramter"
function _scale(dict::Dict{String,<:Any}, key::String, scale::Real)
    if haskey(dict, key)
        dict[key] *= scale
    end
end


"""
Converts a set of short-circuit tests to an equivalent reactance network.
Reference:
R. C. Dugan, “A perspective on transformer modeling for distribution system analysis,”
in 2003 IEEE Power Engineering Society General Meeting (IEEE Cat. No.03CH37491), 2003, vol. 1, pp. 114-119 Vol. 1.
"""
function _sc2br_impedance(Zsc::Dict{Tuple{Int,Int},Complex{Float64}})::Dict{Tuple{Int,Int},Complex}
    N = maximum([maximum(k) for k in keys(Zsc)])
    # check whether no keys are missing
    # Zsc should contain tupples for upper triangle of NxN
    for i in 1:N
        for j in i+1:N
            if !haskey(Zsc, (i,j))
                if haskey(Zsc, (j,i))
                    # Zsc is symmetric; use value of lower triangle if defined
                    Zsc[(i,j)] =  Zsc[(j,i)]
                else
                    error("Short-circuit impedance between winding $i and $j is missing.")
                end
            end
        end
    end

    # if all zero, return all zeros
    if all(values(Zsc).==0.0)
        return Zsc
    end

    # make Zb
    Zb = zeros(Complex{Float64}, N-1,N-1)
    for i in 1:N-1
        Zb[i,i] = Zsc[(1,i+1)]
    end
    for i in 1:N-1
        for j in 1:i-1
            Zb[i,j] = (Zb[i,i]+Zb[j,j]-Zsc[(j+1,i+1)])/2
            Zb[j,i] = Zb[i,j]
        end
    end
    # get Ybus
    Y = LinearAlgebra.pinv(Zb)
    Y = [-Y*ones(N-1) Y]
    Y = [-ones(1,N-1)*Y; Y]
    # extract elements
    Zbr = Dict{Tuple{Int,Int},Complex}()
    for k in keys(Zsc)
        Zbr[k] = (abs(Y[k...])==0) ? Inf : -1/Y[k...]
    end
    return Zbr
end


"loss model builder for transformer decomposition"
function _build_loss_model!(
    data_math::Dict{String,<:Any},
    transformer_name::String,
    to_map::Vector{String},
    r_s::Vector{Float64},
    zsc::Dict{Tuple{Int,Int},Complex{Float64}},
    ysh::Complex{Float64},
    connections::Vector{Int};
    nphases::Int=3,
    status::Int=1,
    )::Vector{Int}

    # precompute the minimal set of buses and lines
    N = length(r_s)
    tr_t_bus = collect(1:N)
    buses = Set(1:2*N)

    zbr = _sc2br_impedance(zsc)

    edges = [[[i,i+N] for i in 1:N]..., [[i+N,j+N] for (i,j) in keys(zbr)]...]
    lines = Dict(enumerate(edges))

    z = Dict(enumerate([r_s..., values(zbr)...]))

    shunts = Dict(2=>ysh)

    # remove Inf lines
    for (l,edge) in lines
        if real(z[l])==Inf || imag(z[l])==Inf
            delete!(lines, l)
            delete!(z, l)
        end
    end

    # merge short circuits
    stack = Set(keys(lines))

    while !isempty(stack)
        l = pop!(stack)
        if z[l] == 0
            (i,j) = lines[l]

            # remove line
            delete!(lines, l)

            # remove  bus j
            delete!(buses, j)

            # update lines
            for (k,(edge)) in lines
                if edge[1] == j
                    edge[1] = i
                end
                if edge[2] == j
                    edge[2] = i
                end
                if edge[1]==edge[2]
                    delete!(lines, k)
                    delete!(stack, k)
                end
            end

            # move shunts
            if haskey(shunts, j)
                if haskey(shunts, i)
                    shunts[i] += shunts[j]
                else
                    shunts[i] = shunts[j]
                end
            end

            # update transformer buses
            for w in 1:N
                if tr_t_bus[w] == j
                    tr_t_bus[w] = i
                end
            end
        end
    end

    bus_ids = Dict{Int,Int}()
    for bus in buses
        bus_obj = Dict{String,Any}(
            "name" => "_virtual_bus.transformer.$(transformer_name)_$(bus)",
            "bus_i" => length(data_math["bus"])+1,
            "vmin" => fill(0.0, nphases),
            "vmax" => fill(Inf, nphases),
            "vm_pair_lb" => Tuple{Any,Any,Real}[],
            "vm_pair_ub" => Tuple{Any,Any,Real}[],
            "terminals" => connections[collect(1:nphases)],
            "grounded" => fill(false, nphases),
            "base_kv" => 1.0,
            "bus_type" => status == 0 ? 4 : 1,
            "source_id" => "transformer.$(transformer_name)",
            "index" => length(data_math["bus"])+1,
        )

        if !get(data_math, "is_kron_reduced", false)
            if bus in tr_t_bus
                bus_obj["terminals"] = collect(1:nphases+1)
                bus_obj["vmin"] = fill(0.0, nphases+1)
                bus_obj["vmax"] = fill(Inf, nphases+1)
                bus_obj["grounded"] = [fill(false, nphases)..., true]
                bus_obj["rg"] = [0.0]
                bus_obj["xg"] = [0.0]
            else
                bus_obj["terminals"] = collect(1:nphases)
                bus_obj["vmin"] = fill(0.0, nphases)
                bus_obj["vmax"] = fill(Inf, nphases)
            end
        end

        data_math["bus"]["$(bus_obj["index"])"] = bus_obj

        bus_ids[bus] = bus_obj["bus_i"]

        push!(to_map, "bus.$(bus_obj["index"])")
    end

    for (l,(i,j)) in lines
        # merge the shunts into the shunts of the pi model of the line
        g_fr = b_fr = g_to = b_to = 0

        if haskey(shunts, i)
            g_fr = real(shunts[i])
            b_fr = imag(shunts[i])
            delete!(shunts, i)
        end

        if haskey(shunts, j)
            g_to = real(shunts[j])
            b_to = imag(shunts[j])
            delete!(shunts, j)
        end

        branch_obj = Dict{String,Any}(
            "name" => "_virtual_branch.transformer.$(transformer_name)_$(l)",
            "source_id" => "_virtual_branch.transformer.$(transformer_name)_$(l)",
            "index" => length(data_math["branch"])+1,
            "br_status"=>status,
            "f_bus"=>bus_ids[i],
            "t_bus"=>bus_ids[j],
            "f_connections"=>data_math["bus"]["$(bus_ids[i])"]["terminals"][collect(1:nphases)],
            "t_connections"=>data_math["bus"]["$(bus_ids[j])"]["terminals"][collect(1:nphases)],
            "br_r" => LinearAlgebra.diagm(0=>fill(real(z[l]), nphases)),
            "br_x" => LinearAlgebra.diagm(0=>fill(imag(z[l]), nphases)),
            "g_fr" => LinearAlgebra.diagm(0=>fill(g_fr, nphases)),
            "b_fr" => LinearAlgebra.diagm(0=>fill(b_fr, nphases)),
            "g_to" => LinearAlgebra.diagm(0=>fill(g_to, nphases)),
            "b_to" => LinearAlgebra.diagm(0=>fill(b_to, nphases)),
            "angmin" => fill(-10.0, nphases),
            "angmax" => fill( 10.0, nphases),
            "c_rating_a" => fill(Inf, nphases),
            "shift" => zeros(nphases),
            "tap" => ones(nphases),
            "switch" => false,
            "transformer" => false,
        )

        data_math["branch"]["$(branch_obj["index"])"] = branch_obj

        push!(to_map, "branch.$(branch_obj["index"])")
    end

    return Vector{Int}([bus_ids[bus] for bus in tr_t_bus])
end


"performs kron reduction on branch"
function _kron_reduce_branch!(object::Dict{String,<:Any}, Zs_keys::Vector{String}, Ys_keys::Vector{String}, terminals::Vector{Int}, neutral::Int)::Vector{Int}
    Zs = Vector{Matrix}([object[k] for k in Zs_keys])
    Ys = Vector{Matrix}([object[k] for k in Ys_keys])
    Zs_kr, Ys_kr, terminals_kr = _kron_reduce_branch(Zs, Ys, terminals, neutral)

    for (i,k) in enumerate(Zs_keys)
        object[k] = Zs_kr[i]
    end

    for (i,k) in enumerate(Ys_keys)
        object[k] = Ys_kr[i]
    end

    return _get_idxs(terminals, terminals_kr)
end


"get locations of terminal in connections list"
function _get_ilocs(vec::Vector{<:Any}, loc::Any)::Vector{Int}
    return collect(1:length(vec))[vec.==loc]
end


"performs kron reduction on branch - helper function"
function _kron_reduce_branch(Zs::Vector{Matrix}, Ys::Vector{Matrix}, terminals::Vector{Int}, neutral::Int)::Tuple{Vector{Matrix}, Vector{Matrix}, Vector{Int}}
    Zs_kr = Vector{Matrix}([deepcopy(Z) for Z in Zs])
    Ys_kr = Vector{Matrix}([deepcopy(Y) for Y in Ys])
    terminals_kr = deepcopy(terminals)

    while neutral in terminals_kr
        n = _get_ilocs(terminals_kr, neutral)[1]
        P = setdiff(collect(1:length(terminals_kr)), n)

        if all(size(Z) == (length(terminals_kr), length(terminals_kr)) for Z in Zs_kr)
            Zs_kr = Vector{Matrix}([Z[P,P]-(1/Z[n,n])*Z[P,[n]]*Z[[n],P] for Z in Zs_kr])
            Ys_kr = Vector{Matrix}([Y[P,P] for Y in Ys_kr])
        end

        terminals_kr = terminals_kr[P]
    end

    return Zs_kr, Ys_kr, terminals_kr
end


"pads properties to have the total number of conductors for the whole system"
function _pad_properties!(object::Dict{String,<:Any}, properties::Vector{String}, connections::Vector{Int}, phases::Vector{Int}; pad_value::Real=0.0)
    @assert(all(c in phases for c in connections))
    inds = _get_idxs(phases, connections)

    for property in properties
        if haskey(object, property)
            if isa(object[property], Vector)
                tmp = fill(pad_value, length(phases))
                tmp[inds] = object[property]
                object[property] = tmp
            elseif isa(object[property], Matrix)
                tmp = fill(pad_value, length(phases), length(phases))
                tmp[inds, inds] = object[property]
                object[property] = tmp
            end
        end
    end
end


"pads properties to have the total number of conductors for the whole system (transformer winding variant)"
function _pad_properties!(object::Dict{String,<:Any}, properties::Vector{String}, wdg::Int, connections::Vector{Int}, phases::Vector{Int}; pad_value::Real=0.0)
    @assert(all(c in phases for c in connections))
    inds = _get_idxs(phases, connections)

    for property in properties
        if haskey(object, property)
            if isa(object[property][wdg], Vector)
                tmp = fill(pad_value, length(phases))
                tmp[inds] = object[property][wdg]
                object[property][wdg] = tmp
            elseif isa(object[property][wdg], Matrix)
                tmp = fill(pad_value, length(phases), length(phases))
                tmp[inds, inds] = object[property][wdg]
                object[property][wdg] = tmp
            end
        end
    end
end


"pads properties to have the total number of conductors for the whole system - delta connection variant"
function _pad_properties_delta!(object::Dict{String,<:Any}, properties::Vector{String}, connections::Vector{Int}, phases::Vector{Int}; invert::Bool=false)
    @assert(all(c in phases for c in connections))
    @assert(length(connections) in [2, 3], "A delta configuration has to have at least 2 or 3 connections!")
    @assert(length(phases)==3, "Padding only possible to a |phases|==3!")

    for property in properties
        if haskey(object, property)
            val = object[property]
            val_length = length(connections)==2 ? 1 : length(connections)
            @assert(isa(val, Vector) && length(val)==val_length)

            # build tmp
            tmp = Dict()
            sign = invert ? -1 : 1
            if val_length==1
                tmp[(connections[1], connections[2])] =      val[1]
                tmp[(connections[2], connections[1])] = sign*val[1]
            else
                tmp[(connections[1], connections[2])] =      val[1]
                tmp[(connections[2], connections[3])] =      val[2]
                tmp[(connections[3], connections[1])] =      val[3]
            end
            merge!(tmp, Dict((k[2], k[1])=>sign*v for (k,v) in tmp))
            get_val(x,y) = haskey(tmp, (x,y)) ? tmp[(x,y)] : 0.0

            object[property] = val_length==1 ? [get_val(connections[1], connections[2]), 0.0,0.0] : [get_val(phases[1], phases[2]), get_val(phases[2], phases[3]), get_val(phases[3], phases[1])]
        end
    end
end


"pads properties to have the total number of conductors for the whole system - delta connection variant"
function _pad_properties_delta!(object::Dict{String,<:Any}, properties::Vector{String}, connections::Vector{Int}, wdg::Int, phases::Vector{Int}; invert::Bool=false)
    @assert(all(c in phases for c in connections))
    @assert(length(connections) in [2, 3], "A delta configuration has to have at least 2 or 3 connections!")
    @assert(length(phases)==3, "Padding only possible to a |phases|==3!")

    for property in properties
        if haskey(object, property)
            val = object[property][wdg]
            val_length = length(connections)==2 ? 1 : length(connections)
            @assert(isa(val, Vector) && length(val)==val_length)

            # build tmp
            tmp = Dict()
            sign = invert ? -1 : 1
            if val_length==1
                tmp[(connections[1], connections[2])] =      val[1]
                tmp[(connections[2], connections[1])] = sign*val[1]
            else
                tmp[(connections[1], connections[2])] =      val[1]
                tmp[(connections[2], connections[3])] =      val[2]
                tmp[(connections[3], connections[1])] =      val[3]
            end
            merge!(tmp, Dict((k[2], k[1])=>sign*v for (k,v) in tmp))
            get_val(x,y) = haskey(tmp, (x,y)) ? tmp[(x,y)] : 0.0

            object[property][wdg] = [get_val(phases[1], phases[2]), get_val(phases[2], phases[3]), get_val(phases[3], phases[1])]
        end
    end
end


"Filters out values of a vector or matrix for certain properties"
function _apply_filter!(obj::Dict{String,<:Any}, properties::Vector{String}, filter::Union{Array,BitArray})
    for property in properties
        if haskey(obj, property)
            if isa(obj[property], Vector)
                obj[property] = obj[property][filter]
            elseif isa(obj[property], Matrix)
                obj[property] = obj[property][filter, filter]
            else
                error("The property $property is not a Vector or a Matrix!")
            end
        end
    end
end


"Filters out values of a vector or matrix for certain properties (transformer winding variant)"
function _apply_filter!(obj::Dict{String,<:Any}, properties::Vector{String}, wdg::Int, filter::Union{Array,BitArray})
    for property in properties
        if haskey(obj, property)
            if isa(obj[property], Vector)
                obj[property][wdg] = obj[property][wdg][filter]
            elseif isa(obj[property], Matrix)
                obj[property][wdg] = obj[property][wdg][filter, filter]
            else
                error("The property $property is not a Vector or a Matrix!")
            end
        end
    end
end


"""
Given a set of addmittances 'y' connected from the conductors 'f_cnds' to the
conductors 't_cnds', this method will return a list of conductors 'cnd' and a
matrix 'Y', which will satisfy I[cnds] = Y*V[cnds].
"""
function _calc_shunt(f_cnds::Vector{Int}, t_cnds::Vector{Int}, y::Vector{<:Union{Real,Vector{<:Real}}})::Tuple{Vector{Int}, Matrix{Real}}
    cnds = unique([f_cnds..., t_cnds...])
    e(f,t) = reshape([c==f ? 1 : c==t ? -1 : 0 for c in cnds], length(cnds), 1)
    Y = sum([e(f_cnds[i], t_cnds[i])*y[i]*e(f_cnds[i], t_cnds[i])' for (i,_y) in enumerate(y)])
    return (cnds, Y)
end


"""
Given a set of terminals 'cnds' with associated shunt admittance 'Y', this
method will calculate the reduced admittance matrix if terminal 'ground' is
grounded.
"""
function _calc_ground_shunt_admittance_matrix(cnds::Vector{Int}, Y::Matrix{T}, ground::Int)::Tuple{Vector{Int}, Matrix{T}} where T <: Number
    if ground in cnds
        cndsr = setdiff(cnds, ground)
        cndsr_inds = _get_idxs(cnds, cndsr)
        Yr = Y[cndsr_inds, cndsr_inds]
        return (cndsr, Yr)
    else
        return cnds, Y
    end
end


"initialization actions for unmapping"
function _init_unmap_eng_obj!(data_eng::Dict{String,<:Any}, eng_obj_type::String, map::Dict{String,<:Any})::Dict{String,Any}
    if !haskey(data_eng, eng_obj_type)
        data_eng[eng_obj_type] = Dict{String,Any}()
    end

    eng_obj = Dict{String,Any}()

    return eng_obj
end


"returns component from the mathematical data model"
function _get_math_obj(data_math::Dict{String,<:Any}, to_id::String)::Dict{String,Any}
    math_type, math_id = split(to_id, '.')
    return haskey(data_math, math_type) && haskey(data_math[math_type], math_id) ? data_math[math_type][math_id] : Dict{String,Any}()
end


"convert cost model names"
function _add_gen_cost_model!(math_obj::Dict{String,<:Any}, eng_obj::Dict{String,<:Any})
    math_obj["model"] = get(eng_obj, "cost_pg_model", 2)
    math_obj["startup"] = 0.0
    math_obj["shutdown"] = 0.0
    math_obj["cost"] = get(eng_obj, "cost_pg_parameters", [1.0, 0.0])
    math_obj["ncost"] = length(math_obj["cost"])
end


"applies a xfmrcode to a transformer in preparation for converting to mathematical model"
function _apply_xfmrcode!(eng_obj::Dict{String,<:Any}, data_eng::Dict{String,<:Any})
    if haskey(eng_obj, "xfmrcode") && haskey(data_eng, "xfmrcode") && haskey(data_eng["xfmrcode"], eng_obj["xfmrcode"])
        xfmrcode = data_eng["xfmrcode"][eng_obj["xfmrcode"]]

        for (k, v) in xfmrcode
            if !haskey(eng_obj, k)
                eng_obj[k] = deepcopy(v)
            elseif haskey(eng_obj, k) && k in ["vm_nom", "sm_nom", "tm_set", "rw"]
                for (w, vw) in enumerate(eng_obj[k])
                    if ismissing(vw)
                        eng_obj[k][w] = deepcopy(v[w])
                    end
                end
            end
        end
    end
end


"applies a linecode to a line in preparation for converting to mathematical model"
function _apply_linecode!(eng_obj::Dict{String,<:Any}, data_eng::Dict{String,<:Any})
    if haskey(eng_obj, "linecode") && haskey(data_eng, "linecode") && haskey(data_eng["linecode"], eng_obj["linecode"])
        linecode = data_eng["linecode"][eng_obj["linecode"]]

        for property in ["rs", "xs", "g_fr", "g_to", "b_fr", "b_to", "cm_ub", "sm_ub"]
            if !haskey(eng_obj, property) && haskey(linecode, property)
                eng_obj[property] = deepcopy(linecode[property])
            end
        end
    end
end


"converts impendance in Ohm/m by multiplying by length"
function _impedance_conversion(data_eng::Dict{String,<:Any}, eng_obj::Dict{String,<:Any}, key::String)
    eng_obj[key] .* get(eng_obj, "length", 1.0)
end


"converts admittance by multiplying by 2πωl"
function _admittance_conversion(data_eng::Dict{String,<:Any}, eng_obj::Dict{String,<:Any}, key::String)
    2.0 .* pi .* data_eng["settings"]["base_frequency"] .* eng_obj[key] .* get(eng_obj, "length", 1.0) ./ 1e9
end


"lossy grounding to perfect grounding and shunts"
function _convert_grounding(terminals, grounded, rg, xg)
    grouped = Dict(t=>[] for t in unique(grounded))
    for (i,t) in enumerate(grounded)
        push!(grouped[t], rg[i]+im*xg[i])
    end
    t_lookup = Dict(t=>i for (i,t) in enumerate(terminals))
    grounded_lossless = fill(false, length(terminals))
    shunts = []
    for (t, zgs) in grouped
        if any(iszero.(zgs))
            grounded_lossless[t_lookup[t]] = true
        else
            ygs = 1 ./zgs
            yg = sum(ygs)
            push!(shunts, ([t], [yg]))
        end
    end
    return grounded_lossless, shunts
end


"slices branches based on connected terminals"
function _slice_branches!(data_math::Dict{String,<:Any})
    for (_, branch) in data_math["branch"]
        if haskey(branch, "f_connections")
            N = length(branch["f_connections"])
            for prop in ["br_r", "br_x", "g_fr", "g_to", "b_fr", "b_to"]
                branch[prop] = branch[prop][1:N,1:N]
            end
        end
    end
end


"finds maximal set of ungrounded phases"
function _get_complete_conductor_set(data::Dict{String,<:Any})
    conductors = Set([])
    for (_, obj) in data["bus"]
        for t in obj["terminals"]
            push!(conductors, t)
        end
    end

    return sort([c for c in conductors])
end


"checks if data structures are equivalent, and if not, will enumerate the differences"
function _check_equal(data1::Dict{String,<:Any}, data2::Dict{String,<:Any}; context::String="", ignore::Vector{String}=Vector{String}(["connections", "f_connections", "t_connections", "terminals"]))
    lines = []
    for (i, obj) in data1
        if !haskey(data2, i)
            push!(lines, "  $i missing in $data2")
        else
            if obj != data2[i]
                if isa(obj, Dict)
                    push!(lines, _check_equal(obj, data2[i]; context="  $context $i"))
                else
                    if !(i in ignore)
                        push!(lines, "  $context $i: $obj != $(data2[i])")
                    end
                end
            end
        end
    end

    return lines
end


"adds conductors to connections during padding process"
function _pad_connections!(eng_obj::Dict{String,<:Any}, connection_key::String, conductors::Union{Vector{Int},Vector{String}})
    for cond in conductors
        if !(cond in eng_obj[connection_key])
            push!(eng_obj[connection_key], cond)
        end
    end
    return eng_obj[connection_key]
end


"adds conductors to connections during padding process, transformer winding variant"
function _pad_connections!(eng_obj::Dict{String,<:Any}, connection_key::String, wdg::Int, conductors::Union{Vector{Int},Vector{String}})
    for cond in conductors
        if !(cond in eng_obj[connection_key][wdg])
            push!(eng_obj[connection_key][wdg], cond)
        end
    end
end


"helper function to map non integer conductor ids into integers"
function _map_conductor_ids!(data_math::Dict{String,<:Any})
    if all(typeof(c) <: Int for c in data_math["conductor_ids"])
        cnd_map = Dict{Any,Int}(c => c for c in data_math["conductor_ids"])
    else
        cnd_map = Dict{Any,Int}(c => idx for (idx, c) in enumerate(data_math["conductor_ids"]))
    end

    data_math["conductor_ids"] = Vector{Int}([cnd_map[c] for c in data_math["conductor_ids"]])

    for type in ["branch", "switch", "transformer"]
        if haskey(data_math, type)
            for (_,obj) in data_math[type]
                obj["f_connections"] = Vector{Int}([cnd_map[c] for c in obj["f_connections"]])
                obj["t_connections"] = Vector{Int}([cnd_map[c] for c in obj["t_connections"]])
            end
        end
    end

    for type in ["load", "shunt", "gen", "storage"]
        if haskey(data_math, type)
            for (_,obj) in data_math[type]
                obj["connections"] = Vector{Int}([cnd_map[c] for c in obj["connections"]])
            end
        end
    end

    for (_,bus) in data_math["bus"]
        bus["terminals"] = Vector{Int}([cnd_map[t] for t in bus["terminals"]])
    end
end


"""
Returns the tightest set of pairwise voltage magnitude bounds,
removing looser bounds which are implied by the tighter ones.
"""
function _get_tight_pairwise_voltage_magnitude_bounds(bus::Dict)
    lb_pairs = Tuple{Any,Any,Real}[]
    ub_pairs = Tuple{Any,Any,Real}[]

    haskey(bus, "vm_pair_lb") && append!(lb_pairs, bus["vm_pair_lb"])
    haskey(bus, "vm_pair_ub") && append!(ub_pairs, bus["vm_pair_ub"])

    haskey(bus, "vm_pn_lb") && append!(lb_pairs, [(p, bus["neutral"], bus["vm_pn_lb"]) for p in bus["phases"]])
    haskey(bus, "vm_pn_ub") && append!(ub_pairs, [(p, bus["neutral"], bus["vm_pn_ub"]) for p in bus["phases"]])

    haskey(bus, "vm_pp_lb") && append!(lb_pairs, [(bus["phases"][i], bus["phases"][j], bus["vm_pp_lb"]) for i in 1:length(bus["phases"]) for j in i+1:length(bus["phases"])])
    haskey(bus, "vm_pp_ub") && append!(ub_pairs, [(bus["phases"][i], bus["phases"][j], bus["vm_pp_ub"]) for i in 1:length(bus["phases"]) for j in i+1:length(bus["phases"])])

    lb_pairs_tight = Tuple{Any,Any,Real}[]
    for (c,d) in unique([(min(n,m), max(n,m)) for (n,m,bound) in lb_pairs])
        bound = maximum([bound for (n,m,bound) in lb_pairs if (n==c&&m==d) || (n==d&&m==c)])
        push!(lb_pairs_tight, (c, d, bound))
    end

    ub_pairs_tight = Tuple{Any,Any,Real}[]
    for (c,d) in unique([(min(n,m), max(n,m)) for (n,m,b) in ub_pairs])
        bound = minimum([bound for (n,m,bound) in ub_pairs if (n==c&&m==d) || (n==d&&m==c)])
        push!(ub_pairs_tight, (c, d, bound))
    end

    return lb_pairs_tight, ub_pairs_tight
end


"""
Returns the tightest set of absolute voltage magnitude bounds,
removing looser bounds which are implied by the tighter ones.
"""
function _get_tight_absolute_voltage_magnitude_bounds(bus::Dict)
    N = length(bus["terminals"])
    vmin = haskey(bus, "vm_lb") ? bus["vm_lb"] : fill(0.0, N)
    vmax = haskey(bus, "vm_ub") ? bus["vm_ub"] : fill(Inf, N)

    if haskey(bus, "vm_ng_ub")
        idx = findfirst(bus["terminals"].==bus["neutral"])
        vmax[idx] = min(vmax[idx], bus["vm_ng_ub"])
    end

    return vmin, vmax
end


"""
When a terminal is grounded, any pairwise bounds it occurs in
imply an absolute bound for the other terminal in the pair.
This method converts such pairwise bounds to absolute ones.
"""
function _add_implicit_absolute_bounds!(bus_math, terminals::Vector)
    grounded_terminals = terminals[bus_math["grounded"]]

    vm_pair_lb = bus_math["vm_pair_lb"]
    vm_pair_ub = bus_math["vm_pair_ub"]
    vmin = bus_math["vmin"]
    vmax = bus_math["vmax"]

    lb_keep_idx = []
    for (i,(a,b,lb)) in enumerate(vm_pair_lb)
        if a in grounded_terminals
            b_idx = findfirst(terminals.==b)
            vmin[b_idx] = max(vmin[b_idx],lb)
        elseif b in grounded_terminals
            a_idx = findfirst(terminals.==a)
            vmin[a_idx] = max(vmin[a_idx],lb)
        else
            push!(lb_keep_idx, i)
        end
    end

    ub_keep_idx = []
    for (i,(a,b,ub)) in enumerate(vm_pair_ub)
        if a in grounded_terminals
            b_idx = findfirst(terminals.==b)
            vmax[b_idx] = min(vmax[b_idx],ub)
        elseif b in grounded_terminals
            a_idx = findfirst(terminals.==a)
            vmax[a_idx] = min(vmax[a_idx],ub)
        else
            push!(ub_keep_idx, i)
        end
    end

    bus_math["vmin"] = vmin
    bus_math["vmax"] = vmax
    bus_math["vm_pair_lb"] = vm_pair_lb[lb_keep_idx]
    bus_math["vm_pair_ub"] = vm_pair_ub[ub_keep_idx]
end


"computes the bus type based on existing bus_type, the status of the generation object, and the control_mode"
function _compute_bus_type(existing_bus_type::Int, gen_status::Int, control_mode::Int)::Int
    bus_type = existing_bus_type

    if gen_status == Int(ENABLED) && bus_type != pmd_math_component_status_inactive["bus"]
        if control_mode == Int(ISOCHRONOUS)
            bus_type = 3
        else
            if bus_type != 3
                bus_type = 2
            end
        end
    end

    return bus_type
end