import DEVS2Agents: time_advance, internal_transition!, external_transition!, confluent_transition!, output!, setup_ports!, format_state, format_message

@enum GenState G_Waiting=1 G_Active=2 G_Passive=3

struct Generate <: DEVSMessage
    activate::UnitRange{Int}
end

@agent struct Generator(AtomicDEVS)
    num_outputs::Int = 1
    period::Float64 = 1.0
    cycles::Int = 1
    current_cycle::Int = 0
    state::GenState = G_Waiting
end

format_state(gen::Generator) = "State.$(gen.state)_Cycle.$(gen.current_cycle)"
format_message(msg::Generate) = "$(msg.activate)"

function setup_ports!(gen::Generator)
    add_out_port!(gen, :o_out)
end

function time_advance(gen::Generator, model)
    if gen.state == G_Active
        return 0.0
    elseif gen.state == G_Waiting
        return gen.period
    else
        return Inf
    end
end

function internal_transition!(gen::Generator, model)
    if gen.current_cycle >= gen.cycles
        gen.state = G_Passive
    elseif gen.state == G_Active
        gen.state = G_Waiting
        gen.current_cycle += 1
    elseif gen.state == G_Waiting
        gen.state = G_Active
    else
        gen.state = Passive
    end
end

function output!(gen::Generator, model)
    if gen.state == G_Active
        return (
            (
                :o_out, (Generate(0:(gen.num_outputs - 1)),
            )),
        )
    end
    return nothing
end