# This is a module for 8.08 - 8.S308 numerics recitation.
module Rec
    #parameters of the model
    mutable struct Param
        L::Int64                # number of sites
        epsilon::Float64        # small hopping rate
    end

    #constructor
    function setParam(L, epsilon)

        param = Param(L, epsilon)
        return param
    end


    #state variables of the model
    mutable struct State
        t::Float64              # current time
        position::Int8          # occupancy field
    end

    #constructor
    function setState(param)
        position = 1
        state = State(0.0, position)
        return state
    end
end

function tower_sampling(w, W, rng)

    ### Implement your tower sampling algorithm
    index = 1
    
    return index
end

function run_simulation!(state, param, n_run, rng)

    t_now = state.t                         # time at the beginning of your simulation
    L, epsilon = param.L, param.epsilon     # loading parameters


    move = 0    # type of your move

    w = zeros(Float64, 2)   # transition rates
    W = 0.0                 # sum of the transition rates
    tau = 0.0               # time sampled

    # move 1: move clockwise, 3->2->1->3
    # move 2: move counter clockwise, 1->2->3->1

    # position 1: move to 2 with a rate 1, move to 3 with a rate epsilon
    # position 2: move to 3 with a rate 1, move to 1 with a rate epsilon

    # position 3: move to 1 with a rtae epsilon, move to 2 with a rate epsilon

    ### write down transition rates
    if state.position==1 || state.position==2
        w[1] =    # rate for move 1
        w[2] =    # rate for move 2
    else
        w[1] =    # rate for move 1
        w[2] =    # rate for move 2
    end

    W = sum(w)

    for i_run in 1:n_run
        ### get time
        tau = 

        # gamble and get your move
        move = tower_sampling(w, W, rng)

        ### write down how your state would change
        if move==1
            # move clockwise, 3->2->1->3
            state.position = 
        else
            # move counter clockwise, 1->2->3->1
            state.position =
        end

        ### write down transition rates
        if state.position==1 || state.position==2
            w[1] =    # rate for move 1
            w[2] =    # rate for move 2
        else
            w[1] =    # rate for move 1
            w[2] =    # rate for move 2
        end
    
        W = sum(w)

        state.t += tau
    end
end

function get_movie!(state, param, rng, n_gap, n_frame, in_fps)

    # arrays for recording time and the number of hopping
    time_array = zeros(Float64, 2*n_frame+1)
    hopping_array = zeros(Int64, 2*n_frame+1)

    # initialize
    time_array[1] = state.t
    hopping_array[1] = 0

    current_position = state.position    

    move = 0

    anim = @animate for frame in 1:n_frame
        run_simulation!(state, param, n_gap, rng)

        # count the number of counter-clockwise move
        if mod(state.position - current_position,3)==1
            move = 1
        else
            move = -1
        end

        current_position = state.position

        time_array[2frame] = state.t
        time_array[2frame+1] = state.t

        hopping_array[2frame] = hopping_array[2frame-1]
        hopping_array[2frame+1] = hopping_array[2frame] + move

        timetitle = "time = "*string( round(state.t, digits = 1) )
        eps_label = "epsilon = "*string( param.epsilon )

        plot( time_array[1:2frame+1], hopping_array[1:2frame+1], m=(2), legend=:bottomright, label=eps_label, title=timetitle)
        plot!(xlabel = "time", ylabel = "# of counter-clockwise motion")
    end

    name = "Rec11_3state_movie.gif"
    gif(anim, name, fps=in_fps)
end