using Plots
using DifferentialEquations

function f(tp)
    t = rem.(tp,5)
    y = 3t .* (t .< 1) .+ (-1/2 * t .+ 7/2) .* ((t .≥ 1) .& (t .< 3))  .+ 2 .* ((t .≥ 3) .& (t .< 4)) .+ (-2x .+ 10) .*((t .≥ 4) .& (t .< 5))
end

function sistem!(dx, x, p, t)
    M1, M2, C1, C2, k1, k2 = p
    F = f(t)
    dx[1] = x[2]
    dx[2] = (1/M1) * (-C1 * x[2] + k1 * x[1] + k2 * (x[1] - x[3]) - F
    dx[3] = x[4]
    dx[4] = (1/M2) * (-C2 * x[4] - k2 * (x[1] - x[3]))
end

params = [2.0, 1.0, 3.0, 6.0, 5.0, 15.0]
pocUsl = [0.0, 0.0, 0.0, 0.0]
interval = (0.0, 10.0)
prob = ODEProblem(sistem!, pocUsl, interval, params)
sol = solve(prob)
brz1 = [sol.u[i][2] for i = 0:length(sol.t)]
brz2 = [sol.u[i][4] for i = 0:length(sol.t)]
plot(sol.t, [brz1, brz2], label = ["v1[t]", "v2[t]"], title = "Brzine", lw = 2, xlabel = "t", ylabel = "v(t)")