using Pkg
Pkg.add("GLMakie")
Pkg.add("FFMPEG")

using GLMakie
using FFMPEG

GLMakie.activate!()

# --------------------------------------------------
# PARAMETRE
# --------------------------------------------------

R = 1.0
frames = 600
break_frame = 300
vx = 0.01

# --------------------------------------------------
# FIGURE
# --------------------------------------------------

fig = Figure(size = (1200, 600))

ax1 = Axis(
    fig[1,1],
    title = "Orbita + odtrhnutie",
    aspect = DataAspect(),
    limits = (-3,3,-3,3)
)

ax2 = Axis(
    fig[1,2],
    title = "Energia",
    xlabel = "čas",
    ylabel = "E"
)

# --------------------------------------------------
# KRUH
# --------------------------------------------------

θ = range(0, 2π, length=400)
lines!(ax1, R .* cos.(θ), R .* sin.(θ), linewidth=3)

# --------------------------------------------------
# NÁHODNÉ BODY
# --------------------------------------------------

orbit_points = [Point2f(R*cos(2π*rand()), R*sin(2π*rand())) for _ in 1:400]

scatter!(ax1, orbit_points, markersize=6, alpha=0.4)

# --------------------------------------------------
# POHYBLIVÁ BODKA
# --------------------------------------------------

particle_pos = Observable(Point2f(R, 0))
scatter!(ax1, particle_pos, color=:red, markersize=18)

# --------------------------------------------------
# ENERGIA (DÔLEŽITÉ: definované PRED record)
# --------------------------------------------------

energy_data = Point2f[]
energy_points = Observable(Point2f[])

lines!(ax2, energy_points, linewidth=3)

# --------------------------------------------------
# FYZIKA
# --------------------------------------------------

function particle_energy(x, y, vx, vy)
    kinetic = 0.5 * (vx^2 + vy^2)
    r = sqrt(x^2 + y^2)
    potential = -1 / max(r, 0.1)
    return kinetic + potential
end

# --------------------------------------------------
# RECORD DO MP4
# --------------------------------------------------

record(fig, "orbit_detach_energy.gif", 1:frames; framerate=60) do frame

    if frame < break_frame
        angle = 0.03 * frame
        x = R * cos(angle)
        y = R * sin(angle)

        particle_pos[] = Point2f(x, y)

        E = particle_energy(x, y, 0.0, 0.03)

    else
        t = frame - break_frame

        x0 = R * cos(0.03 * break_frame)
        y0 = R * sin(0.03 * break_frame)

        x = x0 + vx * t
        y = y0

        particle_pos[] = Point2f(x, y)

        E = particle_energy(x, y, vx, 0.0)
    end

    # update grafu
    push!(energy_data, Point2f(Float32(frame), Float32(E)))
    energy_points[] = copy(energy_data)

    autolimits!(ax2)
end

println("Hotovo: orbit_detach_energy.mp4")
fig