import math as m
import term
import strings
import time { sleep }

const alt = '.,-~:;=!*#$@'

fn rd(cs int, ls int, a f64,
    b f64) {
    tt_spacing, p_spacing := 0.07, 0.02
    r1, r2, k2 := 1, 2, 5
    k1 := cs * k2 * 2 / (20 * (r1 + r2))
    c_a, s_a := m.cos(a), m.sin(a)
    c_b, s_b := m.cos(b), m.sin(b)
    mut o := [][]rune{len: cs, init: []rune{len: ls, init: ` `}}
    mut z_buffer := [][]f64{len: cs, init: []f64{len: ls, init: 0}}
    for tt := f64(0); tt < 2 * m.pi; tt += tt_spacing {
        c_tt, s_tt := m.cos(tt), m.sin(tt)
        for phi := f64(0); phi < 2 * m.pi; phi += p_spacing {
            c_p, s_p := m.cos(phi), m.sin(phi)
            c_x, c_y := r2 + r1 * c_tt, r1 * s_tt
            x := c_x * (c_b * c_p + s_a * s_b * s_p) - c_y * c_a * s_b
            y := c_x * (s_b * c_p - s_a * c_b * s_p) + c_y * c_a * c_b
            z := k2 + c_a * c_x * s_p + c_y * s_a
            ooz := 1 / z
            xp := int(cs / 2 + k1 * ooz * x)
            yp := int(ls / 2 - k1 * ooz * y)
            l := c_p * c_tt * s_b - c_a * c_tt * s_p - s_a * s_tt +
                c_b * (c_a * s_tt - c_tt * s_a * s_p)
            if l > 0 {
                if xp < 0 || yp < 0 || xp >= cs || yp >= ls {
                    continue
                }
                if ooz > z_buffer[int(xp)][int(yp)] {
                    z_buffer[xp][yp] = ooz
                    lui := int(l * 8)
                    o[xp][yp] = alt[lui]
                }
            }
        }
    }
    mut sb := strings.new_builder(ls * cs)
    print('\x1b[H')
    for j := 0; j < ls; j++ {
        for i := 0; i < cs; i++ {
            sb.write_rune(o[i][j])
        }
        sb.write_rune(`\n`)
    }
    print(sb.str())
}

fn main() {
    term.clear()
    cs, ls := 80, 25
    mut a, mut b := f64(0), f64(0)
    for {
        rd(cs, ls, a, b)
        a += 0.05
        b += 0.07
        sleep(15 * time.millisecond)
    }
}