m3te/tests/easing.sx

// Easing-toolkit math foundation (P15.1): pin the pure, headless easing curves in
// board_anim.sx that the organic-animation pass (P16/P17/P18) builds on. NO render
// code calls these yet, so this test is the only consumer — it locks, for each
// curve: the endpoints f(0)/f(1) (and f(0.5) where it's a fixed point), the
// overshoot/undershoot range (bounded + tasteful), and monotonicity where the
// curve must not reverse. Mirrors how tests/gem_pose.sx pins the gem poses; prints
// only booleans (no raw floats) so the snapshot is platform-stable.
//
// P16.2 will APPEND illegal-swap bounce-back assertions here: add a new numbered
// section above the final fails check, in the same `print(...); if !x { fails += 1; }`
// shape. No rendering — pure math over board_anim.sx. Failure is a non-zero exit.
#import "modules/std.sx";
#import "board.sx";
#import "board_anim.sx";

// Local f32 abs (the stdlib generic `abs` mis-types its untyped `0` literal under
// f32; the shipped game never calls abs, so the tests roll their own — matches
// tests/gem_pose.sx).
fabs :: (x: f32) -> f32 { if x < 0.0 then 0.0 - x else x }
approx :: (a: f32, b: f32) -> bool { fabs(a - b) < 0.0001 }

main :: () -> s32 {
    fails : s64 = 0;

    // 1. Endpoints are locked: every curve starts/ends exactly on its rest value
    //    (the in/out curves at 1, the spring at 1, the squash envelope at 0).
    print("== endpoints locked ==\n");
    e_in     := ease_in_cubic(0.0) == 0.0 and ease_in_cubic(1.0) == 1.0;
    e_io     := ease_in_out_cubic(0.0) == 0.0 and ease_in_out_cubic(1.0) == 1.0
                and ease_in_out_cubic(0.5) == 0.5;
    e_back   := ease_out_back(0.0) == 0.0 and ease_out_back(1.0) == 1.0;
    e_spring := spring(0.0) == 0.0 and spring(1.0) == 1.0;
    e_squash := squash_envelope(0.0) == 0.0 and squash_envelope(1.0) == 0.0;
    e_exist  := ease_out_cubic(0.0) == 0.0 and ease_out_cubic(1.0) == 1.0
                and ease_in_quad(0.0) == 0.0 and ease_in_quad(1.0) == 1.0;
    print("ease_in {} ease_in_out {} back {} spring {} squash {} existing {}\n",
          e_in, e_io, e_back, e_spring, e_squash, e_exist);
    if !e_in { fails += 1; }
    if !e_io { fails += 1; }
    if !e_back { fails += 1; }
    if !e_spring { fails += 1; }
    if !e_squash { fails += 1; }
    if !e_exist { fails += 1; }

    // 2. Monotonicity where required: the four plain eases never reverse over a
    //    fine sweep of [0,1] (the overshoot/spring/squash curves are exempt — they
    //    are meant to reverse).
    print("== monotonic where required ==\n");
    mono_in := true; mono_io := true; mono_oc := true; mono_iq := true;
    p_in := ease_in_cubic(0.0);
    p_io := ease_in_out_cubic(0.0);
    p_oc := ease_out_cubic(0.0);
    p_iq := ease_in_quad(0.0);
    for 1..21: (i) {
        t := cast(f32) i / 20.0;
        v_in := ease_in_cubic(t);     if v_in < p_in - 0.000001 { mono_in = false; } p_in = v_in;
        v_io := ease_in_out_cubic(t); if v_io < p_io - 0.000001 { mono_io = false; } p_io = v_io;
        v_oc := ease_out_cubic(t);    if v_oc < p_oc - 0.000001 { mono_oc = false; } p_oc = v_oc;
        v_iq := ease_in_quad(t);      if v_iq < p_iq - 0.000001 { mono_iq = false; } p_iq = v_iq;
    }
    print("ease_in {} ease_in_out {} ease_out_cubic {} ease_in_quad {}\n",
          mono_in, mono_io, mono_oc, mono_iq);
    if !mono_in { fails += 1; }
    if !mono_io { fails += 1; }
    if !mono_oc { fails += 1; }
    if !mono_iq { fails += 1; }

    // 3. Back/overshoot + spring: each shoots above 1 then settles to exactly 1,
    //    with a BOUNDED peak (tasteful) and no dip below 0. The spring additionally
    //    wobbles back below 1 after its overshoot (the damped decay).
    print("== overshoot bounded + settles ==\n");
    back_mx := ease_out_back(0.0); back_mn := ease_out_back(0.0);
    spr_mx  := spring(0.0);        spr_mn  := spring(0.0);
    spr_wobble := false;
    for 1..21: (i) {
        t := cast(f32) i / 20.0;
        b := ease_out_back(t);
        if b > back_mx { back_mx = b; }
        if b < back_mn { back_mn = b; }
        s := spring(t);
        if s > spr_mx { spr_mx = s; }
        if s < spr_mn { spr_mn = s; }
        if t > 0.6 and s < 1.0 { spr_wobble = true; }
    }
    back_overshoots := back_mx > 1.0;
    back_bounded    := back_mx < 1.15 and back_mn >= -0.0001;
    spr_overshoots  := spr_mx > 1.0;
    spr_bounded     := spr_mx < 1.25 and spr_mn >= -0.0001;
    print("back_overshoots {} back_bounded {} spring_overshoots {} spring_bounded {} spring_wobbles {}\n",
          back_overshoots, back_bounded, spr_overshoots, spr_bounded, spr_wobble);
    if !back_overshoots { fails += 1; }
    if !back_bounded { fails += 1; }
    if !spr_overshoots { fails += 1; }
    if !spr_bounded { fails += 1; }
    if !spr_wobble { fails += 1; }

    // 4. Squash envelope: rests at both ends, actually moves in between, has both a
    //    squash (positive) and a stretch (negative) lobe, and stays bounded.
    print("== squash envelope bounded ==\n");
    sq_mx : f32 = 0.0; sq_mn : f32 = 0.0; sq_moves := false;
    for 0..21: (i) {
        t := cast(f32) i / 20.0;
        s := squash_envelope(t);
        if s > sq_mx { sq_mx = s; }
        if s < sq_mn { sq_mn = s; }
        if fabs(s) > 0.01 { sq_moves = true; }
    }
    sq_two_sided := sq_mx > 0.0 and sq_mn < 0.0;
    sq_bounded   := sq_mx < 0.75 and sq_mn > -0.75;
    print("squash_moves {} squash_two_sided {} squash_bounded {}\n",
          sq_moves, sq_two_sided, sq_bounded);
    if !sq_moves { fails += 1; }
    if !sq_two_sided { fails += 1; }
    if !sq_bounded { fails += 1; }

    // 5. Illegal-swap bounce-back (P16.2): the springy lunge-and-settle render_swap
    //    plays for a REJECTED swap. Lock its envelope end to end — rests at BOTH
    //    ends (f(0)=f(1)=0, so the move stays purely visual), a SINGLE lunge peak of
    //    exactly BADSWAP_LUNGE_AMP at BADSWAP_LUNGE_T, then a damped settle that
    //    overshoots past rest by a BOUNDED amount and leaves NO residual at t=1.
    print("== illegal-swap bounce ==\n");
    bb_ends := bad_swap_bounce(0.0) == 0.0 and bad_swap_bounce(1.0) == 0.0;
    bb_mx : f32 = 0.0; bb_mx_t : f32 = 0.0; bb_mn : f32 = 0.0;
    for 0..101: (i) {
        t := cast(f32) i / 100.0;
        v := bad_swap_bounce(t);
        if v > bb_mx { bb_mx = v; bb_mx_t = t; }
        if v < bb_mn { bb_mn = v; }
    }
    bb_peak_amp := approx(bb_mx, BADSWAP_LUNGE_AMP);
    bb_peak_loc := fabs(bb_mx_t - BADSWAP_LUNGE_T) < 0.011;
    bb_overshoots := bb_mn < -0.01;            // springs PAST rest after the peak
    bb_overshoot_bounded := bb_mn > -0.12;     // but the recoil stays tasteful
    bb_settles := approx(bad_swap_bounce(1.0), 0.0);   // no residual displacement
    print("bounce_ends {} peak_amp {} peak_loc {} overshoots {} overshoot_bounded {} settles {}\n",
          bb_ends, bb_peak_amp, bb_peak_loc, bb_overshoots, bb_overshoot_bounded, bb_settles);
    if !bb_ends { fails += 1; }
    if !bb_peak_amp { fails += 1; }
    if !bb_peak_loc { fails += 1; }
    if !bb_overshoots { fails += 1; }
    if !bb_overshoot_bounded { fails += 1; }
    if !bb_settles { fails += 1; }

    if fails == 0 {
        print("ok: easing toolkit endpoints locked + amplitudes bounded\n");
        return 0;
    }
    print("FAIL: {} easing checks failed\n", fails);
    return 1;
}