reasampler/tests/test_theme.cpp

// Standalone tests for reasampler::theme — no REAPER, no LICE, no test framework. Same
// fast assert loop as the sibling pure tests.
//
// The load-bearing test: EVERY text-on-surface pair the kit actually draws clears its WCAG
// floor (AA 4.5:1 body / 3:1 large + state indicators) — the "punch to the floor, not past
// it" rule made testable (brief §1, CONTEXT.md §palette). Plus: the direction constants are
// the single point of change (structural — roleColor is the only color source), the
// interaction-state transform behaves, the WCAG math is correct against known anchors, and
// the Direction C spectral ramp interpolates its endpoints.

#include "../src/theme.h"

#include <cmath>
#include <cstdio>
#include <initializer_list>

using namespace reasampler;

static int g_fail = 0;
#define CHECK(cond) do { if(!(cond)) { \
    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)

// --- WCAG math against known anchors ------------------------------------------

static void testContrastKnownAnchors() {
    const KitColor white{255, 255, 255, 255};
    const KitColor black{0, 0, 0, 255};
    // Black-on-white is the canonical 21:1.
    CHECK(std::fabs(contrastRatio(white, black) - 21.0) < 0.05);
    // Contrast is symmetric (order-independent).
    CHECK(std::fabs(contrastRatio(white, black) - contrastRatio(black, white)) < 1e-9);
    // A color against itself is 1:1 (no contrast).
    CHECK(std::fabs(contrastRatio(white, white) - 1.0) < 1e-9);
    // Luminance ordering: white brightest, black darkest.
    CHECK(relativeLuminance(white) > relativeLuminance(black));
    CHECK(std::fabs(relativeLuminance(black)) < 1e-9);
    CHECK(std::fabs(relativeLuminance(white) - 1.0) < 1e-9);
}

// --- THE load-bearing test: every drawn text-on-surface pair clears its floor -

// The surfaces text lands on (near-black elevation stack).
static void testTextPrimaryClearsBodyFloorOnSurfaces() {
    const KitColor tp = roleColor(Role::TextPrimary);
    // Primary text is body text -> 4.5:1 on every surface it is drawn on.
    CHECK(contrastRatio(tp, roleColor(Role::BgBase))  >= textFloor(TextClass::Body));
    CHECK(contrastRatio(tp, roleColor(Role::BgPanel)) >= textFloor(TextClass::Body));
    CHECK(contrastRatio(tp, roleColor(Role::BgCell))  >= textFloor(TextClass::Body));
}

static void testTextDimClearsItsFloorOnSurfaces() {
    const KitColor td = roleColor(Role::TextDim);
    // Dim/secondary text is used for units/counts (large-ish, low-emphasis) -> the
    // large/state floor 3:1 on the surfaces it appears on. Enforced from the vibrant side:
    // it must not be dimmed BELOW the floor.
    CHECK(contrastRatio(td, roleColor(Role::BgBase))  >= textFloor(TextClass::Large));
    CHECK(contrastRatio(td, roleColor(Role::BgPanel)) >= textFloor(TextClass::Large));
    CHECK(contrastRatio(td, roleColor(Role::BgCell))  >= textFloor(TextClass::Large));
}

static void testAccentClearsStateFloorOnBackground() {
    // The accent is a UI-state indicator (selection border / active fill) -> 3:1 minimum
    // on the base background, "pushed to the floor from the vibrant side".
    CHECK(contrastRatio(roleColor(Role::Accent), roleColor(Role::BgBase))
          >= textFloor(TextClass::Large));
    // The hot (hover) accent is brighter still, so it also clears.
    CHECK(contrastRatio(roleColor(Role::AccentHot), roleColor(Role::BgBase))
          >= textFloor(TextClass::Large));
}

static void testWarnClearsStateFloorOnBackground() {
    // warn (destructive) must be unmistakable -> clears the state floor on the base.
    CHECK(contrastRatio(roleColor(Role::Warn), roleColor(Role::BgBase))
          >= textFloor(TextClass::Large));
}

// Label drawn on an ACTIVE (accent-filled) surface: the shell draws it in bg/base. That
// pairing must also clear the body floor, or active buttons would be unreadable.
static void testLabelOnActiveSurfaceClearsFloor() {
    const KitColor activeFill = roleColorState(Role::BgCell, InteractionState::Active);
    const KitColor labelOnActive = roleColor(Role::BgBase);  // what drawButton uses
    CHECK(contrastRatio(labelOnActive, activeFill) >= textFloor(TextClass::Body));
}

// --- Single point of change (structural guarantee) ----------------------------
//
// roleColor is the ONLY color source; there is no other public accessor that yields a
// palette color, so re-picking the direction is editing the one constants block roleColor
// reads. We assert the roles are DISTINCT (the block actually differentiates them — a
// collapsed/duplicated palette would betray a broken edit) and that the elevation stack
// is monotonic (base darkest -> cell lightest), the invariant the direction must preserve.
static void testRolesAreDistinctAndElevationMonotonic() {
    CHECK(!(roleColor(Role::BgBase) == roleColor(Role::BgPanel)));
    CHECK(!(roleColor(Role::BgPanel) == roleColor(Role::BgCell)));
    CHECK(!(roleColor(Role::TextPrimary) == roleColor(Role::TextDim)));
    CHECK(!(roleColor(Role::Accent) == roleColor(Role::Warn)));
    // Elevation reads as increasing luminance base < panel < cell.
    CHECK(relativeLuminance(roleColor(Role::BgBase)) <
          relativeLuminance(roleColor(Role::BgPanel)));
    CHECK(relativeLuminance(roleColor(Role::BgPanel)) <
          relativeLuminance(roleColor(Role::BgCell)));
    // Primary text is brighter than dim text (the type hierarchy).
    CHECK(relativeLuminance(roleColor(Role::TextPrimary)) >
          relativeLuminance(roleColor(Role::TextDim)));
}

// --- Interaction-state transform ----------------------------------------------

static void testStateRestIsIdentity() {
    for (Role r : {Role::BgBase, Role::BgPanel, Role::BgCell, Role::Accent}) {
        CHECK(roleColorState(r, InteractionState::Rest) == roleColor(r));
    }
}

static void testHoverLightensPressedDarkens() {
    const KitColor rest = roleColor(Role::BgCell);
    const KitColor hover = roleColorState(Role::BgCell, InteractionState::Hover);
    const KitColor pressed = roleColorState(Role::BgCell, InteractionState::Pressed);
    // Hover lightens toward the hot accent; pressed darkens.
    CHECK(relativeLuminance(hover) > relativeLuminance(rest));
    CHECK(relativeLuminance(pressed) < relativeLuminance(rest));
}

static void testActiveIsAccent() {
    CHECK(roleColorState(Role::BgCell, InteractionState::Active) == roleColor(Role::Accent));
}

static void testDisabledDropsAlphaAndDesaturates() {
    const KitColor rest = roleColor(Role::Accent);
    const KitColor dis = roleColorState(Role::Accent, InteractionState::Disabled);
    // Alpha drops to ~40%.
    CHECK(dis.a < rest.a);
    CHECK(dis.a >= 90 && dis.a <= 110);  // 255 * 0.4 ~= 102
}

// --- Direction C spectral ramp ------------------------------------------------

static void testSpectralInterpolatesEndpoints() {
    const KitColor lo = spectralColor(0.0);
    const KitColor hi = spectralColor(1.0);
    // Low is cool (blue-dominant), high is hot (red-dominant) — the identity of the ramp.
    CHECK(lo.b > lo.r);
    CHECK(hi.r > hi.b);
    // Midpoint sits between the endpoints on each channel.
    const KitColor mid = spectralColor(0.5);
    CHECK(mid.r > lo.r && mid.r < hi.r);
    // Clamps out of range.
    CHECK(spectralColor(-1.0) == lo);
    CHECK(spectralColor(2.0) == hi);
}

int main() {
    testContrastKnownAnchors();
    testTextPrimaryClearsBodyFloorOnSurfaces();
    testTextDimClearsItsFloorOnSurfaces();
    testAccentClearsStateFloorOnBackground();
    testWarnClearsStateFloorOnBackground();
    testLabelOnActiveSurfaceClearsFloor();
    testRolesAreDistinctAndElevationMonotonic();
    testStateRestIsIdentity();
    testHoverLightensPressedDarkens();
    testActiveIsAccent();
    testDisabledDropsAlphaAndDesaturates();
    testSpectralInterpolatesEndpoints();

    if (g_fail == 0) std::printf("theme: all tests passed\n");
    else std::printf("theme: %d CHECK(s) FAILED\n", g_fail);
    return g_fail == 0 ? 0 : 1;
}