import { describe, expect, it } from "vitest";
import { contrastRatio, readableColor } from "@/lib/theme-contrast";
import { PRESETS } from "@/lib/theme-presets";

describe("contrastRatio", () => {
  it("calculates the WCAG ratio for black on white", () => {
    expect(contrastRatio("#000000", "#ffffff")).toBe(21);
  });

  it("returns null for unsupported color formats", () => {
    expect(contrastRatio("var(--color-text)", "#ffffff")).toBeNull();
  });
});

describe("built-in theme presets", () => {
  it("derives WCAG-readable public foregrounds for every palette", () => {
    for (const preset of Object.values(PRESETS)) {
      const backgrounds = [preset.color_background, preset.color_surface];
      const foregrounds = [
        readableColor(preset.color_text, backgrounds),
        readableColor(preset.color_text_muted, backgrounds),
        readableColor(preset.color_primary, backgrounds),
        readableColor(preset.color_accent, backgrounds),
      ];

      for (const foreground of foregrounds) {
        for (const background of backgrounds) {
          expect(contrastRatio(foreground, background)).toBeGreaterThanOrEqual(4.5);
        }
      }

      const buttonText = readableColor(preset.button_text_color, [preset.button_primary_color]);
      expect(contrastRatio(buttonText, preset.button_primary_color)).toBeGreaterThanOrEqual(4.5);

      const primaryForeground = readableColor(preset.button_text_color, [preset.color_primary]);
      expect(contrastRatio(primaryForeground, preset.color_primary)).toBeGreaterThanOrEqual(4.5);
    }
  });

  it.each(["#22c55e", "#ef4444"])("derives readable text for default button %s", (background) => {
    const foreground = readableColor("#ffffff", [background]);
    expect(contrastRatio(foreground, background)).toBeGreaterThanOrEqual(4.5);
  });
});

describe("readableColor", () => {
  it("keeps the preferred color when it passes on every background", () => {
    expect(readableColor("#0f172a", ["#ffffff", "#f8fafc"], 4.5)).toBe("#0f172a");
  });

  it("replaces low-contrast golden text with a readable neutral", () => {
    const color = readableColor("#f59e0b", ["#ffffff", "#f8fafc"], 4.5);

    expect(color).toBe("#000000");
    expect(contrastRatio(color, "#ffffff")).toBeGreaterThanOrEqual(4.5);
    expect(contrastRatio(color, "#f8fafc")).toBeGreaterThanOrEqual(4.5);
  });

  it("chooses white text for a dark button when configured text fails", () => {
    expect(readableColor("#777777", ["#111827"], 4.5)).toBe("#ffffff");
  });

  it("preserves unsupported custom colors instead of corrupting CSS", () => {
    expect(readableColor("rgb(1, 2, 3)", ["#ffffff"], 4.5)).toBe("rgb(1, 2, 3)");
  });
});