import { describe, expect, it } from "vitest";
import { contrastRatio, derivePublicForegrounds, 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)");
  });
});

describe("derivePublicForegrounds", () => {
  it.each(Object.entries(PRESETS))("makes every semantic pair readable for %s", (_name, preset) => {
    const result = derivePublicForegrounds(preset);
    for (const pair of result.pairs) {
      expect(contrastRatio(pair.foreground, pair.background), pair.name).toBeGreaterThanOrEqual(4.5);
    }
  });

  it("repairs hostile white-on-white custom colors", () => {
    const result = derivePublicForegrounds({
      color_background: "#ffffff", color_surface: "#ffffff", color_dropdown: "#ffffff",
      color_navbar: "#ffffff", color_navbar_text: "#ffffff", color_text: "#ffffff",
      color_text_muted: "#ffffff", color_primary: "#ffffff", color_accent: "#ffffff",
      button_primary_color: "#ffffff", button_text_color: "#ffffff",
      button_secondary_color: "#ffffff", button_secondary_text_color: "#ffffff",
      button_danger_color: "#ffffff", button_danger_text_color: "#ffffff",
      button_outline_color: "#ffffff", button_outline_text_color: "#ffffff",
      link_color: "#ffffff", link_hover_color: "#ffffff",
    });
    expect(result.pairs.length).toBeGreaterThan(10);
    for (const pair of result.pairs) expect(contrastRatio(pair.foreground, pair.background), pair.name).toBeGreaterThanOrEqual(4.5);
  });
});