package seed

import (
	"testing"

	"github.com/urpi/go-bananas/internal/domain"
	"github.com/urpi/go-bananas/internal/tokenengine"
)

func TestEveryBuiltInThemeValidates(t *testing.T) {
	for _, def := range All() {
		t.Run(def.Slug, func(t *testing.T) {
			theme := def.Theme()
			result := tokenengine.Validate(theme.Tokens)
			if !result.Valid {
				for _, issue := range result.Errors() {
					t.Errorf("%s %s: %s (%s)", issue.Severity, issue.Path, issue.Message, issue.Hint)
				}
				t.Fatal("built-in theme must be valid")
			}
			if result.TokenCount < 50 {
				t.Errorf("theme has only %d tokens; a built-in should be complete", result.TokenCount)
			}
		})
	}
}

func TestEveryBuiltInThemeRendersBothAppearances(t *testing.T) {
	for _, def := range All() {
		t.Run(def.Slug, func(t *testing.T) {
			theme := def.Theme()
			for _, appearance := range []domain.Appearance{domain.AppearanceLight, domain.AppearanceDark} {
				css := tokenengine.Render(theme, tokenengine.RenderOptions{
					Slug:       theme.Slug,
					Appearance: appearance,
					Components: true,
					Derive:     tokenengine.DefaultDerive(),
				})
				if css == "" {
					t.Fatalf("%s/%s rendered an empty stylesheet", theme.Slug, appearance)
				}
				if !contains(css, "--bn-color-semantic-background") {
					t.Errorf("%s/%s is missing the background variable", theme.Slug, appearance)
				}
				if !contains(css, "--bn-color-semantic-text") {
					t.Errorf("%s/%s is missing the text variable", theme.Slug, appearance)
				}
			}
		})
	}
}

func TestBuiltInThemesDeclareDistinctDarkOverrides(t *testing.T) {
	// A theme that declares a dark appearance but supplies no dark overrides
	// would render the light palette in dark mode, which is never intentional.
	for _, def := range All() {
		theme := def.Theme()
		light := tokenengine.Resolve(theme, domain.AppearanceLight)
		dark := tokenengine.Resolve(theme, domain.AppearanceDark)

		lightBG, _ := light.Lookup("color.semantic.background")
		darkBG, _ := dark.Lookup("color.semantic.background")
		if lightBG.CSS == darkBG.CSS {
			t.Errorf("%s: light and dark backgrounds are identical (%s)", def.Slug, lightBG.CSS)
		}
	}
}

func TestTextContrastMeetsAAForEveryBuiltIn(t *testing.T) {
	// This is the check that makes a built-in theme trustworthy: body text must
	// be readable on every surface it is likely to sit on.
	pairs := []struct {
		fgPath, bgPath string
	}{
		{"color.semantic.text", "color.semantic.background"},
		{"color.semantic.text", "color.semantic.surface"},
		{"color.semantic.text", "color.semantic.surface-raised"},
		{"color.semantic.text-muted", "color.semantic.background"},
		{"color.on-primary", "color.semantic.primary"},
		{"color.on-accent", "color.semantic.accent"},
		{"color.on-danger", "color.semantic.danger"},
	}

	for _, def := range All() {
		theme := def.Theme()
		for _, appearance := range []domain.Appearance{domain.AppearanceLight, domain.AppearanceDark} {
			doc := tokenengine.Resolve(theme, appearance)

			for _, pair := range pairs {
				fg, ok := doc.Lookup(pair.fgPath)
				if !ok {
					continue
				}
				bg, ok := doc.Lookup(pair.bgPath)
				if !ok {
					continue
				}
				fgColor, err := tokenengine.ParseColor(fg.CSS)
				if err != nil {
					continue
				}
				bgColor, err := tokenengine.ParseColor(bg.CSS)
				if err != nil {
					continue
				}
				ratio := tokenengine.ContrastRatio(fgColor, bgColor)
				minimum := tokenengine.ContrastAA
				// The high-contrast theme is the escape hatch and is held to the
				// stricter AAA bar instead.
				if def.Slug == "high-contrast" {
					minimum = tokenengine.ContrastAAA
				}
				if ratio < minimum {
					t.Errorf("%s/%s: %s (%s) on %s (%s) = %.2f:1, want at least %.1f:1",
						def.Slug, appearance, pair.fgPath, fg.CSS, pair.bgPath, bg.CSS, ratio, minimum)
				}
			}
		}
	}
}

func TestBuiltInSlugsAreValidAndReservedSafe(t *testing.T) {
	for _, def := range All() {
		if err := domain.ValidateSlug(def.Slug); err != nil {
			t.Errorf("slug %q is invalid: %v", def.Slug, err)
		}
		if _, reserved := domain.ReservedSlugs[def.Slug]; reserved {
			t.Errorf("slug %q collides with a reserved runtime path", def.Slug)
		}
		if def.Appearance == "" {
			t.Errorf("theme %q has no default appearance", def.Slug)
		}
	}
}

func TestBuiltInThemesHaveUniqueIDs(t *testing.T) {
	seen := make(map[string]string)
	for _, theme := range Themes() {
		if previous, dup := seen[theme.ID]; dup {
			t.Errorf("id %q is used by both %q and %q", theme.ID, previous, theme.Slug)
		}
		seen[theme.ID] = theme.Slug
	}
}

func contains(haystack, needle string) bool {
	return len(haystack) >= len(needle) && indexOf(haystack, needle) >= 0
}

func indexOf(haystack, needle string) int {
	for i := 0; i+len(needle) <= len(haystack); i++ {
		if haystack[i:i+len(needle)] == needle {
			return i
		}
	}
	return -1
}