check-safety/internal/theme/colors.go

package theme

import (
	"fmt"
	"math"
	"strconv"
	"strings"
)

// HSLToHex converts an HSL string like "220 14% 96%" to a hex color like "#f4f5f7".
// This is needed for email templates since email clients don't support CSS variables.
func HSLToHex(hsl string) string {
	h, s, l, err := parseHSL(hsl)
	if err != nil {
		// Return a fallback color on parse error
		return "#000000"
	}

	r, g, b := hslToRGB(h, s, l)
	return fmt.Sprintf("#%02x%02x%02x", r, g, b)
}

// parseHSL parses an HSL string like "220 14% 96%" into h (0-360), s (0-1), l (0-1).
func parseHSL(hsl string) (h, s, l float64, err error) {
	// Trim and normalize spaces
	hsl = strings.TrimSpace(hsl)
	parts := strings.Fields(hsl)

	if len(parts) != 3 {
		return 0, 0, 0, fmt.Errorf("invalid HSL format: expected 3 parts, got %d", len(parts))
	}

	// Parse hue (0-360 degrees)
	h, err = strconv.ParseFloat(parts[0], 64)
	if err != nil {
		return 0, 0, 0, fmt.Errorf("invalid hue value: %s", parts[0])
	}

	// Parse saturation (0-100%)
	satStr := strings.TrimSuffix(parts[1], "%")
	s, err = strconv.ParseFloat(satStr, 64)
	if err != nil {
		return 0, 0, 0, fmt.Errorf("invalid saturation value: %s", parts[1])
	}
	s = s / 100.0 // Convert to 0-1 range

	// Parse lightness (0-100%)
	lightStr := strings.TrimSuffix(parts[2], "%")
	l, err = strconv.ParseFloat(lightStr, 64)
	if err != nil {
		return 0, 0, 0, fmt.Errorf("invalid lightness value: %s", parts[2])
	}
	l = l / 100.0 // Convert to 0-1 range

	return h, s, l, nil
}

// hslToRGB converts HSL values to RGB.
// h: 0-360, s: 0-1, l: 0-1
// Returns r, g, b in 0-255 range.
func hslToRGB(h, s, l float64) (r, g, b uint8) {
	// Normalize hue to 0-1 range
	h = h / 360.0

	var rFloat, gFloat, bFloat float64

	if s == 0 {
		// Achromatic (gray)
		rFloat = l
		gFloat = l
		bFloat = l
	} else {
		var q float64
		if l < 0.5 {
			q = l * (1 + s)
		} else {
			q = l + s - l*s
		}
		p := 2*l - q

		rFloat = hueToRGB(p, q, h+1.0/3.0)
		gFloat = hueToRGB(p, q, h)
		bFloat = hueToRGB(p, q, h-1.0/3.0)
	}

	r = uint8(math.Round(rFloat * 255))
	g = uint8(math.Round(gFloat * 255))
	b = uint8(math.Round(bFloat * 255))

	return r, g, b
}

// hueToRGB is a helper function for HSL to RGB conversion.
func hueToRGB(p, q, t float64) float64 {
	if t < 0 {
		t += 1
	}
	if t > 1 {
		t -= 1
	}

	if t < 1.0/6.0 {
		return p + (q-p)*6*t
	}
	if t < 1.0/2.0 {
		return q
	}
	if t < 2.0/3.0 {
		return p + (q-p)*(2.0/3.0-t)*6
	}
	return p
}

// ThemeColorsToEmail converts theme color settings (stored as HSL) to EmailColors (hex).
// This function takes the color map from theme settings and returns hex colors for email inlining.
func ThemeColorsToEmail(colors map[string]string) map[string]string {
	result := make(map[string]string)

	colorKeys := []string{
		"primary", "primary-foreground",
		"secondary", "secondary-foreground",
		"background", "foreground",
		"muted", "muted-foreground",
		"border",
		"card", "card-foreground",
		"accent", "accent-foreground",
		"destructive", "destructive-foreground",
	}

	for _, key := range colorKeys {
		if hsl, ok := colors[key]; ok && hsl != "" {
			result[key] = HSLToHex(hsl)
		}
	}

	return result
}

// ColorSchemeToEmailColors converts a theme ColorScheme (HSL strings) to hex colors for email inlining.
// Email clients don't support CSS variables, so colors must be inlined as hex.
func ColorSchemeToEmailColors(cs *ColorScheme) EmailColors {
	if cs == nil {
		return EmailColors{}
	}

	return EmailColors{
		Primary:             HSLToHex(cs.Primary),
		PrimaryForeground:   HSLToHex(cs.PrimaryForeground),
		Secondary:           HSLToHex(cs.Secondary),
		SecondaryForeground: HSLToHex(cs.SecondaryForeground),
		Background:          HSLToHex(cs.Background),
		Foreground:          HSLToHex(cs.Foreground),
		Muted:               HSLToHex(cs.Muted),
		MutedForeground:     HSLToHex(cs.MutedForeground),
		Border:              HSLToHex(cs.Border),
		Card:                HSLToHex(cs.Card),
		CardForeground:      HSLToHex(cs.CardForeground),
	}
}

// EmailColors contains theme colors converted to hex for email inlining.
// Mirrors templates.EmailColors structure but lives in theme package for conversion.
type EmailColors struct {
	Primary             string
	PrimaryForeground   string
	Secondary           string
	SecondaryForeground string
	Background          string
	Foreground          string
	Muted               string
	MutedForeground     string
	Border              string
	Card                string
	CardForeground      string
}