refactor out into packages for easier unit test writing

pkg/style/style.go

@@ -0,0 +1,130 @@
+package style
+
+import (
+	"context"
+	"crypto/md5"
+	"fmt"
+	"net"
+	"strings"
+
+	"github.com/lucasb-eyer/go-colorful"
+	"github.com/rs/zerolog/log"
+)
+
+var pixl = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNkYAAAAAYAAjCB0C8AAAAASUVORK5CYII="
+
+type Key string
+
+func (s Key) Key() interface{} {
+	return s
+}
+
+type Style struct {
+	Avatar,
+	Cover,
+	Background string
+
+	Palette []string
+}
+
+func GetStyle(ctx context.Context, email string) (*Style, error) {
+	log := log.Ctx(ctx)
+
+	avatarHost, styleHost, err := GetSRV(ctx, email)
+	if err != nil {
+		return nil, err
+	}
+	log.Info().Str("avatar", avatarHost).Str("style", styleHost).Msg("getStyle")
+
+	hash := md5.New()
+	email = strings.TrimSpace(strings.ToLower(email))
+	_, _ = hash.Write([]byte(email))
+	id := hash.Sum(nil)
+
+	style := &Style{}
+
+	style.Palette = GetPalette(fmt.Sprintf("#%x", id[:3]))
+	style.Avatar = fmt.Sprintf("https://%s/avatar/%x", avatarHost, id)
+	style.Cover = pixl
+	style.Background = pixl
+
+	if styleHost != "" {
+		style.Cover = fmt.Sprintf("https://%s/cover/%x", styleHost, id)
+		style.Background = fmt.Sprintf("https://%s/bg/%x", styleHost, id)
+	}
+
+	return style, err
+}
+
+func GetSRV(ctx context.Context, email string) (avatar string, style string, err error) {
+
+	// Defaults
+	style = ""
+	avatar = "www.libravatar.org"
+
+	parts := strings.SplitN(email, "@", 2)
+	if _, srv, err := net.DefaultResolver.LookupSRV(ctx, "style-sec", "tcp", parts[1]); err == nil {
+		if len(srv) > 0 {
+			style = strings.TrimSuffix(srv[0].Target, ".")
+			avatar = strings.TrimSuffix(srv[0].Target, ".")
+
+			return avatar, style, err
+		}
+	}
+
+	if _, srv, err := net.DefaultResolver.LookupSRV(ctx, "avatars-sec", "tcp", parts[1]); err == nil {
+		if len(srv) > 0 {
+			avatar = strings.TrimSuffix(srv[0].Target, ".")
+
+			return avatar, style, err
+		}
+	}
+
+	return
+}
+
+// getPalette maes a complementary color palette. https://play.golang.org/p/nBXLUocGsU5
+func GetPalette(hex string) []string {
+	reference, _ := colorful.Hex(hex)
+	reference = sat(lum(reference, 0, .5), 0, .5)
+
+	white := colorful.Color{R: 1, G: 1, B: 1}
+	black := colorful.Color{R: 0, G: 0, B: 0}
+	accentA := hue(reference, 60)
+	accentB := hue(reference, -60)
+	accentC := hue(reference, -180)
+
+	return append(
+		[]string{},
+
+		white.Hex(),
+		lum(reference, .4, .6).Hex(),
+		reference.Hex(),
+		lum(reference, .4, 0).Hex(),
+		black.Hex(),
+
+		lum(accentA, .4, .6).Hex(),
+		accentA.Hex(),
+		lum(accentA, .4, 0).Hex(),
+
+		lum(accentB, .4, .6).Hex(),
+		accentB.Hex(),
+		lum(accentB, .4, 0).Hex(),
+
+		lum(accentC, .4, .6).Hex(),
+		accentC.Hex(),
+		lum(accentC, .4, 0).Hex(),
+	)
+}
+func hue(in colorful.Color, H float64) colorful.Color {
+	h, s, l := in.Hsl()
+	return colorful.Hsl(h+H, s, l)
+}
+func sat(in colorful.Color, S, V float64) colorful.Color {
+	h, s, l := in.Hsl()
+	return colorful.Hsl(h, V+s*S, l)
+}
+func lum(in colorful.Color, L, V float64) colorful.Color {
+	h, s, l := in.Hsl()
+	return colorful.Hsl(h, s, V+l*L)
+}