to Config struct for configging

config.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"regexp"
+	"slices"
+	"strconv"
+	"strings"
+)
+
+type Config struct {
+	Port int
+	AB   string
+}
+
+func newConfig() (Config, error) {
+	return newConfigFromEnv(os.Getenv)
+}
+
+func newConfigFromEnv(getEnv func(string) string) (Config, error) {
+	def := Config{
+		Port: 8080,
+	}
+
+	var m map[string]any
+	if b, err := json.Marshal(def); err != nil {
+		return Config{}, err
+	} else if err := json.Unmarshal(b, &m); err != nil {
+		return Config{}, err
+	}
+	re := regexp.MustCompile(`[A-Z]`)
+
+	for k, v := range m {
+		envK := k
+		idxes := re.FindAllIndex([]byte(envK), -1)
+		slices.Reverse(idxes)
+		for _, idx := range idxes {
+			if idx[0] > 0 {
+				envK = fmt.Sprintf("%s_%s", envK[:idx[0]], envK[idx[0]:])
+			}
+		}
+		envK = strings.ToUpper(envK)
+		s := getEnv(envK)
+		if s == "" {
+			continue
+		}
+		switch v.(type) {
+		case string:
+			m[k] = s
+		case int64, float64:
+			n, err := strconv.ParseFloat(s, 32)
+			if err != nil {
+				return Config{}, err
+			}
+			m[k] = n
+		}
+	}
+
+	var result Config
+	if b, err := json.Marshal(m); err != nil {
+		return Config{}, err
+	} else if err := json.Unmarshal(b, &result); err != nil {
+		return Config{}, err
+	}
+	return result, nil
+}