add environment variable config

internal/pizza/config.go

@@ -3,6 +3,8 @@ package pizza
 import (
 	"fmt"
 	"os"
+	"strconv"
+	"strings"
 	"time"
 
 	"go.uber.org/zap"
@@ -30,6 +32,8 @@ type Config struct {
 	ShutdownTimeout time.Duration  `yaml:"shutdownTimeout"`
 	Calendar        CalendarConfig `yaml:"calendar"`
 	MetricsPort     int            `yaml:"metricsPort"`
+	UseSQLite       bool           `yaml:"useSQLite"`
+	DBFile          string         `yaml:"dbFile"`
 }
 
 type CalendarConfig struct {
@@ -47,3 +51,48 @@ func LoadConfig(filename string) (Config, error) {
 	err = yaml.Unmarshal(rawBytes, &config)
 	return config, err
 }
+
+func loadStrEnv(name, defaultVal string) string {
+	val, ok := os.LookupEnv(name)
+	if !ok {
+		return defaultVal
+	}
+	return val
+}
+
+func loadBoolEnv(name string, defaultVal bool) bool {
+	val, ok := os.LookupEnv(name)
+	if !ok {
+		return defaultVal
+	}
+	return strings.ToLower(val) == "true" || val == "1"
+}
+
+func loadIntEnv(name string, defaultVal int) int {
+	valStr, ok := os.LookupEnv(name)
+	if !ok {
+		return defaultVal
+	}
+	val, err := strconv.Atoi(valStr)
+	if err != nil {
+		return defaultVal
+	}
+	return val
+}
+
+func LoadConfigEnv(filename string) Config {
+	return Config{
+		Port:            loadIntEnv("PORT", 5000),
+		ReadTimeout:     time.Duration(loadIntEnv("READ_TIMEOUT", 3)) * time.Second,
+		WriteTimeout:    time.Duration(loadIntEnv("WRITE_TIMEOUT", 3)) * time.Second,
+		ShutdownTimeout: time.Duration(loadIntEnv("SHUTDOWN_TIMEOUT", 5)) * time.Second,
+		Calendar: CalendarConfig{
+			CredentialFile: loadStrEnv("CREDENTIAL_FILE", "credentials.json"),
+			TokenFile:      loadStrEnv("TOKEN_FILE", "token.json"),
+			ID:             loadStrEnv("CALENDAR_ID", "primary"),
+		},
+		MetricsPort: loadIntEnv("METRICS_PORT", 5050),
+		UseSQLite:   loadBoolEnv("USE_SQLITE", true),
+		DBFile:      loadStrEnv("DBFILE", "pizza.db"),
+	}
+}