chore: initial commit

internal/pkg/config/config.go

@@ -0,0 +1,70 @@
+// Copyright (C) 2024 Declan Teevan
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package config
+
+import (
+	"os"
+
+	"github.com/hexolan/stocklet/internal/pkg/errors"
+)
+
+// Load an option from an environment variable
+func loadFromEnv(name string) *string {
+	value, exists := os.LookupEnv(name)
+	if !exists || value == "" {
+		return nil
+	}
+
+	return &value
+}
+
+// Require an option from an environment variable
+func RequireFromEnv(name string) (string, error) {
+	value := loadFromEnv(name)
+	if value == nil {
+		return "", errors.NewServiceErrorf(errors.ErrCodeService, "failed to load required cfg option (%s)", name)
+	}
+
+	return *value, nil
+}
+
+// Shared configuration implemented by all services
+type SharedConfig struct {
+	// Env Var: "MODE" (optional)
+	// 'dev' or 'development' -> true
+	// Defaults to false
+	DevMode bool
+
+	Otel OtelConfig
+}
+
+// Load the options in the shared config
+func (cfg *SharedConfig) Load() error {
+	// Determine application mode
+	cfg.DevMode = false
+	if mode, err := RequireFromEnv("MODE"); err == nil && (mode == "dev" || mode == "development") {
+		cfg.DevMode = true
+	}
+
+	// load the Open Telemetry config
+	cfg.Otel = OtelConfig{}
+	if err := cfg.Otel.Load(); err != nil {
+		return err
+	}
+
+	// Config succesfully loaded
+	return nil
+}