Start of creating app structure

app/config.go

@@ -0,0 +1,86 @@
+package app
+
+import (
+	"encoding/json"
+	"fmt"
+	"github.com/Theodor-Springmann-Stiftung/musenalm/helpers"
+	"github.com/kelseyhightower/envconfig"
+	"log/slog"
+	"os"
+)
+
+// WARNING: this is not intended to be used in a multi-threaded environment
+// Instatiate this once on startup before any goroutines are started
+const (
+	DEFAULT_GIT_DIR = "data_git"
+	DEFAULT_GND_DIR = "cache_gnd"
+	DEFAULT_GEO_DIR = "cache_geo"
+	DEFAULT_IMG_DIR = "data_bilder"
+
+	DEFAULT_PORT  = "8080"
+	DEFAULT_ADDR  = "localhost"
+	DEFAULT_HTTPS = false
+
+	ENV_PREFIX = "KGPZ"
+)
+
+type ConfigProvider struct {
+	Files []string
+	*Config
+}
+
+type Config struct {
+	// At least one of these should be set
+}
+
+func NewConfigProvider(files []string) *ConfigProvider {
+	return &ConfigProvider{Files: files}
+}
+
+func (c *ConfigProvider) Read() error {
+	c.Config = &Config{}
+	for _, file := range c.Files {
+		c.Config = readSettingsFile(c.Config, file)
+	}
+	c.Config = readSettingsEnv(c.Config)
+	c.Config = readDefaults(c.Config)
+	return nil
+}
+
+func (c *ConfigProvider) Validate() error {
+	return nil
+}
+
+func readSettingsFile(cfg *Config, path string) *Config {
+	f, err := os.Open(path)
+	if err != nil {
+		slog.Error("Error opening config file ", "path", path, "error", err)
+		return cfg
+	}
+	defer f.Close()
+
+	dec := json.NewDecoder(f)
+	err = dec.Decode(cfg)
+	helpers.Assert(err, "Error decoding config file")
+
+	return cfg
+}
+
+func readSettingsEnv(cfg *Config) *Config {
+	_ = envconfig.Process(ENV_PREFIX, cfg)
+	return cfg
+}
+
+func readDefaults(cfg *Config) *Config {
+
+	return cfg
+}
+
+// Implement stringer
+func (c *Config) String() string {
+	json, err := json.MarshalIndent(c, "", "  ")
+	if err != nil {
+		return fmt.Sprintf("Error marshalling config: %v", err)
+	}
+	return string(json)
+}