Initial commit

internal/config/config.go

@@ -0,0 +1,85 @@
+package config
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/BurntSushi/toml"
+)
+
+type Config struct {
+	Server     ServerConfig     `toml:"server"`
+	EPICS      EPICSConfig      `toml:"datasource.epics"`
+	Synthetic  SyntheticConfig  `toml:"datasource.synthetic"`
+}
+
+type ServerConfig struct {
+	Listen     string `toml:"listen"`
+	StorageDir string `toml:"storage_dir"`
+}
+
+type EPICSConfig struct {
+	Enabled    bool   `toml:"enabled"`
+	CAAddrList string `toml:"ca_addr_list"`
+	ArchiveURL string `toml:"archive_url"`
+}
+
+type SyntheticConfig struct {
+	Enabled         bool   `toml:"enabled"`
+	DefinitionsFile string `toml:"definitions_file"`
+}
+
+func Default() Config {
+	return Config{
+		Server: ServerConfig{
+			Listen:     ":8080",
+			StorageDir: "./interfaces",
+		},
+		EPICS: EPICSConfig{
+			Enabled: true,
+		},
+		Synthetic: SyntheticConfig{
+			Enabled:         true,
+			DefinitionsFile: "./synthetic.json",
+		},
+	}
+}
+
+// Load reads a TOML config file and applies environment variable overrides.
+// Environment variables use the prefix UOPI_ with __ as separator, e.g.
+// UOPI_SERVER_LISTEN=":9090".
+func Load(path string) (Config, error) {
+	cfg := Default()
+
+	if path != "" {
+		if _, err := toml.DecodeFile(path, &cfg); err != nil {
+			return cfg, fmt.Errorf("reading config %q: %w", path, err)
+		}
+	}
+
+	applyEnv(&cfg)
+	return cfg, nil
+}
+
+func applyEnv(cfg *Config) {
+	if v := env("UOPI_SERVER_LISTEN"); v != "" {
+		cfg.Server.Listen = v
+	}
+	if v := env("UOPI_SERVER_STORAGE_DIR"); v != "" {
+		cfg.Server.StorageDir = v
+	}
+	if v := env("UOPI_EPICS_CA_ADDR_LIST"); v != "" {
+		cfg.EPICS.CAAddrList = v
+	}
+	if v := env("UOPI_EPICS_ARCHIVE_URL"); v != "" {
+		cfg.EPICS.ArchiveURL = v
+	}
+	if v := env("UOPI_SYNTHETIC_DEFINITIONS_FILE"); v != "" {
+		cfg.Synthetic.DefinitionsFile = v
+	}
+}
+
+func env(key string) string {
+	return strings.TrimSpace(os.Getenv(key))
+}