Centralize effective config loading and path resolution

internal/core/config/effective_config.go

@@ -0,0 +1,119 @@
+package config
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+type EffectiveConfigErrorKind string
+
+const (
+	EffectiveConfigErrorResolvePath EffectiveConfigErrorKind = "resolve_path"
+	EffectiveConfigErrorLoadFile    EffectiveConfigErrorKind = "load_file"
+	EffectiveConfigErrorApplyFile   EffectiveConfigErrorKind = "apply_file"
+	EffectiveConfigErrorApplyEnv    EffectiveConfigErrorKind = "apply_env"
+)
+
+type EffectiveConfigError struct {
+	Kind EffectiveConfigErrorKind
+	Err  error
+}
+
+func (e *EffectiveConfigError) Error() string {
+	if e == nil || e.Err == nil {
+		return ""
+	}
+	return e.Err.Error()
+}
+
+func (e *EffectiveConfigError) Unwrap() error {
+	if e == nil {
+		return nil
+	}
+	return e.Err
+}
+
+type EffectiveConfig struct {
+	Config        Config
+	ConfigPath    string
+	ConfigSource  string
+	ConfigVersion *int
+}
+
+func ResolveConfigPath(cliConfigPath string, cliConfigPathSet bool) (path string, source string, err error) {
+	return resolveConfigPathWithLookup(cliConfigPath, cliConfigPathSet, os.LookupEnv, os.Stat, DefaultConfigSearchPaths)
+}
+
+func LoadEffectiveConfig(cliConfigPath string, cliConfigPathSet bool) (EffectiveConfig, error) {
+	return loadEffectiveConfigWithLookup(cliConfigPath, cliConfigPathSet, os.LookupEnv, os.Stat, DefaultConfigSearchPaths)
+}
+
+func loadEffectiveConfigWithLookup(cliConfigPath string, cliConfigPathSet bool, lookup func(string) (string, bool), statPath func(string) (os.FileInfo, error), defaultSearchPaths []string) (EffectiveConfig, error) {
+	configPath, configSource, err := resolveConfigPathWithLookup(cliConfigPath, cliConfigPathSet, lookup, statPath, defaultSearchPaths)
+	if err != nil {
+		return EffectiveConfig{}, &EffectiveConfigError{Kind: EffectiveConfigErrorResolvePath, Err: err}
+	}
+
+	cfg := Default()
+	var configVersion *int
+	if configPath != "" {
+		fileCfg, fileErr := LoadFileConfig(configPath)
+		if fileErr != nil {
+			return EffectiveConfig{}, &EffectiveConfigError{Kind: EffectiveConfigErrorLoadFile, Err: fileErr}
+		}
+		if applyErr := cfg.ApplyFileConfig(fileCfg); applyErr != nil {
+			return EffectiveConfig{}, &EffectiveConfigError{Kind: EffectiveConfigErrorApplyFile, Err: applyErr}
+		}
+		configVersion = &fileCfg.Version
+	}
+	if applyEnvErr := cfg.applyEnvOverrides(lookup); applyEnvErr != nil {
+		return EffectiveConfig{}, &EffectiveConfigError{Kind: EffectiveConfigErrorApplyEnv, Err: applyEnvErr}
+	}
+
+	return EffectiveConfig{
+		Config:        cfg,
+		ConfigPath:    configPath,
+		ConfigSource:  configSource,
+		ConfigVersion: configVersion,
+	}, nil
+}
+
+func resolveConfigPathWithLookup(cliConfigPath string, cliConfigPathSet bool, lookup func(string) (string, bool), statPath func(string) (os.FileInfo, error), defaultSearchPaths []string) (path string, source string, err error) {
+	if cliConfigPathSet {
+		path = strings.TrimSpace(cliConfigPath)
+		if path == "" {
+			return "", "", fmt.Errorf("--config requires a non-empty path")
+		}
+		if _, statErr := statPath(path); statErr != nil {
+			if os.IsNotExist(statErr) {
+				return "", "", fmt.Errorf("config file not found: %s", path)
+			}
+			return "", "", fmt.Errorf("cannot access config file %s: %w", path, statErr)
+		}
+		return path, "flag", nil
+	}
+
+	if raw, ok := lookup("AUDITA_CONFIG"); ok {
+		path = strings.TrimSpace(raw)
+		if path == "" {
+			return "", "", fmt.Errorf("AUDITA_CONFIG must not be empty")
+		}
+		if _, statErr := statPath(path); statErr != nil {
+			if os.IsNotExist(statErr) {
+				return "", "", fmt.Errorf("config file not found: %s", path)
+			}
+			return "", "", fmt.Errorf("cannot access config file %s: %w", path, statErr)
+		}
+		return path, "env", nil
+	}
+
+	for _, defaultPath := range defaultSearchPaths {
+		if _, statErr := statPath(defaultPath); statErr == nil {
+			return defaultPath, "default", nil
+		} else if !os.IsNotExist(statErr) {
+			return "", "", fmt.Errorf("cannot access config file %s: %w", defaultPath, statErr)
+		}
+	}
+	return "", "", nil
+}