env_source.go

package confkit

import (
	"context"
	"os"
	"strings"
)

func FromEnv() Source {
	return &envSource{}
}

type envSource struct{}

func (e *envSource) Name() string {
	return "env"
}

func (e *envSource) Lookup(_ context.Context, field *FieldInfo) (any, bool, error) {
	envName := field.Tags["env"]
	if envName == "" {
		return "", false, nil
	}

	prefix := buildEnvPrefix(field.AncestorTags)
	if p := field.Tags["prefix"]; p != "" {
		prefix += p
	}
	fullName := prefix + envName

	value, ok := os.LookupEnv(fullName)
	return value, ok, nil
}

func buildEnvPrefix(ancestorTags []map[string]string) string {
	var prefixes []string
	for _, tags := range ancestorTags {
		if p := tags["prefix"]; p != "" {
			prefixes = append(prefixes, p)
		}
	}
	return strings.Join(prefixes, "")
}

type errorSource struct {
	err error
}

func (e *errorSource) Name() string {
	return "error"
}

func (e *errorSource) Lookup(_ context.Context, _ *FieldInfo) (any, bool, error) {
	return "", false, e.err
}

func NewErrorSource(err error) Source {
	return &errorSource{err: err}
}