Added a /conditions/current endpoint with computed best-guess values for current conditions

internal/application/units/registry.go

@@ -0,0 +1,73 @@
+package units
+
+import (
+	"fmt"
+	"strings"
+)
+
+type Factory interface {
+	System() string
+	New() Converter
+}
+
+type StaticFactory struct {
+	UnitSystem string
+	Converter  Converter
+}
+
+func (f StaticFactory) System() string {
+	return f.UnitSystem
+}
+
+func (f StaticFactory) New() Converter {
+	return f.Converter
+}
+
+type Registry struct {
+	factories map[string]Factory
+}
+
+func NewRegistry() *Registry {
+	return &Registry{factories: map[string]Factory{}}
+}
+
+func (r *Registry) Register(factory Factory) error {
+	if r == nil {
+		return fmt.Errorf("register unit factory: registry is nil")
+	}
+	if factory == nil {
+		return fmt.Errorf("register unit factory: factory is nil")
+	}
+	system := normalize(factory.System())
+	if system == "" {
+		return fmt.Errorf("register unit factory: unit system is empty")
+	}
+	if _, exists := r.factories[system]; exists {
+		return fmt.Errorf("register unit factory: system %q already registered", system)
+	}
+	if factory.New() == nil {
+		return fmt.Errorf("register unit factory: factory returned nil converter for %q", system)
+	}
+	r.factories[system] = factory
+	return nil
+}
+
+func (r *Registry) Resolve(system string) (Converter, error) {
+	if r == nil {
+		return nil, fmt.Errorf("resolve unit converter: registry is nil")
+	}
+	key := normalize(system)
+	factory, ok := r.factories[key]
+	if !ok {
+		return nil, fmt.Errorf("resolve unit converter: unsupported unit system %q", system)
+	}
+	converter := factory.New()
+	if converter == nil {
+		return nil, fmt.Errorf("resolve unit converter: factory for %q returned nil converter", key)
+	}
+	return converter, nil
+}
+
+func normalize(system string) string {
+	return strings.ToLower(strings.TrimSpace(system))
+}