Finish minimal feature set, start with tests

database/accessor/accessor-struct.go

@@ -0,0 +1,149 @@
+package accessor
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+)
+
+// StructAccessor is a json string with get functions.
+type StructAccessor struct {
+	object reflect.Value
+}
+
+// NewStructAccessor adds the Accessor interface to a JSON string.
+func NewStructAccessor(object interface{}) *StructAccessor {
+	return &StructAccessor{
+		object: reflect.ValueOf(object).Elem(),
+	}
+}
+
+// Set sets the value identified by key.
+func (sa *StructAccessor) Set(key string, value interface{}) error {
+	field := sa.object.FieldByName(key)
+	if !field.IsValid() {
+		return errors.New("struct field does not exist")
+	}
+	if !field.CanSet() {
+		return fmt.Errorf("field %s or struct is immutable", field.String())
+	}
+
+	newVal := reflect.ValueOf(value)
+
+	// set directly if type matches
+	if newVal.Kind() == field.Kind() {
+		field.Set(newVal)
+		return nil
+	}
+
+	// handle special cases
+	switch field.Kind() {
+
+	// ints
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		var newInt int64
+		switch newVal.Kind() {
+		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+			newInt = newVal.Int()
+		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+			newInt = int64(newVal.Uint())
+		default:
+			return fmt.Errorf("tried to set field %s (%s) to a %s value", key, field.Kind().String(), newVal.Kind().String())
+		}
+		if field.OverflowInt(newInt) {
+			return fmt.Errorf("setting field %s (%s) to %d would overflow", key, field.Kind().String(), newInt)
+		}
+		field.SetInt(newInt)
+
+		// uints
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		var newUint uint64
+		switch newVal.Kind() {
+		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+			newUint = uint64(newVal.Int())
+		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+			newUint = newVal.Uint()
+		default:
+			return fmt.Errorf("tried to set field %s (%s) to a %s value", key, field.Kind().String(), newVal.Kind().String())
+		}
+		if field.OverflowUint(newUint) {
+			return fmt.Errorf("setting field %s (%s) to %d would overflow", key, field.Kind().String(), newUint)
+		}
+		field.SetUint(newUint)
+
+		// floats
+	case reflect.Float32, reflect.Float64:
+		switch newVal.Kind() {
+		case reflect.Float32, reflect.Float64:
+			field.SetFloat(newVal.Float())
+		default:
+			return fmt.Errorf("tried to set field %s (%s) to a %s value", key, field.Kind().String(), newVal.Kind().String())
+		}
+	default:
+		return fmt.Errorf("tried to set field %s (%s) to a %s value", key, field.Kind().String(), newVal.Kind().String())
+	}
+
+	return nil
+}
+
+// GetString returns the string found by the given json key and whether it could be successfully extracted.
+func (sa *StructAccessor) GetString(key string) (value string, ok bool) {
+	field := sa.object.FieldByName(key)
+	if !field.IsValid() || field.Kind() != reflect.String {
+		return "", false
+	}
+	return field.String(), true
+}
+
+// GetInt returns the int found by the given json key and whether it could be successfully extracted.
+func (sa *StructAccessor) GetInt(key string) (value int64, ok bool) {
+	field := sa.object.FieldByName(key)
+	if !field.IsValid() {
+		return 0, false
+	}
+	switch field.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return field.Int(), true
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		return int64(field.Uint()), true
+	default:
+		return 0, false
+	}
+}
+
+// GetFloat returns the float found by the given json key and whether it could be successfully extracted.
+func (sa *StructAccessor) GetFloat(key string) (value float64, ok bool) {
+	field := sa.object.FieldByName(key)
+	if !field.IsValid() {
+		return 0, false
+	}
+	switch field.Kind() {
+	case reflect.Float32, reflect.Float64:
+		return field.Float(), true
+	default:
+		return 0, false
+	}
+}
+
+// GetBool returns the bool found by the given json key and whether it could be successfully extracted.
+func (sa *StructAccessor) GetBool(key string) (value bool, ok bool) {
+	field := sa.object.FieldByName(key)
+	if !field.IsValid() || field.Kind() != reflect.Bool {
+		return false, false
+	}
+	return field.Bool(), true
+}
+
+// Exists returns the whether the given key exists.
+func (sa *StructAccessor) Exists(key string) bool {
+	field := sa.object.FieldByName(key)
+	if field.IsValid() {
+		return true
+	}
+	return false
+}
+
+// Type returns the accessor type as a string.
+func (sa *StructAccessor) Type() string {
+	return "StructAccessor"
+}