// CheckColumnType verifies that a given value is compatible
// with the type requested by the column. If the value is a
// placeholder, the type of the placeholder gets populated.
func CheckColumnType(col ColumnDescriptor, val parser.Datum, args parser.MapArgs) error {
	if val == parser.DNull {
		return nil
	}

	var ok bool
	var err error
	var set parser.Datum
	switch col.Type.Kind {
	case ColumnType_BOOL:
		_, ok = val.(*parser.DBool)
		set, err = args.SetInferredType(val, parser.TypeBool)
	case ColumnType_INT:
		_, ok = val.(*parser.DInt)
		set, err = args.SetInferredType(val, parser.TypeInt)
	case ColumnType_FLOAT:
		_, ok = val.(*parser.DFloat)
		set, err = args.SetInferredType(val, parser.TypeFloat)
	case ColumnType_DECIMAL:
		_, ok = val.(*parser.DDecimal)
		set, err = args.SetInferredType(val, parser.TypeDecimal)
	case ColumnType_STRING:
		_, ok = val.(*parser.DString)
		set, err = args.SetInferredType(val, parser.TypeString)
	case ColumnType_BYTES:
		_, ok = val.(*parser.DBytes)
		if !ok {
			_, ok = val.(*parser.DString)
		}
		set, err = args.SetInferredType(val, parser.TypeBytes)
	case ColumnType_DATE:
		_, ok = val.(*parser.DDate)
		set, err = args.SetInferredType(val, parser.TypeDate)
	case ColumnType_TIMESTAMP:
		_, ok = val.(*parser.DTimestamp)
		set, err = args.SetInferredType(val, parser.TypeTimestamp)
	case ColumnType_TIMESTAMPTZ:
		_, ok = val.(*parser.DTimestampTZ)
		set, err = args.SetInferredType(val, parser.TypeTimestampTZ)
	case ColumnType_INTERVAL:
		_, ok = val.(*parser.DInterval)
		set, err = args.SetInferredType(val, parser.TypeInterval)
	default:
		return util.Errorf("unsupported column type: %s", col.Type.Kind)
	}
	// Check that the value cast has succeeded.
	// We ignore the case where it has failed because val was a DArg,
	// which is signalled by SetInferredType returning a non-nil assignment.
	if !ok && set == nil {
		return fmt.Errorf("value type %s doesn't match type %s of column %q",
			val.Type(), col.Type.Kind, col.Name)
	}
	return err
}

// marshalColumnValue returns a Go primitive value equivalent of val, of the
// type expected by col. If val's type is incompatible with col, or if
// col's type is not yet implemented, an error is returned.
func marshalColumnValue(col ColumnDescriptor, val parser.Datum, args parser.MapArgs) (interface{}, error) {
	if val == parser.DNull {
		return nil, nil
	}

	switch col.Type.Kind {
	case ColumnType_BOOL:
		if v, ok := val.(parser.DBool); ok {
			return bool(v), nil
		}
		if set, err := args.SetInferredType(val, parser.DummyBool); err != nil {
			return nil, err
		} else if set != nil {
			return nil, nil
		}
	case ColumnType_INT:
		if v, ok := val.(parser.DInt); ok {
			return int64(v), nil
		}
		if set, err := args.SetInferredType(val, parser.DummyInt); err != nil {
			return nil, err
		} else if set != nil {
			return nil, nil
		}
	case ColumnType_FLOAT:
		if v, ok := val.(parser.DFloat); ok {
			return float64(v), nil
		}
		if set, err := args.SetInferredType(val, parser.DummyFloat); err != nil {
			return nil, err
		} else if set != nil {
			return nil, nil
		}
	case ColumnType_DECIMAL:
		if v, ok := val.(*parser.DDecimal); ok {
			return v.Dec, nil
		}
		if set, err := args.SetInferredType(val, parser.DummyDecimal); err != nil {
			return nil, err
		} else if set != nil {
			return nil, nil
		}
	case ColumnType_STRING:
		if v, ok := val.(parser.DString); ok {
			return string(v), nil
		}
		if set, err := args.SetInferredType(val, parser.DummyString); err != nil {
			return nil, err
		} else if set != nil {
			return nil, nil
		}
	case ColumnType_BYTES:
		if v, ok := val.(parser.DBytes); ok {
			return string(v), nil
		}
		if v, ok := val.(parser.DString); ok {
			return string(v), nil
		}
		if set, err := args.SetInferredType(val, parser.DummyBytes); err != nil {
			return nil, err
		} else if set != nil {
			return nil, nil
		}
	case ColumnType_DATE:
		if v, ok := val.(parser.DDate); ok {
			return int64(v), nil
		}
		if set, err := args.SetInferredType(val, parser.DummyDate); err != nil {
			return nil, err
		} else if set != nil {
			return nil, nil
		}
	case ColumnType_TIMESTAMP:
		if v, ok := val.(parser.DTimestamp); ok {
			return v.Time, nil
		}
		if set, err := args.SetInferredType(val, parser.DummyTimestamp); err != nil {
			return nil, err
		} else if set != nil {
			return nil, nil
		}
	case ColumnType_INTERVAL:
		if v, ok := val.(parser.DInterval); ok {
			return v.Duration, nil
		}
		if set, err := args.SetInferredType(val, parser.DummyInterval); err != nil {
			return nil, err
		} else if set != nil {
			return nil, nil
		}
	default:
		return nil, util.Errorf("unsupported column type: %s", col.Type.Kind)
	}
	return nil, fmt.Errorf("value type %s doesn't match type %s of column %q",
		val.Type(), col.Type.Kind, col.Name)
}