add batch get items methods to repository for retrieving multiple items by keys; (#22)

* add batch get items methods to repository for retrieving multiple items by keys;
---------

Co-authored-by: Mehran Dabestani <mehran.dabestani@adjoe.io>

Author: mehran-dabi

dynamo_global_index_interface.go

@@ -4,6 +4,8 @@ import (
 	"context"
 )
 
+//go:generate mockgen -source=dynamo_global_index_interface.go -destination=./mock/dynamo_global_index_interface.go -package=mock .
+
 type GlobalIndexInterface interface {
 	// GetItemWithContext get item from index; it accepts a key interface that is used to get the table name, hash key and range key if it exists;
 	// context which used to enable log with context; the output will be given in item

dynamo_repository.go

@@ -585,3 +585,65 @@ func (repository Repository) ScanIteratorWithContext(ctx context.Context, key Ke
 
 	return itr, nil
 }
+
+// BatchGetItemsWithContext gets multiple items by their keys; all keys must refer to the same table.
+// out must be a pointer to a slice of your model type.
+// Returns (true, nil) if at least one item is found, (false, nil) if none found, or (false, err) on error.
+func (repository *Repository) BatchGetItemsWithContext(ctx context.Context, keys []KeyInterface, out interface{}) (bool, error) {
+	if len(keys) == 0 {
+		return false, nil
+	}
+
+	// Validate keys and ensure they all point to the same table
+	tableName := keys[0].TableName()
+	for i := 0; i < len(keys); i++ {
+		if err := isValidKey(keys[i]); err != nil {
+			repository.log.error(ctx, keys[i].TableName(), err.Error())
+			return false, err
+		}
+		if keys[i].TableName() != tableName {
+			err := errors.New("BatchGetItemsWithContext: all keys must belong to the same table")
+			repository.log.error(ctx, tableName, err.Error())
+			return false, err
+		}
+	}
+
+	// by hash
+	batch := repository.table(tableName).Batch(*keys[0].HashKeyName())
+	// by hash & range
+	if keys[0].RangeKeyName() != nil && keys[0].RangeKey() != nil {
+		batch = repository.table(tableName).Batch(*keys[0].HashKeyName(), *keys[0].RangeKeyName())
+	}
+
+	// Build dynamo keys
+	dKeys := make([]dynamo.Keyed, len(keys))
+	for i := 0; i < len(keys); i++ {
+		dKeys[i] = dynamo.Keyed(keys[i])
+	}
+
+	// Execute batch get
+	err := batch.Get(dKeys...).AllWithContext(ctx, out)
+	if err != nil {
+		if errors.Is(err, dynamo.ErrNotFound) {
+			repository.log.info(ctx, tableName, ErrNoItemFound.Error())
+			return false, nil
+		}
+
+		repository.log.error(ctx, tableName, err.Error())
+		return false, err
+	}
+
+	// Check if slice is empty
+	val := reflect.ValueOf(out)
+	if val.Kind() == reflect.Ptr {
+		val = val.Elem()
+	}
+
+	if val.Kind() == reflect.Array || val.Kind() == reflect.Slice {
+		if val.Len() == 0 {
+			return false, nil
+		}
+	}
+
+	return true, nil
+}

dynamo_repository_interface.go

@@ -4,6 +4,8 @@ import (
 	"context"
 )
 
+//go:generate mockgen -source=dynamo_repository_interface.go -destination=./mock/dynamo_repository_interface.go -package=mock .
+
 // RepositoryInterface provides an interface to enable mocking the AWS dynamodb repository
 // for testing your code.
 type RepositoryInterface interface {
@@ -109,4 +111,9 @@ type RepositoryInterface interface {
 
 	//ConditionalUpdate updates an item if the passed expression and condition evaluates to true
 	ConditionalUpdate(key KeyInterface, item interface{}, expression string, expressionArgs ...interface{}) (bool, error)
+
+	// BatchGetItemsWithContext gets multiple items by their keys; it accepts a slice of keys (all from the same table)
+	// and fills out (pointer to a slice) with any found items.
+	// returns true if at least one item is found, returns false and nil if no items found, returns false and error in case of error
+	BatchGetItemsWithContext(ctx context.Context, keys []KeyInterface, out interface{}) (bool, error)
 }