1 files changed, 63 insertions, 0 deletions
diff --git a/vendor/github.com/hashicorp/terraform/helper/schema/field_reader_multi.go b/vendor/github.com/hashicorp/terraform/helper/schema/field_reader_multi.go
new file mode 100644
index 00000000..89ad3a86
--- /dev/null
+++ b/vendor/github.com/hashicorp/terraform/helper/schema/field_reader_multi.go
@@ -0,0 +1,63 @@
+package schema
+
+import (
+	"fmt"
+)
+
+// MultiLevelFieldReader reads from other field readers,
+// merging their results along the way in a specific order. You can specify
+// "levels" and name them in order to read only an exact level or up to
+// a specific level.
+//
+// This is useful for saying things such as "read the field from the state
+// and config and merge them" or "read the latest value of the field".
+type MultiLevelFieldReader struct {
+	Readers map[string]FieldReader
+	Levels  []string
+}
+
+func (r *MultiLevelFieldReader) ReadField(address []string) (FieldReadResult, error) {
+	return r.ReadFieldMerge(address, r.Levels[len(r.Levels)-1])
+}
+
+func (r *MultiLevelFieldReader) ReadFieldExact(
+	address []string, level string) (FieldReadResult, error) {
+	reader, ok := r.Readers[level]
+	if !ok {
+		return FieldReadResult{}, fmt.Errorf(
+			"Unknown reader level: %s", level)
+	}
+
+	result, err := reader.ReadField(address)
+	if err != nil {
+		return FieldReadResult{}, fmt.Errorf(
+			"Error reading level %s: %s", level, err)
+	}
+
+	return result, nil
+}
+
+func (r *MultiLevelFieldReader) ReadFieldMerge(
+	address []string, level string) (FieldReadResult, error) {
+	var result FieldReadResult
+	for _, l := range r.Levels {
+		if r, ok := r.Readers[l]; ok {
+			out, err := r.ReadField(address)
+			if err != nil {
+				return FieldReadResult{}, fmt.Errorf(
+					"Error reading level %s: %s", l, err)
+			}
+
+			// TODO: computed
+			if out.Exists {
+				result = out
+			}
+		}
+
+		if l == level {
+			break
+		}
+	}
+
+	return result, nil
+}