feat(equalitor): add equalitor interface and hash implementation

Author: njhale

pkg/lib/comparison/equal.go

@@ -0,0 +1,42 @@
+package comparison
+
+import (
+	// "fmt"
+
+	"github.com/mitchellh/hashstructure"
+)
+
+// Equalitor describes an algorithm for equivalence between two data structures.
+type Equalitor interface {
+	Equal(a, b interface{}) bool
+}
+
+// EqualFunc is a function that implements Equalitor.
+type EqualFunc func(a, b interface{}) bool
+
+// Equal allows an EqualFunc to implement Equalitor.
+func (e EqualFunc) Equal(a, b interface{}) bool {
+	return e(a, b)
+}
+
+// NewHashEqualitor returns an EqualFunc that returns true if the hashes of the given
+// arguments are equal, false otherwise.
+//
+// This function panics if an error is encountered generating a hash for either argument.
+func NewHashEqualitor() EqualFunc {
+	return func(a, b interface{}) bool {
+		hashA, err := hashstructure.Hash(a, nil)
+		if err != nil {
+			panic(err.Error())
+		}
+
+		hashB, err := hashstructure.Hash(b, nil)
+		if err != nil {
+			panic(err.Error())
+		}
+
+		// fmt.Printf("hashA: %d, hashB: %d\n", hashA, hashB)
+
+		return hashA == hashB
+	}
+}