From 82f32b99c05f293c5ca990540f99f669ebf10b0a Mon Sep 17 00:00:00 2001
From: Aditya Thebe <contact@adityathebe.com>
Date: Wed, 19 Jun 2024 16:16:35 +0545
Subject: [PATCH] feat: json diff

---
 diff/json.go | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 go.mod       |  1 +
 go.sum       |  2 ++
 3 files changed, 52 insertions(+)
 create mode 100644 diff/json.go

diff --git a/diff/json.go b/diff/json.go
new file mode 100644
index 0000000..9f13af2
--- /dev/null
+++ b/diff/json.go
@@ -0,0 +1,49 @@
+package diff
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/hexops/gotextdiff"
+	"github.com/hexops/gotextdiff/myers"
+)
+
+// JSONCompare calculates the diff (git style) between the given 2 configs.
+func JSONCompare(newConf, prevConfig string) (string, error) {
+	// We want a nicely indented json config with each key-vals in new line
+	// because that gives us a better diff. A one-line json string config produces diff
+	// that's not very helpful.
+	before, err := normalizeJSON(prevConfig)
+	if err != nil {
+		return "", fmt.Errorf("failed to normalize json for previous config: %w", err)
+	}
+
+	after, err := normalizeJSON(newConf)
+	if err != nil {
+		return "", fmt.Errorf("failed to normalize json for new config: %w", err)
+	}
+
+	edits := myers.ComputeEdits("", before, after)
+	if len(edits) == 0 {
+		return "", nil
+	}
+
+	diff := fmt.Sprint(gotextdiff.ToUnified("before", "after", before, edits))
+	return diff, nil
+}
+
+// normalizeJSON returns an indented json string.
+// The keys are sorted lexicographically.
+func normalizeJSON(jsonStr string) (string, error) {
+	var jsonStrMap map[string]any
+	if err := json.Unmarshal([]byte(jsonStr), &jsonStrMap); err != nil {
+		return "", err
+	}
+
+	jsonStrIndented, err := json.MarshalIndent(jsonStrMap, "", "\t")
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonStrIndented), nil
+}
diff --git a/go.mod b/go.mod
index 4d95266..145c2b7 100644
--- a/go.mod
+++ b/go.mod
@@ -7,6 +7,7 @@ require (
 	github.com/google/uuid v1.5.0
 	github.com/hashicorp/go-getter v1.7.3
 	github.com/henvic/httpretty v0.1.2
+	github.com/hexops/gotextdiff v1.0.3
 	github.com/kr/pretty v0.3.1
 	github.com/onsi/gomega v1.27.6
 	github.com/patrickmn/go-cache v2.1.0+incompatible
diff --git a/go.sum b/go.sum
index a7fa0ed..980de02 100644
--- a/go.sum
+++ b/go.sum
@@ -876,6 +876,8 @@ github.com/hashicorp/golang-lru v0.5.0/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ
 github.com/hashicorp/golang-lru v0.5.1/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=
 github.com/henvic/httpretty v0.1.2 h1:EQo556sO0xeXAjP10eB+BZARMuvkdGqtfeS4Ntjvkiw=
 github.com/henvic/httpretty v0.1.2/go.mod h1:ViEsly7wgdugYtymX54pYp6Vv2wqZmNHayJ6q8tlKCc=
+github.com/hexops/gotextdiff v1.0.3 h1:gitA9+qJrrTCsiCl7+kh75nPqQt1cx4ZkudSTLoUqJM=
+github.com/hexops/gotextdiff v1.0.3/go.mod h1:pSWU5MAI3yDq+fZBTazCSJysOMbxWL1BSow5/V2vxeg=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
 github.com/iancoleman/strcase v0.2.0/go.mod h1:iwCmte+B7n89clKwxIoIXy/HfoL7AsD47ZCWhYzw7ho=
 github.com/ianlancetaylor/demangle v0.0.0-20181102032728-5e5cf60278f6/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=