multilinediff: add multilinediff package

Just copy and pasting the stuff from the external multilinediff package
to make it easier to deal with dependency breakages when they happen.

Signed-off-by: braydonk <braydonk@google.com>

engine.go

@@ -4,8 +4,8 @@ import (
 	"fmt"
 	"os"
 
-	"github.com/RageCage64/multilinediff"
 	"github.com/google/yamlfmt/internal/collections"
+	"github.com/google/yamlfmt/internal/multilinediff"
 )
 
 type Operation int

go.mod

@@ -3,11 +3,9 @@ module github.com/google/yamlfmt
 go 1.18
 
 require (
-	github.com/RageCage64/multilinediff v0.2.0
 	github.com/bmatcuk/doublestar/v4 v4.6.0
 	github.com/braydonk/yaml v0.7.0
 	github.com/google/go-cmp v0.5.9
 	github.com/mitchellh/mapstructure v1.5.0
+	github.com/sabhiram/go-gitignore v0.0.0-20210923224102-525f6e181f06
 )
-
-require github.com/sabhiram/go-gitignore v0.0.0-20210923224102-525f6e181f06 // indirect

go.sum

@@ -1,21 +1,21 @@
-github.com/RageCage64/go-assert v0.2.2 h1:wwPA2yibB7XmaQKpw4xk7NfVPdJ1v79GlBvmS8P9ROM=
-github.com/RageCage64/go-assert v0.2.2/go.mod h1:YuWzhAJlE4Z2TW2D4msNx1mNU0wA+6lmAL0lP1l7yd4=
-github.com/RageCage64/multilinediff v0.2.0 h1:yNSpSF5NXIrmo6bRIgO4Q0g7SXqFD4j/WEcBE+BdCFY=
-github.com/RageCage64/multilinediff v0.2.0/go.mod h1:pKr+KLgP0gvRzA+yv0/IUaYQuBYN1ucWysvsL58aMP0=
 github.com/bmatcuk/doublestar/v4 v4.6.0 h1:HTuxyug8GyFbRkrffIpzNCSK4luc0TY3wzXvzIZhEXc=
 github.com/bmatcuk/doublestar/v4 v4.6.0/go.mod h1:xBQ8jztBU6kakFMg+8WGxn0c6z1fTSPVIjEY1Wr7jzc=
 github.com/braydonk/yaml v0.7.0 h1:ySkqO7r0MGoCNhiRJqE0Xe9yhINMyvOAB3nFjgyJn2k=
 github.com/braydonk/yaml v0.7.0/go.mod h1:hcm3h581tudlirk8XEUPDBAimBPbmnL0Y45hCRl47N4=
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
 github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/mitchellh/mapstructure v1.5.0 h1:jeMsZIYE/09sWLaz43PL7Gy6RuMjD2eJVyuac5Z2hdY=
 github.com/mitchellh/mapstructure v1.5.0/go.mod h1:bFUtVrKA4DC2yAKiSyO/QUcy7e+RRV2QTWOzhPopBRo=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/sabhiram/go-gitignore v0.0.0-20210923224102-525f6e181f06 h1:OkMGxebDjyw0ULyrTYWeN0UNCCkmCWfjPnIA2W6oviI=
 github.com/sabhiram/go-gitignore v0.0.0-20210923224102-525f6e181f06/go.mod h1:+ePHsJ1keEjQtpvf9HHw0f4ZeJ0TLRsxhunSI2hYJSs=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
 github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

internal/multilinediff/multilinediff.go

@@ -0,0 +1,116 @@
+package multilinediff
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
+)
+
+// Get the diff between two strings.
+func Diff(a, b, lineSep string) (string, int) {
+	reporter := Reporter{LineSep: lineSep}
+	cmp.Diff(
+		a, b,
+		cmpopts.AcyclicTransformer("multiline", func(s string) []string {
+			return strings.Split(s, lineSep)
+		}),
+		cmp.Reporter(&reporter),
+	)
+	return reporter.String(), reporter.DiffCount
+}
+
+type diffType int
+
+const (
+	diffTypeEqual diffType = iota
+	diffTypeChange
+	diffTypeAdd
+)
+
+type diffLine struct {
+	diff diffType
+	old  string
+	new  string
+}
+
+func (l diffLine) toLine(length int) string {
+	line := ""
+
+	switch l.diff {
+	case diffTypeChange:
+		line += "- "
+	case diffTypeAdd:
+		line += "+ "
+	default:
+		line += "  "
+	}
+
+	line += l.old
+
+	for i := 0; i < length-len(l.old); i++ {
+		line += " "
+	}
+
+	line += "  "
+
+	line += l.new
+
+	return line
+}
+
+// A pretty reporter to pass into cmp.Diff using the cmd.Reporter function.
+type Reporter struct {
+	LineSep   string
+	DiffCount int
+
+	path  cmp.Path
+	lines []diffLine
+}
+
+func (r *Reporter) PushStep(ps cmp.PathStep) {
+	r.path = append(r.path, ps)
+}
+
+func (r *Reporter) Report(rs cmp.Result) {
+	line := diffLine{}
+	vOld, vNew := r.path.Last().Values()
+	if !rs.Equal() {
+		r.DiffCount++
+		if vOld.IsValid() {
+			line.diff = diffTypeChange
+			line.old = fmt.Sprintf("%+v", vOld)
+		}
+		if vNew.IsValid() {
+			if line.diff == diffTypeEqual {
+				line.diff = diffTypeAdd
+			}
+			line.new = fmt.Sprintf("%+v", vNew)
+		}
+	} else {
+		line.old = fmt.Sprintf("%+v", vOld)
+		line.new = fmt.Sprintf("%+v", vOld)
+	}
+	r.lines = append(r.lines, line)
+}
+
+func (r *Reporter) PopStep() {
+	r.path = r.path[:len(r.path)-1]
+}
+
+func (r *Reporter) String() string {
+	maxLen := 0
+	for _, l := range r.lines {
+		if len(l.old) > maxLen {
+			maxLen = len(l.old)
+		}
+	}
+
+	diffLines := []string{}
+	for _, l := range r.lines {
+		diffLines = append(diffLines, l.toLine(maxLen))
+	}
+
+	return strings.Join(diffLines, r.LineSep)
+}