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// Copyright 2024 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
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)
}
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