1// Copyright 2019 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package hooks
6
7import (
8	"fmt"
9
10	"github.com/sergi/go-diff/diffmatchpatch"
11	"golang.org/x/tools/internal/lsp/diff"
12	"golang.org/x/tools/internal/span"
13)
14
15func ComputeEdits(uri span.URI, before, after string) (edits []diff.TextEdit, err error) {
16	// The go-diff library has an unresolved panic (see golang/go#278774).
17	// TOOD(rstambler): Remove the recover once the issue has been fixed
18	// upstream.
19	defer func() {
20		if r := recover(); r != nil {
21			edits = nil
22			err = fmt.Errorf("unable to compute edits for %s: %s", uri.Filename(), r)
23		}
24	}()
25	diffs := diffmatchpatch.New().DiffMain(before, after, true)
26	edits = make([]diff.TextEdit, 0, len(diffs))
27	offset := 0
28	for _, d := range diffs {
29		start := span.NewPoint(0, 0, offset)
30		switch d.Type {
31		case diffmatchpatch.DiffDelete:
32			offset += len(d.Text)
33			edits = append(edits, diff.TextEdit{Span: span.New(uri, start, span.NewPoint(0, 0, offset))})
34		case diffmatchpatch.DiffEqual:
35			offset += len(d.Text)
36		case diffmatchpatch.DiffInsert:
37			edits = append(edits, diff.TextEdit{Span: span.New(uri, start, span.Point{}), NewText: d.Text})
38		}
39	}
40	return edits, nil
41}
42