Expose range information for markdown text nodes [WIP] (#9067)

* Track positions of markdown text

* Add tests for markdown text ranges

2 files changed, 147 insertions, 14 deletions

diff --git a/utils/markdown/inlines.go b/utils/markdown/inlines.go
index 03da2f15c..8a4f7a531 100644
--- a/utils/markdown/inlines.go
+++ b/utils/markdown/inlines.go
@@ -21,7 +21,8 @@ func (inlineBase) IsInline() bool { return true }
 type Text struct {
 	inlineBase
 
-	Text string
+	Text  string
+	Range Range
 }
 
 type CodeSpan struct {
@@ -141,8 +142,10 @@ func (p *inlineParser) parseBackticks() {
 		return
 	}
 	p.position += len(opening)
+	absPos := relativeToAbsolutePosition(p.ranges, p.position-len(opening))
 	p.inlines = append(p.inlines, &Text{
-		Text: opening,
+		Text:  opening,
+		Range: Range{absPos, absPos + len(opening)},
 	})
 }
 
@@ -162,13 +165,17 @@ func (p *inlineParser) parseLineEnding() {
 
 func (p *inlineParser) parseEscapeCharacter() {
 	if p.position+1 < len(p.raw) && isEscapableByte(p.raw[p.position+1]) {
+		absPos := relativeToAbsolutePosition(p.ranges, p.position+1)
 		p.inlines = append(p.inlines, &Text{
-			Text: string(p.raw[p.position+1]),
+			Text:  string(p.raw[p.position+1]),
+			Range: Range{absPos, absPos + len(string(p.raw[p.position+1]))},
 		})
 		p.position += 2
 	} else {
+		absPos := relativeToAbsolutePosition(p.ranges, p.position)
 		p.inlines = append(p.inlines, &Text{
-			Text: `\`,
+			Text:  `\`,
+			Range: Range{absPos, absPos + 1},
 		})
 		p.position++
 	}
@@ -176,18 +183,24 @@ func (p *inlineParser) parseEscapeCharacter() {
 
 func (p *inlineParser) parseText() {
 	if next := strings.IndexAny(p.raw[p.position:], "\r\n\\`&![]"); next == -1 {
+		absPos := relativeToAbsolutePosition(p.ranges, p.position)
 		p.inlines = append(p.inlines, &Text{
-			Text: strings.TrimRightFunc(p.raw[p.position:], isWhitespace),
+			Text:  strings.TrimRightFunc(p.raw[p.position:], isWhitespace),
+			Range: Range{absPos, absPos + len(p.raw[p.position:])},
 		})
 		p.position = len(p.raw)
 	} else {
+		absPos := relativeToAbsolutePosition(p.ranges, p.position)
 		if p.raw[p.position+next] == '\r' || p.raw[p.position+next] == '\n' {
+			s := strings.TrimRightFunc(p.raw[p.position:p.position+next], isWhitespace)
 			p.inlines = append(p.inlines, &Text{
-				Text: strings.TrimRightFunc(p.raw[p.position:p.position+next], isWhitespace),
+				Text:  s,
+				Range: Range{absPos, absPos + len(s)},
 			})
 		} else {
 			p.inlines = append(p.inlines, &Text{
-				Text: p.raw[p.position : p.position+next],
+				Text:  p.raw[p.position : p.position+next],
+				Range: Range{absPos, absPos + next},
 			})
 		}
 		p.position += next
@@ -195,9 +208,11 @@ func (p *inlineParser) parseText() {
 }
 
 func (p *inlineParser) parseLinkOrImageDelimiter() {
+	absPos := relativeToAbsolutePosition(p.ranges, p.position)
 	if p.raw[p.position] == '[' {
 		p.inlines = append(p.inlines, &Text{
-			Text: "[",
+			Text:  "[",
+			Range: Range{absPos, absPos + 1},
 		})
 		p.delimiterStack.PushBack(&delimiter{
 			Type:     linkOpeningDelimiter,
@@ -207,7 +222,8 @@ func (p *inlineParser) parseLinkOrImageDelimiter() {
 		p.position++
 	} else if p.raw[p.position] == '!' && p.position+1 < len(p.raw) && p.raw[p.position+1] == '[' {
 		p.inlines = append(p.inlines, &Text{
-			Text: "![",
+			Text:  "![",
+			Range: Range{absPos, absPos + 2},
 		})
 		p.delimiterStack.PushBack(&delimiter{
 			Type:     imageOpeningDelimiter,
@@ -217,7 +233,8 @@ func (p *inlineParser) parseLinkOrImageDelimiter() {
 		p.position += 2
 	} else {
 		p.inlines = append(p.inlines, &Text{
-			Text: "!",
+			Text:  "!",
+			Range: Range{absPos, absPos + 1},
 		})
 		p.position++
 	}
@@ -347,8 +364,10 @@ func (p *inlineParser) lookForLinkOrImage() {
 			break
 		}
 	}
+	absPos := relativeToAbsolutePosition(p.ranges, p.position)
 	p.inlines = append(p.inlines, &Text{
-		Text: "]",
+		Text:  "]",
+		Range: Range{absPos, absPos + 1},
 	})
 	p.position++
 }
@@ -403,19 +422,23 @@ func CharacterReference(ref string) string {
 }
 
 func (p *inlineParser) parseCharacterReference() {
+	absPos := relativeToAbsolutePosition(p.ranges, p.position)
 	p.position++
 	if semicolon := strings.IndexByte(p.raw[p.position:], ';'); semicolon == -1 {
 		p.inlines = append(p.inlines, &Text{
-			Text: "&",
+			Text:  "&",
+			Range: Range{absPos, 1},
 		})
 	} else if s := CharacterReference(p.raw[p.position : p.position+semicolon]); s != "" {
 		p.position += semicolon + 1
 		p.inlines = append(p.inlines, &Text{
-			Text: s,
+			Text:  s,
+			Range: Range{absPos, absPos + len(s)},
 		})
 	} else {
 		p.inlines = append(p.inlines, &Text{
-			Text: "&",
+			Text:  "&",
+			Range: Range{absPos, 1},
 		})
 	}
 }
diff --git a/utils/markdown/text_range_test.go b/utils/markdown/text_range_test.go
new file mode 100644
index 000000000..9c0efea85
--- /dev/null
+++ b/utils/markdown/text_range_test.go
@@ -0,0 +1,110 @@
+// Copyright (c) 2018-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package markdown
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestTextRanges(t *testing.T) {
+	for name, tc := range map[string]struct {
+		Markdown       string
+		ExpectedRanges []Range
+		ExpectedValues []string
+	}{
+		"simple": {
+			Markdown:       "hello",
+			ExpectedRanges: []Range{{0, 5}},
+			ExpectedValues: []string{"hello"},
+		},
+		"simple2": {
+			Markdown:       "hello!",
+			ExpectedRanges: []Range{{0, 5}, {5, 6}},
+			ExpectedValues: []string{"hello", "!"},
+		},
+		"multiline": {
+			Markdown:       "hello world\nfoobar",
+			ExpectedRanges: []Range{{0, 11}, {12, 18}},
+			ExpectedValues: []string{"hello world", "foobar"},
+		},
+		"code": {
+			Markdown:       "hello `code` world",
+			ExpectedRanges: []Range{{0, 6}, {12, 18}},
+			ExpectedValues: []string{"hello ", " world"},
+		},
+		"notcode": {
+			Markdown:       "hello ` world",
+			ExpectedRanges: []Range{{0, 6}, {6, 7}, {7, 13}},
+			ExpectedValues: []string{"hello ", "`", " world"},
+		},
+		"escape": {
+			Markdown:       "\\*hello\\*",
+			ExpectedRanges: []Range{{1, 2}, {2, 7}, {8, 9}},
+			ExpectedValues: []string{"*", "hello", "*"},
+		},
+		"escapeescape": {
+			Markdown:       "\\\\",
+			ExpectedRanges: []Range{{1, 2}},
+			ExpectedValues: []string{"\\"},
+		},
+		"notescape": {
+			Markdown:       "foo\\x",
+			ExpectedRanges: []Range{{0, 3}, {3, 4}, {4, 5}},
+			ExpectedValues: []string{"foo", "\\", "x"},
+		},
+		"notlink": {
+			Markdown:       "[foo",
+			ExpectedRanges: []Range{{0, 1}, {1, 4}},
+			ExpectedValues: []string{"[", "foo"},
+		},
+		"notlinkend": {
+			Markdown:       "[foo]",
+			ExpectedRanges: []Range{{0, 1}, {1, 4}, {4, 5}},
+			ExpectedValues: []string{"[", "foo", "]"},
+		},
+		"notimage": {
+			Markdown:       "![foo",
+			ExpectedRanges: []Range{{0, 2}, {2, 5}},
+			ExpectedValues: []string{"![", "foo"},
+		},
+		"notimage2": {
+			Markdown:       "!foo",
+			ExpectedRanges: []Range{{0, 1}, {1, 4}},
+			ExpectedValues: []string{"!", "foo"},
+		},
+		"charref": {
+			Markdown:       "&quot;test",
+			ExpectedRanges: []Range{{0, 1}, {6, 10}},
+			ExpectedValues: []string{"\"", "test"},
+		},
+		"notcharref": {
+			Markdown:       "&amp test",
+			ExpectedRanges: []Range{{0, 1}, {1, 9}},
+			ExpectedValues: []string{"&", "amp test"},
+		},
+		"notcharref2": {
+			Markdown:       "&mattermost;",
+			ExpectedRanges: []Range{{0, 1}, {1, 12}},
+			ExpectedValues: []string{"&", "mattermost;"},
+		},
+	} {
+		t.Run(name, func(t *testing.T) {
+			var ranges []Range
+			var values []string
+			Inspect(tc.Markdown, func(node interface{}) bool {
+				if textNode, ok := node.(*Text); ok {
+					ranges = append(ranges, textNode.Range)
+					values = append(values, textNode.Text)
+				}
+				return true
+			})
+			assert.Equal(t, ranges, tc.ExpectedRanges)
+			assert.Equal(t, values, tc.ExpectedValues)
+
+		})
+	}
+
+}