1 files changed, 112 insertions, 0 deletions
diff --git a/utils/markdown/fenced_code.go b/utils/markdown/fenced_code.go
new file mode 100644
index 000000000..8b2ebd4fe
--- /dev/null
+++ b/utils/markdown/fenced_code.go
@@ -0,0 +1,112 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package markdown
+
+import (
+	"strings"
+)
+
+type FencedCodeLine struct {
+	Indentation int
+	Range       Range
+}
+
+type FencedCode struct {
+	blockBase
+	markdown           string
+	didSeeClosingFence bool
+
+	Indentation  int
+	OpeningFence Range
+	RawInfo      Range
+	RawCode      []FencedCodeLine
+}
+
+func (b *FencedCode) Code() (result string) {
+	for _, code := range b.RawCode {
+		result += strings.Repeat(" ", code.Indentation) + b.markdown[code.Range.Position:code.Range.End]
+	}
+	return
+}
+
+func (b *FencedCode) Info() string {
+	return Unescape(b.markdown[b.RawInfo.Position:b.RawInfo.End])
+}
+
+func (b *FencedCode) Continuation(indentation int, r Range) *continuation {
+	if b.didSeeClosingFence {
+		return nil
+	}
+	return &continuation{
+		Indentation: indentation,
+		Remaining:   r,
+	}
+}
+
+func (b *FencedCode) AddLine(indentation int, r Range) bool {
+	s := b.markdown[r.Position:r.End]
+	if indentation <= 3 && strings.HasPrefix(s, b.markdown[b.OpeningFence.Position:b.OpeningFence.End]) {
+		suffix := strings.TrimSpace(s[b.OpeningFence.End-b.OpeningFence.Position:])
+		isClosingFence := true
+		for _, c := range suffix {
+			if c != rune(s[0]) {
+				isClosingFence = false
+				break
+			}
+		}
+		if isClosingFence {
+			b.didSeeClosingFence = true
+			return true
+		}
+	}
+
+	if indentation >= b.Indentation {
+		indentation -= b.Indentation
+	} else {
+		indentation = 0
+	}
+
+	b.RawCode = append(b.RawCode, FencedCodeLine{
+		Indentation: indentation,
+		Range:       r,
+	})
+	return true
+}
+
+func (b *FencedCode) AllowsBlockStarts() bool {
+	return false
+}
+
+func fencedCodeStart(markdown string, indentation int, r Range, matchedBlocks, unmatchedBlocks []Block) []Block {
+	s := markdown[r.Position:r.End]
+
+	if !strings.HasPrefix(s, "```") && !strings.HasPrefix(s, "~~~") {
+		return nil
+	}
+
+	fenceCharacter := rune(s[0])
+	fenceLength := 3
+	for _, c := range s[3:] {
+		if c == fenceCharacter {
+			fenceLength++
+		} else {
+			break
+		}
+	}
+
+	for i := r.Position + fenceLength; i < r.End; i++ {
+		if markdown[i] == '`' {
+			return nil
+		}
+	}
+
+	return []Block{
+		&FencedCode{
+			markdown:     markdown,
+			Indentation:  indentation,
+			RawInfo:      trimRightSpace(markdown, Range{r.Position + fenceLength, r.End}),
+			OpeningFence: Range{r.Position, r.Position + fenceLength},
+		},
+	}
+}