Detect delimiter in CSV rendering (#7869)

* detect csv delimiter in csv rendering

fixes #7868

* make linter happy

* fix failing testcase & use ints where possible

* expose markup type to template

previously all markup had the .markdown class, which is incorrect,
as it applies markdown CSS & JS logic to CSV rendering

* fix build (missing `make css`)

* ignore quoted csv content for delimiter scoring

also fix html generation

2 files changed, 66 insertions, 6 deletions

diff --git a/modules/markup/csv/csv.go b/modules/markup/csv/csv.go
index 077947e774..1e3acc9b47 100644
--- a/modules/markup/csv/csv.go
+++ b/modules/markup/csv/csv.go
@@ -9,12 +9,18 @@ import (
 	"encoding/csv"
 	"html"
 	"io"
+	"regexp"
+	"strings"
 
 	"code.gitea.io/gitea/modules/markup"
+	"code.gitea.io/gitea/modules/util"
 )
 
+var quoteRegexp = regexp.MustCompile(`["'][\s\S]+?["']`)
+
 func init() {
 	markup.RegisterParser(Parser{})
+
 }
 
 // Parser implements markup.Parser for orgmode
@@ -28,12 +34,13 @@ func (Parser) Name() string {
 
 // Extensions implements markup.Parser
 func (Parser) Extensions() []string {
-	return []string{".csv"}
+	return []string{".csv", ".tsv"}
 }
 
 // Render implements markup.Parser
-func (Parser) Render(rawBytes []byte, urlPrefix string, metas map[string]string, isWiki bool) []byte {
+func (p Parser) Render(rawBytes []byte, urlPrefix string, metas map[string]string, isWiki bool) []byte {
 	rd := csv.NewReader(bytes.NewReader(rawBytes))
+	rd.Comma = p.bestDelimiter(rawBytes)
 	var tmpBlock bytes.Buffer
 	tmpBlock.WriteString(`<table class="table">`)
 	for {
@@ -50,9 +57,57 @@ func (Parser) Render(rawBytes []byte, urlPrefix string, metas map[string]string,
 			tmpBlock.WriteString(html.EscapeString(field))
 			tmpBlock.WriteString("</td>")
 		}
-		tmpBlock.WriteString("<tr>")
+		tmpBlock.WriteString("</tr>")
 	}
 	tmpBlock.WriteString("</table>")
 
 	return tmpBlock.Bytes()
 }
+
+// bestDelimiter scores the input CSV data against delimiters, and returns the best match.
+// Reads at most 10k bytes & 10 lines.
+func (p Parser) bestDelimiter(data []byte) rune {
+	maxLines := 10
+	maxBytes := util.Min(len(data), 1e4)
+	text := string(data[:maxBytes])
+	text = quoteRegexp.ReplaceAllLiteralString(text, "")
+	lines := strings.SplitN(text, "\n", maxLines+1)
+	lines = lines[:util.Min(maxLines, len(lines))]
+
+	delimiters := []rune{',', ';', '\t', '|'}
+	bestDelim := delimiters[0]
+	bestScore := 0.0
+	for _, delim := range delimiters {
+		score := p.scoreDelimiter(lines, delim)
+		if score > bestScore {
+			bestScore = score
+			bestDelim = delim
+		}
+	}
+
+	return bestDelim
+}
+
+// scoreDelimiter uses a count & regularity metric to evaluate a delimiter against lines of CSV
+func (Parser) scoreDelimiter(lines []string, delim rune) (score float64) {
+	countTotal := 0
+	countLineMax := 0
+	linesNotEqual := 0
+
+	for _, line := range lines {
+		if len(line) == 0 {
+			continue
+		}
+
+		countLine := strings.Count(line, string(delim))
+		countTotal += countLine
+		if countLine != countLineMax {
+			if countLineMax != 0 {
+				linesNotEqual++
+			}
+			countLineMax = util.Max(countLine, countLineMax)
+		}
+	}
+
+	return float64(countTotal) * (1 - float64(linesNotEqual)/float64(len(lines)))
+}
diff --git a/modules/markup/csv/csv_test.go b/modules/markup/csv/csv_test.go
index f050296cee..4d4e0871e9 100644
--- a/modules/markup/csv/csv_test.go
+++ b/modules/markup/csv/csv_test.go
@@ -13,9 +13,14 @@ import (
 func TestRenderCSV(t *testing.T) {
 	var parser Parser
 	var kases = map[string]string{
-		"a":     "<table class=\"table\"><tr><td>a</td><tr></table>",
-		"1,2":   "<table class=\"table\"><tr><td>1</td><td>2</td><tr></table>",
-		"<br/>": "<table class=\"table\"><tr><td>&lt;br/&gt;</td><tr></table>",
+		"a":                         "<table class=\"table\"><tr><td>a</td></tr></table>",
+		"1,2":                       "<table class=\"table\"><tr><td>1</td><td>2</td></tr></table>",
+		"1;2":                       "<table class=\"table\"><tr><td>1</td><td>2</td></tr></table>",
+		"1\t2":                      "<table class=\"table\"><tr><td>1</td><td>2</td></tr></table>",
+		"1|2":                       "<table class=\"table\"><tr><td>1</td><td>2</td></tr></table>",
+		"1,2,3;4,5,6;7,8,9\na;b;c":  "<table class=\"table\"><tr><td>1,2,3</td><td>4,5,6</td><td>7,8,9</td></tr><tr><td>a</td><td>b</td><td>c</td></tr></table>",
+		"\"1,2,3,4\";\"a\nb\"\nc;d": "<table class=\"table\"><tr><td>1,2,3,4</td><td>a\nb</td></tr><tr><td>c</td><td>d</td></tr></table>",
+		"<br/>":                     "<table class=\"table\"><tr><td>&lt;br/&gt;</td></tr></table>",
 	}
 
 	for k, v := range kases {