Server-side syntax highlighting for all code (#12047)

* Server-side syntax hilighting for all code

This PR does a few things:

* Remove all traces of highlight.js
* Use chroma library to provide fast syntax hilighting directly on the server
* Provide syntax hilighting for diffs
* Re-style both unified and split diffs views
* Add custom syntax hilighting styling for both regular and arc-green

Fixes #7729
Fixes #10157
Fixes #11825
Fixes #7728
Fixes #3872
Fixes #3682

And perhaps gets closer to #9553

* fix line marker

* fix repo search

* Fix single line select

* properly load settings

* npm uninstall highlight.js

* review suggestion

* code review

* forgot to call function

* fix test

* Apply suggestions from code review

suggestions from @silverwind thanks

Co-authored-by: silverwind <me@silverwind.io>

* code review

* copy/paste error

* Use const for highlight size limit

* Update web_src/less/_repository.less

Co-authored-by: Lauris BH <lauris@nix.lv>

* update size limit to 1MB and other styling tweaks

* fix highlighting for certain diff sections

* fix test

* add worker back as suggested

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Lauris BH <lauris@nix.lv>

vendor/github.com/dlclark/regexp2/match.go

@@ -0,0 +1,347 @@
+package regexp2
+
+import (
+	"bytes"
+	"fmt"
+)
+
+// Match is a single regex result match that contains groups and repeated captures
+// 	-Groups
+//    -Capture
+type Match struct {
+	Group //embeded group 0
+
+	regex       *Regexp
+	otherGroups []Group
+
+	// input to the match
+	textpos   int
+	textstart int
+
+	capcount   int
+	caps       []int
+	sparseCaps map[int]int
+
+	// output from the match
+	matches    [][]int
+	matchcount []int
+
+	// whether we've done any balancing with this match.  If we
+	// have done balancing, we'll need to do extra work in Tidy().
+	balancing bool
+}
+
+// Group is an explicit or implit (group 0) matched group within the pattern
+type Group struct {
+	Capture // the last capture of this group is embeded for ease of use
+
+	Name     string    // group name
+	Captures []Capture // captures of this group
+}
+
+// Capture is a single capture of text within the larger original string
+type Capture struct {
+	// the original string
+	text []rune
+	// the position in the original string where the first character of
+	// captured substring was found.
+	Index int
+	// the length of the captured substring.
+	Length int
+}
+
+// String returns the captured text as a String
+func (c *Capture) String() string {
+	return string(c.text[c.Index : c.Index+c.Length])
+}
+
+// Runes returns the captured text as a rune slice
+func (c *Capture) Runes() []rune {
+	return c.text[c.Index : c.Index+c.Length]
+}
+
+func newMatch(regex *Regexp, capcount int, text []rune, startpos int) *Match {
+	m := Match{
+		regex:      regex,
+		matchcount: make([]int, capcount),
+		matches:    make([][]int, capcount),
+		textstart:  startpos,
+		balancing:  false,
+	}
+	m.Name = "0"
+	m.text = text
+	m.matches[0] = make([]int, 2)
+	return &m
+}
+
+func newMatchSparse(regex *Regexp, caps map[int]int, capcount int, text []rune, startpos int) *Match {
+	m := newMatch(regex, capcount, text, startpos)
+	m.sparseCaps = caps
+	return m
+}
+
+func (m *Match) reset(text []rune, textstart int) {
+	m.text = text
+	m.textstart = textstart
+	for i := 0; i < len(m.matchcount); i++ {
+		m.matchcount[i] = 0
+	}
+	m.balancing = false
+}
+
+func (m *Match) tidy(textpos int) {
+
+	interval := m.matches[0]
+	m.Index = interval[0]
+	m.Length = interval[1]
+	m.textpos = textpos
+	m.capcount = m.matchcount[0]
+	//copy our root capture to the list
+	m.Group.Captures = []Capture{m.Group.Capture}
+
+	if m.balancing {
+		// The idea here is that we want to compact all of our unbalanced captures.  To do that we
+		// use j basically as a count of how many unbalanced captures we have at any given time
+		// (really j is an index, but j/2 is the count).  First we skip past all of the real captures
+		// until we find a balance captures.  Then we check each subsequent entry.  If it's a balance
+		// capture (it's negative), we decrement j.  If it's a real capture, we increment j and copy
+		// it down to the last free position.
+		for cap := 0; cap < len(m.matchcount); cap++ {
+			limit := m.matchcount[cap] * 2
+			matcharray := m.matches[cap]
+
+			var i, j int
+
+			for i = 0; i < limit; i++ {
+				if matcharray[i] < 0 {
+					break
+				}
+			}
+
+			for j = i; i < limit; i++ {
+				if matcharray[i] < 0 {
+					// skip negative values
+					j--
+				} else {
+					// but if we find something positive (an actual capture), copy it back to the last
+					// unbalanced position.
+					if i != j {
+						matcharray[j] = matcharray[i]
+					}
+					j++
+				}
+			}
+
+			m.matchcount[cap] = j / 2
+		}
+
+		m.balancing = false
+	}
+}
+
+// isMatched tells if a group was matched by capnum
+func (m *Match) isMatched(cap int) bool {
+	return cap < len(m.matchcount) && m.matchcount[cap] > 0 && m.matches[cap][m.matchcount[cap]*2-1] != (-3+1)
+}
+
+// matchIndex returns the index of the last specified matched group by capnum
+func (m *Match) matchIndex(cap int) int {
+	i := m.matches[cap][m.matchcount[cap]*2-2]
+	if i >= 0 {
+		return i
+	}
+
+	return m.matches[cap][-3-i]
+}
+
+// matchLength returns the length of the last specified matched group by capnum
+func (m *Match) matchLength(cap int) int {
+	i := m.matches[cap][m.matchcount[cap]*2-1]
+	if i >= 0 {
+		return i
+	}
+
+	return m.matches[cap][-3-i]
+}
+
+// Nonpublic builder: add a capture to the group specified by "c"
+func (m *Match) addMatch(c, start, l int) {
+
+	if m.matches[c] == nil {
+		m.matches[c] = make([]int, 2)
+	}
+
+	capcount := m.matchcount[c]
+
+	if capcount*2+2 > len(m.matches[c]) {
+		oldmatches := m.matches[c]
+		newmatches := make([]int, capcount*8)
+		copy(newmatches, oldmatches[:capcount*2])
+		m.matches[c] = newmatches
+	}
+
+	m.matches[c][capcount*2] = start
+	m.matches[c][capcount*2+1] = l
+	m.matchcount[c] = capcount + 1
+	//log.Printf("addMatch: c=%v, i=%v, l=%v ... matches: %v", c, start, l, m.matches)
+}
+
+// Nonpublic builder: Add a capture to balance the specified group.  This is used by the
+//                     balanced match construct. (?<foo-foo2>...)
+//
+// If there were no such thing as backtracking, this would be as simple as calling RemoveMatch(c).
+// However, since we have backtracking, we need to keep track of everything.
+func (m *Match) balanceMatch(c int) {
+	m.balancing = true
+
+	// we'll look at the last capture first
+	capcount := m.matchcount[c]
+	target := capcount*2 - 2
+
+	// first see if it is negative, and therefore is a reference to the next available
+	// capture group for balancing.  If it is, we'll reset target to point to that capture.
+	if m.matches[c][target] < 0 {
+		target = -3 - m.matches[c][target]
+	}
+
+	// move back to the previous capture
+	target -= 2
+
+	// if the previous capture is a reference, just copy that reference to the end.  Otherwise, point to it.
+	if target >= 0 && m.matches[c][target] < 0 {
+		m.addMatch(c, m.matches[c][target], m.matches[c][target+1])
+	} else {
+		m.addMatch(c, -3-target, -4-target /* == -3 - (target + 1) */)
+	}
+}
+
+// Nonpublic builder: removes a group match by capnum
+func (m *Match) removeMatch(c int) {
+	m.matchcount[c]--
+}
+
+// GroupCount returns the number of groups this match has matched
+func (m *Match) GroupCount() int {
+	return len(m.matchcount)
+}
+
+// GroupByName returns a group based on the name of the group, or nil if the group name does not exist
+func (m *Match) GroupByName(name string) *Group {
+	num := m.regex.GroupNumberFromName(name)
+	if num < 0 {
+		return nil
+	}
+	return m.GroupByNumber(num)
+}
+
+// GroupByNumber returns a group based on the number of the group, or nil if the group number does not exist
+func (m *Match) GroupByNumber(num int) *Group {
+	// check our sparse map
+	if m.sparseCaps != nil {
+		if newNum, ok := m.sparseCaps[num]; ok {
+			num = newNum
+		}
+	}
+	if num >= len(m.matchcount) || num < 0 {
+		return nil
+	}
+
+	if num == 0 {
+		return &m.Group
+	}
+
+	m.populateOtherGroups()
+
+	return &m.otherGroups[num-1]
+}
+
+// Groups returns all the capture groups, starting with group 0 (the full match)
+func (m *Match) Groups() []Group {
+	m.populateOtherGroups()
+	g := make([]Group, len(m.otherGroups)+1)
+	g[0] = m.Group
+	copy(g[1:], m.otherGroups)
+	return g
+}
+
+func (m *Match) populateOtherGroups() {
+	// Construct all the Group objects first time called
+	if m.otherGroups == nil {
+		m.otherGroups = make([]Group, len(m.matchcount)-1)
+		for i := 0; i < len(m.otherGroups); i++ {
+			m.otherGroups[i] = newGroup(m.regex.GroupNameFromNumber(i+1), m.text, m.matches[i+1], m.matchcount[i+1])
+		}
+	}
+}
+
+func (m *Match) groupValueAppendToBuf(groupnum int, buf *bytes.Buffer) {
+	c := m.matchcount[groupnum]
+	if c == 0 {
+		return
+	}
+
+	matches := m.matches[groupnum]
+
+	index := matches[(c-1)*2]
+	last := index + matches[(c*2)-1]
+
+	for ; index < last; index++ {
+		buf.WriteRune(m.text[index])
+	}
+}
+
+func newGroup(name string, text []rune, caps []int, capcount int) Group {
+	g := Group{}
+	g.text = text
+	if capcount > 0 {
+		g.Index = caps[(capcount-1)*2]
+		g.Length = caps[(capcount*2)-1]
+	}
+	g.Name = name
+	g.Captures = make([]Capture, capcount)
+	for i := 0; i < capcount; i++ {
+		g.Captures[i] = Capture{
+			text:   text,
+			Index:  caps[i*2],
+			Length: caps[i*2+1],
+		}
+	}
+	//log.Printf("newGroup! capcount %v, %+v", capcount, g)
+
+	return g
+}
+
+func (m *Match) dump() string {
+	buf := &bytes.Buffer{}
+	buf.WriteRune('\n')
+	if len(m.sparseCaps) > 0 {
+		for k, v := range m.sparseCaps {
+			fmt.Fprintf(buf, "Slot %v -> %v\n", k, v)
+		}
+	}
+
+	for i, g := range m.Groups() {
+		fmt.Fprintf(buf, "Group %v (%v), %v caps:\n", i, g.Name, len(g.Captures))
+
+		for _, c := range g.Captures {
+			fmt.Fprintf(buf, "  (%v, %v) %v\n", c.Index, c.Length, c.String())
+		}
+	}
+	/*
+		for i := 0; i < len(m.matchcount); i++ {
+			fmt.Fprintf(buf, "\nGroup %v (%v):\n", i, m.regex.GroupNameFromNumber(i))
+
+			for j := 0; j < m.matchcount[i]; j++ {
+				text := ""
+
+				if m.matches[i][j*2] >= 0 {
+					start := m.matches[i][j*2]
+					text = m.text[start : start+m.matches[i][j*2+1]]
+				}
+
+				fmt.Fprintf(buf, "  (%v, %v) %v\n", m.matches[i][j*2], m.matches[i][j*2+1], text)
+			}
+		}
+	*/
+	return buf.String()
+}