scripts: replace dark-variant.sh with go scripts/variants

uses regex mostly, resulting in a significantly faster execution (old:
~2s, new: ~31ms). Only matches classList.add/remove and class="..."
(won't touch string literal variables or colours), but these weren't
really used anyway. Supports multi-line classList.add/remove, which was
the reason I wrote this anyway (formatting the codebase introduced some
of these).

scripts/variants/go.mod

@@ -0,0 +1,3 @@
+module github.com/hrfee/jfa-go/scripts/variants
+
+go 1.25.4

scripts/variants/main.go

@@ -0,0 +1,146 @@
+// Package variants provides a script to comb through typescript/javascript files and
+// find (most) instances of a a17t color (~neutral...) being used without
+// an accompanying dark version (dark:~d_neutral...) and insert one.
+// Not fully feature-matched with the old bash version, only matching classList.add/remove and class="...",
+// but doesn't break on multi line function params, and is probably much faster.
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"io/fs"
+	"log"
+	"os"
+	"path/filepath"
+	"regexp"
+)
+
+var classList = func() *regexp.Regexp {
+	classList, err := regexp.Compile(`classList\.(add|remove)(\((?:[^()]*|\((?:[^()]*|\([^()]*\))\))*\))`)
+	if err != nil {
+		panic(err)
+	}
+	return classList
+}()
+var color = func() *regexp.Regexp {
+	color, err := regexp.Compile(`\~(neutral|positive|warning|critical|info|urge|gray)`)
+	if err != nil {
+		panic(err)
+	}
+	return color
+}()
+var quotedColor = func() *regexp.Regexp {
+	quotedColor, err := regexp.Compile(`("|'|\x60)\~(neutral|positive|warning|critical|info|urge|gray)("|'|\x60)`)
+	if err != nil {
+		panic(err)
+	}
+	return quotedColor
+}()
+var htmlClassList = func() *regexp.Regexp {
+	htmlClassList, err := regexp.Compile(`class="[^"]*\~(neutral|positive|warning|critical|info|urge|gray)[^"]*"`)
+	if err != nil {
+		panic(err)
+	}
+	return htmlClassList
+}()
+
+func ParseDir(in, out string) error {
+	err := filepath.WalkDir(in, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		info, err := d.Info()
+		if err != nil {
+			return err
+		}
+		perm := info.Mode()
+		rel, err := filepath.Rel(in, path)
+		outFile := filepath.Join(out, rel)
+		if d.IsDir() {
+			return os.MkdirAll(outFile, perm)
+		}
+		log.Printf("\"%s\" => \"%s\"\n", path, outFile)
+		if err != nil {
+			return err
+		}
+		return ParseFile(path, outFile, &perm)
+	})
+	return err
+}
+
+func ParseFile(in, out string, perm *fs.FileMode) error {
+	file, err := os.ReadFile(in)
+	if err != nil {
+		return err
+	}
+	if perm == nil {
+		f, err := os.Stat(in)
+		if err != nil {
+			return err
+		}
+		p := f.Mode()
+		perm = &p
+	}
+
+	outText := classList.ReplaceAllFunc(file, func(match []byte) []byte {
+		if bytes.Contains(match, []byte("dark:~d_")) {
+			log.Printf("Skipping pre-set dark colour: `%s`\n", string(match))
+			return match
+		}
+		submatches := quotedColor.FindSubmatch(match)
+		if len(submatches) == 0 {
+			return match
+		}
+		quote := string(submatches[1])
+		color := string(submatches[2])
+		fmt.Printf("Matched quote %s, color %s\n", quote, color)
+		newVal := bytes.Replace(match, []byte(quote+"~"+color+quote), []byte(quote+"~"+color+quote+", "+quote+"dark:~d_"+color+quote), 1)
+		fmt.Printf("`%s` => `%s`\n", string(match), string(newVal))
+		return newVal
+	})
+
+	outText = htmlClassList.ReplaceAllFunc(outText, func(match []byte) []byte {
+		if bytes.Contains(match, []byte("dark:~d_")) {
+			log.Printf("Skipping pre-set dark colour: `%s`\n", string(match))
+			return match
+		}
+		// Sucks we can't get a submatch from ReplaceAllFunc
+		submatches := color.FindSubmatch(match)
+		if len(submatches) == 0 {
+			return match
+		}
+		c := submatches[1]
+		newVal := bytes.Replace(match, []byte("~"+string(c)), []byte("~"+string(c)+" dark:~d_"+string(c)), 1)
+		fmt.Printf("`%s` => `%s`\n", string(match), string(newVal))
+		return newVal
+	})
+	err = os.WriteFile(out, outText, *perm)
+	return err
+}
+
+func main() {
+	var inFile, inDir, out string
+	flag.StringVar(&inFile, "file", "", "Input of an individual file.")
+	flag.StringVar(&inDir, "dir", "", "Input of a whole directory.")
+	flag.StringVar(&out, "out", "", "Output filepath/directory, depending on if -file or -dir passed.")
+	flag.Parse()
+
+	if out == "" {
+		flag.PrintDefaults()
+		os.Exit(1)
+	}
+	var err error
+	if inFile != "" {
+		err = ParseFile(inFile, out, nil)
+	} else if inDir != "" {
+		err = ParseDir(inDir, out)
+	} else {
+		flag.PrintDefaults()
+		os.Exit(1)
+	}
+	if err != nil {
+		log.Fatalf("failed: %v\n", err)
+		os.Exit(1)
+	}
+}