package service

import (
	"errors"
	"os"
	"path/filepath"
	"regexp"
	"strings"
	"syscall"

	"github.com/ssgo/u"
	"github.com/tdewolff/minify/v2"
	"github.com/tdewolff/minify/v2/css"
	"github.com/tdewolff/minify/v2/html"
	"github.com/tdewolff/minify/v2/js"
	"github.com/tdewolff/minify/v2/json"
	"github.com/tdewolff/minify/v2/svg"
	"github.com/tdewolff/minify/v2/xml"
)

var m *minify.M

func init() {
	m = minify.New()
	m.AddFunc("text/html", html.Minify)
	m.AddFunc("text/css", css.Minify)
	m.AddFunc("image/svg+xml", svg.Minify)
	m.AddFuncRegexp(regexp.MustCompile("^(application|text)/(x-)?(java|ecma)script$"), js.Minify)
	m.AddFuncRegexp(regexp.MustCompile("[/+]json$"), json.Minify)
	m.AddFuncRegexp(regexp.MustCompile("[/+]xml$"), xml.Minify)
}

var reJSBacktickContent = regexp.MustCompile("(?s)`([^`]*)`")
var reHTMLBetweenTags = regexp.MustCompile(`>\s+<`)

func Minify(from, to string) error {
	srcStat := u.GetFileInfo(from)
	if srcStat == nil {
		return errors.New("file not found: " + from)
	}
	dstStat := u.GetFileInfo(to)
	if dstStat != nil && !srcStat.ModTime.After(dstStat.ModTime) {
		return nil
	}

	tmpTo := filepath.Join(filepath.Dir(to), "."+filepath.Base(to))
	dst, err := os.OpenFile(tmpTo, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
	if err != nil {
		return err
	}
	defer os.Remove(tmpTo)
	defer dst.Close()

	if syscall.Flock(int(dst.Fd()), syscall.LOCK_EX) == nil {
		defer syscall.Flock(int(dst.Fd()), syscall.LOCK_UN)
	}

	dstStat = u.GetFileInfo(to)
	if dstStat != nil && !srcStat.ModTime.After(dstStat.ModTime) {
		return nil
	}

	input := u.ReadFileN(from)
	processedInput := reJSBacktickContent.ReplaceAllStringFunc(input, func(s string) string {
		return "`" + reHTMLBetweenTags.ReplaceAllString(strings.TrimSpace(s[1:len(s)-1]), "><") + "`"
	})

	minifiedOutput, err := m.String(getMimeType(from), processedInput)
	if err != nil {
		return err
	}

	if _, err = dst.WriteString(minifiedOutput); err != nil {
		return err
	}
	if err = dst.Close(); err == nil {
		err = os.Rename(tmpTo, to)
	}
	return err
}

func getMimeType(filename string) string {
	switch filepath.Ext(filename) {
	case ".html", ".htm":
		return "text/html"
	case ".css":
		return "text/css"
	case ".js":
		return "application/javascript"
	case ".json":
		return "application/json"
	case ".svg":
		return "image/svg+xml"
	case ".xml":
		return "text/xml"
	default:
		return "text/plain"
	}
}