package main

import (
	"bytes"
	"fmt"
	"io"
	"io/fs"
	"log"
	"math"
	"net/url"
	"os"
	"os/signal"
	"path/filepath"
	"regexp"
	"runtime"
	"sort"
	"strings"
	"time"

	"github.com/djherbis/atime"

	"github.com/tdewolff/argp"
	min "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"
)

// Version is the current minify version.
var Version = "built from source"

var extMap = map[string]string{
	"asp":         "text/asp",
	"css":         "text/css",
	"ejs":         "text/x-ejs-template",
	"gohtml":      "text/x-go-template",
	"handlebars":  "text/x-handlebars-template",
	"htm":         "text/html",
	"html":        "text/html",
	"js":          "application/javascript",
	"json":        "application/json",
	"mjs":         "application/javascript",
	"mustache":    "text/x-mustache-template",
	"php":         "application/x-httpd-php",
	"rss":         "application/rss+xml",
	"svg":         "image/svg+xml",
	"tmpl":        "text/x-template",
	"webmanifest": "application/manifest+json",
	"xhtml":       "application/xhtml+xml",
	"xml":         "text/xml",
}

var (
	help               bool
	hidden             bool
	inplace            bool
	list               bool
	m                  *min.M
	matches            []string
	matchesRegexp      []*regexp.Regexp
	filters            []string
	filtersRegexp      []*regexp.Regexp
	extensions         map[string]string
	recursive          bool
	quiet              bool
	verbose            int
	version            bool
	watch              bool
	sync               bool
	bundle             bool
	preserve           []string
	preserveMode       bool
	preserveOwnership  bool
	preserveTimestamps bool
	preserveLinks      bool
	mimetype           string
	oldmimetype        string
)

type Matches struct {
	matches *[]string
}

func (m Matches) Help() (string, string) {
	val := ""
	if 0 < len(*m.matches) {
		val = fmt.Sprint(*m.matches)
	}
	return val, "[]string"
}

func (m Matches) Scan(name string, s []string) (int, error) {
	n := 0
	for _, item := range s {
		if strings.HasPrefix(item, "-") {
			break
		}
		*m.matches = append(*m.matches, item)
		n++
	}
	return n, nil
}

type Includes struct {
	filters *[]string
}

func (m Includes) Help() (string, string) {
	val := ""
	if 0 < len(*m.filters) {
		val = fmt.Sprint(*m.filters)
	}
	return val, "[]string"
}

func (m Includes) Scan(name string, s []string) (int, error) {
	n := 0
	for _, item := range s {
		if strings.HasPrefix(item, "-") {
			break
		}
		*m.filters = append(*m.filters, "+"+item)
		n++
	}
	return n, nil
}

type Excludes struct {
	filters *[]string
}

func (m Excludes) Help() (string, string) {
	val := ""
	if 0 < len(*m.filters) {
		val = fmt.Sprint(*m.filters)
	}
	return val, "[]string"
}

func (m Excludes) Scan(name string, s []string) (int, error) {
	n := 0
	for _, item := range s {
		if strings.HasPrefix(item, "-") {
			break
		}
		*m.filters = append(*m.filters, "-"+item)
		n++
	}
	return n, nil
}

// Task is a minify task.
type Task struct {
	root string
	srcs []string
	dst  string
	sync bool
}

// NewTask returns a new Task.
func NewTask(root, input, output string, sync bool) (Task, error) {
	if output == "" {
		output = input // in-place
	} else if output != "-" && (output == "." || output[len(output)-1] == os.PathSeparator || output[len(output)-1] == '/') {
		rel, err := filepath.Rel(root, input)
		if err != nil {
			return Task{}, err
		}
		output = filepath.Join(output, rel)
	}
	return Task{root, []string{input}, output, sync}, nil
}

// Loggers.
var (
	Error   *log.Logger
	Warning *log.Logger
	Info    *log.Logger
	Debug   *log.Logger
)

func main() {
	// os.Exit doesn't execute pending defer calls, this is fixed by encapsulating run()
	os.Exit(run())
}

func run() int {
	var inputs []string
	var output string
	var siteurl string

	cssMinifier := css.Minifier{}
	htmlMinifier := html.Minifier{}
	jsMinifier := js.Minifier{}
	jsonMinifier := json.Minifier{}
	svgMinifier := svg.Minifier{}
	xmlMinifier := xml.Minifier{}

	preserve := []string{"mode", "timestamps"}
	if supportsGetOwnership {
		preserve = []string{"mode", "ownership", "timestamps"}
	}

	f := argp.New("minify")
	f.AddRest(&inputs, "inputs", "Input files or directories, leave blank to use stdin")
	f.AddOpt(&output, "o", "output", "Output file or directory, leave blank to use stdout")
	f.AddOpt(&inplace, "i", "inplace", "Minify input files in-place instead of setting output")
	f.AddOpt(&oldmimetype, "", "mime", "Mimetype (eg. text/css), optional for input filenames (DEPRECATED, use --type)")
	f.AddOpt(&mimetype, "", "type", "Filetype (eg. css or text/css), optional when specifying inputs")
	f.AddOpt(Matches{&matches}, "", "match", "Filename matching pattern, only matching filenames are processed")
	f.AddOpt(Includes{&filters}, "", "include", "Path inclusion pattern, includes paths previously excluded")
	f.AddOpt(Excludes{&filters}, "", "exclude", "Path exclusion pattern, excludes paths from being processed")
	f.AddOpt(&extensions, "", "ext", "Filename extension mapping to filetype (eg. css or text/css)")
	f.AddOpt(&recursive, "r", "recursive", "Recursively minify directories")
	f.AddOpt(&hidden, "a", "all", "Minify all files, including hidden files and files in hidden directories")
	f.AddOpt(&list, "l", "list", "List all accepted filetypes")
	f.AddOpt(&quiet, "q", "quiet", "Quiet mode to suppress all output")
	f.AddOpt(argp.Count{&verbose}, "v", "verbose", "Verbose mode, set twice for more verbosity")
	f.AddOpt(&watch, "w", "watch", "Watch files and minify upon changes")
	f.AddOpt(&sync, "s", "sync", "Copy all files to destination directory and minify when filetype matches")
	f.AddOpt(&preserve, "p", "preserve", "Preserve options (mode, ownership, timestamps, links, all)")
	f.AddOpt(&bundle, "b", "bundle", "Bundle files by concatenation into a single file")
	f.AddOpt(&version, "", "version", "Version")

	f.AddOpt(&siteurl, "", "url", "URL of file to enable URL minification")
	f.AddOpt(&cssMinifier.Precision, "", "css-precision", "Number of significant digits to preserve in numbers, 0 is all")
	f.AddOpt(&cssMinifier.Version, "", "css-version", "CSS version to toggle supported optimizations (e.g. 2), by default 0 is the latest version")
	f.AddOpt(&htmlMinifier.KeepComments, "", "html-keep-comments", "Preserve all comments")
	f.AddOpt(&htmlMinifier.KeepConditionalComments, "", "html-keep-conditional-comments", "Preserve all IE conditional comments (DEPRECATED)")
	f.AddOpt(&htmlMinifier.KeepSpecialComments, "", "html-keep-special-comments", "Preserve all IE conditionals and SSI tags")
	f.AddOpt(&htmlMinifier.KeepDefaultAttrVals, "", "html-keep-default-attrvals", "Preserve default attribute values")
	f.AddOpt(&htmlMinifier.KeepDocumentTags, "", "html-keep-document-tags", "Preserve html, head and body tags")
	f.AddOpt(&htmlMinifier.KeepEndTags, "", "html-keep-end-tags", "Preserve all end tags")
	f.AddOpt(&htmlMinifier.KeepWhitespace, "", "html-keep-whitespace", "Preserve whitespace characters but still collapse multiple into one")
	f.AddOpt(&htmlMinifier.KeepQuotes, "", "html-keep-quotes", "Preserve quotes around attribute values")
	//f.AddOpt(&htmlMinifier.TemplateDelims, "", "html-template-delims", "Set template delimiters explicitly, for example <?,?> for PHP or {{,}} for Go templates") // TODO: fix parsing {{ }} in tdewolff/argp
	f.AddOpt(&jsMinifier.Precision, "", "js-precision", "Number of significant digits to preserve in numbers, 0 is all")
	f.AddOpt(&jsMinifier.KeepVarNames, "", "js-keep-var-names", "Preserve original variable names")
	f.AddOpt(&jsMinifier.Version, "", "js-version", "ECMAScript version to toggle supported optimizations (e.g. 2019, 2020), by default 0 is the latest version")
	f.AddOpt(&jsonMinifier.Precision, "", "json-precision", "Number of significant digits to preserve in numbers, 0 is all")
	f.AddOpt(&jsonMinifier.KeepNumbers, "", "json-keep-numbers", "Preserve original numbers instead of minifying them")
	f.AddOpt(&svgMinifier.KeepComments, "", "svg-keep-comments", "Preserve all comments")
	f.AddOpt(&svgMinifier.Precision, "", "svg-precision", "Number of significant digits to preserve in numbers, 0 is all")
	f.AddOpt(&svgMinifier.KeepNamespaces, "", "svg-keep-namespaces", "Namespaces to keep, besides xlink")
	f.AddOpt(&xmlMinifier.KeepWhitespace, "", "xml-keep-whitespace", "Preserve whitespace characters but still collapse multiple into one")
	f.Parse()

	if version {
		if !quiet {
			fmt.Printf("minify %s\n", Version)
		}
		return 0
	}

	for ext, filetype := range extensions {
		if mimetype, ok := extMap[filetype]; ok {
			filetype = mimetype
		}
		extMap[ext] = filetype
	}

	if list {
		if !quiet {
			n := 0
			var keys []string
			for k := range extMap {
				keys = append(keys, k)
				if n < len(k) {
					n = len(k)
				}
			}
			sort.Strings(keys)
			for _, k := range keys {
				fmt.Println(k + strings.Repeat(" ", n-len(k)+2) + extMap[k])
			}
		}
		return 0
	}

	if len(inputs) == 1 && inputs[0] == "-" {
		inputs = inputs[:0] // stdin
	} else if !inplace && output == "" {
		output = "-" // stdout
	}
	useStdin := len(inputs) == 0

	Error = log.New(io.Discard, "", 0)
	Warning = log.New(io.Discard, "", 0)
	Info = log.New(io.Discard, "", 0)
	Debug = log.New(io.Discard, "", 0)
	if !quiet {
		Error = log.New(os.Stderr, "ERROR: ", 0)
		Warning = log.New(os.Stderr, "WARNING: ", 0)
		if 0 < verbose {
			Info = log.New(os.Stderr, "INFO: ", 0)
		}
		if 1 < verbose {
			Debug = log.New(os.Stderr, "DEBUG: ", 0)
		}
	}

	// compile matches and regexps
	var err error
	if 0 < len(matches) {
		matchesRegexp = make([]*regexp.Regexp, len(matches))
		for i, pattern := range matches {
			if matchesRegexp[i], err = compilePattern(pattern); err != nil {
				Error.Println(err)
				return 1
			}
		}
	}
	if 0 < len(filters) {
		filtersRegexp = make([]*regexp.Regexp, len(filters))
		for i, pattern := range filters {
			if filtersRegexp[i], err = compilePattern(pattern[1:]); err != nil {
				Error.Println(err)
				return 1
			}
		}
	}

	// detect mimetype, mimetype=="" means we'll infer mimetype from file extensions
	if oldmimetype != "" {
		Error.Printf("deprecated use of '--mime %v', please use '--type %v' instead", oldmimetype, oldmimetype)
		mimetype = oldmimetype
	}
	if slash := strings.Index(mimetype, "/"); slash == -1 && 0 < len(mimetype) {
		var ok bool
		if mimetype, ok = extMap[mimetype]; !ok {
			Error.Printf("unknown filetype %v", mimetype)
			return 1
		}
	}

	if inplace && (useStdin || output != "") {
		if useStdin {
			Error.Println("--inplace doesn't work with stdin, specify input")
		}
		if output != "" {
			Error.Println("cannot specify both --inplace and --output")
		}
		return 1
	} else if (useStdin || output == "-") && (watch || sync) {
		if watch {
			Error.Println("--watch doesn't work with stdin and stdout, specify input and output")
		}
		if sync {
			Error.Println("--sync doesn't work with stdin and stdout, specify input and output")
		}
		return 1
	} else if useStdin && (bundle || recursive) {
		if bundle {
			Error.Println("--bundle doesn't work with stdin, specify input")
		}
		if recursive {
			Error.Println("--recursive doesn't work with stdin, specify input")
		}
		return 1
	} else if output == "-" && recursive && !bundle {
		Error.Println("--recursive doesn't work with stdout, specify output or use --bundle")
		return 1
	}
	if mimetype == "" && useStdin {
		Error.Println("must specify --type for stdin")
		return 1
	} else if mimetype != "" && sync {
		Error.Println("must specify either --sync or --type")
		return 1
	}
	if mimetype == "" {
		Debug.Println("infer mimetype from file extensions")
	} else {
		Debug.Printf("use mimetype %v", mimetype)
	}
	if 0 < len(preserve) && (useStdin || output == "") {
		if f.IsSet("preserve") {
			Error.Println("--preserve cannot be used together with stdin, stdout or --inplace")
			return 1
		}
		preserve = preserve[:0]
	}
	for _, option := range preserve {
		switch option {
		case "all":
			preserveMode = true
			preserveOwnership = true
			preserveTimestamps = true
			preserveLinks = true
		case "mode":
			preserveMode = true
		case "ownership":
			preserveOwnership = true
		case "timestamps":
			preserveTimestamps = true
		case "links":
			preserveLinks = true
		}
	}
	if preserveOwnership && !supportsGetOwnership {
		Warning.Println(fmt.Errorf("preserve ownership not supported on platform"))
	}

	////////////////

	for i, input := range inputs {
		if input == "-" {
			Error.Println("cannot mix files and stdin as input")
			return 1
		}
		inputs[i] = filepath.Clean(input)
		if input[len(input)-1] == os.PathSeparator || input[len(input)-1] == '/' {
			inputs[i] += string(os.PathSeparator)
		}
	}

	// set output file or directory, empty means stdout
	dirDst := false
	if output != "" && output != "-" {
		if 0 < len(output) && (output[len(output)-1] == os.PathSeparator || output[len(output)-1] == '/') {
			dirDst = true
		} else if !bundle && 1 < len(inputs) {
			dirDst = true
		} else if !bundle && len(inputs) == 1 && IsDir(inputs[0]) {
			dirDst = true
		}

		if dirDst && bundle {
			Error.Println("--bundle requires destination to be stdout or a file")
			return 1
		}

		output = filepath.Clean(output)
		if dirDst {
			output += string(os.PathSeparator)
		}
	} else if output == "-" && !bundle && 1 < len(inputs) {
		Error.Println("must specify --bundle for multiple input files with stdout destination")
		return 1
	} else if inplace && bundle {
		Error.Println("--bundle cannot be used together with --inplace")
		return 1
	}
	if useStdin {
		Debug.Println("minify from stdin")
	}
	if inplace {
		Debug.Println("minify in-place")
	} else if output == "-" {
		Debug.Println("minify to stdout")
	} else if !dirDst {
		Debug.Printf("minify to output file %v", output)
	} else if output == "."+string(os.PathSeparator) {
		Debug.Println("minify to current working directory")
	} else {
		Debug.Printf("minify to output directory %v", output)
	}

	var tasks []Task
	var roots []string
	if useStdin {
		task, err := NewTask("", "-", output, false)
		if err != nil {
			Error.Println(err)
			return 1
		}
		tasks = append(tasks, task)
		roots = append(roots, "")
	} else {
		fsys := NewFS()
		tasks, roots, err = createTasks(fsys, inputs, output)
		if err != nil {
			Error.Println(err)
			return 1
		}
	}

	// concatenate
	if 1 < len(tasks) && bundle {
		// Task.sync == false because dirDst == false
		for _, task := range tasks[1:] {
			tasks[0].srcs = append(tasks[0].srcs, task.srcs[0])
		}
		tasks = tasks[:1]
	}

	// make output directory
	if dirDst {
		if err := os.MkdirAll(output, 0755); err != nil {
			Error.Println(err)
			return 1
		}
	}

	////////////////

	m = min.New()
	m.Add("text/css", &cssMinifier)
	m.Add("text/html", &htmlMinifier)
	m.Add("image/svg+xml", &svgMinifier)
	m.AddRegexp(regexp.MustCompile("^(application|text)/(x-)?(java|ecma|j|live)script(1\\.[0-5])?$|^module$"), &jsMinifier)
	m.AddRegexp(regexp.MustCompile("[/+]json$"), &jsonMinifier)
	m.AddRegexp(regexp.MustCompile("[/+]xml$"), &xmlMinifier)

	m.Add("importmap", &jsonMinifier)
	m.Add("speculationrules", &jsonMinifier)

	aspMinifier := htmlMinifier
	aspMinifier.TemplateDelims = [2]string{"<%", "%>"}
	m.Add("text/asp", &aspMinifier)
	m.Add("text/x-ejs-template", &aspMinifier)

	phpMinifier := htmlMinifier
	phpMinifier.TemplateDelims = [2]string{"<?", "?>"} // also handles <?php
	m.Add("application/x-httpd-php", &phpMinifier)

	tmplMinifier := htmlMinifier
	tmplMinifier.TemplateDelims = [2]string{"{{", "}}"}
	m.Add("text/x-template", &tmplMinifier)
	m.Add("text/x-go-template", &tmplMinifier)
	m.Add("text/x-mustache-template", &tmplMinifier)
	m.Add("text/x-handlebars-template", &tmplMinifier)

	if m.URL, err = url.Parse(siteurl); err != nil {
		Error.Println(err)
		return 1
	}

	fails := 0
	start := time.Now()
	if !watch && (len(tasks) == 1 || 0 < verbose) {
		for _, task := range tasks {
			if ok := minify(task); !ok {
				fails++
			}
		}
	} else {
		numWorkers := runtime.NumCPU()
		if 0 < verbose {
			numWorkers = 1
		} else if numWorkers < 4 {
			numWorkers = 4
		}

		chanTasks := make(chan Task, 20)
		chanFails := make(chan int, numWorkers)
		for n := 0; n < numWorkers; n++ {
			go minifyWorker(chanTasks, chanFails)
		}

		if !watch {
			for _, task := range tasks {
				chanTasks <- task
			}
		} else {
			watcher, err := NewWatcher(recursive)
			if err != nil {
				Error.Println(err)
				return 1
			}
			defer watcher.Close()
			changes := watcher.Run()

			taskMap := map[string]*Task{}
			for _, task := range tasks {
				for _, src := range task.srcs {
					taskMap[src] = &task
					watcher.AddPath(src)
				}
				watcher.IgnoreNext(task.dst) // skip change on output
				chanTasks <- task
			}

			c := make(chan os.Signal, 1)
			signal.Notify(c, os.Interrupt)
			for changes != nil {
				select {
				case <-c:
					watcher.Close()
				case file, ok := <-changes:
					if !ok {
						changes = nil
						break
					}

					task, ok := taskMap[filepath.Clean(file)]
					if !ok {
						continue
					}
					watcher.IgnoreNext(task.dst) // skip change on output
					chanTasks <- *task
				}
			}
		}
		close(chanTasks)
		for n := 0; n < numWorkers; n++ {
			fails += <-chanFails
		}
	}

	if !watch {
		Info.Printf("finished in %v", time.Since(start))
	}
	if 0 < fails {
		return 1
	}
	return 0
}

func minifyWorker(chanTasks <-chan Task, chanFails chan<- int) {
	fails := 0
	for task := range chanTasks {
		if ok := minify(task); !ok {
			fails++
		}
	}
	chanFails <- fails
}

// compilePattern returns *regexp.Regexp or glob.Glob
func compilePattern(pattern string) (*regexp.Regexp, error) {
	if len(pattern) == 0 || pattern[0] != '~' {
		sep := regexp.QuoteMeta(string(filepath.Separator))
		if strings.HasPrefix(pattern, `\~`) {
			pattern = pattern[1:]
		}
		pattern = regexp.QuoteMeta(pattern)
		pattern = strings.ReplaceAll(pattern, `\\\*`, `\*`)
		pattern = strings.ReplaceAll(pattern, `\\\?`, `\?`)
		pattern = strings.ReplaceAll(pattern, `\*\*`, `.*`)
		pattern = strings.ReplaceAll(pattern, `\*`, fmt.Sprintf(`[^%s]*`, sep))
		pattern = strings.ReplaceAll(pattern, `\?`, fmt.Sprintf(`[^%s]`, sep))
		pattern = "^" + pattern + "$"
	} else {
		pattern = pattern[1:]
	}
	return regexp.Compile(pattern)
}

func fileFilter(filename string) bool {
	if 0 < len(matches) {
		match := false
		base := filepath.Base(filename)
		for _, re := range matchesRegexp {
			if re.MatchString(base) {
				match = true
				break
			}
		}
		if !match {
			return false
		}
	}
	match := true
	for i, re := range filtersRegexp {
		if re.MatchString(filename) {
			match = filters[i][0] == '+'
		}
	}
	return match
}

func fileMatches(filename string) bool {
	if !fileFilter(filename) {
		return false
	} else if mimetype != "" {
		return true
	}

	ext := filepath.Ext(filename)
	if 0 < len(ext) {
		ext = ext[1:]
	}
	if _, ok := extMap[ext]; !ok {
		return false
	}
	return true
}

func createTasks(fsys fs.FS, inputs []string, output string) ([]Task, []string, error) {
	tasks := []Task{}
	roots := []string{}
	for _, input := range inputs {
		root := filepath.Clean(filepath.Dir(input))
		input = filepath.Clean(input)

		var err error
		var info os.FileInfo
		if !preserveLinks {
			// follow and dereference symlinks
			info, err = fs.Stat(fsys, input)
		} else {
			info, err = os.Lstat(input)
		}
		if err != nil {
			Error.Println(err)
			continue
		}

		if preserveLinks && info.Mode()&os.ModeSymlink != 0 {
			// copy symlink as is
			if !sync {
				return nil, nil, fmt.Errorf("--sync not specified, omitting symbolic link %v", input)
			}
			task, err := NewTask(root, input, output, true)
			if err != nil {
				return nil, nil, err
			}
			tasks = append(tasks, task)
		} else if info.Mode().IsRegular() {
			valid := fileFilter(input) // don't filter mimetype
			if valid || sync {
				if mimetype == "" && !sync {
					ext := filepath.Ext(input)
					if 0 < len(ext) {
						ext = ext[1:]
					}
					if _, ok := extMap[ext]; !ok {
						return nil, nil, fmt.Errorf("cannot infer mimetype from extension in %v, set --type explicitly", input)
					}
				}
				task, err := NewTask(root, input, output, !valid)
				if err != nil {
					return nil, nil, err
				}
				tasks = append(tasks, task)
			}
		} else if info.Mode().IsDir() {
			if !recursive {
				Warning.Printf("--recursive not specified, omitting directory %v", input)
				continue
			}

			var walkFn func(string, fs.DirEntry, error) error
			walkFn = func(input string, d fs.DirEntry, err error) error {
				if err != nil {
					return err
				} else if d.Name() == "." || d.Name() == ".." {
					return nil
				} else if d.Name() == "" || !hidden && d.Name()[0] == '.' {
					if d.IsDir() {
						return fs.SkipDir
					}
					return nil
				}

				if !preserveLinks && d.Type()&os.ModeSymlink != 0 {
					// follow and dereference symlinks
					info, err := fs.Stat(fsys, input)
					if err != nil {
						Error.Println(err)
						return nil
					}
					if info.IsDir() {
						return fs.WalkDir(fsys, input, walkFn)
					}
					d = fs.FileInfoToDirEntry(info)
				}

				if preserveLinks && d.Type()&os.ModeSymlink != 0 {
					// copy symlink as is
					if !sync {
						Warning.Printf("--sync not specified, omitting symbolic link %v", input)
						return nil
					}
					task, err := NewTask(root, input, output, true)
					if err != nil {
						return err
					}
					tasks = append(tasks, task)
				} else if d.Type().IsRegular() {
					valid := fileMatches(input)
					if valid || sync {
						task, err := NewTask(root, input, output, !valid)
						if err != nil {
							return err
						}
						tasks = append(tasks, task)
					}
				}
				return nil
			}
			if err := fs.WalkDir(fsys, input, walkFn); err != nil {
				return nil, nil, err
			}
			roots = append(roots, root)
		} else {
			return nil, nil, fmt.Errorf("not a file or directory %s", input)
		}
	}
	return tasks, roots, nil
}

func minify(t Task) bool {
	// synchronizing files that are not minified but just copied to the same directory, no action needed
	if t.sync {
		if t.srcs[0] == t.dst {
			return true
		} else if info, err := os.Lstat(t.srcs[0]); preserveLinks && err == nil && info.Mode()&os.ModeSymlink != 0 {
			if src, err := os.Readlink(t.srcs[0]); err != nil {
				Error.Println(err)
				return false
			} else if err := createSymlink(src, t.dst); err != nil {
				Error.Println(err)
				return false
			}
			return true
		}
	}

	fileMimetype := mimetype
	if mimetype == "" && !t.sync {
		for _, src := range t.srcs {
			ext := filepath.Ext(src)
			if 0 < len(ext) {
				ext = ext[1:]
			}
			if srcMimetype, ok := extMap[ext]; !ok {
				Warning.Printf("cannot infer mimetype from extension in %v, set --type explicitly", src)
				return false
			} else if fileMimetype == "" {
				fileMimetype = srcMimetype
			} else if srcMimetype != fileMimetype {
				Warning.Printf("inferred mimetype %v of %v for concatenation unequal to previous mimetypes, set --type explicitly", srcMimetype, src)
				return false
			}
		}
	}

	srcs := append([]string{}, t.srcs...)
	srcName := strings.Join(srcs, " + ")
	if len(srcs) > 1 {
		srcName = "(" + srcName + ")"
	}
	if srcName == "" {
		srcName = "stdin"
	}
	dstName := t.dst
	if dstName == "-" {
		dstName = "stdout"
	} else {
		// rename original when overwriting
		for i := range srcs {
			if sameFile, _ := SameFile(srcs[i], t.dst); sameFile {
				srcs[i] += ".bak"
				err := retry(5, func() error {
					return os.Rename(t.dst, srcs[i])
				})
				if err != nil {
					Error.Println(err)
					return false
				}
				break
			}
		}
	}

	var err error
	var fr io.ReadCloser
	var fw io.WriteCloser
	if len(srcs) == 1 {
		fr, err = openInputFile(srcs[0])
	} else {
		var sep []byte
		if err == nil && fileMimetype == extMap["js"] {
			sep = []byte(";\n")
		}
		fr, err = openInputFiles(srcs, sep)
	}
	if err != nil {
		Error.Println(err)
		return false
	}

	fw, err = openOutputFile(t.dst)
	if err != nil {
		Error.Println(err)
		fr.Close()
		return false
	}

	// synchronize file
	if t.sync {
		_, err = io.Copy(fw, fr)
		fr.Close()
		fw.Close()
		if err != nil {
			Error.Println(err)
			return false
		}
		preserveAttributes(srcs, t.root, t.dst)
		Info.Printf("copy %v to %v", srcName, dstName)
		return true
	}

	b, err := io.ReadAll(fr)
	if err != nil {
		fr.Close()
		fw.Close()
		Error.Printf("cannot minify %v: %v", srcName, err)
		return false
	}
	w := bytes.NewBuffer(make([]byte, 0, len(b)))

	success := true
	startTime := time.Now()
	if err = m.Minify(fileMimetype, w, bytes.NewReader(b)); err != nil {
		w = bytes.NewBuffer(b) // copy original
		Error.Printf("cannot minify %v: %v", srcName, err)
		success = false
	}

	rLen, wLen := len(b), w.Len()
	_, err = io.Copy(fw, w)
	fr.Close()
	fw.Close()

	if !quiet {
		dur := time.Since(startTime)
		speed := "Inf MB"
		if 0 < dur {
			speed = formatBytes(uint64(float64(rLen) / dur.Seconds()))
		}
		ratio := 1.0
		if 0 < rLen {
			ratio = float64(wLen) / float64(rLen)
		}

		stats := fmt.Sprintf("(%6v, %6v, %6v, %5.1f%%, %6v/s)", formatDuration(dur), formatBytes(uint64(rLen)), formatBytes(uint64(wLen)), ratio*100.0, speed)
		if srcName != dstName {
			fmt.Printf("%v - %v to %v\n", stats, srcName, dstName)
		} else {
			fmt.Printf("%v - %v\n", stats, srcName)
		}
	}

	if t.dst != "-" {
		// remove original that was renamed, when overwriting files
		for i := range srcs {
			if srcs[i] == t.dst+".bak" {
				if err == nil {
					if err = os.Remove(srcs[i]); err != nil {
						Error.Println(err)
						return false
					}
				} else {
					if err = os.Remove(t.dst); err != nil {
						Error.Println(err)
						return false
					} else if err = os.Rename(srcs[i], t.dst); err != nil {
						Error.Println(err)
						return false
					}
				}
				srcs[i] = t.dst
				break
			}
		}
		preserveAttributes(srcs, t.root, t.dst)
	}
	return success
}

func retry(attempts int, fn func() error) (err error) {
	for ; 0 < attempts; attempts-- {
		if err = fn(); err == nil {
			return
		}
	}
	return
}

func preserveAttributes(srcs []string, root, dst string) {
	if len(srcs) == 0 || dst == "" {
		return
	}

	// only with --bundle we allow 1 < len(srcs)

	// make sure we only set attributes on directories and files inside the root destination
	var err error
	for i := range srcs {
		if srcs[i], err = filepath.Rel(root, srcs[i]); err != nil {
			// should never occur
			Error.Printf("src is not part of root path: src=%s root=%s", srcs[i], root)
			return
		}
	}

	srcInfos := make([]os.FileInfo, len(srcs))
Next:
	for i := range srcs {
		if srcInfos[i], err = os.Stat(filepath.Join(root, srcs[i])); err != nil {
			Warning.Println(err)
			return
		}
	}

	if preserveMode {
		valid := true
		perm := srcInfos[0].Mode().Perm()
		for _, srcInfo := range srcInfos[1:] {
			if srcInfo.Mode().Perm() != perm {
				Warning.Println("src permissions are different, won't set dst permissions")
				valid = false
				break
			}
		}
		if valid {
			if err = os.Chmod(dst, perm); err != nil {
				Warning.Println(err)
			}
		}
	}
	if preserveOwnership {
		if uid, gid, ok := getOwnership(srcInfos[0]); ok {
			valid := true
			for _, srcInfo := range srcInfos[1:] {
				if uid2, gid2, ok2 := getOwnership(srcInfo); !ok2 || uid2 != uid || gid2 != gid {
					Warning.Println("src ownership is different, won't set dst ownership")
					valid = false
					break
				}
			}
			if valid {
				if err = os.Chown(dst, uid, gid); err != nil {
					Warning.Println(err)
				}
			}
		} else {
			Warning.Println("unable to set file ownership")
		}
	}
	if preserveTimestamps {
		accessTime := atime.Get(srcInfos[0])
		modTime := srcInfos[0].ModTime()
		for _, srcInfo := range srcInfos[1:] {
			if accessTime2 := atime.Get(srcInfo); accessTime2.After(accessTime) {
				accessTime = accessTime2
			}
			if modTime2 := srcInfo.ModTime(); modTime2.After(modTime) {
				modTime = modTime2
			}
		}
		if err = os.Chtimes(dst, accessTime, modTime); err != nil {
			Warning.Println(err)
		}
	}

	// when using --bundle there are no directories to preserve
	if 1 < len(srcs) {
		return
	}

	dst = filepath.Dir(dst)
	if srcs[0] = filepath.Dir(srcs[0]); srcs[0] != "." {
		// go up to but excluding the root path
		goto Next
	}
}

func formatBytes(size uint64) string {
	if size < 10 {
		return fmt.Sprintf("%d B", size)
	}

	units := []string{"B", "kB", "MB", "GB", "TB", "PB", "EB"}
	scale := int(math.Floor((math.Log10(float64(size)) + math.Log10(2.0)) / 3.0))
	value := float64(size) / math.Pow10(scale*3.0)
	format := "%.0f %s"
	if value < 10.0 {
		format = "%.1f %s"
	}
	return fmt.Sprintf(format, value, units[scale])
}

func formatDuration(dur time.Duration) string {
	str := ""
	if 1.0 <= dur.Hours() {
		hours, _ := math.Modf(dur.Hours())
		str += fmt.Sprintf("%dh", int(hours+0.5))
		dur -= time.Duration(int(hours+0.5) * 3600 * 1e9)
	}
	if 1.0 <= dur.Minutes() {
		minutes, _ := math.Modf(dur.Minutes())
		str += fmt.Sprintf("%dm", int(minutes+0.5))
		dur -= time.Duration(int(minutes+0.5) * 60 * 1e9)
	}
	if 1.0 <= dur.Seconds() {
		seconds, _ := math.Modf(dur.Seconds())
		str += fmt.Sprintf("%ds", int(seconds+0.5))
		dur -= time.Duration(int(seconds+0.5) * 1e9)
	}
	if 0 < len(str) {
		return str
	} else if dur == 0 {
		return "0s"
	} else if dur < 10 {
		return fmt.Sprintf("%d ns", dur)
	}

	size := dur.Nanoseconds()
	units := []string{"ns", "µs", "ms", "s"}
	scale := int(math.Floor((math.Log10(float64(size)) + math.Log10(2.0)) / 3.0))
	value := float64(size) / math.Pow10(scale*3.0)
	format := "%.0f %s"
	if value < 10.0 {
		format = "%.1f %s"
	}
	return fmt.Sprintf(format, value, units[scale])
}
