[Breaking Change] Another overhaul of the code

This was made possible by the previous overhaul and cleanup

* Code now uses strings.Builder instead of slices
* Fixed --add-frame flag to only work for PNG
* Moved --format to only work as ?format=
* Added --free-style to replace previous --format functionality
* Added explicit --download flag to download instead of print
* Added explicit --file-name flag to specify a file name to use
* Renamed --extra-information to --export-mode
* Updated the --export-mode with more useful information

main.go

@@ -79,12 +79,17 @@ func (w weather) print(resp *http.Response) {
 
 // `weather` method to download the weather
 func (w weather) download(resp *http.Response) {
+	var fName string
+	if *fileName != "" {
+		fName = *fileName
+	} else {
 		splitURL := strings.Split(w.url, "/")
-	filename := splitURL[len(splitURL)-1]
+		fName = splitURL[len(splitURL)-1]
+	}
 
-	f, err := os.Create(filename)
+	f, err := os.Create(fName)
 	if err != nil {
-		return
+		log.Fatal(err)
 	}
 	defer f.Close()
 
@@ -104,76 +109,116 @@ func getWheather(url string, headers map[string]string, download bool) {
 // This will figure out if we need to download the PNG image
 // as well.
 func generateParamFormat() (string, bool, error) {
-	var params []string
+	var params strings.Builder
-	var prefix []string
+	var prefix = "?"
-	var download bool
+	var downloadMode = *download
 
-	prefix = append(prefix, "?")
+	// If --free-syle is specified, let's not bother and simply return it
-
+	if *freeStyle != "" {
-	// If --format is specified, let's not bother and simply return it
+		return *freeStyle, downloadMode, nil
-	if *format != "" {
-		return *format, false, nil
 	}
 
+	// If --format is specified, let's return the format the user wants
+	if *format != "" {
+		var str strings.Builder
+		str.WriteString("?format=\"")
+		str.WriteString(*format)
+		str.WriteString("\"")
+		return str.String(), downloadMode, nil
+	}
 	// If --one-liner is specified, we know the format is set so let's return it
 	if *oneLiner {
-		return "?format=3", false, nil
+		return "?format=3", downloadMode, nil
 	}
 
 	for i := range switches {
 		if *switches[i] {
-			params = append(params, switchesFlags[i])
+			params.WriteString(switchesFlags[i])
 		}
 	}
 
 	if *png {
-		prefix[0] = "_"
+		prefix = "_"
 
-		if *transparency >= 0 && *transparency <= 100 {
+		if *addFrame {
-			params = append(params, strings.Join([]string{"_transparency=", string(*transparency)}, ""))
+			params.WriteString(switchesFlags[12])
 		}
 
-		params = append(params, ".png")
+		if *transparency >= 0 && *transparency <= 255 {
-		download = true
+			params.WriteString("_transparency=")
+			params.WriteString(string(*transparency))
 		}
 
-	params = append(prefix, strings.Join(params, ""))
+		params.WriteString(".png")
+		downloadMode = true
+	}
 
-	return strings.Join(params, ""), download, nil
+	var affix strings.Builder
+	affix.WriteString(prefix)
+	affix.WriteString(params.String())
+
+	return affix.String(), downloadMode, nil
 }
 
 // Defining the command-line interface
 var (
 	app      = kingpin.New("go-cmw", "A small terminal wrapper around the wttr.in weather endpoint.")
+	location = app.Flag("location", "Specify explicite location").Short('L').OverrideDefaultFromEnvar("GO_CMW_LOCATION").String()
+	language = app.Flag("language", "Specify explicite language").Short('l').OverrideDefaultFromEnvar("GO_CMW_LANGUAGE").String()
+	v2       = app.Flag("v2", "Display Data-Rich output").Default("false").Bool()
 	switches = [13]*bool{
 		app.Flag("metric", "Display weather in metric").Short('m').Default("false").Bool(),
 		app.Flag("uscs", "Display weather in imperial").Short('u').Default("false").Bool(),
 		app.Flag("meter-second", "Display wind in m/s").Short('M').Default("false").Bool(),
-		app.Flag("zero", "Show the weather now").Short('z').Default("false").Bool(),
+		app.Flag("zero", "Display current weather").Short('z').Default("false").Bool(),
-		app.Flag("one", "Show the weather for one day").Short('o').Default("false").Bool(),
+		app.Flag("one", "Display current weather + 1 day").Short('o').Default("false").Bool(),
-		app.Flag("two", "Show the weather for two days").Short('w').Default("false").Bool(),
+		app.Flag("two", "Display current weather + 2 days").Short('w').Default("false").Bool(),
-		app.Flag("ignore-user-agent", "Request ignoring the user agent").Short('A').Default("false").Bool(),
+		app.Flag("ignore-user-agent", "Ignore User-Agent and force ANSI output").Short('A').Default("false").Bool(),
-		app.Flag("follow-link", "Follow link redirect").Short('F').Default("true").Bool(),
+		app.Flag("follow-link", "Do not display the 'Follow' line").Short('F').Default("true").Bool(),
-		app.Flag("narrow", "Display weather in narrow view").Short('n').Default("false").Bool(),
+		app.Flag("narrow", "Display narrow view (only day/night)").Short('n').Default("false").Bool(),
-		app.Flag("quiet", "Add the quiet flag").Short('q').Default("false").Bool(),
+		app.Flag("quiet", "Display quiet version (no weather report)").Short('q').Default("false").Bool(),
-		app.Flag("super-quiet", "Add the super quiet flag").Short('Q').Default("false").Bool(),
+		app.Flag("super-quiet", "Display super quiet version (no weather report and no city)").Short('Q').Default("false").Bool(),
-		app.Flag("no-colors", "Disable displaying colors (always enabled on windows").Short('N').Default("false").Bool(),
+		app.Flag("no-colors", "Display no colors (always enabled on windows").Short('N').Default("false").Bool()}
-		app.Flag("add-frame", "Add a frame to the output").Short('p').Default("false").Bool()}
+
 	png          = app.Flag("png", "Download a weather PNG image").Short('P').Default("false").Bool()
-	v2               = app.Flag("v2", "Use the v2 endpoint").Default("false").Bool()
+	addFrame     = app.Flag("add-frame", "Add a frame to the output (PNG only)").Short('p').Default("false").Bool()
-	transparency     = app.Flag("transparency", "Set transparency level (0-100) (PNG only)").Short('t').Default("0").Int()
+	transparency = app.Flag("transparency", "Set transparency level (0-255) (PNG only)").OverrideDefaultFromEnvar("GO_CMW_TRANSPARENCY").Short('t').Default("0").Int()
-	format           = app.Flag("format", "Query format (overrides everything else)").Short('f').OverrideDefaultFromEnvar("GO_CMW_FORMAT").String()
+	download     = app.Flag("download", "Enables download mode").Short('d').Default("false").Bool()
-	location         = app.Flag("location", "Specify explicite location").Short('L').OverrideDefaultFromEnvar("GO_CMW_LOCATION").String()
+	fileName     = app.Flag("file-name", "Name download file").OverrideDefaultFromEnvar("GO_CMW_FILE_NAME").Default("").String()
-	language         = app.Flag("language", "Specify explicite language").Short('l').OverrideDefaultFromEnvar("GO_CMW_LANGUAGE").String()
 	oneLiner     = app.Flag("one-liner", "One liner outpet (for the terminal multiplexer lovers out there)").Short('O').Default("false").Bool()
-	extraInformation = app.Flag("extra-information", "Print extra information").Default("false").Bool()
+	format       = app.Flag("format", "Specify a format query (e.g. \"%l:+%c+%t\") (--expert-mode)").OverrideDefaultFromEnvar("GO_CMW_FORMAT").String()
+	freeStyle    = app.Flag("free-style", "Specify a free-style API call (--expert-mode)").OverrideDefaultFromEnvar("GO_CMW_FREE_STYLE").String()
+	expertMode   = app.Flag("expert-mode", "Print expert mode information").Default("false").Bool()
 )
 
 // Special help menu
-func printExtraInformation() {
+func printExpertMode() {
 	eInfo := `
+Expert Mode
+-----------
+
+All commands flagged with --expert-mode override
+values/flags added by go-cmw. 
+
+This gives the user full control over
+the queries requested.
+
+Environment Variables
+---------------------
+
+go-cmw makes use of the following environment
+variables:
+
+* GO_CMW_LOCATION for --location
+* GO_CMW_LANGUAGE for --language
+* GO_CMW_FORMAT for --format
+* GO_CMW_FREE_STYLE for --free-style
+* GO_CMW_FILE_NAME for --file-name
+* GO_CMW_TRANSPARENCY for --transparency
+
 Supported Location Types
 ------------------------
+
 City name:                  Paris
 Unicode name:               Москва
 Airport code (3 letters):   muc
@@ -183,15 +228,32 @@ GPS coordinates:            -78.46,106.79
 
 Special Location
 ----------------
+
 Moon phase (add ,+US or
 ,+France for these cities): moon
 Moon phase for a date:      moon@2016-10-25
 
+Format Flags (--format)
+------------
+
+c                           Weather condition
+C                           Weather condition textual name
+h                           Humidity
+t                           Temperature
+w                           Wind
+l                           Location
+m                           Moonphase
+M                           Moonday
+p                           precipitation (mm)
+o                           Probability of Precipitation
+P                           pressure (hPa)
+
 Supported languages
 -------------------
 
-Supported: af da de el et fr fa hu id it nb nl
+Supported: af be ca da de el et fr fa hu id it
-           pl pt-br ro ru tr uk vi
+           nb nl pl pt-br ro ru tr th uk vi
+           zh-cn zh-tw
 `
 
 	println(eInfo)
@@ -206,8 +268,8 @@ func flagParser() {
 
 	kingpin.MustParse(app.Parse(os.Args[1:]))
 
-	if *extraInformation {
+	if *expertMode {
-		printExtraInformation()
+		printExpertMode()
 		os.Exit(0)
 	}
 
@@ -219,38 +281,39 @@ func flagParser() {
 }
 
 // Create a function to generate the url that we'll be calling shortly.
-func generateURL(domain string, v2 bool, location string, lang string, affix string) ([]string, map[string]string) {
+func generateURL(domain string, v2 bool, location string, lang string, affix string) (string, map[string]string) {
-	var link []string
+	var link strings.Builder
 	var headers = make(map[string]string)
 
-	link = append(link, "https://")
+	link.WriteString("https://")
 
 	if v2 {
-		link = append(link, "v2.")
+		link.WriteString("v2.")
 	}
 
-	link = append(link, domain, "/")
+	link.WriteString(domain)
+	link.WriteString("/")
 
 	if location != "" {
-		link = append(link, location)
+		link.WriteString(location)
 	}
 
 	if affix != "" {
-		link = append(link, affix)
+		link.WriteString(affix)
 	}
 
 	if lang != "" {
 		headers["Accept-Language"] = lang
 	}
 
-	return link, headers
+	return link.String(), headers
 }
 
 // This is the main function that glues everything together.
 func main() {
 	var domain string = "wttr.in"
 	flagParser()
-	affix, download, _ := generateParamFormat()
+	affix, downloadFile, _ := generateParamFormat()
 	link, headers := generateURL(domain, *v2, *location, *language, affix)
-	getWheather(strings.Join(link, ""), headers, download)
+	getWheather(link, headers, downloadFile)
 }