go-cmw/main.go

package main

import (
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"strings"

	kingpin "gopkg.in/alecthomas/kingpin.v2"
)

// VERSION The version release
const VERSION = "0.0.3"

// AUTHOR The author name
const AUTHOR = "Elia el Lazkani"

// Create a list of constants to figure out
// the command line flags and translate them
// into uri flags.
const (
	METRIC = 1 << iota
	USCS
	METERSECOND
	ZERO
	ONE
	TWO
	IGNOREUSERAGENT
	FOLLOWLINK
	NARROW
	QUIET
	SUPERQUIET
	NOCOLORS
	ADDFRAME
	MIDTRANSPARENCY
	LOCATION
	LANGUAGE
	PNG
	VTWO
)

// Create a list of constants to define
// uri switches by flag.
const (
	MetricSwitch          = "m"
	UscsSwitch            = "u"
	MeterSecondSwitch     = "M"
	ZeroSwitch            = "0"
	OneSwitch             = "1"
	TwoSwitch             = "2"
	IgnoreUserAgentSwitch = "A"
	FollowLinkSwitch      = "F"
	NarrowSwitch          = "n"
	QuietSwitch           = "q"
	SuperQuietSwitch      = "Q"
	NoColorsSwitch        = "T"
	AddFrameSwitch        = "p"
	MidTransparencySwitch = "T"
)

// We create a weather struct with the url
type weather struct {
	url string
}

// `weather` method to handle creating new requests with proper headers
func (w weather) newRequest(headers map[string]string) *http.Request {
	req, err := http.NewRequest("GET", w.url, nil)
	if err != nil {
		log.Fatal("Error reading request. ", err)
	}
	return w.formatHeader(req, headers)
}

// `weather` method to format the headers and inject required ones
func (w weather) formatHeader(req *http.Request, headers map[string]string) *http.Request {
	req.Header.Set("Content-Type", "text/plain; charset=utf-8")
	// I had to read the wttr.in code to figure this one out.
	// It wasn't Golang, it was 2 wasted hours that I won't be getting back.
	req.Header.Set("User-Agent", "curl")

	for key, value := range headers {
		req.Header.Add(key, value)
	}
	return req
}

// `weather` method to create a client and get a weather response
// This method handles printing or downloading the weather
func (w weather) get(req *http.Request, download bool) {
	client := &http.Client{}
	client.Jar = nil

	resp, err := client.Do(req)
	if err != nil {
		log.Fatal("Error reading response. ", err)
	}
	defer resp.Body.Close()

	if download {
		w.download(resp)
	} else {
		w.print(resp)
	}
}

// `weather` method to print the weather
func (w weather) print(resp *http.Response) {
	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		log.Fatal("Error reading body. ", err)
	}
	fmt.Printf("%s\n", body)
}

// `weather` method to download the weather
func (w weather) download(resp *http.Response) {
	splitURL := strings.Split(w.url, "/")
	filename := splitURL[len(splitURL)-1]

	f, err := os.Create(filename)
	if err != nil {
		return
	}
	defer f.Close()

	_, err = io.Copy(f, resp.Body)
}

// Wraper function around the weather struct
func getWheather(url string, headers map[string]string, download bool) {

	w := weather{url}
	req := w.newRequest(headers)
	w.get(req, download)
}

// Define a command parameters struct.
// This will hold all the configurations
// set by the command line parameters provided.
type cmdParams struct {
	Flags        int
	Transparency int
	Location     string
	Language     string
}

// Create a method to figure out the command parameters
// provided and translate them into uri parameters.
// This will figure out if we need to download the PNG image
// as well.
func (cmdP *cmdParams) generateParamFormat() (string, bool, error) {
	var params []string
	var prefix []string
	var download bool
	prefix = append(prefix, "?")

	if cmdP.Flags&METRIC == METRIC {
		params = append(params, MetricSwitch)
	}

	if cmdP.Flags&USCS == USCS {
		params = append(params, UscsSwitch)
	}

	if cmdP.Flags&METERSECOND == METERSECOND {
		params = append(params, MeterSecondSwitch)
	}

	if cmdP.Flags&ZERO == ZERO {
		params = append(params, ZeroSwitch)
	}

	if cmdP.Flags&ONE == ONE {
		params = append(params, OneSwitch)
	}

	if cmdP.Flags&TWO == TWO {
		params = append(params, TwoSwitch)
	}

	if cmdP.Flags&IGNOREUSERAGENT == IGNOREUSERAGENT {
		params = append(params, IgnoreUserAgentSwitch)
	}

	if cmdP.Flags&FOLLOWLINK == FOLLOWLINK {
		params = append(params, FollowLinkSwitch)
	}

	if cmdP.Flags&NARROW == NARROW {
		params = append(params, NarrowSwitch)
	}

	if cmdP.Flags&QUIET == QUIET {
		params = append(params, QuietSwitch)
	}

	if cmdP.Flags&SUPERQUIET == SUPERQUIET {
		params = append(params, SuperQuietSwitch)
	}

	if cmdP.Flags&NOCOLORS == NOCOLORS {
		params = append(params, NoColorsSwitch)
	}

	if cmdP.Flags&ADDFRAME == ADDFRAME {
		params = append(params, AddFrameSwitch)
	}

	if cmdP.Flags&PNG == PNG {
		prefix[0] = "_"

		if cmdP.Flags&MIDTRANSPARENCY == MIDTRANSPARENCY {
			params = append(params, MidTransparencySwitch)
		}

		if cmdP.Transparency >= 0 && cmdP.Transparency <= 100 {
			params = append(params, strings.Join([]string{"_transparency=", string(cmdP.Transparency)}, ""))
		}

		params = append(params, ".png")
		download = true
	}

	params = append(prefix, strings.Join(params, ""))

	return strings.Join(params, ""), download, nil
}

// Defining the command-line interface
var (
	app             = kingpin.New("go-cmw", "A small terminal wrapper around the wttr.in weather endpoint.")
	metric          = app.Flag("metric", "Display weather in metric").Short('m').Default("false").Bool()
	uscs            = app.Flag("uscs", "Display weather in imperial").Short('u').Default("false").Bool()
	meterSecond     = app.Flag("meter-second", "Display wind in m/s").Short('M').Default("false").Bool()
	zero            = app.Flag("zero", "Show the weather now").Short('z').Default("false").Bool()
	one             = app.Flag("one", "Show the weather for one day").Short('o').Default("false").Bool()
	two             = app.Flag("two", "Show the weather for two days").Short('w').Default("false").Bool()
	ignoreUserAgent = app.Flag("ignore-user-agent", "Request ignoring the user agent").Short('A').Default("false").Bool()
	followLink      = app.Flag("follow-link", "Follow link redirect").Short('F').Default("true").Bool()
	narrow          = app.Flag("narrow", "Display weather in narrow view").Short('n').Default("false").Bool()
	quiet           = app.Flag("quiet", "Add the quiet flag").Short('q').Default("false").Bool()
	superQuiet      = app.Flag("super-quiet", "Add the super quiet flag").Short('Q').Default("false").Bool()
	noColors        = app.Flag("no-colors", "Disable displaying colors (always enabled on windows").Short('N').Default("false").Bool()
	addFrame        = app.Flag("add-frame", "Add a frame to the output").Short('p').Default("false").Bool()
	midTransparency = app.Flag("mid-transparency", "Enable mid-transparency (PNG only)").Short('T').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()
	transparency    = app.Flag("transparency", "Set transparency level (0-100) (PNG only)").Short('t').Default("0").Int()
	location        = app.Flag("location", "Specify explicite location").Short('L').String()
	language        = app.Flag("language", "Specify explicite language").Short('l').String()
)

// Create a function to parse all the command line parameters
// provided and save them in the parameter struct.
func flagParser(cmdP *cmdParams) {

	app.Version(VERSION)
	app.Author(AUTHOR)

	kingpin.MustParse(app.Parse(os.Args[1:]))

	// Windows does not have color encoding
	// so let's make sure windows users are happy
	term := os.Getenv("TERM")
	if term == "" {
		*noColors = true
	}

	if *metric {
		cmdP.Flags += METRIC
	}

	if *uscs {
		cmdP.Flags += USCS
	}

	if *meterSecond {
		cmdP.Flags += METERSECOND
	}

	if *zero {
		cmdP.Flags += ZERO
	}

	if *one {
		cmdP.Flags += ONE
	}

	if *two {
		cmdP.Flags += TWO
	}

	if *ignoreUserAgent {
		cmdP.Flags += IGNOREUSERAGENT
	}

	if *followLink {
		cmdP.Flags += FOLLOWLINK
	}

	if *narrow {
		cmdP.Flags += NARROW
	}

	if *quiet {
		cmdP.Flags += QUIET
	}

	if *superQuiet {
		cmdP.Flags += SUPERQUIET
	}

	if *noColors {
		cmdP.Flags += NOCOLORS
	}

	if *addFrame {
		cmdP.Flags += ADDFRAME
	}

	if *midTransparency {
		cmdP.Flags += MIDTRANSPARENCY
	}

	if *transparency >= 0 && *transparency <= 100 {
		cmdP.Transparency = *transparency
	}

	if *png {
		cmdP.Flags += PNG
	}

	if *v2 {
		cmdP.Flags += VTWO
	}

	if *location != "" {
		cmdP.Flags += LOCATION
		cmdP.Location = *location
	}

	if *language != "" {
		cmdP.Flags += LANGUAGE
		cmdP.Language = *language
	}

}

// Create a function to generate the url that we'll be calling shortly.
func generateURL(domain string, v2 bool, location string, lang string, format string) ([]string, map[string]string) {
	var link []string
	var headers = make(map[string]string)

	link = append(link, "https://")

	if v2 {
		link = append(link, "v2.")
	}

	link = append(link, domain, "/")

	if location != "" {
		link = append(link, location)
	}

	if format != "" {
		link = append(link, format)
	}

	if lang != "" {
		headers["Accept-Language"] = lang
	}

	return link, headers
}

// This is the main function that glues everything together.
func main() {
	var params cmdParams = cmdParams{}
	var domain string = "wttr.in"
	flagParser(&params)
	format, download, _ := params.generateParamFormat()
	link, headers := generateURL(domain, params.Flags&VTWO == VTWO, params.Location, params.Language, format)
	getWheather(strings.Join(link, ""), headers, download)
}