Episode 26 - Creating a CLI for a REST API

.gitignore

@@ -23,6 +23,8 @@ glide
 linux-amd64
 glide-v0.12.0-linux-amd64.tar.gz
 
+.envrc
+
 *.exe
 *.test
 *.prof
@@ -46,3 +48,5 @@ episode25/tmp
 episode25/tmp/episode25-build
 episode25/node_modules
 episode25/public/assets
+
+episode26/ds

episode26/Makefile

@@ -0,0 +1,4 @@
+test:
+	go test -test.v ./...
+build:
+	go build -o episode20

episode26/README.md

@@ -0,0 +1,41 @@
+# Consuming a REST API in Go
+
+Go in 5 Minutes, episode 26.
+
+In this screencast, we're going to build a command line client to consume the awesome [Dark Sky API](https://darksky.net/dev/docs).
+
+We'll be using [cobra](https://github.com/spf13/cobra) to build our command line client, and I did a previous episode on that package. If you haven't seen [episode 18](https://www.goin5minutes.com/screencast/episode_18_cli_with_cobra/), you might want to go review that before you look at this one.
+
+Instead of using an already-built Dark Sky API client (there are a [few](https://darksky.net/dev/docs/libraries) for Go), we're going to build our own client according to the API documentation to show some tips and tricks for building clients for any REST API.
+
+In this screencast, we'll use the awesome [gorequest](https://github.com/parnurzeal/gorequest) package to help us build a DarkSky client from scratch.
+
+# Outline
+
+1. Quick primer on Cobra
+1. Quick primer on gorequest
+1. Let's check out the code!
+
+# How to Run This Code
+
+You'll need Go version 1.11 or above to run this code. If you have an appropriate version, simply run `go build -o darksky .` to build. 
+
+Before you run the binary, you'll need an environment variable called `DARKSKY_API_KEY` set to your DarkSky API key (if you don't have one, get it from your [account](https://darksky.net/dev/account), or [create](https://darksky.net/dev/register) an account if you haven't already).
+
+Then, call the binary like so, ensuring that `DARKSKY_API_KEY` is set in your environment:
+
+```console
+$ ./darksky temp --lat 45.512230 --long -122.658722
+```
+
+The `lat` and `long` flags are set to the latitude and longitude (respectively) of the location for which to get the temperature.
+
+>The latitude and longitude in the above example are set to Portland, OR, USA. If you'd like to try another location, you can use https://www.latlong.net/
+
+# Show Notes
+
+- [Dark Sky API](https://darksky.net/dev/docs)
+- [gorequest](https://github.com/parnurzeal/gorequest)
+- [Cobra CLI Package](https://github.com/spf13/cobra)
+- [Cobra Code Generation CLI](https://github.com/spf13/cobra/blob/master/cobra/README.md)
+- A different way to decode JSON: [dcode](https://github.com/go-functional/dcode)

episode26/cmd/root.go

@@ -0,0 +1,89 @@
+package cmd
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+
+	homedir "github.com/mitchellh/go-homedir"
+	"github.com/spf13/viper"
+)
+
+var cfgFile string
+
+// rootCmd represents the base command when called without any subcommands
+var rootCmd = &cobra.Command{
+	Use:   "episode26",
+	Short: "A brief description of your application",
+	Long: `A longer description that spans multiple lines and likely contains
+examples and usage of using your application. For example:
+
+Cobra is a CLI library for Go that empowers applications.
+This application is a tool to generate the needed files
+to quickly create a Cobra application.`,
+	// Uncomment the following line if your bare application
+	// has an action associated with it:
+	//	Run: func(cmd *cobra.Command, args []string) { },
+}
+
+// Execute adds all child commands to the root command and sets flags appropriately.
+// This is called by main.main(). It only needs to happen once to the rootCmd.
+func Execute() {
+	if err := rootCmd.Execute(); err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+}
+
+func init() {
+	apiKey := os.Getenv("DARKSKY_API_KEY")
+	if apiKey == "" {
+		fmt.Println("No DARKSKY_API_KEY environment variable set")
+		os.Exit(1)
+	}
+	cobra.OnInitialize(initConfig)
+
+	// Here you will define your flags and configuration settings.
+	// Cobra supports persistent flags, which, if defined here,
+	// will be global for your application.
+
+	rootCmd.PersistentFlags().StringVar(&cfgFile, "config", "", "config file (default is $HOME/.episode26.yaml)")
+
+	// Cobra also supports local flags, which will only run
+	// when this action is called directly.
+	rootCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
+
+	tempCmd, err := temp(apiKey)
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	rootCmd.AddCommand(tempCmd)
+}
+
+// initConfig reads in config file and ENV variables if set.
+func initConfig() {
+	if cfgFile != "" {
+		// Use config file from the flag.
+		viper.SetConfigFile(cfgFile)
+	} else {
+		// Find home directory.
+		home, err := homedir.Dir()
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(1)
+		}
+
+		// Search config in home directory with name ".episode26" (without extension).
+		viper.AddConfigPath(home)
+		viper.SetConfigName(".episode26")
+	}
+
+	viper.AutomaticEnv() // read in environment variables that match
+
+	// If a config file is found, read it in.
+	if err := viper.ReadInConfig(); err == nil {
+		fmt.Println("Using config file:", viper.ConfigFileUsed())
+	}
+}

episode26/cmd/temp.go

@@ -0,0 +1,40 @@
+package cmd
+
+import (
+	"fmt"
+
+	"github.com/arschles/go-in-5-minutes/episode26/dsclient"
+	"github.com/spf13/cobra"
+)
+
+func temp(apiKey string) (*cobra.Command, error) {
+	cl, err := dsclient.New(apiKey)
+	if err != nil {
+		return nil, err
+	}
+	cmd := &cobra.Command{
+		Use: "temp",
+	}
+	flags := cmd.PersistentFlags()
+	lat := flags.Float64("lat", 0, "The Latitude to fetch")
+	long := flags.Float64("long", 0, "The Longitude to fetch")
+	cmd.RunE = func(*cobra.Command, []string) error {
+		fmt.Printf("Getting temp for (%f, %f)\n", *lat, *long)
+		fcast, err := cl.Forecast(*lat, *long)
+		if err != nil {
+			return err
+		}
+		if len(fcast.Hourly.Data) < 1 {
+			return fmt.Errorf("No hourly data returned!")
+		}
+		hourly := fcast.Hourly.Data[0]
+		fmt.Printf(
+			"Temperature for your location (%f, %f): %f\n",
+			*lat,
+			*long,
+			hourly.ApparentTemp, // the API only allows apparent temp on hourly
+		)
+		return nil
+	}
+	return cmd, nil
+}

episode26/dsclient/client.go

@@ -0,0 +1,38 @@
+package dsclient
+
+import (
+	"fmt"
+
+	multierr "github.com/hashicorp/go-multierror"
+	"github.com/parnurzeal/gorequest"
+)
+
+type Client struct {
+	apiKey string
+	cl     *gorequest.SuperAgent
+}
+
+func New(apiKey string) (*Client, error) {
+	if apiKey == "" {
+		return nil, fmt.Errorf("No API key passed")
+	}
+	return &Client{apiKey: apiKey, cl: gorequest.New()}, nil
+}
+
+func (c *Client) Forecast(lat, long float64) (*Response, error) {
+	forecastURL := fmt.Sprintf(
+		"https://api.darksky.net/forecast/%s/%f,%f",
+		c.apiKey,
+		lat,
+		long,
+	)
+	resp := &Response{}
+	httpRes, _, errs := c.cl.Get(forecastURL).EndStruct(resp)
+	if len(errs) > 0 {
+		return nil, &multierr.Error{Errors: errs}
+	}
+	if httpRes.StatusCode != 200 {
+		return nil, fmt.Errorf("HTTP Status Code %d returned!", httpRes.StatusCode)
+	}
+	return resp, nil
+}

episode26/dsclient/data_block.go

@@ -0,0 +1,9 @@
+package dsclient
+
+type DataBlock struct {
+	Data    []DataPoint `json:"data"`
+	Summary string      `json:"summary"`
+	Icon    string      `json:"icon"`
+	// There are way more fields in a data block.
+	// see https://darksky.net/dev/docs#data-block for all of them
+}

episode26/dsclient/data_point.go

@@ -0,0 +1,7 @@
+package dsclient
+
+type DataPoint struct {
+	ApparentTemp float64 `json:"apparentTemperature"`
+	// There are way more fields in a data point.
+	// see https://darksky.net/dev/docs#data-point for all of them
+}

episode26/dsclient/response.go

@@ -0,0 +1,11 @@
+package dsclient
+
+type Response struct {
+	Latitude  float64   `json:"latitude"`
+	Longitude float64   `json:"longitude"`
+	Timezone  string    `json:"timezone"`
+	Currently DataPoint `json:"currently"`
+	Minutely  DataBlock `json:"minutely"`
+	Hourly    DataBlock `json:"hourly"`
+	Daily     DataBlock `json:"daily"`
+}

episode26/go.mod

@@ -0,0 +1,24 @@
+module github.com/arschles/go-in-5-minutes/episode26
+
+go 1.12
+
+require (
+	github.com/elazarl/goproxy v0.0.0-20190703090003-6125c262ffb0 // indirect
+	github.com/elazarl/goproxy/ext v0.0.0-20190703090003-6125c262ffb0 // indirect
+	github.com/hashicorp/go-multierror v1.0.0
+	github.com/magiconair/properties v1.8.1 // indirect
+	github.com/mitchellh/go-homedir v1.1.0
+	github.com/moul/http2curl v1.0.0 // indirect
+	github.com/parnurzeal/gorequest v0.2.15
+	github.com/pelletier/go-toml v1.4.0 // indirect
+	github.com/pkg/errors v0.8.1 // indirect
+	github.com/smartystreets/goconvey v0.0.0-20190330032615-68dc04aab96a // indirect
+	github.com/spf13/afero v1.2.2 // indirect
+	github.com/spf13/cobra v0.0.5
+	github.com/spf13/jwalterweatherman v1.1.0 // indirect
+	github.com/spf13/viper v1.4.0
+	github.com/stretchr/testify v1.3.0 // indirect
+	golang.org/x/net v0.0.0-20190628185345-da137c7871d7 // indirect
+	golang.org/x/sys v0.0.0-20190626221950-04f50cda93cb // indirect
+	golang.org/x/text v0.3.2 // indirect
+)