add watch command output (#20)

Author: 饺子w

README.md

@@ -12,6 +12,7 @@ Gotify-CLI is a command line client for pushing messages to [gotify/server][goti
 * initialization wizard
 * piping support (`echo message | gotify push`)
 * simple to use
+* watch and push script result changes (`gotify watch "curl http://example.com/api | jq '.data'"`)
 
 ## Alternatives
 
@@ -61,35 +62,55 @@ $ gotify push "my message"
 $ echo my message | gotify push
 $ gotify push < somefile
 $ gotify push -t "my title" -p 10 "my message"
+$ gotify watch "curl http://example.com/api | jq '.data'"
 ```
 
 ## Help
 
-**Uses version `v1.2.0`**
+**Uses version `v2.1.0`**
 
 ```bash
-$ gotify help
 NAME:
    Gotify - The official Gotify-CLI
 
 USAGE:
-   gotify [global options] command [command options] [arguments...]
+   cli [global options] command [command options] [arguments...]
 
 VERSION:
-   1.2.0
+   2.1.0
 
 COMMANDS:
      init        Initializes the Gotify-CLI
      version, v  Shows the version
      config      Shows the config
      push, p     Pushes a message
+     watch       watch the result of a command and pushes output difference
      help, h     Shows a list of commands or help for one command
 
 GLOBAL OPTIONS:
    --help, -h     show help
    --version, -v  print the version
 ```
 
+### Watch help
+
+```
+NAME:
+   cli watch - watch the result of a command and pushes output difference
+
+USAGE:
+   cli watch [command options] <cmd>
+
+OPTIONS:
+   --interval value, -n value  watch interval (sec) (default: 2)
+   --priority value, -p value  Set the priority (default: 0)
+   --exec value, -x value      Pass command to exec (default to "sh -c")
+   --title value, -t value     Set the title (empty for command)
+   --token value               Override the app token
+   --url value                 Override the Gotify URL
+   --output value, -o value    Output verbosity (short|default|long) (default: "default")
+```
+
 ### Push help
 
 ```bash

cli.go

@@ -29,6 +29,7 @@ func main() {
 		command.Version(),
 		command.Config(),
 		command.Push(),
+		command.Watch(),
 	}
 	err := app.Run(os.Args)
 	if err != nil {

command/push.go

@@ -16,7 +16,6 @@ import (
 	"gopkg.in/urfave/cli.v1"
 )
 
-
 func Push() cli.Command {
 	return cli.Command{
 		Name:        "push",

command/watch.go

@@ -0,0 +1,148 @@
+package command
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"net/url"
+	"os/exec"
+	"strings"
+	"time"
+
+	"github.com/gotify/cli/v2/config"
+	"github.com/gotify/cli/v2/utils"
+	"github.com/gotify/go-api-client/v2/models"
+	"gopkg.in/urfave/cli.v1"
+)
+
+func Watch() cli.Command {
+	return cli.Command{
+		Name:      "watch",
+		Usage:     "watch the result of a command and pushes output difference",
+		ArgsUsage: "<cmd>",
+		Flags: []cli.Flag{
+			cli.Float64Flag{Name: "interval,n", Usage: "watch interval (sec)", Value: 2},
+			cli.IntFlag{Name: "priority,p", Usage: "Set the priority"},
+			cli.StringFlag{Name: "exec,x", Usage: "Pass command to exec", Value: "sh -c"},
+			cli.StringFlag{Name: "title,t", Usage: "Set the title (empty for command)"},
+			cli.StringFlag{Name: "token", Usage: "Override the app token"},
+			cli.StringFlag{Name: "url", Usage: "Override the Gotify URL"},
+			cli.StringFlag{Name: "output,o", Usage: "Output verbosity (short|default|long)", Value: "default"},
+		},
+		Action: doWatch,
+	}
+}
+
+func doWatch(ctx *cli.Context) {
+	conf, confErr := config.ReadConfig(config.GetLocations())
+
+	cmdArgs := ctx.Args()
+	cmdStringNotation := strings.Join(cmdArgs, " ")
+	execArgs := strings.Split(ctx.String("exec"), " ")
+	cmdArgs = append(execArgs[1:], cmdStringNotation)
+	execCmd := execArgs[0]
+
+	outputMode := ctx.String("output")
+	if !(outputMode == "default" || outputMode == "long" || outputMode == "short") {
+		utils.Exit1With("output mode should be short|default|long")
+		return
+	}
+	interval := ctx.Float64("interval")
+	priority := ctx.Int("priority")
+	title := ctx.String("title")
+	if title == "" {
+		title = cmdStringNotation
+	}
+	token := ctx.String("token")
+	if token == "" {
+		if confErr != nil {
+			utils.Exit1With("token is not configured, run 'gotify init'")
+			return
+		}
+		token = conf.Token
+	}
+	stringURL := ctx.String("url")
+	if stringURL == "" {
+		if confErr != nil {
+			utils.Exit1With("url is not configured, run 'gotify init'")
+			return
+		}
+		stringURL = conf.URL
+	}
+	parsedURL, err := url.Parse(stringURL)
+	if err != nil {
+		utils.Exit1With("invalid url", stringURL)
+		return
+	}
+
+	watchInterval := time.Duration(interval*1000) * time.Millisecond
+
+	evalCmdOutput := func() (string, error) {
+		cmd := exec.Command(execCmd, cmdArgs...)
+		timeOut := time.After(watchInterval)
+		outputBuf := bytes.NewBuffer([]byte{})
+		cmd.Stdout = outputBuf
+		cmd.Stderr = outputBuf
+		err := cmd.Start()
+		if err != nil {
+			return "", fmt.Errorf("command failed to invoke: %v", err)
+		}
+		done := make(chan error)
+		go func() {
+			err := cmd.Wait()
+			if err != nil {
+				done <- fmt.Errorf("command failed to invoke: %v", err)
+			}
+			done <- nil
+		}()
+		select {
+		case err := <-done:
+			return outputBuf.String(), err
+		case <-timeOut:
+			cmd.Process.Kill()
+			return outputBuf.String(), errors.New("command timed out")
+		}
+	}
+
+	lastOutput, err := evalCmdOutput()
+	if err != nil {
+		utils.Exit1With("first run failed", err)
+	}
+	for range time.NewTicker(watchInterval).C {
+		output, err := evalCmdOutput()
+		if err != nil {
+			output += fmt.Sprintf("\n!== <%v> ==!", err)
+		}
+		if output != lastOutput {
+			msgData := bytes.NewBuffer([]byte{})
+
+			switch outputMode {
+			case "long":
+				fmt.Fprintf(msgData, "command output for \"%s\" changed:\n\n", cmdStringNotation)
+				fmt.Fprintln(msgData, "== BEGIN OLD OUTPUT ==")
+				fmt.Fprint(msgData, lastOutput)
+				fmt.Fprintln(msgData, "== END OLD OUTPUT ==")
+				fmt.Fprintln(msgData, "== BEGIN NEW OUTPUT ==")
+				fmt.Fprint(msgData, output)
+				fmt.Fprintln(msgData, "== END NEW OUTPUT ==")
+			case "default":
+				fmt.Fprintf(msgData, "command output for \"%s\" changed:\n\n", cmdStringNotation)
+				fmt.Fprintln(msgData, "== BEGIN NEW OUTPUT ==")
+				fmt.Fprint(msgData, output)
+				fmt.Fprintln(msgData, "== END NEW OUTPUT ==")
+			case "short":
+				fmt.Fprintf(msgData, output)
+			}
+
+			msgString := msgData.String()
+			fmt.Println(msgString)
+			pushMessage(parsedURL, token, models.MessageExternal{
+				Title:    title,
+				Message:  msgString,
+				Priority: priority,
+			}, true)
+			lastOutput = output
+		}
+	}
+
+}