Refactor cmd execution function chain to be more readable

The execution was originaly build to be used as a lib, but this is no
longer the case and so I removed all the `io.Writer` and `io.Reader`
interactions. The app reads now from Stdin and writes to Stdout as it
did before.
It also redoes the error handling so that all errors that are not
treated are being handled in the `main` function.

cli/entry.go

@@ -1,84 +0,0 @@
-package cli
-
-import (
-	"bufio"
-	"fmt"
-	"io"
-	"log"
-	"os"
-	"strings"
-
-	"github.com/hamburghammer/rcon"
-)
-
-// Start a interactive connection. Uses the given reader and writer to inteact with the created connection.
-func Start(hostPort string, password string, in io.Reader, out io.Writer) {
-	remoteConsole, err := rcon.Dial(hostPort, password)
-	if err != nil {
-		log.Fatal("Failed to connect to RCON server", err)
-	}
-	defer remoteConsole.Close()
-
-	scanner := bufio.NewScanner(in)
-	out.Write([]byte("To quit the session type 'exit'.\n"))
-	out.Write([]byte("> "))
-	for scanner.Scan() {
-		cmd := scanner.Text()
-		if cmd == "exit" {
-			return
-		}
-
-		reqID, err := remoteConsole.Write(cmd)
-		if err != nil {
-			fmt.Fprintln(os.Stderr, "Failed to send command:", err.Error())
-			continue
-		}
-
-		resp, respID, err := remoteConsole.Read()
-		if err != nil {
-			if err == io.EOF {
-				return
-			}
-			fmt.Fprintln(os.Stderr, "Failed to read command:", err.Error())
-			continue
-		}
-
-		if reqID != respID {
-			fmt.Fprintln(out, "Weird. This response is for another request.")
-		}
-
-		fmt.Fprintln(out, resp)
-		out.Write([]byte("> "))
-	}
-
-	if err := scanner.Err(); err != nil {
-		fmt.Fprintln(os.Stderr, "reading standard input:", err)
-	}
-}
-
-// Execute runs the given command against the remote console and writes the response into the writer.
-func Execute(hostPort string, password string, out io.Writer, command ...string) {
-	remoteConsole, err := rcon.Dial(hostPort, password)
-	if err != nil {
-		log.Fatal("Failed to connect to RCON server", err)
-	}
-	defer remoteConsole.Close()
-
-	preparedCmd := strings.Join(command, " ")
-	reqID, err := remoteConsole.Write(preparedCmd)
-
-	resp, respID, err := remoteConsole.Read()
-	if err != nil {
-		if err == io.EOF {
-			return
-		}
-		fmt.Fprintln(os.Stderr, "Failed to read command:", err.Error())
-		return
-	}
-
-	if reqID != respID {
-		fmt.Fprintln(out, "Weird. This response is for another request.")
-	}
-
-	fmt.Fprintln(out, resp)
-}

main.go

@@ -1,11 +1,15 @@
 package main
 
 import (
+	"bufio"
+	"errors"
 	"fmt"
+	"io"
 	"net"
 	"os"
+	"strings"
 
-	"github.com/itzg/rcon-cli/cli"
+	"github.com/hamburghammer/rcon"
 	flags "github.com/spf13/pflag"
 )
 
@@ -34,7 +38,11 @@ func main() {
 		return
 	}
 
-	run(commands...)
+	err := run(strings.Join(commands, " "))
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err.Error())
+		os.Exit(1)
+	}
 }
 
 func parseArgs(args []string) ([]string, error) {
@@ -70,14 +78,25 @@ func loadEnvIfNotSet() {
 	}
 }
 
-func run(args ...string) {
+func run(cmd string) error {
 	hostPort := net.JoinHostPort(host, port)
-
-	if len(args) == 0 {
-		cli.Start(hostPort, password, os.Stdin, os.Stdout)
-	} else {
-		cli.Execute(hostPort, password, os.Stdout, args...)
+	remoteConsole, err := rcon.Dial(hostPort, password)
+	if err != nil {
+		return fmt.Errorf("failed to connect to RCON server: %w", err)
 	}
+	defer remoteConsole.Close()
+
+	if len(cmd) == 0 {
+		err = executeInteractive(remoteConsole)
+	} else {
+		resp, err := execute(cmd, remoteConsole)
+		if err != nil {
+			return err
+		}
+		fmt.Println(resp)
+	}
+
+	return err
 }
 
 func printHelp() {
@@ -100,3 +119,49 @@ EXAMPLES:
 	%sPORT=25575 rcon-cli stop
 `, envVarPrefix, envVarPrefix)
 }
+
+func executeInteractive(remoteConsole *rcon.RemoteConsole) error {
+	scanner := bufio.NewScanner(os.Stdin)
+	fmt.Println("To quit the session type 'exit'.")
+	for scanner.Scan() {
+		fmt.Print("> ")
+		cmd := scanner.Text()
+		if cmd == "exit" {
+			return nil
+		}
+		resp, err := execute(cmd, remoteConsole)
+		if err != nil {
+			return err
+		}
+
+		fmt.Println(resp)
+	}
+
+	if err := scanner.Err(); err != nil {
+		return fmt.Errorf("reading standard input: %w", err)
+	}
+
+	return nil
+}
+
+func execute(cmd string, remoteConsole *rcon.RemoteConsole) (string, error) {
+	resp := ""
+	reqID, err := remoteConsole.Write(cmd)
+	if err != nil {
+		return resp, fmt.Errorf("failed to send command: %w", err)
+	}
+
+	resp, respID, err := remoteConsole.Read()
+	if err != nil {
+		if err == io.EOF {
+			return resp, nil
+		}
+		return resp, fmt.Errorf("failed to read command: %w", err)
+	}
+
+	if reqID != respID {
+		return resp, errors.New("the response id didn't match the request id")
+	}
+
+	return resp, nil
+}