Add mastertinner's solution (#46)

Author: Tobi Fuhrimann

students/mastertinner/main.go

@@ -0,0 +1,118 @@
+package main
+
+import (
+	"bufio"
+	"encoding/csv"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"math/rand"
+	"os"
+	"strings"
+	"time"
+)
+
+// problem is a problem to be solved by a user.
+type problem struct {
+	challenge     string
+	correctAnswer string
+}
+
+// scoreboard keeps track of a user's score.
+type scoreboard struct {
+	total   int64
+	correct int64
+}
+
+func main() {
+	var (
+		csvFileName = flag.String("csv", "problems.csv", "the location of the CSV file")
+		timeLimit   = flag.Int("time-limit", 30, "the time limit for the user to answer all problems")
+		doShuffle   = flag.Bool("shuffle", false, "whether to shuffle the order of problems or not")
+	)
+	flag.Parse()
+
+	problems, err := readProblemsFromCSVFile(*csvFileName)
+	if err != nil {
+		log.Fatal(fmt.Errorf("error reading problems from CSV file: %s", err))
+	}
+	if *doShuffle {
+		rand.Seed(time.Now().Unix())
+		rand.Shuffle(len(problems), func(i, j int) { problems[i], problems[j] = problems[j], problems[i] })
+	}
+
+	doneCh := make(chan bool)
+	scr := &scoreboard{
+		total: int64(len(problems)),
+	}
+
+	go func() {
+		for i, p := range problems {
+			fmt.Printf("What is %s?\n", p.challenge)
+			inputReader := bufio.NewReader(os.Stdin)
+			fmt.Print("Answer: ")
+			answer, err := inputReader.ReadString('\n')
+			if err != nil {
+				log.Fatal(fmt.Errorf("error reading user input: %s", err))
+			}
+			if purifyString(answer) == purifyString(p.correctAnswer) {
+				scr.correct++
+				fmt.Println("You are correct!")
+			} else {
+				fmt.Printf("Unfortunately not... The correct answer is %s\n", p.correctAnswer)
+			}
+			fmt.Printf("Your current score is %v/%v\n\n", scr.correct, scr.total)
+			if i == len(problems)-1 {
+				doneCh <- true
+			}
+		}
+	}()
+
+	go func() {
+		timer := time.NewTimer(time.Duration(*timeLimit) * time.Second)
+		<-timer.C
+		fmt.Println("")
+		fmt.Println("")
+		fmt.Println("Your time is up...")
+		doneCh <- true
+	}()
+
+	<-doneCh
+	fmt.Println("")
+	fmt.Printf("Your final score is %v/%v\n\n", scr.correct, scr.total)
+}
+
+// readProblemsFromCSVFile reads problems from a CSV file.
+func readProblemsFromCSVFile(fileName string) ([]problem, error) {
+	csvFile, err := os.Open(fileName)
+	if err != nil {
+		return nil, fmt.Errorf("error opening file: %s", err)
+	}
+	reader := csv.NewReader(bufio.NewReader(csvFile))
+	var problems []problem
+	for {
+		line, err := reader.Read()
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			return nil, fmt.Errorf("error reading CSV line: %s", err)
+		}
+		if len(line) != 2 {
+			return nil, errors.New("invalid line in CSV")
+		}
+		p := problem{
+			challenge:     line[0],
+			correctAnswer: line[1],
+		}
+		problems = append(problems, p)
+	}
+	return problems, nil
+}
+
+// purifyString strips all unneeded variations from a string.
+func purifyString(str string) string {
+	return strings.TrimSpace(strings.ToLower(str))
+}