Add CLI utility for testing

.gitignore

@@ -1 +1,3 @@
 main
+most-specific-period
+tests/

main.go

@@ -4,11 +4,11 @@ import (
 	"bufio"
 	"flag"
 	"fmt"
-	"log"
 	"os"
-)
+	"time"
 
-var addr = flag.String("addr", "0.0.0.0:8080", "http service address")
+	"github.com/taigrr/most-specific-period/msp"
+)
 
 func init() {
 	flag.Usage = func() {
@@ -16,11 +16,76 @@ func init() {
 		flag.PrintDefaults()
 	}
 }
+func warnMessage() {
+	fmt.Print("Please type your date formats as follows, hit return between each field (RFC 3339), and hit Control+D to signal you are complete: \nIdentifier: id\nStartTime: 2019-10-12T07:20:50.52Z\nEndTime: 2019-10-12T07:20:50.52Z\n")
+
+}
 
 func main() {
 	flag.Parse()
+	terminal := false
+	fi, _ := os.Stdin.Stat()
+	if (fi.Mode() & os.ModeCharDevice) == 0 {
+		// this is a file being read in, no need to print the prompt just yet
+	} else {
+		// this is a terminal, let's help the user out
+		terminal = true
+		warnMessage()
+	}
 	s := bufio.NewScanner(os.Stdin)
+	count := 1
+
+	if terminal {
+		fmt.Print("Identifier: ")
+	}
+
+	periods := []msp.Period{}
+
 	for s.Scan() {
-		log.Println("line", s.Text())
+		input := s.Text()
+		if input == "" {
+			continue
+		}
+		if count%3 == 0 {
+			t, err := time.Parse(time.RFC3339, input)
+			if err != nil {
+				fmt.Printf("ERROR: Invalid timestamp: %v", t)
+				os.Exit(1)
+			}
+			periods[(count-1)/3].EndTime = t
+
+			if terminal {
+				fmt.Print("Identifier: ")
 			}
 		}
+		if count%3 == 1 {
+			periods = append(periods, msp.Period{Identifier: s.Text()})
+			if terminal {
+				fmt.Print("StartTime: ")
+			}
+		}
+		if count%3 == 2 {
+			t, err := time.Parse(time.RFC3339, input)
+			if err != nil {
+				fmt.Printf("ERROR: Invalid timestamp: %v", t)
+				os.Exit(1)
+			}
+			periods[(count-1)/3].StartTime = t
+
+			if terminal {
+				fmt.Print("EndTime: ")
+			}
+		}
+		count++
+	}
+
+	m, err := msp.MostSpecificPeriod(time.Now(), periods...)
+	if err != nil {
+		fmt.Printf("Error: %v\n", err)
+		os.Exit(1)
+	}
+	if terminal {
+		fmt.Printf("The MSP from the list was: ")
+	}
+	fmt.Printf("%s\n", m)
+}