Move code out of cmd

day1/example.txt

@@ -0,0 +1,10 @@
+L68
+L30
+R48
+L5
+R60
+L55
+L1
+L99
+R14
+L82

day1/main.go

@@ -0,0 +1,147 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+)
+
+func main() {
+	debug := flag.Bool("debug", false, "Debug flag.")
+	flag.Parse()
+
+	d1 := dial{n: 50}
+	d2 := dial{n: 50}
+	if *debug {
+		fmt.Println("LINE d1 d2")
+		fmt.Println("     50 50")
+	}
+
+	sc := bufio.NewScanner(os.Stdin)
+	for sc.Scan() {
+		if sc.Text() == "" {
+			log.Fatal("empty line")
+		}
+		n, err := strconv.ParseUint(sc.Text()[1:], 10, 0)
+		if err != nil {
+			log.Fatal(err)
+		}
+		i := int(n)
+		if sc.Text()[0] == 'L' {
+			i = -int(n)
+		}
+
+		// if err := handleLine(d1.Add1, sc.Text()); err != nil {
+		// 	log.Fatal(err)
+		// }
+		if err := handleLine(d1.Add1, sc.Text()); err != nil {
+			log.Fatal(err)
+		}
+		if err := handleLine(d2.Add2, sc.Text()); err != nil {
+			log.Fatal(err)
+		}
+		if *debug {
+			fmt.Printf("%+4d %2d %2d (%+3d %+3d)\n", i, d1.n, d2.n, d1.lastClicks, d2.lastClicks)
+		}
+	}
+	if err := sc.Err(); err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println("zeros:", d1.zeros, d2.zeros)
+	fmt.Println("zero passes:", d1.zeroClicks, d2.zeroClicks)
+}
+
+func handleLine(add func(int), line string) error {
+	if line == "" {
+		return errors.New("empty line")
+	}
+	n, err := strconv.ParseUint(line[1:], 10, 0)
+	if err != nil {
+		return err
+	}
+	switch line[0] {
+	case 'L':
+		add(-int(n))
+		return nil
+	case 'R':
+		add(int(n))
+		return nil
+	default:
+		return fmt.Errorf("unexpected line: %q", line)
+	}
+}
+
+type dial struct {
+	n          int
+	lastClicks int
+	zeros      int
+	zeroClicks int
+}
+
+func (d *dial) Add1(n int) {
+	wasAtZero := d.n == 0
+	d.n += n
+	step := +100
+	if d.n < 0 {
+		step = -100
+	}
+	d.lastClicks = 0
+	for d.n < 0 || d.n > 99 {
+		d.lastClicks++
+		d.n -= step
+	}
+	if d.lastClicks > 0 && wasAtZero {
+		d.lastClicks--
+	}
+	if d.n == 0 {
+		d.zeros++
+		if d.lastClicks == 0 {
+			d.lastClicks++
+		}
+	}
+	d.zeroClicks += d.lastClicks
+}
+
+func (d *dial) Add2(diff int) {
+	n := d.n + diff
+
+	var clicks int
+	switch {
+	case n < 0:
+		wasAtZero := d.n == 0
+		for n < 0 {
+			if wasAtZero {
+				wasAtZero = false
+			} else {
+				clicks++
+			}
+			n += 100
+		}
+		if n == 0 && !wasAtZero {
+			clicks++
+		}
+
+	case n > 99:
+		for n > 99 {
+			clicks++
+			n -= 100
+		}
+
+	default:
+		if n == 0 && d.n != 0 {
+			clicks++
+		}
+	}
+
+	if n == 0 {
+		d.zeros++
+	}
+	d.n = n
+	d.lastClicks = clicks
+	d.zeroClicks += clicks
+}

day1/main_test.go

@@ -0,0 +1,80 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_dial_Add2(t *testing.T) {
+	tests := []struct {
+		start      int
+		turn       int
+		want       int
+		wantClicks int
+	}{
+		{
+			start:      50,
+			turn:       300,
+			want:       50,
+			wantClicks: 3,
+		},
+		{
+			start:      50,
+			turn:       -300,
+			want:       50,
+			wantClicks: 3,
+		},
+
+		{
+			start:      0,
+			turn:       -100,
+			want:       0,
+			wantClicks: 1,
+		},
+		{
+			start:      1,
+			turn:       -101,
+			want:       0,
+			wantClicks: 2,
+		},
+		{
+			start:      99,
+			turn:       -199,
+			want:       0,
+			wantClicks: 2,
+		},
+
+		{
+			start:      0,
+			turn:       100,
+			want:       0,
+			wantClicks: 1,
+		},
+		{
+			start:      99,
+			turn:       101,
+			want:       0,
+			wantClicks: 2,
+		},
+		{
+			start:      1,
+			turn:       199,
+			want:       0,
+			wantClicks: 2,
+		},
+	}
+	for _, tt := range tests {
+		name := fmt.Sprintf("R%d", tt.turn)
+		if tt.turn < 0 {
+			name = fmt.Sprintf("L%d", -tt.turn)
+		}
+		t.Run(name, func(t *testing.T) {
+			d := dial{n: tt.start}
+			d.Add2(tt.turn)
+			assert.Equal(t, tt.want, d.n, "dial")
+			assert.Equal(t, tt.wantClicks, d.zeroClicks, "clicks")
+		})
+	}
+}