feat: add up/down key support

client/editor/editor.go

@@ -126,18 +126,146 @@ func (e *Editor) showPositions() {
 }
 
 // MoveCursor updates the Cursor position.
-func (e *Editor) MoveCursor(x, _ int) {
+func (e *Editor) MoveCursor(x, y int) {
+	if len(e.Text) == 0 {
+		return
+	}
+	// Move cursor horizontally.
 	newCursor := e.Cursor + x
 
-	if newCursor < 0 {
-		newCursor = 0
+	// Move cursor vertically.
+	if y > 0 {
+		newCursor = e.calcCursorDown()
 	}
+
+	if y < 0 {
+		newCursor = e.calcCursorUp()
+	}
+
+	// Reset to bounds.
 	if newCursor > len(e.Text) {
 		newCursor = len(e.Text)
 	}
+
+	if newCursor < 0 {
+		newCursor = 0
+	}
+
 	e.Cursor = newCursor
 }
 
+// For the functions calcCursorUp and calcCursorDown, newline characters are found by iterating
+// backward and forward from the current Cursor position. These characters are taken as the "start"
+// and "end" of the current line. The "offset" from the start of the current line to the Cursor
+// is calculated and used to determine the final Cursor position on the target line, based on whether the
+// offset is greater than the length of the target line. "pos" is used as a placeholder variable for
+// the Cursor.
+
+// calcCursorUp calculates the intended Cursor position after moving the Cursor up one line.
+func (e *Editor) calcCursorUp() int {
+	pos := e.Cursor
+	offset := 0
+
+	// If the initial cursor is out of the bounds of the Text or already on a newline, move it.
+	if pos == len(e.Text) || e.Text[pos] == '\n' {
+		offset++
+		pos--
+	}
+
+	if pos < 0 {
+		pos = 0
+	}
+
+	start, end := pos, pos
+
+	// Find the start of the current line.
+	for start > 0 && e.Text[start] != '\n' {
+		start--
+	}
+
+	// If the Cursor is already on the first line, move to the beginning of the Text.
+	if start == 0 {
+		return 0
+	}
+
+	// Find the end of the current line.
+	for end < len(e.Text) && e.Text[end] != '\n' {
+		end++
+	}
+
+	// Find the start of the previous line.
+	prevStart := start - 1
+	for prevStart >= 0 && e.Text[prevStart] != '\n' {
+		prevStart--
+	}
+
+	// Calculate the distance from the start of the current line to the Cursor.
+	offset += pos - start
+	if offset <= start-prevStart {
+		return prevStart + offset
+	} else {
+		return start
+	}
+}
+
+func (e *Editor) calcCursorDown() int {
+	pos := e.Cursor
+	offset := 0
+
+	// If the initial Cursor is out of the bounds of the Text or already on a newline, move it.
+	if pos == len(e.Text) || e.Text[pos] == '\n' {
+		offset++
+		pos--
+	}
+
+	if pos < 0 {
+		pos = 0
+	}
+
+	start, end := pos, pos
+
+	// Find the start of the current line.
+	for start > 0 && e.Text[start] != '\n' {
+		start--
+	}
+
+	// This handles the case where the Cursor is on the first line. This is necessary because the start
+	// of the first line is not a newline character, unlike the other lines in the Text.
+	if start == 0 && e.Text[start] != '\n' {
+		offset++
+	}
+
+	// Find the end of the current line.
+	for end < len(e.Text) && e.Text[end] != '\n' {
+		end++
+	}
+
+	// This handles the case where the Cursor is on a newline. end has to be incremented, otherwise
+	// start == end.
+	if e.Text[pos] == '\n' && e.Cursor != 0 {
+		end++
+	}
+
+	// If the Cursor is already on the last line, move to the end of the Text.
+	if end == len(e.Text) {
+		return len(e.Text)
+	}
+
+	// Find the end of the next line.
+	nextEnd := end + 1
+	for nextEnd < len(e.Text) && e.Text[nextEnd] != '\n' {
+		nextEnd++
+	}
+
+	// Calculate the distance from the start of the current line to the Cursor.
+	offset += pos - start
+	if offset < nextEnd-end {
+		return end + offset
+	} else {
+		return nextEnd
+	}
+}
+
 // calcCursorXY calculates Cursor position from the index obtained from the content.
 func (e *Editor) calcCursorXY(index int) (int, int) {
 	x := 1

client/editor/editor_test.go

@@ -65,20 +65,92 @@ func TestMoveCursor(t *testing.T) {
 		description    string
 		cursor         int
 		x              int
+		y              int
 		expectedCursor int
+		text           []rune
 	}{
-		{description: "move forward", cursor: 0, x: 1, expectedCursor: 1},
-		{description: "move backward", cursor: 1, x: -1, expectedCursor: 0},
-		{description: "negative (out of bounds)", cursor: 0, x: -10, expectedCursor: 0},
-		{description: "positive (out of bounds)", cursor: 12, x: 2, expectedCursor: 12},
+		// test horizontal movement
+		{description: "move forward (empty document)", cursor: 0, x: 1, expectedCursor: 0,
+			text: []rune("")},
+		{description: "move backward (empty document)", cursor: 0, x: -1, expectedCursor: 0,
+			text: []rune("")},
+		{description: "move forward", cursor: 0, x: 1, expectedCursor: 1,
+			text: []rune("foo\n")},
+		{description: "move backward", cursor: 1, x: -1, expectedCursor: 0,
+			text: []rune("foo\n")},
+		{description: "move backward (out of bounds)", cursor: 0, x: -10, expectedCursor: 0,
+			text: []rune("foo\n")},
+		{description: "move forward (out of bounds)", cursor: 3, x: 2, expectedCursor: 4,
+			text: []rune("foo\n")},
+		// test vertical movement
+		{description: "move up", cursor: 6, y: -1, expectedCursor: 2,
+			text: []rune("foo\nbar")},
+		{description: "move down", cursor: 1, y: 2, expectedCursor: 5,
+			text: []rune("foo\nbar")},
+		{description: "move up (empty document)", cursor: 0, y: -1, expectedCursor: 0,
+			text: []rune("")},
+		{description: "move down (empty document)", cursor: 0, y: 1, expectedCursor: 0,
+			text: []rune("")},
+		{description: "move up (first line)", cursor: 1, y: -1, expectedCursor: 0,
+			text: []rune("foo\nbar")},
+		{description: "move down (last line)", cursor: 4, y: 1, expectedCursor: 7,
+			text: []rune("foo\nbar")},
+		{description: "move up (middle line)", cursor: 5, y: -1, expectedCursor: 1,
+			text: []rune("foo\nbar\nbaz")},
+		{description: "move down (middle line)", cursor: 5, y: 1, expectedCursor: 9,
+			text: []rune("foo\nbar\nbaz")},
+		{description: "move up (on newline)", cursor: 3, y: -1, expectedCursor: 0,
+			text: []rune("foo\nbar\nbaz")},
+		{description: "move down (on newline)", cursor: 3, y: 1, expectedCursor: 7,
+			text: []rune("foo\nbar\nbaz")},
+		{description: "move up (on newline, first line)", cursor: 3, y: -1, expectedCursor: 0,
+			text: []rune("foo\nbar\nbaz")},
+		{description: "move down (on newline, last line)", cursor: 7, y: 1, expectedCursor: 11,
+			text: []rune("foo\nbar\nbaz")},
+		{description: "move up (different lengths, short to long)", cursor: 8, y: -1, expectedCursor: 3,
+			text: []rune("fool\nbar\nbaz")},
+		{description: "move down (different lengths, short to long)", cursor: 3, y: 1, expectedCursor: 7,
+			text: []rune("foo\nbare\nbaz")},
+		{description: "move up (different lengths, long to short)", cursor: 8, y: -1, expectedCursor: 3,
+			text: []rune("foo\nbare\nbaz")},
+		{description: "move down (different lengths, long to short)", cursor: 4, y: 1, expectedCursor: 8,
+			text: []rune("fool\nbar\nbaz")},
+		{description: "move up (from empty line)", cursor: 4, y: -1, expectedCursor: 0,
+			text: []rune("foo\n\nbaz")},
+		{description: "move down (from empty line)", cursor: 4, y: 1, expectedCursor: 5,
+			text: []rune("fool\n\nbaz")},
+		{description: "move up (from empty line to empty line)", cursor: 5, y: -1, expectedCursor: 4,
+			text: []rune("foo\n\n\n")},
+		{description: "move down (from empty line to empty line)", cursor: 1, y: 1, expectedCursor: 2,
+			text: []rune("\n\n\nfoo")},
+		{description: "move up (from empty last line to empty line)", cursor: 3, y: -1, expectedCursor: 2,
+			text: []rune("\n\n\n")},
+		{description: "move down (from empty first line to empty line)", cursor: 0, y: 1, expectedCursor: 1,
+			text: []rune("\n\n\n")},
+		{description: "move up (from empty last line)", cursor: 6, y: -1, expectedCursor: 2,
+			text: []rune("\n\nfoo\n")},
+		{description: "move down (from empty first line)", cursor: 0, y: 1, expectedCursor: 1,
+			text: []rune("\nfoo\n\n")},
+		{description: "move up (from empty first line)", cursor: 0, y: -1, expectedCursor: 0,
+			text: []rune("\n\nfoo\n")},
+		{description: "move down (from empty last line)", cursor: 6, y: 1, expectedCursor: 6,
+			text: []rune("\nfoo\n\n")},
+		{description: "move up (from last line to empty line)", cursor: 2, y: -1, expectedCursor: 1,
+			text: []rune("\n\nfoo")},
+		{description: "move down (from first line to empty line)", cursor: 2, y: 1, expectedCursor: 4,
+			text: []rune("foo\n\n")},
+		{description: "move up (from empty line to empty line 2)", cursor: 2, y: -1, expectedCursor: 1,
+			text: []rune("\n\n\n\n\n")},
+		{description: "move down (from empty line to empty line 2)", cursor: 2, y: 1, expectedCursor: 3,
+			text: []rune("\n\n\n\n\n")},
 	}
 
 	e := NewEditor()
-	e.Text = []rune("content\ntest")
 
 	for _, tc := range tests {
 		e.Cursor = tc.cursor
-		e.MoveCursor(tc.x, 0)
+		e.Text = tc.text
+		e.MoveCursor(tc.x, tc.y)
 
 		got := e.Cursor
 		expected := tc.expectedCursor

client/main.go

@@ -295,6 +295,10 @@ func handleTermboxEvent(ev termbox.Event, conn *websocket.Conn) error {
 			e.MoveCursor(-1, 0)
 		case termbox.KeyArrowRight, termbox.KeyCtrlF:
 			e.MoveCursor(1, 0)
+		case termbox.KeyArrowUp, termbox.KeyCtrlP:
+			e.MoveCursor(0, -1)
+		case termbox.KeyArrowDown, termbox.KeyCtrlN:
+			e.MoveCursor(0, 1)
 		case termbox.KeyHome:
 			e.SetX(0)
 		case termbox.KeyEnd:
@@ -353,17 +357,14 @@ func performOperation(opType int, ev termbox.Event, conn *websocket.Conn) {
 	case OperationDelete:
 		logger.Infof("LOCAL DELETE:  cursor position %v\n", e.Cursor)
 		if e.Cursor-1 <= 0 {
-			e.Cursor = 1
+			e.Cursor = 0
 		}
 		text := doc.Delete(e.Cursor)
 		e.SetText(text)
 		msg = message{Type: "operation", Operation: Operation{Type: "delete", Position: e.Cursor}}
 		e.MoveCursor(-1, 0)
 	}
 
-	// Print document state to logs.
-	printDoc(doc)
-
 	err := conn.WriteJSON(msg)
 	if err != nil {
 		e.StatusMsg = "lost connection!"

go.mod

@@ -14,6 +14,7 @@ require (
 )
 
 require (
+	github.com/Pallinder/go-randomdata v1.2.0 // indirect
 	github.com/mattn/go-colorable v0.1.9 // indirect
 	github.com/mattn/go-isatty v0.0.16 // indirect
 	github.com/rivo/uniseg v0.2.0 // indirect