From 011952386749770db068cd63bf0be95799198bbe Mon Sep 17 00:00:00 2001
From: Aki Kareha <aki@kareha.org>
Date: Wed, 25 Mar 2026 21:38:10 +0900
Subject: [PATCH] Refine print

---
 internal/console/console.go |  8 -------
 internal/editor/editor.go   | 47 ++++++++++++++++++++-----------------
 internal/editor/screen.go   | 12 +++-------
 internal/util/util.go       | 35 +++++++++++++++++++++++++--
 4 files changed, 62 insertions(+), 40 deletions(-)

diff --git a/internal/console/console.go b/internal/console/console.go
index 511865e..22fee89 100644
--- a/internal/console/console.go
+++ b/internal/console/console.go
@@ -97,11 +97,3 @@ func ReadRune() rune {
 	}
 	return r
 }
-
-func Print(s string) {
-	fmt.Print(s)
-}
-
-func Printf(format string, a ...any) (n int, err error) {
-	return fmt.Printf(format, a...)
-}
diff --git a/internal/editor/editor.go b/internal/editor/editor.go
index 9f0243a..353744a 100644
--- a/internal/editor/editor.go
+++ b/internal/editor/editor.go
@@ -110,7 +110,7 @@ func (ed *Editor) drawBuffer() {
 		}
 
 		console.MoveCursor(0, y)
-		console.Print(line)
+		util.Print(line)
 
 		y += ed.lineHeight(line)
 		if y >= h-1 {
@@ -120,7 +120,7 @@ func (ed *Editor) drawBuffer() {
 
 	for ; y < h-1; y++ {
 		console.MoveCursor(0, y)
-		console.Print("~")
+		util.Print("~")
 	}
 }
 
@@ -130,9 +130,9 @@ func (ed *Editor) drawStatus() {
 	console.MoveCursor(0, h-1)
 	switch ed.mode {
 	case modeCommand:
-		console.Print("c")
+		util.Print("c")
 	case modeInsert:
-		console.Print("i")
+		util.Print("i")
 	}
 }
 
@@ -159,22 +159,23 @@ func (ed *Editor) updateCursor() {
 
 	if ed.row < ed.vrow {
 		ed.vrow = ed.row
-	} else if ed.vrow+h-2 <= ed.row {
-		ed.vrow = ed.row - (h - 2)
 	}
 
 	y := 0
 	for i := ed.vrow; i < ed.row; i++ {
-		var line string
-		if ed.mode == modeInsert && i == ed.row {
-			line = ed.head + ed.insert.String() + ed.tail
-		} else {
-			line = ed.lines[i]
-		}
-
-		y += ed.lineHeight(line)
+		y += ed.lineHeight(ed.lines[i])
 	}
 	ed.y = y + dy
+
+	for ed.y >= h-1 {
+		ed.vrow++
+
+		y := 0
+		for i := ed.vrow; i < ed.row; i++ {
+			y += ed.lineHeight(ed.lines[i])
+		}
+		ed.y = y + dy
+	}
 }
 
 func (ed *Editor) repaint() {
@@ -202,16 +203,20 @@ func (ed *Editor) exitInsert() {
 }
 
 func (ed *Editor) insertNewline() {
-	lines := make([]string, 0, len(ed.lines)+1)
-	lines = append(lines, ed.lines[:ed.row+1]...)
-	lines = append(lines, "")
+	before := make([]string, 0, len(ed.lines)+1)
+	before = append(before, ed.lines[:ed.row]...)
+	var after []string
 	if ed.row+1 < len(ed.lines) {
-		lines = append(lines, ed.lines[ed.row+1:]...)
+		after = ed.lines[ed.row+1:]
+	} else {
+		after = []string{}
 	}
+	newLines := []string{
+		ed.head + ed.insert.String(),
+		ed.tail,
+	}
+	ed.lines = append(append(before, newLines...), after...)
 
-	lines[ed.row] = ed.head + ed.insert.String()
-	lines[ed.row+1] = ed.tail
-	ed.lines = lines
 	ed.row++
 
 	ed.col = 0
diff --git a/internal/editor/screen.go b/internal/editor/screen.go
index 38372d4..c308e4c 100644
--- a/internal/editor/screen.go
+++ b/internal/editor/screen.go
@@ -4,18 +4,12 @@ import (
 	"tea.kareha.org/lab/levi/internal/console"
 )
 
-type screen struct {
-	w, h int
-}
+type screen struct{}
 
 func newScreen() screen {
-	w, h := console.Size()
-	return screen{
-		w: w,
-		h: h,
-	}
+	return screen{}
 }
 
 func (scr *screen) size() (int, int) {
-	return scr.w, scr.h
+	return console.Size()
 }
diff --git a/internal/util/util.go b/internal/util/util.go
index 569dd7b..1493d22 100644
--- a/internal/util/util.go
+++ b/internal/util/util.go
@@ -1,6 +1,7 @@
 package util
 
 import (
+	"fmt"
 	"unicode"
 )
 
@@ -20,7 +21,14 @@ func isEmoji(r rune) bool {
 	return r >= 0x1f300 && r <= 0x1faff
 }
 
-func runeWidth(r rune) int {
+const tabWidth = 4
+
+func runeWidth(r rune, x int) int {
+	// tab
+	if r == '\t' {
+		return tabWidth - (x % tabWidth)
+	}
+
 	// control code
 	if r == 0 {
 		return 0
@@ -54,8 +62,31 @@ func StringWidth(s string, col int) int {
 		if i >= col {
 			break
 		}
-		sum += runeWidth(r)
+		w := runeWidth(r, sum)
+		sum += w
 		i++
 	}
 	return sum
 }
+
+func Print(s string) {
+	x := 0
+	for _, r := range s {
+		if r == '\t' {
+			spaces := tabWidth - (x % tabWidth)
+			for i := 0; i < spaces; i++ {
+				fmt.Print(" ")
+			}
+			x += spaces
+		} else {
+			fmt.Printf("%c", r)
+			x += runeWidth(r, x)
+		}
+	}
+}
+
+func Printf(format string, a ...any) (n int, err error) {
+	s := fmt.Sprintf(format, a...)
+	Print(s)
+	return len(s), nil
+}