Add editor packages

internal/editor/buffer/edit.go

@@ -0,0 +1,99 @@
+package buffer
+
+import (
+	"unicode"
+	"unicode/utf8"
+
+	"code.chimeric.al/dwrz/wen/internal/editor/buffer/glyph"
+	"code.chimeric.al/dwrz/wen/internal/editor/buffer/line"
+)
+
+func (b *Buffer) Backspace() {
+	var cl = b.CursorLine()
+
+	switch {
+	// Don't do anything at the beginning of the buffer.
+	case b.cursor.line == 0 && b.cursor.index == 0:
+
+	// Delete empty lines.
+	case cl.Length() == 0:
+		b.lines = append(
+			b.lines[:b.cursor.line],
+			b.lines[b.cursor.line+1:]...,
+		)
+
+		b.CursorUp()
+		b.CursorEnd()
+
+	// Append to the previous line.
+	case b.cursor.line != 0 && b.cursor.index == 0:
+		index := b.cursor.line
+
+		b.CursorUp()
+		b.CursorEnd()
+
+		b.lines[index-1].Append(cl.String())
+
+		b.lines = append(
+			b.lines[:index],
+			b.lines[index+1:]...,
+		)
+
+	// Delete a rune.
+	default:
+		b.CursorLeft()
+		b.CursorLine().DeleteRune(b.cursor.index)
+	}
+}
+
+func (b *Buffer) Insert(r rune) {
+	switch {
+	case r == '\n' || r == '\r':
+		b.Newline()
+
+	case r == '\t':
+		b.CursorLine().Insert(b.cursor.index, r)
+		b.cursor.index += utf8.RuneLen(r)
+		b.cursor.glyph += glyph.Width(r)
+
+	// Ignore all other non-printable characters.
+	case !unicode.IsPrint(r):
+		return
+
+	default:
+		b.CursorLine().Insert(b.cursor.index, r)
+		b.cursor.index += utf8.RuneLen(r)
+		b.cursor.glyph += glyph.Width(r)
+	}
+}
+
+// At the start of a line, create a new line above.
+// At the end of the line, create a new line below.
+// In the middle of a line, any remaining runes go to the next line.
+// TODO: using the cursor index will probably break with marks.
+func (b *Buffer) Newline() {
+	var cl = b.CursorLine()
+
+	switch {
+	case b.cursor.index == 0:
+		b.lines = append(
+			b.lines[:b.cursor.line+1],
+			b.lines[b.cursor.line:]...,
+		)
+		b.lines[b.cursor.line] = line.New("")
+
+	default:
+		text := cl.String()
+		rest := line.New(text[b.cursor.index:])
+
+		b.lines = append(
+			b.lines[:b.cursor.line+1],
+			b.lines[b.cursor.line:]...,
+		)
+		b.lines[b.cursor.line] = line.New(text[:b.cursor.index])
+		b.lines[b.cursor.line+1] = rest
+	}
+
+	b.CursorDown()
+	b.CursorHome()
+}