export function setupInput(buffer, cursor, onChange) {
  document.addEventListener("keydown", (e) => {
    if (e.key === "ArrowUp") {
      e.preventDefault();
      if (cursor.line > 0) cursor.line--;
      cursor.col = Math.min(cursor.col, buffer[cursor.line].length);
      onChange();
      return;
    }
    if (e.key === "ArrowDown") {
      e.preventDefault();
      if (cursor.line < buffer.length - 1) cursor.line++;
      cursor.col = Math.min(cursor.col, buffer[cursor.line].length);
      onChange();
      return;
    }
    if (e.key === "ArrowLeft") {
      e.preventDefault();
      if (cursor.col > 0) cursor.col--;
      else if (cursor.line > 0) {
        cursor.line--;
        cursor.col = buffer[cursor.line].length;
      }
      onChange();
      return;
    }
    if (e.key === "ArrowRight") {
      e.preventDefault();
      if (cursor.col < buffer[cursor.line].length) cursor.col++;
      else if (cursor.line < buffer.length - 1) {
        cursor.line++;
        cursor.col = 0;
      }
      onChange();
      return;
    }
    if (e.key === "Backspace") {
      e.preventDefault();
      if (cursor.col > 0) {
        const line = buffer[cursor.line];
        buffer[cursor.line] = line.slice(0, cursor.col - 1) + line.slice(cursor.col);
        cursor.col--;
      } else if (cursor.line > 0) {
        cursor.col = buffer[cursor.line - 1].length;
        buffer[cursor.line - 1] += buffer[cursor.line];
        buffer.splice(cursor.line, 1);
        cursor.line--;
      }
      onChange();
      return;
    }
    if (e.key === "Enter") {
      e.preventDefault();
      const line = buffer[cursor.line];
      const rest = line.slice(cursor.col);
      buffer[cursor.line] = line.slice(0, cursor.col);
      buffer.splice(cursor.line + 1, 0, rest);
      cursor.line++;
      cursor.col = 0;
      onChange();
      return;
    }
    if (e.key.length === 1) {
      e.preventDefault();
      const line = buffer[cursor.line];
      buffer[cursor.line] = line.slice(0, cursor.col) + e.key + line.slice(cursor.col);
      cursor.col++;
      onChange();
    }
  });
}