package tokenize

import "fmt"

// Cursor represents the position of a cursor in various ways.
type Cursor struct {
	Byte   int // The cursor offset in bytes
	Rune   int // The cursor offset in UTF8 runes
	Column int // The column at which the cursor is (0-indexed)
	Line   int // The line at which the cursor is (0-indexed)
}

// String produces a string representation of the cursor position.
func (c Cursor) String() string {
	if c.Line == 0 && c.Column == 0 {
		return fmt.Sprintf("start of file")
	}
	return fmt.Sprintf("line %d, column %d", c.Line+1, c.Column+1)
}

// move updates the position of the cursor, based on the provided input string.
// The input string represents the runes that the cursor must be moved over.
// This method will take newlines into account to keep track of line numbers and
// column positions automatically.
func (c *Cursor) move(input string) *Cursor {
	c.Byte += len(input)
	for _, r := range input {
		c.Rune++
		if r == '\n' {
			c.Column = 0
			c.Line++
		} else {
			c.Column++
		}
	}
	return c
}