package lexer

import "fmt"

// Position indicates a line and column pair on a file.
// Counting starts at 1.
type Position struct {
	Line   int
	Column int
}

// String generates a pretty "(Line, Column)"" representation of the Position
func (p Position) String() string {
	if p.Line == 0 {
		p.Reset()
	}

	return fmt.Sprintf("(%v, %v)", p.Line, p.Column)
}

// GoString generates a string representation of the Position for %#v usage
func (p Position) GoString() string {
	if p.Line == 0 {
		p.Reset()
	}

	return fmt.Sprintf("lexer.Position{%v, %v}", p.Line, p.Column)
}

// Reset places a position at (1,1)
func (p *Position) Reset() {
	p.Line, p.Column = 1, 1
}

// Step moves the column one place
func (p *Position) Step() {
	if p.Line == 0 {
		p.Reset()
	}

	p.Column++
}

// StepN moves the column N places forward
func (p *Position) StepN(n int) {
	if p.Line == 0 {
		p.Reset()
	}

	switch {
	case n > 0:
		p.Column += n
	default:
		panic(fmt.Errorf("invalid %v increment", n))
	}
}

// StepLine moves position to the start of the next line
func (p *Position) StepLine() {
	if p.Line == 0 {
		p.Reset()
	}

	p.Line++
	p.Column = 1
}

// Add adds a relative position considering
// potential new lines
func (p *Position) Add(rel Position) {
	if p.Line == 0 {
		p.Reset()
	}

	switch {
	case rel.Line == 0:
		// nothing
	case rel.Line > 1:
		// includes new lines
		p.Line += rel.Line - 1
		p.Column = rel.Column
	default:
		// same line
		p.Column += rel.Column - 1
	}
}