"strings"
	"text/scanner"

	"cmd/internal/src"
)

// A ScanToken represents an input item. It is a simple wrapping of rune, as
// returned by text/scanner.Scanner, plus a couple of extra values.
type ScanToken rune

const (
	// Asm defines some two-character lexemes. We make up
	// a rune/ScanToken value for them - ugly but simple.
	LSH          ScanToken = -1000 - iota // << Left shift.

	}
	tok = p.next()
	if tok.ScanToken == '+' {
		if p.next().ScanToken != scanner.Int {
			return "", obj.ABI0, false
		}
		tok = p.next()
	}
	if tok.ScanToken != '(' {
		return "", obj.ABI0, false
	}
	if reg := p.next(); reg.ScanToken != scanner.Ident || reg.String() != "SB" {
		return "", obj.ABI0, false
	}
	if p.next().ScanToken != ')' || p.peek() != scanner.EOF {

	return &Slice{
		tokens: tokens,
		base:   base,
		line:   line,
		pos:    -1, // Next will advance to zero.
	}
}

func (s *Slice) Next() ScanToken {
	s.pos++
	if s.pos >= len(s.tokens) {
		return scanner.EOF
	}
	return s.tokens[s.pos].ScanToken
}

func (s *Slice) Text() string {
	return s.tokens[s.pos].text
}

func (s *Slice) File() string {
	return s.base.Filename()
}

	Stack
	includes        []string
	beginningOfLine bool
	ifdefStack      []bool
	macros          map[string]*Macro
	text            string // Text of last token returned by Next.
	peek            bool
	peekToken       ScanToken
	peekText        string
}

// NewInput returns an Input from the given path.
func NewInput(name string) *Input {
	return &Input{
		// include directories: look in source dir, then -I directories.

		if result != test.output {
			t.Errorf("%d: %q evaluated to %d; expected %d", i, test.input, result, test.output)
		}
		tok := p.next()
		if test.atEOF && tok.ScanToken != scanner.EOF {
			t.Errorf("%d: %q: at EOF got %s", i, test.input, tok)
		} else if !test.atEOF && tok.ScanToken == scanner.EOF {
			t.Errorf("%d: %q: expected not EOF but at EOF", i, test.input)
		}
	}
}

type badExprTest struct {
	input string

	// Parse left to right.
	op := operands[next]
	if len(op) < 2 || op[0].ScanToken != '$' {
		p.errorf("TEXT %s: frame size must be an immediate constant", name)
		return
	}
	op = op[1:]
	negative := false
	if op[0].ScanToken == '-' {
		negative = true
		op = op[1:]
	}
	if len(op) == 0 || op[0].ScanToken != scanner.Int {
		p.errorf("TEXT %s: frame size must be an immediate constant", name)
		return