package gcss

import (
	"fmt"
	"strings"
)

const unicodeSpace = 32

const indentTop = 0

// line represents a line of codes.
type line struct {
	no     int
	s      string
	indent int
}

// isEmpty returns true if the line's s is zero value.
func (ln *line) isEmpty() bool {
	return strings.TrimSpace(ln.s) == ""
}

// isTopIndent returns true if the line's indent is the top level.
func (ln *line) isTopIndent() bool {
	return ln.indent == indentTop
}

// childOf returns true if the line is a child of the parent.
func (ln *line) childOf(parent element) (bool, error) {
	var ok bool
	var err error

	switch pIndent := parent.Base().ln.indent; {
	case ln.indent == pIndent+1:
		ok = true
	case ln.indent > pIndent+1:
		err = fmt.Errorf("indent is invalid [line: %d]", ln.no)
	}

	return ok, err
}

// isDeclaration returns true if the line is a declaration.
func (ln *line) isDeclaration() bool {
	_, _, err := declarationPV(ln)
	return err == nil
}

// isAtRule returns true if the line is an at-rule.
func (ln *line) isAtRule() bool {
	return strings.HasPrefix(strings.TrimSpace(ln.s), atMark)
}

// isVariable returns true if the line is a variable.
func (ln *line) isVariable() bool {
	if !ln.isTopIndent() {
		return false
	}

	_, _, err := variableNV(ln)

	return err == nil
}

// isMixinDeclaration returns true if the line is a mixin declaration.
func (ln *line) isMixinDeclaration() bool {
	if !ln.isTopIndent() {
		return false
	}

	_, _, err := mixinNP(ln, true)

	return err == nil
}

// isMixinInvocation returns true if the line is a mixin invocation.
func (ln *line) isMixinInvocation() bool {
	if ln.isTopIndent() {
		return false
	}

	_, _, err := mixinNP(ln, false)

	return err == nil
}

// isComment returns true if the line is a comment.
func (ln *line) isComment() bool {
	return strings.HasPrefix(strings.TrimSpace(ln.s), doubleSlash)
}

// newLine creates and returns a line.
func newLine(no int, s string) *line {
	return &line{
		no:     no,
		s:      s,
		indent: indent(s),
	}
}

// indent returns the string's indent.
func indent(s string) int {
	var i int

	for _, b := range s {
		if b != unicodeSpace {
			break
		}
		i++
	}

	return i / 2
}