package tss

import "io"
import "strconv"
import "git.tebibyte.media/sashakoshka/goparse"

type parser struct {
	parse.Parser
	sheet Sheet
	lexer parse.Lexer
}

func newParser (lexer parse.Lexer) *parser {
	return &parser {
		sheet: Sheet {
			Variables: make(map[string] ValueList),
		},
		Parser: parse.Parser {
			Lexer:      lexer,
			TokenNames: tokenNames,
		},
	}
}

func Parse (lexer parse.Lexer) (Sheet, error) {
	parser := newParser(lexer)
	err := parser.parse()
	if err == io.EOF { err = nil }
	if err != nil { return Sheet { }, err }
	return parser.sheet, nil
}

func (this *parser) parse () error {
	err := this.Next()
	if err != nil { return err }
	for this.Token.Kind != parse.EOF {
		err = this.parseTopLevel()
		if err != nil { return err }
	}
	return nil
}

func (this *parser) parseTopLevel () error {
	err := this.ExpectDesc("variable or rule", Dollar, Ident, Star)
	if err != nil { return err }
	if this.EOF() { return nil }
	pos := this.Pos()
	
	switch this.Kind() {
	case Dollar:
		name, variable, err := this.parseVariable()
		if err != nil { return err }
		if _, exists := this.sheet.Variables[name]; exists {
			return parse.Errorf(pos, "variable %s already declared", name)
		}
		this.sheet.Variables[name] = variable
		
	case Ident, Star:
		rule, err := this.parseRule()
		if err != nil { return err }
		this.sheet.Rules = append(this.sheet.Rules, rule)
	}
	return nil
}

func (this *parser) parseVariable () (string, ValueList, error) {
	err := this.Expect(Dollar)
	if err != nil { return "", nil, err }
	err = this.ExpectNext(Ident)
	if err != nil { return "", nil, err }
	name := this.Value()
	err = this.ExpectNext(Equals)
	if err != nil { return "", nil, err }
	this.Next()
	values, err := this.parseValueList()
	if err != nil { return "", nil, err }
	err = this.Expect(Semicolon)
	if err != nil { return "", nil, err }
	return name, values, this.Next()
}

func (this *parser) parseRule () (Rule, error) {
	rule := Rule {
		Attrs: make(map[string] []ValueList),
	}
	
	selector, err := this.parseSelector()
	if err != nil { return Rule { }, err }
	rule.Selector = selector
	err = this.Expect(LBrace)
	if err != nil { return Rule { }, err }
	
	for {
		this.Next()
		if this.Is(RBrace) { break }
		pos := this.Pos()
		name, attr, err := this.parseAttr()
		if err != nil { return Rule { }, err }
		err = this.Expect(Semicolon)
		if err != nil { return Rule { }, err }
		if _, exists := rule.Attrs[name]; exists {
			return Rule { }, parse.Errorf (
				pos,
				"attribute %s already declared in this rule",
				name)
		}
		rule.Attrs[name] = attr
	}
	
	return rule, this.Next()
}

func (this *parser) parseSelector () (Selector, error) {
	selector := Selector { }

	// package
	err := this.ExpectDesc("selector", Ident, Star)
	if err != nil { return Selector { }, err }
	if this.Is(Ident) {
		selector.Package = this.Value()
	}
	
	err = this.ExpectNext(Dot)
	if err != nil { return Selector { }, err }

	// object
	err = this.ExpectNext(Ident, Star)
	if err != nil { return Selector { }, err }
	if this.Is(Ident) {
		selector.Object = this.Value()
	}

	// tags
	err = this.ExpectNext(LBracket)
	if err == nil {
		for {
			this.Next()
			err := this.Expect(Ident, String, RBracket)
			if err != nil { return Selector { }, err }
			if this.Is(RBracket) { break       }
			if this.Is(Comma)    { this.Next() }
			selector.Tags = append(selector.Tags, this.Value())
			err = this.ExpectNext(Comma, RBracket)
			if err != nil { return Selector { }, err }
			if this.Is(RBracket) { break }
		}
		this.Next()
	}
	
	return selector, nil
}

func (this *parser) parseAttr () (string, []ValueList, error) {
	err := this.ExpectDesc("attr", Ident)
	if err != nil { return "", nil, err }
	name := this.Value()

	err = this.ExpectNext(Colon)
	if err != nil { return "", nil, err }

	attr := []ValueList { }
	this.Next()
	for {
		err := this.ExpectDesc (
			"value, Comma, or Semicolon",
			Number, Color, String, Ident, Dollar, Slash,
			Comma, Semicolon)
		if err != nil { return "", nil, err }
		if this.Is(Semicolon) { break       }
		if this.Is(Comma)     { this.Next() }
		valueList, err := this.parseValueList()
		if err != nil { return "", nil, err }
		attr = append(attr, valueList)
		err = this.Expect(Comma, Semicolon)
		if err != nil { return "", nil, err }
	}
	
	return name, attr, nil
}

func (this *parser) parseValueList () (ValueList, error) {
	list := ValueList { }
	for {
		err := this.ExpectDesc (
			"value",
			Number, Color, String, Ident, Dollar, Slash)
		if err != nil { break }
		switch this.Kind() {
		case Number:
			number, err := strconv.Atoi(this.Value())
			if err != nil { return nil, err }
			list = append(list, ValueNumber(number))
		case Color:
			color, ok := parseColor([]rune(this.Value()))
			if !ok {
				return nil, parse.Errorf (
					this.Pos(),
					"malformed color literal")
			}
			list = append(list, ValueColor(color))
		case String:
			list = append(list, ValueString(this.Value()))
		case Ident:
			list = append(list, ValueKeyword(this.Value()))
		case Dollar:
			err := this.ExpectNext(Ident)
			if err != nil { return nil, err }
			list = append(list, ValueVariable(this.Value()))
		case Slash:
			list = append(list, ValueCut { })
		}
		this.Next()
	}
	return list, nil
}

func parseColor (runes []rune) (uint32, bool) {
	digits := make([]uint32, len(runes))
	for index, run := range runes {
		digit := hexDigit(run)
		if digit < 0 { return 0, false }
		digits[index] = uint32(digit)
	}
	switch len(runes) {
	case 3:
		return  digits[0] << 28 | digits[0] << 24 |
			digits[1] << 20 | digits[1] << 16 |
			digits[2] << 12 | digits[2] <<  8 | 0xFF, true
	case 6:
		return  digits[0] << 28 | digits[1] << 24 |
			digits[2] << 20 | digits[3] << 16 |
			digits[4] << 12 | digits[5] <<  8 | 0xFF, true
	case 4:
		return  digits[0] << 28 | digits[0] << 24 |
			digits[1] << 20 | digits[1] << 16 |
			digits[2] << 12 | digits[2] <<  8 |
			digits[3] <<  4 | digits[3] <<  0, true
	case 8:
		return  digits[0] << 28 | digits[1] << 24 |
			digits[2] << 20 | digits[3] << 16 |
			digits[4] << 12 | digits[5] <<  8 |
			digits[6] <<  4 | digits[7] <<  0, true
	default: return 0, false
	}
}

func hexDigit (digit rune) int {
	switch {
	case digit >= '0' && digit <= '9': return int(digit - '0')
	case digit >= 'a' && digit <= 'f': return int(digit - 'a') + 10
	case digit >= 'A' && digit <= 'F': return int(digit - 'A') + 10
	default: return -1
	}
}