// Package parser parses dosini-style files
package parser

import (
	"io"
	"log"

	"asciigoat.org/core/lexer"
)

// Parser parses a dosini-style document
type Parser struct {
	src *lexer.Reader
	pos lexer.Position

	// OnToken is called for each identified token. if it returns an error
	// parsing is interrupted.
	OnToken func(pos lexer.Position, typ TokenType, value string) error

	// OnError is called in case of a parsing error, and it's allowed
	// to replace the error returned by [Parser.Run].
	// OnError is called for io.EOF, but [Parser.Run] will consider it
	// normal termination.
	OnError func(pos lexer.Position, content string, err error) error
}

func defaultOnToken(pos lexer.Position, typ TokenType, value string) error {
	log.Printf("%s:%v:%v: %q", typ, pos.Line, pos.Column, value)
	return nil
}

func defaultOnError(pos lexer.Position, content string, err error) error {
	log.Printf("%s:%v:%v: %q: %s", "error", pos.Line, pos.Column, content, err)

	return lexer.Error{
		Line:   pos.Line,
		Column: pos.Column,

		Content: content,
		Err:     err,
	}
}

func (p *Parser) setDefaults() {
	if p.OnToken == nil {
		p.OnToken = defaultOnToken
	}
	if p.OnError == nil {
		p.OnError = defaultOnError
	}
}

func (p *Parser) emitString(typ TokenType) error {
	s := p.src.Emit()
	err := p.OnToken(p.pos, typ, s)
	p.pos.StepN(len(s))

	return err
}

func (p *Parser) emitError(content string, err error) (lexer.StateFn, error) {
	err2 := p.OnError(p.pos, content, err)
	switch {
	case err2 != nil:
		// return wrapped error
		return nil, err2
	default:
		// return original error
		return nil, err
	}
}

func (p *Parser) emitInvalidRune(r rune) (lexer.StateFn, error) {
	return p.emitError(string([]rune{r}), lexer.ErrUnacceptableRune)
}

// stepLine discards the data and moves the position
// to the next line.
func (p *Parser) stepLine() {
	p.src.Discard()
	p.pos.StepLine()
}

// stepRune discards the data and moves the position
// one rune forward on the same line.
func (p *Parser) stepRune() {
	p.src.Discard()
	p.pos.Step()
}

// stepString discards the data and moves the position
// forward on the same line the length of the discarded
// content.
func (p *Parser) stepString() {
	s := p.src.Emit()
	p.pos.StepN(len(s))
}

// NewParser creates a dosini-style parser using
// an [io.Reader] as source
func NewParser(r io.Reader) *Parser {
	if r == nil {
		return nil
	}

	return &Parser{
		src: lexer.NewReader(r),
	}
}