// Package parser parses dosini-style files
package parser

import (
	"io"

	"asciigoat.org/core/lexer"
)

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

	pos   lexer.Position
	queue []Token

	// OnSection is called after a [section] is parsed.
	// Returning an error will abort the process.
	OnSection func(pos lexer.Position, name, subname string, hasSubname bool) error

	// OnField is called after a `key = value` entry is parsed
	// Returning an error will abort the process.
	OnField func(pos lexer.Position, key, value string) error

	// OnComment is called after a comment is parsed
	// Returning an error will abort the process.
	OnComment func(pos lexer.Position, comment string) error

	// OnError is called after each parsing error, which you are allowed to
	// override.
	// OnError is called for EOF as well, but this error isn't returned as such by
	// Parser.Run(). The caller will receive (nil, nil) instead indicating the
	// processes terminated correctly.
	OnError func(pos lexer.Position, content string, err error) error
}

func defaultOnSection(_ lexer.Position, _, _ string, _ bool) error { return nil }
func defaultOnField(_ lexer.Position, _, _ string) error           { return nil }
func defaultOnComment(_ lexer.Position, _ string) error            { return nil }

func defaultOnError(pos lexer.Position, content string, err error) error {
	return &lexer.Error{
		Line:    pos.Line,
		Column:  pos.Column,
		Content: content,
		Err:     err,
	}
}

func (p *Parser) setDefaults() {
	if p.OnSection == nil {
		p.OnSection = defaultOnSection
	}

	if p.OnField == nil {
		p.OnField = defaultOnField
	}

	if p.OnComment == nil {
		p.OnComment = defaultOnComment
	}

	if p.OnError == nil {
		p.OnError = defaultOnError
	}
}

// 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),
	}
}