package main

import (
	"fmt"
	"io"
	"os"
)

type Mode uint

const (
	CheckBranches Mode = 1 << iota
)

type Error struct {
	Pos Pos
	Msg string
}

func (err Error) Error() string {
	return fmt.Sprintf("%s: %s", err.Pos, err.Msg)
}

var _ error = Error{}

type ErrorHandler func(err error)

type Pragma interface{}

type PragmaHandler func(pos Pos, blank bool, text string, current Pragma) Pragma

func Parse(base *PosBase, src io.Reader, errh ErrorHandler, pragh PragmaHandler, mode Mode) (_ *File, first error) {
	defer func() {
		if p := recover(); p != nil {
			if err, ok := p.(Error); ok {
				first = err
				return
			}
			panic(p)
		}
	}()

	var p Parser
	p.init(base, src, errh, pragh, mode)
	p.Next()
	return p.fileOrNil(), p.First
}

func ParseFile(filename string, errh ErrorHandler, pragh PragmaHandler, mode Mode) (*File, error) {
	f, err := os.Open(filename)
	if err != nil {
		if errh != nil {
			errh(err)
		}
		return nil, err
	}
	defer f.Close()
	return Parse(NewFileBase(filename), f, errh, pragh, mode)
}