package main

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"os"
)

type Ledger struct {
	path string
}

func NewLedger(path string) (Ledger, error) {
	info, err := os.Stat(path)
	if err == nil && info.IsDir() {
		return Ledger{}, errors.New("path is dir")
	}
	return Ledger{
		path: path,
	}, err
}

func (ledger Ledger) Transactions() ([]Transaction, error) {
	f, err := ledger.open()
	if err != nil {
		return nil, err
	}
	defer f.Close()
	transactions := make([]Transaction, 0)
	for err == nil {
		var transaction Transaction
		transaction, err = readTransaction(f)
		if err == io.EOF {
		} else if err == nil {
			transactions = append(transactions, transaction)
		} else {
			err = fmt.Errorf("error parsing transaction #%d: %v", len(transactions), err)
		}
	}
	if err == io.EOF {
		err = nil
	}
	return transactions, err
}

func (ledger Ledger) open() (io.ReadCloser, error) {
	f, err := os.Open(ledger.path)
	if os.IsNotExist(err) {
		return ioutil.NopCloser(bytes.NewReader([]byte{})), nil
	}
	return f, err
}