package analyzer

import (
	"encoding/json"
	"errors"
	"fmt"
	"os"
)

// Transaction represents a transaction from our upstream source.
// URL: https://catalog.data.gov/dataset/purchase-card-pcard-fiscal-year-2014
type Transaction struct {
	Category               string `json:"MerchantCategory"`
	Vendor                 string
	Description            string
	AgencyName             string
	CardholderLastName     string
	TransactionDate        string
	Amount                 Amount `json:",string"`
	YearMonth              string
	CardholderFirstInitial string
	AgencyNumber           string
	PostedDate             string
}

func (trn Transaction) String() string {
	if trn.Amount < 0 {
		return trn.stringifyRefund()
	}
	return trn.stringifyExpense()
}

func (trn Transaction) stringifyRefund() string {
	amount := trn.Amount * -1.0
	return fmt.Sprintf("%s refunded %s %s", trn.Vendor, trn.stringifyCardholder(), amount.FormatUSD())
}

func (trn Transaction) stringifyExpense() string {
	return fmt.Sprintf("%s spent %s at %s", trn.stringifyCardholder(), trn.Amount.FormatUSD(), trn.Vendor)
}

func (trn Transaction) stringifyCardholder() string {
	return fmt.Sprintf("%s. %s", trn.CardholderFirstInitial, trn.CardholderLastName)
}

// Transactions represents a list of Transaction
type Transactions []Transaction

// Sum adds all transactions together.
func (trns Transactions) Sum() Amount {
	result := Amount(0.0)
	for i := range trns {
		result += trns[i].Amount
	}
	return result
}

// Count is the number of unique Transactions.
func (trns Transactions) Count() int {
	return len(trns)
}

func TransactionsFromFile(path string) (Transactions, error) {
	jsonFile, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer jsonFile.Close()

	var transactions Transactions
	if err := json.NewDecoder(jsonFile).Decode(&transactions); err != nil {
		return nil, err
	}

	return transactions, nil
}

func TransactionsFromURLs(url ...string) (Transactions, error) {
	return nil, errors.New("not implemented")
}