package main

import (
	"fmt"
	"time"
)

type BillService struct {
	db    *DB
	bills map[int64]Bill
}

const paymentColumns = "id, billid, monthFor, paymentDate"
const billColumns = "id, name"

func (s *BillService) GetPaymentsForDate(date time.Time) ([]Payment, error) {
	res := []Payment{}
	if s == nil {
		return res, fmt.Errorf("calling GetPaymentsFor on nil BillService")
	}
	if s.db == nil || !s.db.Ready {
		return res, fmt.Errorf("cannot get payments, db is nil or not ready - %v", s.db)
	}

	rows, err := s.db.readConn.Query(fmt.Sprintf(`
SELECT %s
FROM Payment
WHERE monthFor = date(strftime('%%Y-%%m-01', ?));
`, paymentColumns), date)
	if err != nil {
		return res, fmt.Errorf("query for payments of %s failed with error: %v", date, err)
	}

	for rows.Next() {
		payment := Payment{}
		err = rows.Scan(&payment.Id, &payment.BillId, &payment.MonthFor, &payment.PaymentDate)
		if err != nil {
			Error.Printf("failed to scan row: %v", err)
			continue
		}
		res = append(res, payment)
	}

	return res, nil
}

func (s *BillService) GetPaymentForBillAndDate(billid int64, date time.Time) (Payment, error) {
	res := Payment{}
	if s == nil {
		return res, fmt.Errorf("calling GetPaymentsFor on nil BillService")
	}
	if s.db == nil || !s.db.Ready {
		return res, fmt.Errorf("cannot get payments, db is nil or not ready - %v", s.db)
	}

	row := s.db.readConn.QueryRow(fmt.Sprintf(`
SELECT %s
FROM Payment
WHERE billid = ? AND monthFor = date(strftime('%%Y-%%m-01', ?));
`, paymentColumns), billid, date)

	err := row.Scan(&res.Id, &res.BillId, &res.MonthFor, &res.PaymentDate)
	if err != nil {
		return res, fmt.Errorf("failed scanning row: %v", err)
	}

	return res, nil
}

func (s *BillService) GetAllBills() ([]Bill, error) {
	res := []Bill{}
	if s == nil {
		return res, fmt.Errorf("calling GetAllBills on nil BillService")
	}
	if s.db == nil || !s.db.Ready {
		return res, fmt.Errorf("cannot get bills, db is nil or not ready - %v", s.db)
	}

	rows, err := s.db.readConn.Query(fmt.Sprintf(`SELECT %s FROM Bill ORDER BY name`, billColumns))
	if err != nil {
		return res, fmt.Errorf("failed to query for bills: %w", err)
	}

	for rows.Next() {
		bill := Bill{}
		err := rows.Scan(&bill.Id, &bill.Name)
		if err != nil {
			Error.Printf("failed to scan row: %v", err)
			continue
		}
		res = append(res, bill)
	}

	s.bills = make(map[int64]Bill)
	for _, bill := range res {
		s.bills[bill.Id] = bill
	}

	return res, nil
}

func (s *BillService) MarkPaid(billid int64, monthFor time.Time, when time.Time) (Payment, error) {
	res := Payment{}
	if s == nil {
		return res, fmt.Errorf("calling MarkPaid on nil BillService")
	}
	if s.db == nil || !s.db.Ready {
		return res, fmt.Errorf("cannot mark bill paid, db is nil or not ready - %v", s.db)
	}

	qres, err := s.db.writeConn.Exec(`
INSERT INTO Payment (billid, monthFor, paymentDate)
VALUES (?, date(strftime('%Y-%m-01', ?)), ?)
ON CONFLICT(billid, monthFor) DO UPDATE SET
	paymentDate = excluded.paymentDate
WHERE Payment.paymentDate IS NULL
	`, billid, monthFor, when)
	if err != nil {
		return res, fmt.Errorf("failed upserting into payment with error: %w", err)
	}

	rows, err := qres.RowsAffected()
	if err != nil {
		return res, fmt.Errorf("failed to get rows affected: %w", err)
	}
	if rows == 0 {
		return res, fmt.Errorf("no rows affected")
	}

	return s.GetPaymentForBillAndDate(billid, monthFor)
}