/
service.go
173 lines (152 loc) · 4.44 KB
/
service.go
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package bingo
import (
"context"
"errors"
"fmt"
"math/rand"
"strconv"
"strings"
"sync"
"github.com/divyanshgaba/bingo/game"
"github.com/divyanshgaba/bingo/ticket"
)
// ErrInvalidArgument is returned when one or more arguments are invalid.
var (
ErrInvalidArgument = errors.New("bingo: invalid argument")
ErrMaxNumbersGenerated = errors.New("bingo: max number of numbers generated for the game")
)
// Service is the interface that provides bingo methods.
type Service interface {
// create a new bingo game and return its ID
CreateGame(context.Context) (game.ID, error)
// create a new ticket for gameID with username
CreateTicket(context.Context, game.ID, string) (ticket.ID, error)
// display ticket as HTML
ShowTicket(context.Context, ticket.ID) (Ticket, error)
// generate a random number, which has not been picked earlier for this game
GenerateNumber(context.Context, game.ID) (int64, error)
// returns all numbers generated so far for a game
GetAllNumbers(context.Context, game.ID) ([]int64, error)
// returns stats for a game.
GetStats(context.Context, game.ID) (numbersDrawn, ticketsGenerated int, err error)
}
type service struct {
games game.Repository
tickets ticket.Repository
mutex *sync.Mutex
}
// NewService returns implementation of `Service`.
func NewService(games game.Repository, tickets ticket.Repository) Service {
s := &service{
games: games,
tickets: tickets,
mutex: &sync.Mutex{},
}
return s
}
func (s service) CreateGame(ctx context.Context) (game.ID, error) {
return s.games.Insert(ctx, game.Game{Tickets: []ticket.ID{}, Numbers: []int64{}})
}
func (s service) CreateTicket(ctx context.Context, gameID game.ID, username string) (ticket.ID, error) {
_, err := s.games.Find(ctx, gameID)
if err != nil {
return "", err
}
ticket := ticket.Ticket{
Username: username,
Cells: generateRandomCells(),
}
ticketID, err := s.tickets.Insert(ctx, ticket)
if err != nil {
return "", err
}
err = s.games.AddTicket(ctx, gameID, ticketID)
return ticketID, err
}
func (s service) ShowTicket(ctx context.Context, ticketID ticket.ID) (Ticket, error) {
t, err := s.tickets.Find(ctx, ticketID)
if err != nil {
return Ticket{}, err
}
return Ticket{Username: t.Username, Cells: parseCellString(t.Cells)}, nil
}
func (s service) GenerateNumber(ctx context.Context, gameID game.ID) (int64, error) {
s.mutex.Lock()
defer s.mutex.Unlock()
game, err := s.games.Find(ctx, gameID)
if err != nil {
return -1, err
}
prev := game.Numbers
if len(prev) == 100 {
return -1, ErrMaxNumbersGenerated
}
set := make(map[int64]bool)
for _, n := range prev {
set[n] = true
}
perm := rand.Perm(100)
var number int64
for _, n := range perm {
if !set[int64(n)] { // not drawn before
number = int64(n)
break
}
}
err = s.games.AddNumber(ctx, gameID, number)
return number, err
}
func (s service) GetAllNumbers(ctx context.Context, gameID game.ID) ([]int64, error) {
g, err := s.games.Find(ctx, gameID)
if err != nil {
return []int64{}, err
}
return g.Numbers, nil
}
func (s service) GetStats(ctx context.Context, gameID game.ID) (numbersDrawn, ticketsGenerated int, err error) {
g, err := s.games.Find(ctx, gameID)
if err != nil {
return 0, 0, err
}
return len(g.Numbers), len(g.Tickets), nil
}
// Ticket is a read model for tickets.
type Ticket struct {
Username string `json:"username,omitempty"`
Cells []int64 `json:"cells,omitempty"`
}
func parseCellString(cells string) []int64 {
strVals := strings.Split(cells, ";")
intVals := make([]int64, len(strVals))
for i, sv := range strVals {
nv, _ := strconv.ParseInt(sv, 10, 32)
intVals[i] = nv
}
return intVals
}
func generateRandomCells() string {
perm := rand.Perm(100)[0:15] // ticket will have exactly 15 numbers, in range [0,100)
var cells []int
cells = append(cells, createRow(9, perm[:5])...)
cells = append(cells, createRow(9, perm[5:10])...)
cells = append(cells, createRow(9, perm[10:])...)
return arrayToString(cells, ";")
}
func arrayToString(a []int, delim string) string {
return strings.Trim(strings.Replace(fmt.Sprint(a), " ", delim, -1), "[]")
}
// create row of `size` with `values` randomly populated. Lenght of `values` must be less than or equal to size.
func createRow(size int, values []int) []int {
if len(values) >= size { // limit
values = values[:size]
}
perm := rand.Perm(size)[:len(values)]
row := make([]int, size)
for i := range row {
row[i] = -1
}
for i := range values {
row[perm[i]] = values[i]
}
return row
}