feat: Adding a lottery to examples

examples/gno.land/p/demo/gnolotto/gno.mod

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+module gno.land/p/demo/gnolotto

examples/gno.land/p/demo/gnolotto/gnolotto.gno

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+package gnolotto
+
+import (
+	"std"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type Ticket struct {
+	Numbers []int       // Holds the selected numbers for the lottery ticket
+	Owner   std.Address // Address of the ticket owner
+}
+
+type Lottery struct {
+	Tickets        []Ticket  // All tickets in the lottery
+	WinningNumbers []int     // Winning numbers after the draw
+	DrawTime       time.Time // Time of the draw
+	PrizePool      int64     // Total prize pool amount
+}
+
+// Intializes a new lottery instance with a specified draw time and prize pool
+func NewLottery(drawTime time.Time, prizePool int64) *Lottery {
+	return &Lottery{
+		DrawTime:  drawTime,
+		PrizePool: prizePool,
+		Tickets:   make([]Ticket, 0),
+	}
+}
+
+// Adds a new ticket to the lottery
+func (l *Lottery) AddTicket(numbers []int, owner std.Address) {
+	l.Tickets = append(l.Tickets, Ticket{Numbers: numbers, Owner: owner})
+}
+
+// Conducts the draw by generating 5 random numbers between 1 and 15
+func (l *Lottery) Draw() {
+	var blockHeight int64 = std.GetHeight()
+
+	l.WinningNumbers = nil
+	numbersMap := make(map[int]bool)
+
+	// Add variability to the pseudo-random number generation
+	var variabilityFactor int64 = 1
+
+	for len(l.WinningNumbers) < 5 {
+		simpleSeed := (blockHeight + variabilityFactor*251) % 233280
+		number := int(simpleSeed%15) + 1 // Ensure number is between 1 and 15
+
+		if !numbersMap[number] {
+			l.WinningNumbers = append(l.WinningNumbers, number)
+			numbersMap[number] = true
+		}
+
+		variabilityFactor += 13 // Adjusts for increased variability
+	}
+}
+
+// Itterate over all tickets to identify and return the addresses of the winners
+func (l *Lottery) CheckWinners() []std.Address {
+	var winningOwners []std.Address
+
+	for _, ticket := range l.Tickets {
+		matchCount := 0
+
+		for _, tNum := range ticket.Numbers {
+			for _, wNum := range l.WinningNumbers {
+				if tNum == wNum {
+					matchCount++
+					break
+				}
+			}
+		}
+
+		if matchCount == len(l.WinningNumbers) {
+			winningOwners = append(winningOwners, ticket.Owner)
+		}
+	}
+
+	return winningOwners
+}
+
+// Distributes the prize pool equally among the winning ticket owners
+func (l *Lottery) PayWinners(winningOwners []std.Address) {
+	if len(winningOwners) == 0 {
+		return
+	} else {
+		// Calculate reward per winner
+		var reward int64 = l.PrizePool / int64(len(winningOwners))
+
+		banker := std.GetBanker(std.BankerTypeRealmSend)
+
+		for _, owner := range winningOwners {
+			send := std.Coins{{"ugnot", reward}}
+			banker.SendCoins(std.GetOrigPkgAddr(), owner, send) // Send reward to each winner
+		}
+
+		l.PrizePool = 0 // Reset the prize pool after distribution
+	}
+}