SC-20200209

C Solution

// This code is written in Solidity as the task requires developing a smart contract.
// However, since the request is to provide a C solution with inline comments,
// we will simulate the functionality of the smart contract in C.
// Note: The actual implementation of randomness and blockchain interaction would require Solidity or similar language.

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <stdbool.h>

#define MIN_ENTRY_FEE 0.1 // Minimum entry fee in ether (simulated)
#define LOTTERY_INTERVAL 86400 // Lottery runs once every 24 hours (in seconds)

typedef struct {
    char address[50]; // Simulating an Ethereum address as a string
    double payment; // Amount paid by the participant in ether
} Participant;

Participant participants[100]; // Array to store participants (maximum 100 for simplicity)
int participantCount = 0; // Current number of participants
bool lotteryRunning = false; // Status of the current lottery round
time_t lastLotteryTime = 0; // Timestamp of the last lottery run

double totalPrizePool = 0.0; // Total prize pool in ether

// Function to simulate entering the lottery
void enterLottery(char* address, double payment) {
    if (!lotteryRunning) {
        printf("\"Error: Lottery is not running. Please try again later.\"\n");
        return;
    }
    if (payment < MIN_ENTRY_FEE) {
        printf("\"Error: Entry fee must be at least %f ether.\"\n", MIN_ENTRY_FEE);
        return;
    }

    // Add participant to the list
    strcpy(participants[participantCount].address, address);
    participants[participantCount].payment = payment;
    participantCount++;
    totalPrizePool += payment;

    // Log event for entering the lottery
    printf("\"Event: %s has entered the lottery with a payment of %f ether.\"\n", address, payment);
}

// Function to simulate ending the lottery and selecting a winner
void endLottery() {
    if (participantCount == 0) {
        printf("\"Error: No participants in this round. Lottery cannot be ended.\"\n");
        return;
    }

    // Seed random number generator with current time
    srand(time(NULL));
    int winnerIndex = rand() % participantCount; // Randomly select a winner index
    Participant winner = participants[winnerIndex];

    // Log event for ending the lottery and declaring the winner
    printf("\"Event: Lottery has ended. Winner is %s with a prize of %f ether.\"\n", winner.address, totalPrizePool);

    // Reset lottery parameters
    participantCount = 0;
    totalPrizePool = 0.0;
    lastLotteryTime = time(NULL);
    lotteryRunning = false;
}

// Function to start the next lottery round if conditions are met
void startNextLottery() {
    time_t currentTime = time(NULL);
    if ((currentTime - lastLotteryTime) >= LOTTERY_INTERVAL) {
        printf("\"Starting new lottery round...\"\n");
        lotteryRunning = true;
    } else {
        printf("\"Error: Next lottery can only start after 24 hours. Please try again later.\"\n");
    }
}

int main() {
    // Simulate the lifecycle of a lottery round
    startNextLottery();
    enterLottery("0x123456789abcdef", 0.5);
    enterLottery("0xfedcba987654321", 0.75);
    endLottery();

    // Start another round after the required interval (simulated)
    sleep(LOTTERY_INTERVAL + 1); // Wait for more than 24 hours
    startNextLottery();
    enterLottery("0xabcdef123456789", 0.5);
    endLottery();

    return 0;
}