impost/example-app/server/api/pow/challenge.get.ts

import { defineEventHandler } from 'h3'
import { config } from '~~/server/utils/config';
import { generate_challenge } from '@impost/lib/validator';
import { ChallengeStrategy } from '@impost/lib';
import { CHALLENGE_TIMEOUT_MS, outstandingChallenges } from '~~/server/utils/pow';

export default defineEventHandler(async () => {
    let challenge_config;
    switch (config.strategy) {
        case ChallengeStrategy.LeadingZeroes:
            challenge_config = {
                parameters: { expires_at: CHALLENGE_TIMEOUT_MS },
                strategy: config.strategy,
                difficulty: config.leading_zeroes?.difficulty!,
            };
            break;
        case ChallengeStrategy.TargetNumber:
            challenge_config = {
                parameters: { expires_at: CHALLENGE_TIMEOUT_MS },
                strategy: config.strategy,
                max_number: config.target_number.max_number,
            };
            break;
    }

    let challenge = await generate_challenge(challenge_config);
    if (challenge === null) {
        throw createError({
            statusCode: 500,
            statusMessage: 'Failed to generate challenge'
        });
    }

    outstandingChallenges.set(challenge.salt, {
        challenge, timeout: setTimeout(() => {
            console.log("Challenge timed out:", challenge.salt);
            outstandingChallenges.delete(challenge.salt);
        }, CHALLENGE_TIMEOUT_MS)
    });

    return {
        challenge,
    }
})