dapp-part-1.scala

@Callable(i)
func startFunding(id: Int, fundraisingEndTimestamp: Int, implmenetationEndTimestamp: Int, targetSum: Int) = {
    # current time
    let lastBlockTimestamp = lastBlock.timestamp
    
    # The campaign end cannot be less than 60 seconds
    if (fundraisingEndTimestamp - lastBlockTimestamp - 60 < 0) then throw("End time should at least 60 seconds more than the last block time") else

  	# The campaign end time cannot be less than the project execution time
    if (implmenetationEndTimestamp < fundraisingEndTimestamp) then throw("Implementation end time should more or equal to endTimestamp") else

  	# Campaign ID has to be unique
    if (isDefined(getInteger(this, keyFunding(id)))) then throw("Funding with the same ID already exists") else

  	# Minimum token amount for collection is 1000
    if (targetSum < 1000) then throw("You cannot fundraise less than 1000 tokens")
    else {
        let fundingPrefix = "funding_" + id.toString()
        [
          	# saving the height at which the campaign began
            IntegerEntry(fundingPrefix, height),
          	# saving the campaign end time
            IntegerEntry(fundingPrefix + "_timestamp", fundraisingEndTimestamp),
          	# saving the project execution tim
            IntegerEntry(fundingPrefix + "_impl_timestamp", implmenetationEndTimestamp),
          	# saving the amount of collected tokens for the campaign to be successful
            IntegerEntry(fundingPrefix + "_targetSum", targetSum),
          	# creating a key in which the current number of collected tokens will be held and put 0 as the starting value 
            IntegerEntry(fundingPrefix + "_raised", 0),
          	# creating a key in which the number of votes confirming that the project has been executed and put 0 as the starting value
            IntegerEntry(fundingPrefix + "_release_votes", 0),
          	# saving the campaign initiator’s private key (in the form of a line for easy reading in the explorer)
            StringEntry(fundingPrefix + "_owner", i.callerPublicKey.toBase58String(),
            # creating a key in which we will store data on whether the campaign initiator has received their tokens after the voting and put false as the starting value
            BooleanEntry(keyReleasedTokens(id), false)
        ]
    }
}