const findUnusedTransactions = async (bc, address, amount = -1) => {
    try {
        const iterator = bc.getIterator()
        const pendingTrxns = await bc.getTransactions()
        const result = filterUnusedTransactions(iterator, pendingTrxns, address, amount)
        return Promise.resolve(result)
    } catch(error) {
        return Promise.reject(error)
    }
}

const filterUnusedTransactions = (iterator, pendingTrxns, address, amount = -1) => {
    return new Promise(async (resolve, reject) => {
        let sum = 0
        let usedTrxns = {}
        let unusedTrxns = {}

        // Add pending trxns to used
        pendingTrxns.map((trxn) => {
            trxn.vin.map((vinTrxn) => {
                if (address == vinTrxn.signature) {
                    usedTrxns[vinTrxn.id] = {
                        id: vinTrxn.id,
                        voutIdx: vinTrxn.vout
                    }
                }
            })
        })

        while (true) {

            // Loop though all block in blockchain
            const next = await iterator.next()
            if (next) {
                next.transactions.map((trxn) => {

                    // Mask Vin Trxn as Used Trxns
                    trxn.vin.map((vinTrxn) => {

                        // Only Target Address Filter
                        if (address == vinTrxn.signature) {
                            usedTrxns[vinTrxn.id] = {
                                id: vinTrxn.id,
                                voutIdx: vinTrxn.vout
                            }
                        }
                    })

                    trxn.vout.map((vout, voutIdx) => {
                        if (!usedTrxns[trxn.id]) {
                            if (address == vout.address) {
                                unusedTrxns[trxn.id] = {
                                    idx: voutIdx,
                                    value: vout.value
                                }

                                sum += vout.value
                            }
                        }
                    })
                })
            } else {
                break;
            }
        }

        return resolve({
            sum: sum,
            trxns: unusedTrxns
        })
    })
}