zcash-android-wallet-sdk/sdk-lib/src/main/java/cash/z/ecc/android/sdk/internal/transaction/TransactionEncoderImpl.kt

package cash.z.ecc.android.sdk.internal.transaction

import cash.z.ecc.android.sdk.exception.TransactionEncoderException
import cash.z.ecc.android.sdk.ext.masked
import cash.z.ecc.android.sdk.internal.Backend
import cash.z.ecc.android.sdk.internal.SaplingParamTool
import cash.z.ecc.android.sdk.internal.Twig
import cash.z.ecc.android.sdk.internal.createToAddress
import cash.z.ecc.android.sdk.internal.getBranchIdForHeight
import cash.z.ecc.android.sdk.internal.model.EncodedTransaction
import cash.z.ecc.android.sdk.internal.network
import cash.z.ecc.android.sdk.internal.repository.DerivedDataRepository
import cash.z.ecc.android.sdk.internal.shieldToAddress
import cash.z.ecc.android.sdk.model.TransactionRecipient
import cash.z.ecc.android.sdk.model.UnifiedSpendingKey
import cash.z.ecc.android.sdk.model.Zatoshi

/**
 * Class responsible for encoding a transaction in a consistent way. This bridges the gap by
 * behaving like a stateless API so that callers can request [createTransaction] and receive a
 * result, even though there are intermediate database interactions.
 *
 * @property rustBackend the instance of RustBackendWelding to use for creating and validating.
 * @property repository the repository that stores information about the transactions being created
 * such as the raw bytes and raw txId.
 */
internal class TransactionEncoderImpl(
    private val backend: Backend,
    private val saplingParamTool: SaplingParamTool,
    private val repository: DerivedDataRepository
) : TransactionEncoder {

    /**
     * Creates a transaction, throwing an exception whenever things are missing. When the provided
     * wallet implementation doesn't throw an exception, we wrap the issue into a descriptive
     * exception ourselves (rather than using double-bangs for things).
     *
     * @param usk the unified spending key associated with the notes that will be spent.
     * @param amount the amount of zatoshi to send.
     * @param toAddress the recipient's address.
     * @param memo the optional memo to include as part of the transaction.
     *
     * @return the successfully encoded transaction or an exception
     */
    override suspend fun createTransaction(
        usk: UnifiedSpendingKey,
        amount: Zatoshi,
        recipient: TransactionRecipient,
        memo: ByteArray?
    ): EncodedTransaction {
        require(recipient is TransactionRecipient.Address)

        val transactionId = createSpend(usk, amount, recipient.addressValue, memo)
        return repository.findEncodedTransactionById(transactionId)
            ?: throw TransactionEncoderException.TransactionNotFoundException(transactionId)
    }

    override suspend fun createShieldingTransaction(
        usk: UnifiedSpendingKey,
        recipient: TransactionRecipient,
        memo: ByteArray?
    ): EncodedTransaction {
        require(recipient is TransactionRecipient.Account)

        val transactionId = createShieldingSpend(usk, memo)
        return repository.findEncodedTransactionById(transactionId)
            ?: throw TransactionEncoderException.TransactionNotFoundException(transactionId)
    }

    /**
     * Utility function to help with validation. This is not called during [createTransaction]
     * because this class asserts that all validation is done externally by the UI, for now.
     *
     * @param address the address to validate
     *
     * @return true when the given address is a valid z-addr
     */
    override suspend fun isValidShieldedAddress(address: String): Boolean =
        backend.isValidShieldedAddr(address)

    /**
     * Utility function to help with validation. This is not called during [createTransaction]
     * because this class asserts that all validation is done externally by the UI, for now.
     *
     * @param address the address to validate
     *
     * @return true when the given address is a valid t-addr
     */
    override suspend fun isValidTransparentAddress(address: String): Boolean =
        backend.isValidTransparentAddr(address)

    /**
     * Utility function to help with validation. This is not called during [createTransaction]
     * because this class asserts that all validation is done externally by the UI, for now.
     *
     * @param address the address to validate
     *
     * @return true when the given address is a valid ZIP 316 Unified Address
     */
    override suspend fun isValidUnifiedAddress(address: String): Boolean =
        backend.isValidUnifiedAddr(address)

    override suspend fun getConsensusBranchId(): Long {
        val height = repository.lastScannedHeight()
        if (height < backend.network.saplingActivationHeight) {
            throw TransactionEncoderException.IncompleteScanException(height)
        }
        return backend.getBranchIdForHeight(height)
    }

    /**
     * Does the proofs and processing required to create a transaction to spend funds and inserts
     * the result in the database. On average, this call takes over 10 seconds.
     *
     * @param usk the unified spending key associated with the notes that will be spent.
     * @param amount the amount of zatoshi to send.
     * @param toAddress the recipient's address.
     * @param memo the optional memo to include as part of the transaction.
     *
     * @return the row id in the transactions table that contains the spend transaction or -1 if it
     * failed.
     */
    private suspend fun createSpend(
        usk: UnifiedSpendingKey,
        amount: Zatoshi,
        toAddress: String,
        memo: ByteArray? = byteArrayOf()
    ): Long {
        Twig.debug {
            "creating transaction to spend $amount zatoshi to" +
                " ${toAddress.masked()} with memo $memo"
        }

        @Suppress("TooGenericExceptionCaught")
        return try {
            saplingParamTool.ensureParams(saplingParamTool.properties.paramsDirectory)
            Twig.debug { "params exist! attempting to send..." }
            backend.createToAddress(
                usk,
                toAddress,
                amount.value,
                memo
            )
        } catch (t: Throwable) {
            Twig.debug(t) { "Caught exception while creating transaction." }
            throw t
        }.also { result ->
            Twig.debug { "result of sendToAddress: $result" }
        }
    }

    private suspend fun createShieldingSpend(
        usk: UnifiedSpendingKey,
        memo: ByteArray? = byteArrayOf()
    ): Long {
        @Suppress("TooGenericExceptionCaught")
        return try {
            saplingParamTool.ensureParams(saplingParamTool.properties.paramsDirectory)
            Twig.debug { "params exist! attempting to shield..." }
            backend.shieldToAddress(
                usk,
                memo
            )
        } catch (t: Throwable) {
            // TODO [#680]: if this error matches: Insufficient balance (have 0, need 1000 including fee)
            //  then consider custom error that says no UTXOs existed to shield
            // TODO [#680]: https://github.com/zcash/zcash-android-wallet-sdk/issues/680
            Twig.debug(t) { "Shield failed" }
            throw t
        }.also { result ->
            Twig.debug { "result of shieldToAddress: $result" }
        }
    }
}