/*
 * This file is part of GNU Taler
 * (C) 2020 Taler Systems S.A.
 *
 * GNU Taler is free software; you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 3, or (at your option) any later version.
 *
 * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
 */

package net.taler.wallet.payment

import android.util.Log
import androidx.annotation.UiThread
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.asStateFlow
import kotlinx.coroutines.launch
import kotlinx.serialization.Serializable
import net.taler.common.Amount
import net.taler.common.ContractTerms
import net.taler.wallet.TAG
import net.taler.wallet.accounts.PaytoUriIban
import net.taler.wallet.backend.TalerErrorInfo
import net.taler.wallet.backend.WalletBackendApi
import net.taler.wallet.payment.PayStatus.AlreadyPaid
import net.taler.wallet.payment.PayStatus.InsufficientBalance
import net.taler.wallet.payment.PreparePayResponse.AlreadyConfirmedResponse
import net.taler.wallet.payment.PreparePayResponse.InsufficientBalanceResponse
import net.taler.wallet.payment.PreparePayResponse.PaymentPossibleResponse

val REGEX_PRODUCT_IMAGE = Regex("^data:image/(jpeg|png);base64,([A-Za-z0-9+/=]+)$")

sealed class PayStatus {
    object None : PayStatus()
    object Loading : PayStatus()
    data class Prepared(
        val contractTerms: ContractTerms,
        val proposalId: String,
        val amountRaw: Amount,
        val amountEffective: Amount,
    ) : PayStatus()

    data class InsufficientBalance(
        val contractTerms: ContractTerms,
        val amountRaw: Amount,
    ) : PayStatus()

    // TODO bring user to fulfilment URI
    object AlreadyPaid : PayStatus()
    data class Error(val error: String) : PayStatus()
    data class Success(val currency: String) : PayStatus()
}

class PaymentManager(
    private val api: WalletBackendApi,
    private val scope: CoroutineScope,
) {

    private val mPayStatus = MutableLiveData<PayStatus>(PayStatus.None)
    internal val payStatus: LiveData<PayStatus> = mPayStatus

    private val mDepositState = MutableStateFlow<DepositState>(DepositState.Start)
    internal val depositState = mDepositState.asStateFlow()

    @UiThread
    fun preparePay(url: String) = scope.launch {
        mPayStatus.value = PayStatus.Loading
        api.request("preparePayForUri", PreparePayResponse.serializer()) {
            put("talerPayUri", url)
        }.onError {
            handleError("preparePayForUri", it)
        }.onSuccess { response ->
            mPayStatus.value = when (response) {
                is PaymentPossibleResponse -> response.toPayStatusPrepared()
                is InsufficientBalanceResponse -> InsufficientBalance(
                    response.contractTerms,
                    response.amountRaw
                )
                is AlreadyConfirmedResponse -> AlreadyPaid
            }
        }
    }

    fun confirmPay(proposalId: String, currency: String) = scope.launch {
        api.request("confirmPay", ConfirmPayResult.serializer()) {
            put("proposalId", proposalId)
        }.onError {
            handleError("confirmPay", it)
        }.onSuccess {
            mPayStatus.postValue(PayStatus.Success(currency))
        }
    }

    @UiThread
    fun abortPay() {
        val ps = payStatus.value
        if (ps is PayStatus.Prepared) {
            abortProposal(ps.proposalId)
        }
        resetPayStatus()
    }

    internal fun abortProposal(proposalId: String) = scope.launch {
        Log.i(TAG, "aborting proposal")
        api.request<Unit>("abortProposal") {
            put("proposalId", proposalId)
        }.onError {
            Log.e(TAG, "received error response to abortProposal")
            handleError("abortProposal", it)
        }.onSuccess {
            mPayStatus.postValue(PayStatus.None)
        }
    }

    @UiThread
    fun resetPayStatus() {
        mPayStatus.value = PayStatus.None
    }

    private fun handleError(operation: String, error: TalerErrorInfo) {
        Log.e(TAG, "got $operation error result $error")
        mPayStatus.value = PayStatus.Error(error.userFacingMsg)
    }

    /* Deposits */

    @UiThread
    fun onDepositButtonClicked(amount: Amount, receiverName: String, iban: String, bic: String) {
        val paytoUri: String = PaytoUriIban(
            iban = iban,
            bic = bic,
            targetPath = "",
            params = mapOf("receiver-name" to receiverName),
        ).paytoUri

        if (depositState.value.showFees) {
            val effectiveDepositAmount = depositState.value.effectiveDepositAmount
                ?: Amount.zero(amount.currency)
            makeDeposit(paytoUri, amount, effectiveDepositAmount)
        } else {
            prepareDeposit(paytoUri, amount)
        }
    }

    private fun prepareDeposit(paytoUri: String, amount: Amount) {
        mDepositState.value = DepositState.CheckingFees
        scope.launch {
            api.request("prepareDeposit", PrepareDepositResponse.serializer()) {
                put("depositPaytoUri", paytoUri)
                put("amount", amount.toJSONString())
            }.onError {
                Log.e(TAG, "Error prepareDeposit $it")
                mDepositState.value = DepositState.Error(it.userFacingMsg)
            }.onSuccess {
                mDepositState.value = DepositState.FeesChecked(
                    effectiveDepositAmount = it.effectiveDepositAmount,
                )
            }
        }
    }

    private fun makeDeposit(
        paytoUri: String,
        amount: Amount,
        effectiveDepositAmount: Amount,
    ) {
        mDepositState.value = DepositState.MakingDeposit(effectiveDepositAmount)
        scope.launch {
            api.request("createDepositGroup", CreateDepositGroupResponse.serializer()) {
                put("depositPaytoUri", paytoUri)
                put("amount", amount.toJSONString())
            }.onError {
                Log.e(TAG, "Error createDepositGroup $it")
                mDepositState.value = DepositState.Error(it.userFacingMsg)
            }.onSuccess {
                mDepositState.value = DepositState.Success
            }
        }
    }

    @UiThread
    fun resetDepositState() {
        mDepositState.value = DepositState.Start
    }
}

@Serializable
data class PrepareDepositResponse(
    val totalDepositCost: Amount,
    val effectiveDepositAmount: Amount,
)

@Serializable
data class CreateDepositGroupResponse(
    val depositGroupId: String,
    val transactionId: String,
)