/*
 * This file is part of GNU Taler
 * (C) 2022 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.peer

import android.util.Log
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.launch
import kotlinx.serialization.encodeToString
import kotlinx.serialization.json.Json
import net.taler.common.Amount
import net.taler.common.Timestamp
import net.taler.wallet.TAG
import net.taler.wallet.backend.TalerErrorCode.UNKNOWN
import net.taler.wallet.backend.TalerErrorInfo
import net.taler.wallet.backend.WalletBackendApi
import net.taler.wallet.exchanges.ExchangeItem
import net.taler.wallet.exchanges.ExchangeManager
import org.json.JSONObject
import java.util.concurrent.TimeUnit.HOURS

const val MAX_LENGTH_SUBJECT = 100
val DEFAULT_EXPIRY = ExpirationOption.DAYS_1

class PeerManager(
    private val api: WalletBackendApi,
    private val exchangeManager: ExchangeManager,
    private val scope: CoroutineScope,
) {

    private val _outgoingPullState = MutableStateFlow<OutgoingState>(OutgoingIntro)
    val pullState: StateFlow<OutgoingState> = _outgoingPullState

    private val _outgoingPushState = MutableStateFlow<OutgoingState>(OutgoingIntro)
    val pushState: StateFlow<OutgoingState> = _outgoingPushState

    private val _incomingPullState = MutableStateFlow<IncomingState>(IncomingChecking)
    val incomingPullState: StateFlow<IncomingState> = _incomingPullState

    private val _incomingPushState = MutableStateFlow<IncomingState>(IncomingChecking)
    val incomingPushState: StateFlow<IncomingState> = _incomingPushState

    fun checkPeerPullCredit(amount: Amount) {
        _outgoingPullState.value = OutgoingChecking
        scope.launch(Dispatchers.IO) {
            val exchangeItem = exchangeManager.findExchange(amount.currency)
            if (exchangeItem == null) {
                _outgoingPullState.value = OutgoingError(
                    TalerErrorInfo(UNKNOWN, "No exchange found for ${amount.currency}")
                )
                return@launch
            }
            api.request("checkPeerPullCredit", CheckPeerPullCreditResponse.serializer()) {
                put("exchangeBaseUrl", exchangeItem.exchangeBaseUrl)
                put("amount", amount.toJSONString())
            }.onSuccess {
                _outgoingPullState.value = OutgoingChecked(
                    amountRaw = it.amountRaw,
                    amountEffective = it.amountEffective,
                    exchangeItem = exchangeItem,
                )
            }.onError { error ->
                Log.e(TAG, "got checkPeerPullCredit error result $error")
                _outgoingPullState.value = OutgoingError(error)
            }
        }
    }

    fun initiatePeerPullCredit(amount: Amount, summary: String, expirationHours: Long, exchange: ExchangeItem) {
        _outgoingPullState.value = OutgoingCreating
        scope.launch(Dispatchers.IO) {
            val expiry = Timestamp.fromMillis(System.currentTimeMillis() + HOURS.toMillis(expirationHours))
            api.request("initiatePeerPullCredit", InitiatePeerPullPaymentResponse.serializer()) {
                put("exchangeBaseUrl", exchange.exchangeBaseUrl)
                put("partialContractTerms", JSONObject().apply {
                    put("amount", amount.toJSONString())
                    put("summary", summary)
                    put("purse_expiration", JSONObject(Json.encodeToString(expiry)))
                })
            }.onSuccess {
                _outgoingPullState.value = OutgoingResponse(it.transactionId)
            }.onError { error ->
                Log.e(TAG, "got initiatePeerPullCredit error result $error")
                _outgoingPullState.value = OutgoingError(error)
            }
        }
    }

    fun resetPullPayment() {
        _outgoingPullState.value = OutgoingIntro
    }

    fun checkPeerPushDebit(amount: Amount) {
        _outgoingPushState.value = OutgoingChecking
        scope.launch(Dispatchers.IO) {
            api.request("checkPeerPushDebit", CheckPeerPushDebitResponse.serializer()) {
                put("amount", amount.toJSONString())
            }.onSuccess { response ->
                _outgoingPushState.value = OutgoingChecked(
                    amountRaw = response.amountRaw,
                    amountEffective = response.amountEffective,
                    // FIXME add exchangeItem once available in API
                )
            }.onError { error ->
                Log.e(TAG, "got checkPeerPushDebit error result $error")
                _outgoingPushState.value = OutgoingError(error)
            }
        }
    }

    fun initiatePeerPushDebit(amount: Amount, summary: String, expirationHours: Long) {
        _outgoingPushState.value = OutgoingCreating
        scope.launch(Dispatchers.IO) {
            val expiry = Timestamp.fromMillis(System.currentTimeMillis() + HOURS.toMillis(expirationHours))
            api.request("initiatePeerPushDebit", InitiatePeerPushDebitResponse.serializer()) {
                put("amount", amount.toJSONString())
                put("partialContractTerms", JSONObject().apply {
                    put("amount", amount.toJSONString())
                    put("summary", summary)
                    put("purse_expiration", JSONObject(Json.encodeToString(expiry)))
                })
            }.onSuccess { response ->
                _outgoingPushState.value = OutgoingResponse(response.transactionId)
            }.onError { error ->
                Log.e(TAG, "got initiatePeerPushDebit error result $error")
                _outgoingPushState.value = OutgoingError(error)
            }
        }
    }

    fun resetPushPayment() {
        _outgoingPushState.value = OutgoingIntro
    }

    fun preparePeerPullDebit(talerUri: String) {
        _incomingPullState.value = IncomingChecking
        scope.launch(Dispatchers.IO) {
            api.request("preparePeerPullDebit", PreparePeerPullDebitResponse.serializer()) {
                put("talerUri", talerUri)
            }.onSuccess { response ->
                _incomingPullState.value = IncomingTerms(
                    amountRaw = response.amountRaw,
                    amountEffective = response.amountEffective,
                    contractTerms = response.contractTerms,
                    id = response.transactionId,
                )
            }.onError { error ->
                Log.e(TAG, "got preparePeerPullDebit error result $error")
                _incomingPullState.value = IncomingError(error)
            }
        }
    }

    fun confirmPeerPullDebit(terms: IncomingTerms) {
        _incomingPullState.value = IncomingAccepting(terms)
        scope.launch(Dispatchers.IO) {
            api.request<Unit>("confirmPeerPullDebit") {
                put("transactionId", terms.id)
            }.onSuccess {
                _incomingPullState.value = IncomingAccepted
            }.onError { error ->
                Log.e(TAG, "got confirmPeerPullDebit error result $error")
                _incomingPullState.value = IncomingError(error)
            }
        }
    }

    fun preparePeerPushCredit(talerUri: String) {
        _incomingPushState.value = IncomingChecking
        scope.launch(Dispatchers.IO) {
            api.request("preparePeerPushCredit", PreparePeerPushCreditResponse.serializer()) {
                put("talerUri", talerUri)
            }.onSuccess { response ->
                _incomingPushState.value = IncomingTerms(
                    amountRaw = response.amountRaw,
                    amountEffective = response.amountEffective,
                    contractTerms = response.contractTerms,
                    id = response.transactionId,
                )
            }.onError { error ->
                Log.e(TAG, "got preparePeerPushCredit error result $error")
                _incomingPushState.value = IncomingError(error)
            }
        }
    }

    fun confirmPeerPushCredit(terms: IncomingTerms) {
        _incomingPushState.value = IncomingAccepting(terms)
        scope.launch(Dispatchers.IO) {
            api.request<Unit>("confirmPeerPushCredit") {
                put("transactionId", terms.id)
            }.onSuccess {
                _incomingPushState.value = IncomingAccepted
            }.onError { error ->
                Log.e(TAG, "got confirmPeerPushCredit error result $error")
                _incomingPushState.value = IncomingError(error)
            }
        }
    }

}