/*
 * 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.transactions

import androidx.annotation.UiThread
import androidx.annotation.WorkerThread
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.switchMap
import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.module.kotlin.readValue
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch
import net.taler.wallet.backend.WalletBackendApi
import org.json.JSONObject
import java.util.*

sealed class TransactionsResult {
    object Error : TransactionsResult()
    class Success(val transactions: List<Transaction>) : TransactionsResult()
}

class TransactionManager(
    private val walletBackendApi: WalletBackendApi,
    private val scope: CoroutineScope,
    private val mapper: ObjectMapper
) {

    private val mProgress = MutableLiveData<Boolean>()
    val progress: LiveData<Boolean> = mProgress

    var selectedCurrency: String? = null
    var selectedTransaction: Transaction? = null

    val searchQuery = MutableLiveData<String>(null)
    private val allTransactions = HashMap<String, List<Transaction>>()
    private val mTransactions = HashMap<String, MutableLiveData<TransactionsResult>>()
    val transactions: LiveData<TransactionsResult>
        @UiThread
        get() = searchQuery.switchMap { query ->
            val currency = selectedCurrency
            check(currency != null) { "Did not select currency before getting transactions" }
            loadTransactions(query)
            mTransactions[currency]!! // non-null because filled in [loadTransactions]
        }

    @UiThread
    fun loadTransactions(searchQuery: String? = null) {
        val currency = selectedCurrency ?: return
        val liveData = mTransactions.getOrPut(currency) { MutableLiveData() }
        if (searchQuery == null && allTransactions.containsKey(currency)) {
            liveData.value = TransactionsResult.Success(allTransactions[currency]!!)
        }
        if (liveData.value == null) mProgress.value = true
        val request = JSONObject(mapOf("currency" to currency))
        searchQuery?.let { request.put("search", it) }
        walletBackendApi.sendRequest("getTransactions", request) { isError, result ->
            if (isError) {
                liveData.postValue(TransactionsResult.Error)
            } else {
                val currencyToUpdate = if (searchQuery == null) currency else null
                scope.launch(Dispatchers.Default) {
                    onTransactionsLoaded(liveData, currencyToUpdate, result)
                }
            }
        }
    }

    @WorkerThread
    private fun onTransactionsLoaded(
        liveData: MutableLiveData<TransactionsResult>,
        currency: String?,  // only non-null if we should update all transactions cache
        result: JSONObject
    ) {
        val transactionsArray = result.getString("transactions")
        val transactions: LinkedList<Transaction> = mapper.readValue(transactionsArray)
        // TODO remove when fixed in wallet-core
        transactions.sortWith(compareBy({ it.pending }, { it.timestamp.ms }, { it.transactionId }))
        transactions.reverse()  // show latest first
        mProgress.postValue(false)
        liveData.postValue(TransactionsResult.Success(transactions))
        // update all transactions on UiThread if there was a currency
        currency?.let {
            scope.launch(Dispatchers.Main) { allTransactions[currency] = transactions }
        }
    }

    @UiThread
    fun hasPending(currency: String): Boolean {
        val result = mTransactions[currency]?.value ?: return false
        return if (result is TransactionsResult.Success) {
            result.transactions.any { it.pending }
        } else false
    }

}