bitchat-android/app/src/main/java/com/bitchat/android/nostr/NostrDirectMessageHandler.kt

package com.bitchat.android.nostr

import android.app.Application
import android.util.Log
import com.bitchat.android.model.BitchatMessage
import com.bitchat.android.model.DeliveryStatus
import com.bitchat.android.protocol.BitchatPacket
import com.bitchat.android.services.SeenMessageStore
import com.bitchat.android.ui.ChatState
import com.bitchat.android.ui.MeshDelegateHandler
import com.bitchat.android.ui.PrivateChatManager
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext
import java.util.Date

class NostrDirectMessageHandler(
    private val application: Application,
    private val state: ChatState,
    private val privateChatManager: PrivateChatManager,
    private val meshDelegateHandler: MeshDelegateHandler,
    private val scope: CoroutineScope,
    private val repo: GeohashRepository
) {
    companion object { private const val TAG = "NostrDirectMessageHandler" }

    private val seenStore by lazy { SeenMessageStore.getInstance(application) }

    // Simple event deduplication
    private val processedIds = ArrayDeque<String>()
    private val seen = HashSet<String>()
    private val max = 2000

    private fun dedupe(id: String): Boolean {
        if (seen.contains(id)) return true
        seen.add(id)
        processedIds.addLast(id)
        if (processedIds.size > max) {
            val old = processedIds.removeFirst()
            seen.remove(old)
        }
        return false
    }

    fun onGiftWrap(giftWrap: NostrEvent, geohash: String, identity: NostrIdentity) {
        scope.launch(Dispatchers.Default) {
            try {
                if (dedupe(giftWrap.id)) return@launch

                val messageAge = System.currentTimeMillis() / 1000 - giftWrap.createdAt
                if (messageAge > 173700) return@launch // 48 hours + 15 mins

                val decryptResult = NostrProtocol.decryptPrivateMessage(giftWrap, identity)
                if (decryptResult == null) {
                    Log.w(TAG, "Failed to decrypt Nostr message")
                    return@launch
                }

                val (content, senderPubkey, rumorTimestamp) = decryptResult
                if (!content.startsWith("bitchat1:")) return@launch

                val base64Content = content.removePrefix("bitchat1:")
                val packetData = base64URLDecode(base64Content) ?: return@launch
                val packet = BitchatPacket.fromBinaryData(packetData) ?: return@launch

                if (packet.type != com.bitchat.android.protocol.MessageType.NOISE_ENCRYPTED.value) return@launch

                val noisePayload = com.bitchat.android.model.NoisePayload.decode(packet.payload) ?: return@launch
                val messageTimestamp = Date(giftWrap.createdAt * 1000L)
                val convKey = "nostr_${senderPubkey.take(16)}"
                repo.putNostrKeyMapping(convKey, senderPubkey)
                com.bitchat.android.nostr.GeohashAliasRegistry.put(convKey, senderPubkey)
                if (geohash.isNotEmpty()) {
                    // Remember which geohash this conversation belongs to so we can subscribe on-demand
                    repo.setConversationGeohash(convKey, geohash)
                    GeohashConversationRegistry.set(convKey, geohash)
                }

                // Ensure sender appears in geohash people list even if they haven't posted publicly yet
                if (geohash.isNotEmpty()) {
                    // Cache a best-effort nickname and mark as participant
                    val cached = repo.getCachedNickname(senderPubkey)
                    if (cached == null) {
                        val base = repo.displayNameForNostrPubkeyUI(senderPubkey).substringBefore("#")
                        repo.cacheNickname(senderPubkey, base)
                    }
                    repo.updateParticipant(geohash, senderPubkey, messageTimestamp)
                }

                val senderNickname = repo.displayNameForNostrPubkeyUI(senderPubkey)

                processNoisePayload(noisePayload, convKey, senderNickname, messageTimestamp, senderPubkey, identity)

            } catch (e: Exception) {
                Log.e(TAG, "onGiftWrap error: ${e.message}")
            }
        }
    }

    private suspend fun processNoisePayload(
        payload: com.bitchat.android.model.NoisePayload,
        convKey: String,
        senderNickname: String,
        timestamp: Date,
        senderPubkey: String,
        recipientIdentity: NostrIdentity
    ) {
        when (payload.type) {
            com.bitchat.android.model.NoisePayloadType.PRIVATE_MESSAGE -> {
                val pm = com.bitchat.android.model.PrivateMessagePacket.decode(payload.data) ?: return
                val existingMessages = state.getPrivateChatsValue()[convKey] ?: emptyList()
                if (existingMessages.any { it.id == pm.messageID }) return

                val message = BitchatMessage(
                    id = pm.messageID,
                    sender = senderNickname,
                    content = pm.content,
                    timestamp = timestamp,
                    isRelay = false,
                    isPrivate = true,
                    recipientNickname = state.getNicknameValue(),
                    senderPeerID = convKey,
                    deliveryStatus = DeliveryStatus.Delivered(to = state.getNicknameValue() ?: "Unknown", at = Date())
                )

                val isViewing = state.getSelectedPrivateChatPeerValue() == convKey
                val suppressUnread = seenStore.hasRead(pm.messageID)

                withContext(Dispatchers.Main) {
                    privateChatManager.handleIncomingPrivateMessage(message, suppressUnread)
                }

                if (!seenStore.hasDelivered(pm.messageID)) {
                    val nostrTransport = NostrTransport.getInstance(application)
                    nostrTransport.sendDeliveryAckGeohash(pm.messageID, senderPubkey, recipientIdentity)
                    seenStore.markDelivered(pm.messageID)
                }

                if (isViewing && !suppressUnread) {
                    val nostrTransport = NostrTransport.getInstance(application)
                    nostrTransport.sendReadReceiptGeohash(pm.messageID, senderPubkey, recipientIdentity)
                    seenStore.markRead(pm.messageID)
                }
            }
            com.bitchat.android.model.NoisePayloadType.DELIVERED -> {
                val messageId = String(payload.data, Charsets.UTF_8)
                withContext(Dispatchers.Main) {
                    meshDelegateHandler.didReceiveDeliveryAck(messageId, convKey)
                }
            }
            com.bitchat.android.model.NoisePayloadType.READ_RECEIPT -> {
                val messageId = String(payload.data, Charsets.UTF_8)
                withContext(Dispatchers.Main) {
                    meshDelegateHandler.didReceiveReadReceipt(messageId, convKey)
                }
            }
        }
    }

    private fun base64URLDecode(input: String): ByteArray? {
        return try {
            val padded = input.replace("-", "+")
                .replace("_", "/")
                .let { str ->
                    val padding = (4 - str.length % 4) % 4
                    str + "=".repeat(padding)
                }
            android.util.Base64.decode(padded, android.util.Base64.DEFAULT)
        } catch (e: Exception) {
            Log.e(TAG, "Failed to decode base64url: ${e.message}")
            null
        }
    }
}