import Foundation
import Postbox
import SwiftSignalKit
import TelegramApi
import MtProtoKit

import SyncCore

private typealias SignalKitTimer = SwiftSignalKit.Timer

private final class ManagedAutoremoveMessageOperationsHelper {
    var entry: (TimestampBasedMessageAttributesEntry, MetaDisposable)?
    
    func update(_ head: TimestampBasedMessageAttributesEntry?) -> (disposeOperations: [Disposable], beginOperations: [(TimestampBasedMessageAttributesEntry, MetaDisposable)]) {
        var disposeOperations: [Disposable] = []
        var beginOperations: [(TimestampBasedMessageAttributesEntry, MetaDisposable)] = []
        
        if self.entry?.0.index != head?.index {
            if let (_, disposable) = self.entry {
                self.entry = nil
                disposeOperations.append(disposable)
            }
            if let head = head {
                let disposable = MetaDisposable()
                self.entry = (head, disposable)
                beginOperations.append((head, disposable))
            }
        }
        
        return (disposeOperations, beginOperations)
    }
    
    func reset() -> [Disposable] {
        if let entry = entry {
            return [entry.1]
        } else {
            return []
        }
    }
}

func managedAutoremoveMessageOperations(network: Network, postbox: Postbox) -> Signal<Void, NoError> {
    return Signal { _ in
        let helper = Atomic(value: ManagedAutoremoveMessageOperationsHelper())
        
        let timeOffsetOnce = Signal<Double, NoError> { subscriber in
            subscriber.putNext(network.globalTimeDifference)
            return EmptyDisposable
        }
        
        let timeOffset = (
            timeOffsetOnce
            |> then(
                Signal<Double, NoError>.complete()
                |> delay(1.0, queue: .mainQueue())
            )
        )
        |> restart
        |> map { value -> Double in
            round(value)
        }
        |> distinctUntilChanged
        
        let disposable = combineLatest(timeOffset, postbox.timestampBasedMessageAttributesView(tag: 0)).start(next: { timeOffset, view in
            let (disposeOperations, beginOperations) = helper.with { helper -> (disposeOperations: [Disposable], beginOperations: [(TimestampBasedMessageAttributesEntry, MetaDisposable)]) in
                return helper.update(view.head)
            }
            
            for disposable in disposeOperations {
                disposable.dispose()
            }
            
            for (entry, disposable) in beginOperations {
                let timestamp = CFAbsoluteTimeGetCurrent() + NSTimeIntervalSince1970 + timeOffset
                let signal = Signal<Void, NoError>.complete()
                |> suspendAwareDelay(max(0.0, Double(entry.timestamp) - timestamp), queue: Queue.concurrentDefaultQueue())
                |> then(postbox.transaction { transaction -> Void in
                    if let message = transaction.getMessage(entry.messageId) {
                        var action: AutoremoveTimeoutMessageAttribute.Action = .remove
                        for attribute in message.attributes {
                            if let attribute = attribute as? AutoremoveTimeoutMessageAttribute {
                                action = attribute.action
                            }
                        }
                        
                        if message.id.peerId.namespace == Namespaces.Peer.SecretChat || action == .remove {
                            deleteMessages(transaction: transaction, mediaBox: postbox.mediaBox, ids: [entry.messageId])
                        } else {
                            transaction.updateMessage(message.id, update: { currentMessage in
                                var storeForwardInfo: StoreMessageForwardInfo?
                                if let forwardInfo = currentMessage.forwardInfo {
                                    storeForwardInfo = StoreMessageForwardInfo(authorId: forwardInfo.author?.id, sourceId: forwardInfo.source?.id, sourceMessageId: forwardInfo.sourceMessageId, date: forwardInfo.date, authorSignature: forwardInfo.authorSignature, psaType: forwardInfo.psaType, flags: forwardInfo.flags)
                                }
                                var updatedMedia = currentMessage.media
                                for i in 0 ..< updatedMedia.count {
                                    if let _ = updatedMedia[i] as? TelegramMediaImage {
                                        updatedMedia[i] = TelegramMediaExpiredContent(data: .image)
                                    } else if let _ = updatedMedia[i] as? TelegramMediaFile {
                                        updatedMedia[i] = TelegramMediaExpiredContent(data: .file)
                                    }
                                }
                                var updatedAttributes = currentMessage.attributes
                                for i in 0 ..< updatedAttributes.count {
                                    if let _ = updatedAttributes[i] as? AutoremoveTimeoutMessageAttribute {
                                        updatedAttributes.remove(at: i)
                                        break
                                    }
                                }
                                return .update(StoreMessage(id: currentMessage.id, globallyUniqueId: currentMessage.globallyUniqueId, groupingKey: currentMessage.groupingKey, threadId: currentMessage.threadId, timestamp: currentMessage.timestamp, flags: StoreMessageFlags(currentMessage.flags), tags: currentMessage.tags, globalTags: currentMessage.globalTags, localTags: currentMessage.localTags, forwardInfo: storeForwardInfo, authorId: currentMessage.author?.id, text: currentMessage.text, attributes: updatedAttributes, media: updatedMedia))
                            })
                        }
                    }
                })
                disposable.set(signal.start())
            }
        })
        
        return ActionDisposable {
            disposable.dispose()
            let disposables = helper.with { helper -> [Disposable] in
                return helper.reset()
            }
            for disposable in disposables {
                disposable.dispose()
            }
        }
    }
}