// Copyright © 2023 Rangeproof Pty Ltd. All rights reserved.

import Foundation
import Combine
import GRDB
import SessionUtilitiesKit
import SessionSnodeKit

public enum ExpirationUpdateJob: JobExecutor {
    public static var maxFailureCount: Int = -1
    public static var requiresThreadId: Bool = true
    public static var requiresInteractionId: Bool = false
    
    public static func run<S: Scheduler>(
        _ job: Job,
        scheduler: S,
        success: @escaping (Job, Bool) -> Void,
        failure: @escaping (Job, Error, Bool) -> Void,
        deferred: @escaping (Job) -> Void,
        using dependencies: Dependencies
    ) {
        guard
            let detailsData: Data = job.details,
            let details: Details = try? JSONDecoder(using: dependencies).decode(Details.self, from: detailsData)
        else { return failure(job, JobRunnerError.missingRequiredDetails, true) }
        
        dependencies[singleton: .storage]
            .readPublisher { db in
                try SnodeAPI
                    .preparedUpdateExpiry(
                        serverHashes: details.serverHashes,
                        updatedExpiryMs: details.expirationTimestampMs,
                        shortenOnly: true,
                        authMethod: try Authentication.with(
                            db,
                            swarmPublicKey: dependencies[cache: .general].sessionId.hexString,
                            using: dependencies
                        ),
                        using: dependencies
                    )
            }
            .flatMap { $0.send(using: dependencies) }
            .subscribe(on: scheduler, using: dependencies)
            .receive(on: scheduler, using: dependencies)
            .map { _, response -> [UInt64: [String]] in
                guard
                    let results: [UpdateExpiryResponseResult] = response
                        .compactMap({ _, value in value.didError ? nil : value })
                        .nullIfEmpty(),
                    let unchangedMessages: [UInt64: [String]] = results
                        .reduce([:], { result, next in result.updated(with: next.unchanged) })
                        .groupedByValue()
                        .nullIfEmpty()
                else { return [:] }
                
                return unchangedMessages
            }
            .sinkUntilComplete(
                receiveCompletion: { result in
                    switch result {
                        case .finished: success(job, false)
                        case .failure(let error): failure(job, error, true)
                    }
                },
                receiveValue: { unchangedMessages in
                    guard !unchangedMessages.isEmpty else { return }
                    
                    dependencies[singleton: .storage].writeAsync { db in
                        unchangedMessages.forEach { updatedExpiry, hashes in
                            hashes.forEach { hash in
                                guard
                                    let interaction: Interaction = try? Interaction
                                        .filter(Interaction.Columns.serverHash == hash)
                                        .fetchOne(db),
                                    let expiresInSeconds: TimeInterval = interaction.expiresInSeconds
                                else { return }
                                
                                let expiresStartedAtMs: Double = Double(updatedExpiry - UInt64(expiresInSeconds * 1000))
                                
                                dependencies[singleton: .jobRunner].upsert(
                                    db,
                                    job: DisappearingMessagesJob.updateNextRunIfNeeded(
                                        db,
                                        interaction: interaction,
                                        startedAtMs: expiresStartedAtMs,
                                        using: dependencies
                                    ),
                                    canStartJob: true
                                )
                            }
                        }
                    }
                }
            )
    }
}

// MARK: - ExpirationUpdateJob.Details

extension ExpirationUpdateJob {
    public struct Details: Codable {
        private enum CodingKeys: String, CodingKey {
            case serverHashes
            case expirationTimestampMs
        }
        
        public let serverHashes: [String]
        public let expirationTimestampMs: Int64
        
        // MARK: - Initialization
        
        public init(
            serverHashes: [String],
            expirationTimestampMs: Int64
        ) {
            self.serverHashes = serverHashes
            self.expirationTimestampMs = expirationTimestampMs
        }
        
        // MARK: - Codable
        
        public init(from decoder: Decoder) throws {
            let container: KeyedDecodingContainer<CodingKeys> = try decoder.container(keyedBy: CodingKeys.self)
            
            self = Details(
                serverHashes: try container.decode([String].self, forKey: .serverHashes),
                expirationTimestampMs: try container.decode(Int64.self, forKey: .expirationTimestampMs)
            )
        }
        
        public func encode(to encoder: Encoder) throws {
            var container: KeyedEncodingContainer<CodingKeys> = encoder.container(keyedBy: CodingKeys.self)

            try container.encode(serverHashes, forKey: .serverHashes)
            try container.encode(expirationTimestampMs, forKey: .expirationTimestampMs)
        }
    }
}