session-ios/SessionMessagingKit/Sending & Receiving/Message Handling/MessageReceiver+ExpirationTimers.swift

// Copyright © 2022 Rangeproof Pty Ltd. All rights reserved.

import Foundation
import GRDB
import SessionUtilitiesKit

extension MessageReceiver {
    internal static func handleExpirationTimerUpdate(
        _ db: Database,
        threadId: String,
        threadVariant: SessionThread.Variant,
        message: ExpirationTimerUpdate
    ) throws {
        guard
            // Only process these for contact and legacy groups (new groups handle it separately)
            (threadVariant == .contact || threadVariant == .legacyGroup),
            let sender: String = message.sender
        else { throw MessageReceiverError.invalidMessage }
        
        // Generate an updated configuration
        //
        // Note: Messages which had been sent during the previous configuration will still
        // use it's settings (so if you enable, send a message and then disable disappearing
        // message then the message you had sent will still disappear)
        let config: DisappearingMessagesConfiguration = try DisappearingMessagesConfiguration
            .filter(id: threadId)
            .fetchOne(db)
            .defaulting(to: DisappearingMessagesConfiguration.defaultWith(threadId))
            .with(
                // If there is no duration then we should disable the expiration timer
                isEnabled: ((message.duration ?? 0) > 0),
                durationSeconds: (
                    message.duration.map { TimeInterval($0) } ??
                    DisappearingMessagesConfiguration.defaultDuration
                )
            )
        let timestampMs: Int64 = Int64(message.sentTimestamp ?? 0)   // Default to `0` if not set
        
        // Only actually make the change if SessionUtil says we can (we always want to insert the info
        // message though)
        let canPerformChange: Bool = SessionUtil.canPerformChange(
            db,
            threadId: threadId,
            targetConfig: {
                switch threadVariant {
                    case .contact:
                        let currentUserPublicKey: String = getUserHexEncodedPublicKey(db)
                        
                        return (threadId == currentUserPublicKey ? .userProfile : .contacts)
                        
                    default: return .userGroups
                }
            }(),
            changeTimestampMs: timestampMs
        )
        
        // Only update libSession if we can perform the change
        if canPerformChange {
            // Legacy closed groups need to update the SessionUtil
            switch threadVariant {
                case .legacyGroup:
                    try SessionUtil
                        .update(
                            db,
                            groupPublicKey: threadId,
                            disappearingConfig: config
                        )
                    
                default: break
            }
        }
        
        // Add an info message for the user
        let currentUserPublicKey: String = getUserHexEncodedPublicKey(db)
        _ = try Interaction(
            serverHash: nil, // Intentionally null so sync messages are seen as duplicates
            threadId: threadId,
            authorId: sender,
            variant: .infoDisappearingMessagesUpdate,
            body: config.messageInfoString(
                with: (sender != currentUserPublicKey ?
                    Profile.displayName(db, id: sender) :
                    nil
                )
            ),
            timestampMs: timestampMs,
            wasRead: SessionUtil.timestampAlreadyRead(
                threadId: threadId,
                threadVariant: threadVariant,
                timestampMs: (timestampMs * 1000),
                userPublicKey: currentUserPublicKey,
                openGroup: nil
            )
        ).inserted(db)
        
        // Only save the updated config if we can perform the change
        if canPerformChange {
            // Finally save the changes to the DisappearingMessagesConfiguration (If it's a duplicate
            // then the interaction unique constraint will prevent the code from getting here)
            try config.save(db)
        }
    }
}