Sources/SophaxChatCore/DHT/DHTStore.swift

1// DHTStore.swift
2// SophaxChatCore
3//
4// Local key-value store for DHT STORE requests.
5// Keyed by full 256-bit nodeID (hex). Secondary index allows prefix lookup
6// by 16-char peerID so callers need not know the full key.
7
8import Foundation
9
10public actor DHTStore {
11
12    /// Default TTL — slightly longer than the 24h republish interval.
13    public static let defaultTTL: TimeInterval = 25 * 60 * 60
14
15    private struct Entry {
16        let bundle: PreKeyBundle
17        let expiresAt: Date
18    }
19
20    /// nodeID(hex64) → Entry
21    private var entries: [String: Entry] = [:]
22    /// peerID(hex16) → nodeID(hex64) — built from the first 16 chars of each stored nodeID.
23    private var prefixIndex: [String: String] = [:]
24
25    public init() {}
26
27    // MARK: - Mutations
28
29    public func store(nodeID: String, bundle: PreKeyBundle,
30                      expiresAt: Date = Date().addingTimeInterval(DHTStore.defaultTTL)) {
31        entries[nodeID] = Entry(bundle: bundle, expiresAt: expiresAt)
32        let prefix = String(nodeID.prefix(16))
33        prefixIndex[prefix] = nodeID
34    }
35
36    public func remove(nodeID: String) {
37        let prefix = String(nodeID.prefix(16))
38        if prefixIndex[prefix] == nodeID { prefixIndex.removeValue(forKey: prefix) }
39        entries.removeValue(forKey: nodeID)
40    }
41
42    public func purgeExpired() {
43        let now = Date()
44        let expired = entries.filter { $0.value.expiresAt < now }.map(\.key)
45        for key in expired { remove(nodeID: key) }
46    }
47
48    // MARK: - Queries
49
50    /// Lookup by full 256-bit nodeID (hex64).
51    public func lookup(nodeID: String) -> PreKeyBundle? {
52        guard let entry = entries[nodeID], entry.expiresAt > Date() else { return nil }
53        return entry.bundle
54    }
55
56    /// Lookup by 16-char peerID prefix.
57    public func lookupByPrefix(_ peerID: String) -> PreKeyBundle? {
58        guard let nodeID = prefixIndex[peerID] else { return nil }
59        return lookup(nodeID: nodeID)
60    }
61
62    /// Full nodeID for a given peerID prefix, if known.
63    public func nodeID(forPeerID peerID: String) -> String? {
64        prefixIndex[peerID]
65    }
66
67    public func allNodeIDs() -> [String] { Array(entries.keys) }
68}