//
// PerformanceBaselineTests.swift
// bitchatTests
//
// Performance baselines for hot paths so regressions are measured, not
// guessed. Uses XCTest `measure {}` (swift-testing has no equivalent) with
// NO recorded baselines — these tests record timing in CI logs but never
// fail on timing, so they cannot flake.
//
// Each benchmark builds its fixtures OUTSIDE the measure block with fixed
// seeds/content so every iteration does deterministic work: no network,
// no Tor, no sleeps.
//
// Skippable via the BITCHAT_SKIP_PERF_BASELINES=1 environment variable;
// runs by default.
//

import XCTest
import SwiftUI
import BitFoundation
@testable import bitchat

@MainActor
final class PerformanceBaselineTests: XCTestCase {

    override func setUpWithError() throws {
        try XCTSkipIf(
            ProcessInfo.processInfo.environment["BITCHAT_SKIP_PERF_BASELINES"] == "1",
            "Performance baselines skipped via BITCHAT_SKIP_PERF_BASELINES"
        )
    }

    override func tearDown() {
        // Drain main-queue tasks spawned by coordinators (handlePublicMessage
        // hops etc.) so they don't bleed into the next test's measure block.
        RunLoop.current.run(until: Date().addingTimeInterval(0.05))
        super.tearDown()
    }

    /// Reports one human-readable throughput line per benchmark so CI logs
    /// are readable without parsing XCTest's measure output.
    private func reportThroughput(_ name: String, samples: [TimeInterval], operations: Int, unit: String) {
        guard !samples.isEmpty else { return }
        let avg = samples.reduce(0, +) / Double(samples.count)
        let opsPerSec = avg > 0 ? Double(operations) / avg : .infinity
        print(String(
            format: "PERF[%@]: %.0f %@/sec (avg %.3f ms per pass of %d, %d passes)",
            name, opsPerSec, unit, avg * 1000, operations, samples.count
        ))
    }

    // MARK: - 1a. Nostr inbound event handling (fresh events)

    /// `NostrInboundPipeline.handleNostrEvent` for never-seen geo events
    /// (kind 20000): signature verification, dedup record, presence/nickname
    /// bookkeeping, and public-message ingest scheduling.
    func testNostrInboundEventHandling_freshEvents() throws {
        let events = try Self.makeSignedGeohashEvents(count: 500)
        // A fresh context per measure pass so every event takes the
        // first-seen path on every iteration. Kept alive so the weakly
        // captured Task hops stay valid.
        var keepAlive: [(PerfNostrContext, ChatNostrCoordinator)] = []
        var samples: [TimeInterval] = []

        measure {
            let context = PerfNostrContext()
            let coordinator = ChatNostrCoordinator(context: context)
            keepAlive.append((context, coordinator))
            let start = Date()
            for event in events {
                coordinator.inbound.handleNostrEvent(event)
            }
            samples.append(Date().timeIntervalSince(start))
            XCTAssertEqual(context.processedEventCount, events.count)
        }

        reportThroughput("nostrInbound.fresh", samples: samples, operations: events.count, unit: "events")
    }

    // MARK: - 1b. Nostr inbound event handling (duplicate events)

    /// The dedup-hit path: identical events replayed. Duplicates dominate
    /// real relay traffic (the same event arrives from several relays), so
    /// this path runs hundreds of times a minute in busy geohashes. Note it
    /// still pays full Schnorr signature verification before the dedup check.
    func testNostrInboundEventHandling_duplicateEvents() throws {
        let events = try Self.makeSignedGeohashEvents(count: 500)
        let context = PerfNostrContext()
        let coordinator = ChatNostrCoordinator(context: context)
        // Pre-warm: every event is now recorded as processed.
        for event in events {
            coordinator.inbound.handleNostrEvent(event)
        }
        XCTAssertEqual(context.processedEventCount, events.count)
        var samples: [TimeInterval] = []

        measure {
            let start = Date()
            for event in events {
                coordinator.inbound.handleNostrEvent(event)
            }
            samples.append(Date().timeIntervalSince(start))
        }

        // Dedup held: nothing was re-processed.
        XCTAssertEqual(context.processedEventCount, events.count)
        reportThroughput("nostrInbound.duplicate", samples: samples, operations: events.count, unit: "events")
    }

    // MARK: - 2. BLE inbound packet pipeline (decode + dedup)

    /// Binary encode/decode round trip plus `MessageDeduplicator` at
    /// realistic mesh sizes: 1000 packets with 100-300 byte payloads, each
    /// dedup-checked twice (first-seen insert, then duplicate hit) the way
    /// relayed packets arrive on multiple links.
    func testBLEInboundPacketPipeline() throws {
        var rng = SeededGenerator(seed: 0xB17C4A7)
        let baseTimestamp = UInt64(1_700_000_000_000)
        var packets: [BitchatPacket] = []
        var dedupIDs: [String] = []
        packets.reserveCapacity(1000)
        dedupIDs.reserveCapacity(1000)
        for index in 0..<1000 {
            let senderID = Data((0..<8).map { _ in UInt8.random(in: 0...255, using: &rng) })
            let payloadSize = Int.random(in: 100...300, using: &rng)
            let payload = Data((0..<payloadSize).map { _ in UInt8.random(in: 0...255, using: &rng) })
            let packet = BitchatPacket(
                type: MessageType.message.rawValue,
                senderID: senderID,
                recipientID: nil,
                timestamp: baseTimestamp + UInt64(index),
                payload: payload,
                signature: nil,
                ttl: 7
            )
            packets.append(packet)
            // Same dedup key shape BLEService uses: sender-timestamp-type.
            dedupIDs.append("\(senderID.hexEncodedString())-\(packet.timestamp)-\(packet.type)")
        }
        let deduplicator = MessageDeduplicator()
        var samples: [TimeInterval] = []

        measure {
            deduplicator.reset() // identical work every pass
            let start = Date()
            var decodedCount = 0
            var duplicateCount = 0
            for (index, packet) in packets.enumerated() {
                guard let data = packet.toBinaryData(),
                      let decoded = BitchatPacket.from(data) else { continue }
                decodedCount += 1
                _ = decoded.payload.count
                if deduplicator.isDuplicate(dedupIDs[index]) { duplicateCount += 1 }
            }
            for id in dedupIDs where deduplicator.isDuplicate(id) {
                duplicateCount += 1
            }
            samples.append(Date().timeIntervalSince(start))
            XCTAssertEqual(decodedCount, packets.count)
            XCTAssertEqual(duplicateCount, packets.count)
        }

        reportThroughput("bleInbound.roundTripAndDedup", samples: samples, operations: packets.count, unit: "packets")
    }

    // MARK: - 3. GCS sync filters

    /// `GCSFilter.buildFilter` + `decodeToSortedSet` at the production gossip
    /// config (`TransportConfig.syncGCSMaxBytes` / `syncGCSTargetFpr`) with
    /// 1000 candidate packet IDs (the filter caps to its byte budget).
    func testGCSFilterBuildAndDecode() {
        var rng = SeededGenerator(seed: 0x6C5F11)
        let ids: [Data] = (0..<1000).map { _ in
            Data((0..<16).map { _ in UInt8.random(in: 0...255, using: &rng) })
        }
        let maxBytes = TransportConfig.syncGCSMaxBytes
        let targetFpr = TransportConfig.syncGCSTargetFpr
        let repsPerPass = 20
        var samples: [TimeInterval] = []

        measure {
            let start = Date()
            var decodedTotal = 0
            for _ in 0..<repsPerPass {
                let params = GCSFilter.buildFilter(ids: ids, maxBytes: maxBytes, targetFpr: targetFpr)
                let decoded = GCSFilter.decodeToSortedSet(p: params.p, m: params.m, data: params.data)
                decodedTotal += decoded.count
                XCTAssertLessThanOrEqual(params.data.count, maxBytes)
            }
            samples.append(Date().timeIntervalSince(start))
            XCTAssertGreaterThan(decodedTotal, 0)
        }

        reportThroughput("gcs.buildAndDecode", samples: samples, operations: repsPerPass, unit: "filters")
    }

    // MARK: - 4a. Delivery location index (incremental path)

    /// `ChatDeliveryCoordinator.updateMessageDeliveryStatus` against a warm
    /// location index: 2000 public + 50x40 private messages, 500 status
    /// updates per pass. Statuses alternate sent <-> delivered so every call
    /// performs a real update (never the skip path).
    func testDeliveryStatusIncrementalUpdates() {
        let context = PerfDeliveryContext.makeCorpus(publicCount: 2000, peerCount: 50, messagesPerPeer: 40)
        let coordinator = ChatDeliveryCoordinator(context: context)
        // Warm the index so the measure block exercises the incremental path.
        XCTAssertTrue(coordinator.updateMessageDeliveryStatus(context.messages[0].id, status: .sent))

        // 250 public + 250 private IDs spread across the corpus.
        var targetIDs: [String] = []
        for i in stride(from: 0, to: 2000, by: 8) { targetIDs.append(context.messages[i].id) }
        let peerIDs = context.privateChats.keys.sorted { $0.id < $1.id }
        for (offset, peer) in peerIDs.enumerated() where offset < 25 {
            guard let chat = context.privateChats[peer] else { continue }
            for i in stride(from: 0, to: chat.count, by: 4) { targetIDs.append(chat[i].id) }
        }
        XCTAssertEqual(targetIDs.count, 500)

        let fixedDate = Date(timeIntervalSince1970: 1_700_000_000)
        var toggle = false
        var samples: [TimeInterval] = []

        measure {
            toggle.toggle()
            let status: DeliveryStatus = toggle ? .delivered(to: "peer", at: fixedDate) : .sent
            let start = Date()
            var updated = 0
            for id in targetIDs where coordinator.updateMessageDeliveryStatus(id, status: status) {
                updated += 1
            }
            samples.append(Date().timeIntervalSince(start))
            XCTAssertEqual(updated, targetIDs.count)
        }

        reportThroughput("delivery.incrementalUpdate", samples: samples, operations: targetIDs.count, unit: "updates")
    }

    // MARK: - 4b. Delivery location index (rebuild path)

    /// The expensive path: a non-append insertion (out-of-order arrival at
    /// the head of the timeline) invalidates the index, so the next status
    /// update triggers a full rebuild over ~4000 message locations.
    func testDeliveryStatusIndexRebuild() {
        let context = PerfDeliveryContext.makeCorpus(publicCount: 2000, peerCount: 50, messagesPerPeer: 40)
        let coordinator = ChatDeliveryCoordinator(context: context)
        // Warm the index before the first insertion invalidates it.
        XCTAssertTrue(coordinator.updateMessageDeliveryStatus(context.messages[0].id, status: .sent))

        // Pre-built head insertions, one consumed per measure pass.
        let insertions: [BitchatMessage] = (0..<32).map { i in
            BitchatMessage(
                id: "insert-\(i)",
                sender: "alice",
                content: "out-of-order arrival \(i)",
                timestamp: Date(timeIntervalSince1970: 1_690_000_000),
                isRelay: false
            )
        }
        let probeID = context.messages[1000].id
        let fixedDate = Date(timeIntervalSince1970: 1_700_000_000)
        var pass = 0
        var toggle = false
        var samples: [TimeInterval] = []

        measure {
            precondition(pass < insertions.count, "add more pre-built insertions")
            context.messages.insert(insertions[pass], at: 0)
            pass += 1
            toggle.toggle()
            let status: DeliveryStatus = toggle ? .delivered(to: "peer", at: fixedDate) : .sent
            let start = Date()
            let updated = coordinator.updateMessageDeliveryStatus(probeID, status: status)
            samples.append(Date().timeIntervalSince(start))
            XCTAssertTrue(updated)
        }

        reportThroughput("delivery.indexRebuild", samples: samples, operations: 1, unit: "rebuilds")
    }

    // MARK: - 5. Message formatting

    /// `MessageFormattingEngine.formatMessage` over 200 messages with
    /// mentions, hashtags, and URLs. Formatting caches per message, so each
    /// measure pass consumes a fresh pre-built batch (cache-miss path, which
    /// is the cost paid when messages first render).
    func testMessageFormatting() {
        let context = PerfFormattingContext(nickname: "carol")
        let batchCount = 16 // > XCTest's default 10 measure iterations
        let batchSize = 200
        let contents: [(String, [String]?)] = [
            ("hello mesh, anyone around tonight?", nil),
            ("@carol#a1b2 did you see this? https://example.com/threads/42", ["carol"]),
            ("checking in from the harbor #bitchat #mesh", nil),
            ("@bob#0042 ping me when you get this", ["bob#0042"]),
            ("long form update with a link https://news.example.org/articles/2026/06/mesh-networks and a tag #geohash", nil),
        ]
        let batches: [[BitchatMessage]] = (0..<batchCount).map { batch in
            (0..<batchSize).map { i in
                let (content, mentions) = contents[i % contents.count]
                return BitchatMessage(
                    id: "fmt-\(batch)-\(i)",
                    sender: "alice#a1b\(i % 10)",
                    content: content,
                    timestamp: Date(timeIntervalSince1970: 1_700_000_000 + Double(i)),
                    isRelay: false,
                    senderPeerID: PeerID(str: "abcdef123456789\(i % 10)"),
                    mentions: mentions
                )
            }
        }
        var pass = 0
        var samples: [TimeInterval] = []

        measure {
            precondition(pass < batches.count, "add more pre-built batches")
            let batch = batches[pass]
            pass += 1
            let start = Date()
            var formattedCharacters = 0
            for message in batch {
                let formatted = MessageFormattingEngine.formatMessage(message, context: context, colorScheme: .light)
                formattedCharacters += formatted.characters.count
            }
            samples.append(Date().timeIntervalSince(start))
            XCTAssertGreaterThan(formattedCharacters, 0)
        }

        reportThroughput("formatting.formatMessage", samples: samples, operations: batchSize, unit: "messages")
    }

    // MARK: - Fixtures

    /// Builds deterministic signed kind-20000 geohash events. Content cycles
    /// through realistic chat lines; a handful of sender identities mimics a
    /// busy channel.
    private static func makeSignedGeohashEvents(count: Int) throws -> [NostrEvent] {
        let senders = try (0..<8).map { _ in try NostrIdentity.generate() }
        let lines = [
            "hello from the geohash",
            "anyone near the station?",
            "@bob#0042 are you on mesh too?",
            "check this out https://example.com/p/123 #bitchat",
            "teleport check, who's local?",
        ]
        return try (0..<count).map { i in
            try NostrProtocol.createEphemeralGeohashEvent(
                content: "\(lines[i % lines.count]) [\(i)]",
                geohash: "u4pruyd",
                senderIdentity: senders[i % senders.count],
                nickname: "peer\(i % senders.count)",
                teleported: i % 25 == 0
            )
        }
    }
}

// MARK: - Deterministic RNG

private struct SeededGenerator: RandomNumberGenerator {
    private var state: UInt64
    init(seed: UInt64) { state = seed }
    mutating func next() -> UInt64 {
        state &+= 0x9E37_79B9_7F4A_7C15
        var z = state
        z = (z ^ (z >> 30)) &* 0xBF58_476D_1CE4_E5B9
        z = (z ^ (z >> 27)) &* 0x94D0_49BB_1331_11EB
        return z ^ (z >> 31)
    }
}

// MARK: - Mock ChatNostrContext

/// Minimal `ChatNostrContext` for benchmarking the `ChatNostrCoordinator`
/// stack (`NostrInboundPipeline` in particular) without a `ChatViewModel`
/// (mirrors `ChatNostrCoordinatorContextTests`).
/// Callbacks are cheap dictionary/array operations so the measured cost is
/// the coordinator's own pipeline.
@MainActor
private final class PerfNostrContext: ChatNostrContext {
    var activeChannel: ChannelID = .location(GeohashChannel(level: .neighborhood, geohash: "u4pruyd"))
    var currentGeohash: String? = "u4pruyd"
    var geoSubscriptionID: String?
    var geoDmSubscriptionID: String?
    var geoSamplingSubs: [String: String] = [:]
    var lastGeoNotificationAt: [String: Date] = [:]
    var nostrRelayManager: NostrRelayManager? { nil }

    func setGeoChatSubscriptionID(_ id: String?) { geoSubscriptionID = id }
    func setGeoDmSubscriptionID(_ id: String?) { geoDmSubscriptionID = id }
    func addGeoSamplingSub(_ subID: String, forGeohash geohash: String) { geoSamplingSubs[subID] = geohash }
    func removeGeoSamplingSub(_ subID: String) { geoSamplingSubs.removeValue(forKey: subID) }

    func clearGeoSamplingSubs() -> [String] {
        defer { geoSamplingSubs.removeAll() }
        return Array(geoSamplingSubs.keys)
    }

    var messages: [BitchatMessage] = []
    func resetPublicMessagePipeline() {}
    func updatePublicMessagePipelineChannel(_ channel: ChannelID) {}
    func refreshVisibleMessages(from channel: ChannelID?) {}
    func addPublicSystemMessage(_ content: String) {}
    func drainPendingGeohashSystemMessages() -> [String] { [] }
    func appendGeohashMessageIfAbsent(_ message: BitchatMessage, toGeohash geohash: String) -> Bool { true }
    func synchronizePublicConversationStore(forGeohash geohash: String) {}

    private(set) var handledPublicMessageCount = 0
    func handlePublicMessage(_ message: BitchatMessage) { handledPublicMessageCount += 1 }
    func checkForMentions(_ message: BitchatMessage) {}
    func sendHapticFeedback(for message: BitchatMessage) {}
    func parseMentions(from content: String) -> [String] {
        MessageFormattingEngine.extractMentions(from: content)
    }

    var selectedPrivateChatPeer: PeerID?
    var nostrKeyMapping: [PeerID: String] = [:]
    func registerNostrKeyMapping(_ pubkey: String, for peerID: PeerID) { nostrKeyMapping[peerID] = pubkey }
    func handlePrivateMessage(_ payload: NoisePayload, senderPubkey: String, convKey: PeerID, id: NostrIdentity, messageTimestamp: Date) {}
    func handleDelivered(_ payload: NoisePayload, senderPubkey: String, convKey: PeerID) {}
    func handleReadReceipt(_ payload: NoisePayload, senderPubkey: String, convKey: PeerID) {}
    func startPrivateChat(with peerID: PeerID) {}

    private struct NoIdentity: Error {}
    var geohashIdentities: [String: NostrIdentity] = [:]
    func deriveNostrIdentity(forGeohash geohash: String) throws -> NostrIdentity {
        guard let identity = geohashIdentities[geohash] else { throw NoIdentity() }
        return identity
    }
    func currentNostrIdentity() -> NostrIdentity? { nil }
    func isNostrBlocked(pubkeyHexLowercased: String) -> Bool { false }
    func displayNameForNostrPubkey(_ pubkeyHex: String) -> String { "anon#\(pubkeyHex.prefix(4))" }

    private var processedNostrEventIDs: Set<String> = []
    var processedEventCount: Int { processedNostrEventIDs.count }
    func hasProcessedNostrEvent(_ eventID: String) -> Bool { processedNostrEventIDs.contains(eventID) }
    func recordProcessedNostrEvent(_ eventID: String) { processedNostrEventIDs.insert(eventID) }
    func clearProcessedNostrEvents() { processedNostrEventIDs.removeAll() }

    var geoNicknames: [String: String] = [:]
    private var teleportedKeys: Set<String> = []
    var teleportedGeoCount: Int { teleportedKeys.count }
    func startGeoParticipantRefreshTimer() {}
    func stopGeoParticipantRefreshTimer() {}
    func setActiveParticipantGeohash(_ geohash: String?) {}
    private(set) var participantRecords = 0
    func recordGeoParticipant(pubkeyHex: String) { participantRecords += 1 }
    func recordGeoParticipant(pubkeyHex: String, geohash: String) { participantRecords += 1 }
    func geoParticipantCount(for geohash: String) -> Int { 0 }
    func setGeoNickname(_ nickname: String, forPubkey pubkeyHex: String) { geoNicknames[pubkeyHex.lowercased()] = nickname }
    func markGeoTeleported(_ pubkeyHexLowercased: String) { teleportedKeys.insert(pubkeyHexLowercased) }
    func clearGeoTeleported(_ pubkeyHexLowercased: String) { teleportedKeys.remove(pubkeyHexLowercased) }
    func clearTeleportedGeo() { teleportedKeys.removeAll() }
    func clearGeoNicknames() { geoNicknames.removeAll() }
    func visibleGeohashPeople() -> [GeoPerson] { [] }

    var isTeleported = false
    func isGeohashOutsideRegionalChannels(_ geohash: String) -> Bool { false }

    func routeFavoriteNotification(to peerID: PeerID, isFavorite: Bool) {}
    func sendGeohashDeliveryAck(for messageID: String, toRecipientHex recipientHex: String, from identity: NostrIdentity) {}
    func sendGeohashReadReceipt(_ messageID: String, toRecipientHex recipientHex: String, from identity: NostrIdentity) {}
}

// MARK: - Mock ChatDeliveryContext

@MainActor
private final class PerfDeliveryContext: ChatDeliveryContext {
    var messages: [BitchatMessage] = []
    var privateChats: [PeerID: [BitchatMessage]] = [:]
    var sentReadReceipts: Set<String> = []
    var isStartupPhase: Bool { false }
    func notifyUIChanged() {}
    func markMessageDelivered(_ messageID: String) {}

    func pruneSentReadReceipts(keeping validMessageIDs: Set<String>) -> Int {
        let oldCount = sentReadReceipts.count
        sentReadReceipts = sentReadReceipts.intersection(validMessageIDs)
        return oldCount - sentReadReceipts.count
    }

    /// 2000 public + `peerCount` x `messagesPerPeer` private messages with
    /// deterministic IDs and timestamps.
    static func makeCorpus(publicCount: Int, peerCount: Int, messagesPerPeer: Int) -> PerfDeliveryContext {
        let context = PerfDeliveryContext()
        let base = Date(timeIntervalSince1970: 1_700_000_000)
        context.messages = (0..<publicCount).map { i in
            BitchatMessage(
                id: "pub-\(i)",
                sender: "peer\(i % 20)",
                content: "public message number \(i)",
                timestamp: base.addingTimeInterval(Double(i)),
                isRelay: false
            )
        }
        for p in 0..<peerCount {
            let peerID = PeerID(str: String(format: "%016x", 0xA000_0000 + p))
            context.privateChats[peerID] = (0..<messagesPerPeer).map { i in
                BitchatMessage(
                    id: "dm-\(p)-\(i)",
                    sender: "peer\(p)",
                    content: "private message \(i) for peer \(p)",
                    timestamp: base.addingTimeInterval(Double(i)),
                    isRelay: false,
                    isPrivate: true,
                    recipientNickname: "me",
                    senderPeerID: peerID
                )
            }
        }
        return context
    }
}

// MARK: - Mock MessageFormattingContext

@MainActor
private final class PerfFormattingContext: MessageFormattingContext {
    let nickname: String
    init(nickname: String) { self.nickname = nickname }
    func isSelfMessage(_ message: BitchatMessage) -> Bool { false }
    func senderColor(for message: BitchatMessage, isDark: Bool) -> Color { .blue }
    func peerURL(for peerID: PeerID) -> URL? { URL(string: "bitchat://peer/\(peerID.id)") }
}