import Foundation
import IOKit
import WhatCableCore

/// Watches `IOPortTransportComponentCCUSBPDSOP` (port partner) and
/// `IOPortTransportComponentCCUSBPDSOPp` (cable e-marker SOP') services.
/// macOS exposes these as separate IOKit classes, so we have to match both.
/// Some hardware also exposes SOP'' as a third class.
@MainActor
public final class USBPDSOPWatcher: ObservableObject {
    @Published public private(set) var identities: [USBPDSOP] = []

    private static let matchedClasses = [
        "IOPortTransportComponentCCUSBPDSOP",
        "IOPortTransportComponentCCUSBPDSOPp",
        "IOPortTransportComponentCCUSBPDSOPpp",
    ]

    private var notifyPort: IONotificationPortRef?
    private var iterators: [io_iterator_t] = []

    public init() {}

    public func start() {
        guard notifyPort == nil else { return }
        let port = IONotificationPortCreate(kIOMainPortDefault)
        IONotificationPortSetDispatchQueue(port, DispatchQueue.main)
        notifyPort = port

        let selfPtr = Unmanaged.passUnretained(self).toOpaque()

        let added: IOServiceMatchingCallback = { refcon, iter in
            guard let refcon else { return }
            let w = Unmanaged<USBPDSOPWatcher>.fromOpaque(refcon).takeUnretainedValue()
            Task { @MainActor in w.handleAdded(iter) }
        }
        let removed: IOServiceMatchingCallback = { refcon, iter in
            guard let refcon else { return }
            let w = Unmanaged<USBPDSOPWatcher>.fromOpaque(refcon).takeUnretainedValue()
            Task { @MainActor in w.handleRemoved(iter) }
        }

        for className in Self.matchedClasses {
            var addedIter: io_iterator_t = 0
            if IOServiceAddMatchingNotification(port, kIOMatchedNotification,
                IOServiceMatching(className),
                added, selfPtr, &addedIter) == KERN_SUCCESS {
                handleAdded(addedIter)
                iterators.append(addedIter)
            }

            var removedIter: io_iterator_t = 0
            if IOServiceAddMatchingNotification(port, kIOTerminatedNotification,
                IOServiceMatching(className),
                removed, selfPtr, &removedIter) == KERN_SUCCESS {
                handleRemoved(removedIter)
                iterators.append(removedIter)
            }
        }
    }

    public func stop() {
        for iter in iterators where iter != 0 { IOObjectRelease(iter) }
        iterators.removeAll()
        if let p = notifyPort { IONotificationPortDestroy(p); notifyPort = nil }
        identities.removeAll()
    }

    public func refresh() {
        // Build locally and assign once so subscribers never see a transient
        // empty list mid-refresh. See issue #227.
        var rebuilt: [USBPDSOP] = []
        for className in Self.matchedClasses {
            var iter: io_iterator_t = 0
            if IOServiceGetMatchingServices(kIOMainPortDefault,
                IOServiceMatching(className), &iter) == KERN_SUCCESS {
                while case let service = IOIteratorNext(iter), service != 0 {
                    if let identity = makeIdentity(from: service),
                       !rebuilt.contains(where: { $0.id == identity.id }) {
                        rebuilt.append(identity)
                    }
                    IOObjectRelease(service)
                }
                IOObjectRelease(iter)
            }
        }
        if rebuilt != identities { identities = rebuilt }
    }

    private func handleAdded(_ iter: io_iterator_t) {
        while case let service = IOIteratorNext(iter), service != 0 {
            if let identity = makeIdentity(from: service),
               !identities.contains(where: { $0.id == identity.id }) {
                identities.append(identity)
            }
            IOObjectRelease(service)
        }
    }

    private func handleRemoved(_ iter: io_iterator_t) {
        while case let service = IOIteratorNext(iter), service != 0 {
            var entryID: UInt64 = 0
            IORegistryEntryGetRegistryEntryID(service, &entryID)
            identities.removeAll { $0.id == entryID }
            IOObjectRelease(service)
        }
    }

    private func makeIdentity(from service: io_service_t) -> USBPDSOP? {
        var entryID: UInt64 = 0
        IORegistryEntryGetRegistryEntryID(service, &entryID)

        // Read keys individually rather than fetching the full property
        // dictionary. The bulk fetch (IORegistryEntryCreateCFProperties)
        // can abort the process from inside IOCFUnserializeBinary when
        // the kernel returns a malformed serialised properties blob,
        // typically when the service is being torn down mid-read. The
        // per-key call has no such failure path. See issue #181.
        func read(_ key: String) -> Any? {
            IORegistryEntryCreateCFProperty(service, key as CFString, kCFAllocatorDefault, 0)?.takeRetainedValue()
        }

        var classNameBuf = [CChar](repeating: 0, count: 128)
        let className: String? = (IOObjectGetClass(service, &classNameBuf) == KERN_SUCCESS)
            ? String(cString: classNameBuf)
            : nil

        let endpoint = Self.endpoint(read: read, className: className)
        let parent = Self.parentPortIdentity(read: read)
        let specRev = (read("Specification Revision") as? NSNumber)?.intValue ?? 0

        let metadata = Self.metadataDictionary(read: read)
        let vendorID = Self.vendorID(read: read, metadata: metadata)
        let productID = Self.productID(read: read, metadata: metadata)
        let bcdDevice = Self.bcdDevice(from: metadata)

        let vdos: [UInt32] = ((metadata["VDOs"] as? [Any]) ?? []).compactMap { value in
            guard let data = value as? Data else { return nil }
            return PDVDO.vdoFromData(data)
        }

        return USBPDSOP(
            id: entryID,
            endpoint: endpoint,
            parentPortType: parent.type,
            parentPortNumber: parent.number,
            vendorID: vendorID,
            productID: productID,
            bcdDevice: bcdDevice,
            vdos: vdos,
            specRevision: specRev
        )
    }

    nonisolated static func endpointName(read: (String) -> Any?) -> String {
        (read("ComponentName") as? String)
            ?? (read("AddressDescription") as? String)
            ?? (read("Address Description") as? String)
            ?? (read("TransportTypeDescription") as? String)
            ?? "Unknown"
    }

    nonisolated static func endpoint(read: (String) -> Any?, className: String? = nil) -> USBPDSOP.Endpoint {
        if let name = (read("ComponentName") as? String)
            ?? (read("AddressDescription") as? String)
            ?? (read("Address Description") as? String) {
            return USBPDSOP.Endpoint(rawValue: name) ?? .unknown
        }
        // The IOKit class name is the most reliable signal: macOS exposes
        // SOP' as a separate `IOPortTransportComponentCCUSBPDSOPp` class
        // (and SOP'' as `...SOPpp`), even when ComponentName is absent.
        switch className {
        case "IOPortTransportComponentCCUSBPDSOP": return .sop
        case "IOPortTransportComponentCCUSBPDSOPp": return .sopPrime
        case "IOPortTransportComponentCCUSBPDSOPpp": return .sopDoublePrime
        default: break
        }
        // MagSafe CC transport has no ComponentName; map "CC" only from
        // TransportTypeDescription so a future node with ComponentName="CC"
        // is not misclassified as a cable e-marker.
        switch read("TransportTypeDescription") as? String {
        case "SOP": return .sop
        case "SOP'", "CC": return .sopPrime
        case "SOP''": return .sopDoublePrime
        default: return .unknown
        }
    }

    /// Reads the parent port type and number from the service's properties.
    /// Same approach as `PowerSourceWatcher.parentPortIdentity(read:)`. The
    /// BuiltIn keys must take priority so PD identity and power data resolve
    /// to the same portKey for a given physical port.
    nonisolated static func parentPortIdentity(read: (String) -> Any?) -> (type: Int, number: Int) {
        let type = (read("ParentBuiltInPortType") as? NSNumber)?.intValue
            ?? (read("ParentPortType") as? NSNumber)?.intValue
            ?? 0
        let number = (read("ParentBuiltInPortNumber") as? NSNumber)?.intValue
            ?? (read("ParentPortNumber") as? NSNumber)?.intValue
            ?? Int(((read("Priority") as? NSNumber)?.uint64Value ?? 0) & 0xFF)
        return (type, number)
    }

    nonisolated static func metadataDictionary(read: (String) -> Any?) -> [String: Any] {
        let raw = read("Metadata")
        if let metadata = raw as? [String: Any] {
            return metadata
        }
        if let nsMetadata = raw as? NSDictionary {
            var converted: [String: Any] = [:]
            for case let (key, value) as (String, Any) in nsMetadata {
                converted[key] = value
            }
            return converted
        }
        return [:]
    }

    nonisolated static func vendorID(read: (String) -> Any?, metadata: [String: Any]) -> Int {
        (metadata["Vendor ID"] as? NSNumber)?.intValue
            ?? (metadata["Vendor ID (SOP1)"] as? NSNumber)?.intValue
            ?? (read("Vendor ID (SOP1)") as? NSNumber)?.intValue
            ?? (read("Vendor ID") as? NSNumber)?.intValue
            ?? 0
    }

    nonisolated static func productID(read: (String) -> Any?, metadata: [String: Any]) -> Int {
        (metadata["Product ID"] as? NSNumber)?.intValue
            ?? (metadata["Product ID (SOP1)"] as? NSNumber)?.intValue
            ?? (read("Product ID (SOP1)") as? NSNumber)?.intValue
            ?? (read("Product ID") as? NSNumber)?.intValue
            ?? 0
    }

    nonisolated static func bcdDevice(from metadata: [String: Any]) -> Int {
        (metadata["bcdDevice"] as? NSNumber)?.intValue ?? 0
    }

    public func identities(for port: AppleHPMInterface) -> [USBPDSOP] {
        guard let key = port.portKey else { return [] }
        return identities.filter { $0.portKey == key }
    }
}