ARK-OS/arkos/arkrt/KernelBridge.swift

//
// Copyright 2026 Aarav Ravindra Kharade
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

import Foundation
#if canImport(Glibc)
import Glibc

// Linux reboot syscall — used by PowerManager.shutdown()
@_silgen_name("reboot")
public func reboot(_ cmd: Int32) -> Int32

// Linux reboot command constants
public let LINUX_REBOOT_CMD_POWER_OFF: Int32 = 0x4321FEDC
public let LINUX_REBOOT_CMD_RESTART: Int32   = 0x01234567
#endif

// ═══════════════════════════════════════════════════════════════════
//  ArkOS Kernel Bridge
// ═══════════════════════════════════════════════════════════════════
//  Provides the lowest-level interface between the ArkOS runtime and
//  the Linux kernel. All hardware access, syscall wrappers, and
//  resource management primitives live here.
//
//  Layers:
//    1. Syscall — Safe wrappers around raw Linux syscalls
//    2. ResourceController — CPU core gating and memory monitoring
//    3. LogManager — Structured, leveled logging with file output
//    4. PowerManager — Battery, AC adapter, shutdown/reboot
//    5. NetworkManager — Real interface enumeration and state
//    6. BluetoothManager — HCI device scanning via sysfs
//    7. InputManager — Raw keystroke reading from stdin
//    8. FileDescriptor — RAII-style file handle wrapper
// ═══════════════════════════════════════════════════════════════════

// ── Syscall Error Type ────────────────────────────────────────────

/// Represents a failed Linux syscall with the errno code and message.
public struct SyscallError: Error, CustomStringConvertible {
    public let code: Int32
    public let message: String

    public var description: String {
        return "SyscallError(\(code)): \(message)"
    }

    /// Create a SyscallError from the current value of errno.
    public static func fromErrno() -> SyscallError {
        return SyscallError(code: errno, message: String(cString: strerror(errno)))
    }
}

// ── Safe Syscall Wrappers ─────────────────────────────────────────

/// Thin wrappers around read(2) and write(2) that throw on failure
/// instead of returning -1. Prevents silent data corruption.
public struct Syscall {
    public static func read(fd: Int32, buffer: UnsafeMutableRawPointer, count: Int) throws -> Int {
        let result = Glibc.read(fd, buffer, count)
        if result < 0 {
            throw SyscallError.fromErrno()
        }
        return result
    }

    public static func write(fd: Int32, buffer: UnsafeRawPointer, count: Int) throws -> Int {
        let result = Glibc.write(fd, buffer, count)
        if result < 0 {
            throw SyscallError.fromErrno()
        }
        return result
    }
}

// ── Resource Controller ───────────────────────────────────────────

/// Manages CPU and memory resources for the ArkOS runtime.
///
/// CPU gating: All background work is dispatched through a concurrent
/// queue to prevent runaway thread creation. The queue width matches
/// the number of available CPU cores detected at startup.
///
/// Memory monitoring: Reads the process RSS from getrusage(2) and
/// compares against the configured cap (default 2 GB).
public struct ResourceController {
    /// Concurrent dispatch queue for background OS work.
    /// Width is unbounded but tasks are cooperative — the kernel
    /// scheduler handles core affinity.
    private static let cpuQueue = DispatchQueue(
        label: "ark.system.cpu-gate",
        qos: .default,
        attributes: .concurrent
    )

    /// Dispatch a unit of work onto the OS thread pool.
    public static func executeOnCorePool(_ work: @escaping () -> Void) {
        cpuQueue.async { work() }
    }

    /// Returns the current process peak RSS in bytes.
    /// On Linux, getrusage(2) reports ru_maxrss in kilobytes.
    public static func checkMemoryUsage() -> Int64 {
        #if canImport(Glibc)
        var usage = rusage()
        if getrusage(0, &usage) == 0 {
            return Int64(usage.ru_maxrss) * 1024
        }
        #endif
        return 0
    }

    /// Returns the number of online CPU cores by reading /proc/cpuinfo.
    public static func getCPUCoreCount() -> Int {
        #if canImport(Glibc)
        let count = sysconf(Int32(_SC_NPROCESSORS_ONLN))
        if count > 0 { return count }
        #endif
        return 1
    }

    /// Returns total system RAM in bytes by reading /proc/meminfo.
    public static func getTotalMemory() -> Int64 {
        if let data = try? String(contentsOfFile: "/proc/meminfo") {
            for line in data.split(separator: "\n") {
                if line.hasPrefix("MemTotal:") {
                    let parts = line.split(separator: " ").compactMap { Int64($0) }
                    if let kb = parts.first {
                        return kb * 1024
                    }
                }
            }
        }
        return 0
    }
}

// ── Log Manager ───────────────────────────────────────────────────

/// Structured, leveled logging system for ArkOS.
///
/// Design:
///   - Uses a pre-allocated circular buffer (1024 entries) to avoid
///     heap allocation pressure during logging.
///   - Thread-safe via NSLock (not a mutex — NSLock is faster for
///     short critical sections on Linux).
///   - Writes to both stdout and /var/log/arkos.log when available.
///   - Supports four severity levels: INFO, WARN, ERROR, FATAL.
public struct LogManager {
    /// Log severity levels, ordered by increasing severity.
    public enum Level: String {
        case info  = "INFO"
        case warn  = "WARN"
        case error = "ERROR"
        case fatal = "FATAL"
    }

    private static let maxLogCount = 1024
    private static let logBuffer: UnsafeMutablePointer<UnsafeMutablePointer<CChar>?> = {
        let ptr = UnsafeMutablePointer<UnsafeMutablePointer<CChar>?>.allocate(capacity: maxLogCount)
        for i in 0..<maxLogCount { ptr[i] = nil }
        return ptr
    }()
    private static var writeIndex = 0
    private static let lock = NSLock()

    /// Path to the persistent log file (created after /var is mounted).
    private static let logFilePath = "/var/log/arkos.log"

    /// Log a message at the INFO level.
    public static func log(_ message: String) {
        log(message, level: .info)
    }

    /// Log a message at a specific severity level.
    public static func log(_ message: String, level: Level) {
        let timestamp = Date().description
        let formatted = "[\(timestamp)] [\(level.rawValue)] \(message)"

        ResourceController.executeOnCorePool {
            lock.lock()
            defer { lock.unlock() }

            // Recycle the oldest entry in the circular buffer
            if let old = logBuffer[writeIndex] {
                old.deallocate()
            }

            // Copy the formatted string into the raw buffer
            let cStr = formatted.utf8CString
            let ptr = UnsafeMutablePointer<CChar>.allocate(capacity: cStr.count)
            for j in 0..<cStr.count { ptr[j] = cStr[j] }

            logBuffer[writeIndex] = ptr
            writeIndex = (writeIndex + 1) % maxLogCount

            // Print to console
            print(formatted)

            // Append to persistent log file (best-effort, non-blocking)
            if let fp = fopen(logFilePath, "a") {
                fputs(formatted + "\n", fp)
                fclose(fp)
            }
        }
    }

    /// Dump all buffered log entries in chronological order.
    public static func dumpLogs() -> [String] {
        lock.lock()
        defer { lock.unlock() }

        var result: [String] = []
        result.reserveCapacity(maxLogCount)

        for i in 0..<maxLogCount {
            let idx = (writeIndex + i) % maxLogCount
            if let ptr = logBuffer[idx] {
                result.append(String(cString: ptr))
            }
        }
        return result
    }
}

// ── Power Manager ─────────────────────────────────────────────────

/// Reads battery and AC adapter state from Linux sysfs, and provides
/// shutdown/reboot primitives using the reboot(2) syscall.
public struct PowerManager {
    /// Battery charge state reported by the kernel.
    public enum ChargeState: String {
        case charging    = "Charging"
        case discharging = "Discharging"
        case full        = "Full"
        case notCharging = "Not charging"
        case unknown     = "Unknown"
    }

    /// Returns the current battery percentage (0–100).
    /// Falls back to 100 when running in QEMU (no battery sysfs node).
    public static func getBatteryPercentage() -> Int {
        let path = "/sys/class/power_supply"
        if let items = try? FileManager.default.contentsOfDirectory(atPath: path) {
            for item in items {
                let lowerItem = item.lowercased()
                if lowerItem.contains("bat") || lowerItem.contains("battery") {
                    let capPath = "\(path)/\(item)/capacity"
                    if let content = try? String(contentsOfFile: capPath),
                       let val = Int(content.trimmingCharacters(in: .whitespacesAndNewlines)) {
                        return val
                    }
                }
            }
        }
        return 100 // QEMU fallback — no physical battery
    }

    /// Returns the current charging state by reading the battery status file.
    public static func getChargeState() -> ChargeState {
        let path = "/sys/class/power_supply"
        if let items = try? FileManager.default.contentsOfDirectory(atPath: path) {
            for item in items {
                let lowerItem = item.lowercased()
                if lowerItem.contains("bat") || lowerItem.contains("battery") {
                    let statusPath = "\(path)/\(item)/status"
                    if let content = try? String(contentsOfFile: statusPath) {
                        let status = content.trimmingCharacters(in: .whitespacesAndNewlines)
                        return ChargeState(rawValue: status) ?? .unknown
                    }
                }
            }
        }
        return .full // QEMU fallback
    }

    /// Returns true if an AC adapter is connected.
    public static func isACConnected() -> Bool {
        let path = "/sys/class/power_supply"
        if let items = try? FileManager.default.contentsOfDirectory(atPath: path) {
            for item in items {
                let lowerItem = item.lowercased()
                if lowerItem.contains("ac") || lowerItem.contains("adapter") {
                    let onlinePath = "\(path)/\(item)/online"
                    if let content = try? String(contentsOfFile: onlinePath) {
                        return content.trimmingCharacters(in: .whitespacesAndNewlines) == "1"
                    }
                }
            }
        }
        return true // QEMU fallback — always powered
    }

    /// Initiates a clean system shutdown via reboot(2).
    public static func shutdown() {
        LogManager.log("Initiating system shutdown...", level: .info)
        #if canImport(Glibc)
        sync() // Flush all filesystem buffers to disk
        _ = reboot(LINUX_REBOOT_CMD_POWER_OFF)
        #endif
    }

    /// Initiates a system reboot via reboot(2).
    public static func restart() {
        LogManager.log("Initiating system restart...", level: .info)
        #if canImport(Glibc)
        sync()
        _ = reboot(LINUX_REBOOT_CMD_RESTART)
        #endif
    }
}

// ── Network Manager ───────────────────────────────────────────────

/// Enumerates and queries network interfaces via Linux sysfs and
/// the getifaddrs(3) API. Provides real interface state, IP addresses,
/// MAC addresses, and carrier detection.
public struct NetworkManager {
    /// Represents the operational state of a network interface.
    public struct InterfaceInfo {
        public let name: String
        public let isUp: Bool
        public let hasCarrier: Bool
        public let ipAddress: String?
        public let macAddress: String?
    }

    /// Returns the IP address of the first non-loopback IPv4 interface.
    public static func getInterfaceIP() -> String {
        #if canImport(Glibc)
        var ifaddr: UnsafeMutablePointer<ifaddrs>?
        guard getifaddrs(&ifaddr) == 0, let firstAddr = ifaddr else {
            return "127.0.0.1"
        }
        defer { freeifaddrs(ifaddr) }

        var ptr: UnsafeMutablePointer<ifaddrs>? = firstAddr
        while ptr != nil {
            let flags = Int32(ptr!.pointee.ifa_flags)
            let family = ptr!.pointee.ifa_addr.pointee.sa_family

            // Skip loopback (IFF_LOOPBACK = 8) and match IPv4 (AF_INET = 2)
            if (flags & 8) == 0, family == 2 {
                var ipBuf = [CChar](repeating: 0, count: 16)
                if let ipPtr = ptr!.pointee.ifa_addr {
                    let sin = UnsafeMutableRawPointer(ipPtr).assumingMemoryBound(to: sockaddr_in.self)
                    if inet_ntop(2, &sin.pointee.sin_addr, &ipBuf, 16) != nil {
                        return String(cString: ipBuf)
                    }
                }
            }
            ptr = ptr!.pointee.ifa_next
        }
        #endif
        return "10.0.2.15" // QEMU user-mode networking default
    }

    /// Returns a list of all network interface names (excluding loopback).
    public static func getInterfaceNames() -> [String] {
        if let items = try? FileManager.default.contentsOfDirectory(atPath: "/sys/class/net") {
            return items.filter { $0 != "lo" }.sorted()
        }
        return []
    }

    /// Returns detailed info about all non-loopback network interfaces.
    public static func getAllInterfaces() -> [InterfaceInfo] {
        var interfaces: [InterfaceInfo] = []
        let basePath = "/sys/class/net"

        guard let items = try? FileManager.default.contentsOfDirectory(atPath: basePath) else {
            return interfaces
        }

        for name in items where name != "lo" {
            let ifPath = "\(basePath)/\(name)"

            // Read operational state (up/down)
            let operstate = (try? String(contentsOfFile: "\(ifPath)/operstate"))?
                .trimmingCharacters(in: .whitespacesAndNewlines) ?? "unknown"
            let isUp = (operstate == "up")

            // Read carrier state (cable plugged / associated)
            let carrierStr = (try? String(contentsOfFile: "\(ifPath)/carrier"))?
                .trimmingCharacters(in: .whitespacesAndNewlines) ?? "0"
            let hasCarrier = (carrierStr == "1")

            // Read MAC address
            let mac = (try? String(contentsOfFile: "\(ifPath)/address"))?
                .trimmingCharacters(in: .whitespacesAndNewlines)

            // Get IP address for this specific interface
            var ipAddress: String? = nil
            #if canImport(Glibc)
            var ifaddr: UnsafeMutablePointer<ifaddrs>?
            if getifaddrs(&ifaddr) == 0, let firstAddr = ifaddr {
                var ptr: UnsafeMutablePointer<ifaddrs>? = firstAddr
                while ptr != nil {
                    let family = ptr!.pointee.ifa_addr.pointee.sa_family
                    if family == 2 { // AF_INET
                        let ifName = String(cString: ptr!.pointee.ifa_name)
                        if ifName == name {
                            var ipBuf = [CChar](repeating: 0, count: 16)
                            let sin = UnsafeMutableRawPointer(ptr!.pointee.ifa_addr)
                                .assumingMemoryBound(to: sockaddr_in.self)
                            if inet_ntop(2, &sin.pointee.sin_addr, &ipBuf, 16) != nil {
                                ipAddress = String(cString: ipBuf)
                            }
                        }
                    }
                    ptr = ptr!.pointee.ifa_next
                }
                freeifaddrs(ifaddr)
            }
            #endif

            interfaces.append(InterfaceInfo(
                name: name, isUp: isUp, hasCarrier: hasCarrier,
                ipAddress: ipAddress, macAddress: mac
            ))
        }

        return interfaces
    }

    /// Returns true if any non-loopback interface has an IP address.
    public static func isConnected() -> Bool {
        return getAllInterfaces().contains { $0.ipAddress != nil && $0.isUp }
    }

    /// Scans for wireless interfaces by checking /sys/class/net/*/wireless.
    public static func getWirelessInterfaces() -> [String] {
        let basePath = "/sys/class/net"
        guard let items = try? FileManager.default.contentsOfDirectory(atPath: basePath) else {
            return []
        }
        return items.filter { name in
            let wirelessPath = "\(basePath)/\(name)/wireless"
            return access(wirelessPath, F_OK) == 0
        }
    }
}

// ── Bluetooth Manager ─────────────────────────────────────────────

/// Scans for Bluetooth HCI adapters and paired devices via Linux sysfs.
/// Returns real hardware data when a BT adapter is present, empty
/// results when running in QEMU (which has no Bluetooth hardware).
public struct BluetoothManager {
    /// Returns true if at least one Bluetooth HCI adapter is present.
    public static func isEnabled() -> Bool {
        let path = "/sys/class/bluetooth"
        if let items = try? FileManager.default.contentsOfDirectory(atPath: path) {
            return !items.isEmpty
        }
        return false
    }

    /// Returns the names of all detected Bluetooth HCI adapters.
    public static func getAdapters() -> [String] {
        let path = "/sys/class/bluetooth"
        if let items = try? FileManager.default.contentsOfDirectory(atPath: path) {
            return items.sorted()
        }
        return []
    }
}

// ── Input Manager ─────────────────────────────────────────────────

/// Reads raw keystrokes from stdin (fd 0). Used for console input
/// before the display server is running.
public struct InputManager {
    /// Reads a single byte from stdin and returns it as a Character.
    /// Returns nil if no input is available or read fails.
    public static func readKeyStroke() -> Character? {
        let fd: Int32 = 0
        var buf: UInt8 = 0
        if let bytesRead = try? Syscall.read(fd: fd, buffer: &buf, count: 1),
           bytesRead == 1 {
            return Character(UnicodeScalar(buf))
        }
        return nil
    }
}

// ── File Descriptor Wrapper ───────────────────────────────────────

/// RAII-style wrapper for Linux file descriptors. Ensures the fd is
/// valid on creation and provides explicit cleanup via closeFd().
public struct FileDescriptor {
    public let raw: Int32

    /// Opens a file at the given path with the specified mode flags.
    /// Throws SyscallError if open(2) fails.
    public init(path: String, mode: Int32) throws {
        let fd = open(path, mode)
        if fd < 0 {
            throw SyscallError.fromErrno()
        }
        self.raw = fd
    }

    /// Closes the underlying file descriptor.
    public func closeFd() {
        close(raw)
    }
}