//
// 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

// ═══════════════════════════════════════════════════════════════════
//  ArkOS Command Router
// ═══════════════════════════════════════════════════════════════════
//  Routes incoming IPC requests to the appropriate system handler.
//  Uses a binary header protocol for efficient, type-safe communication
//  without string parsing overhead.
//
//  Wire Format (all multi-byte values are big-endian):
//    Request:  [Command_ID (2B)][Payload_Length (4B)][Payload_Data]
//    Response: [Command_ID (2B)][Payload_Length (4B)][Response_Data]
//
//  Command Registry:
//    100 — Reserved
//    101 — GET_TIME         → Current date/time string
//    102 — GET_IP           → Primary IPv4 address
//    103 — GET_BATTERY      → Battery percentage and charge state
//    104 — GET_BLUETOOTH    → Bluetooth adapter status
//    105 — SHUTDOWN         → Initiate system shutdown
//    106 — DUMP_LOGS        → Retrieve system log buffer
//    107 — GET_INTERFACES   → List all network interfaces with state
//    108 — GET_SERVICES     → Service status report
//    109 — RESTART_SERVICE  → Restart a named service
//    110 — GET_SYSTEM_INFO  → CPU, RAM, uptime summary
// ═══════════════════════════════════════════════════════════════════

// ── Public API Namespaces ─────────────────────────────────────────

/// The `ark` namespace provides the developer-facing API surface
/// for querying OS state. These are high-level wrappers around the
/// raw managers in KernelBridge.swift.
public struct ark {
    public struct system {
        /// Time and uptime queries.
        public struct time {
            /// Returns the current date and time as a formatted string.
            public static func getCurrentTime() -> String {
                let formatter = DateFormatter()
                formatter.timeStyle = .medium
                formatter.dateStyle = .medium
                return formatter.string(from: Date())
            }

            /// Returns the system uptime in seconds by reading /proc/uptime.
            public static func getUptime() -> Double {
                if let data = try? String(contentsOfFile: "/proc/uptime") {
                    let parts = data.split(separator: " ")
                    if let first = parts.first, let uptimeVal = Double(first) {
                        return uptimeVal
                    }
                }
                return 0.0
            }

            /// Returns uptime as a human-readable string (e.g. "2h 15m 30s").
            public static func getUptimeFormatted() -> String {
                let total = Int(getUptime())
                let hours = total / 3600
                let minutes = (total % 3600) / 60
                let seconds = total % 60
                if hours > 0 {
                    return "\(hours)h \(minutes)m \(seconds)s"
                } else if minutes > 0 {
                    return "\(minutes)m \(seconds)s"
                }
                return "\(seconds)s"
            }
        }

        /// Network state queries.
        public struct network {
            /// Returns the primary IPv4 address.
            public static func getIPAddress() -> String {
                return NetworkManager.getInterfaceIP()
            }

            /// Returns names of all non-loopback interfaces.
            public static func getInterfaceNames() -> [String] {
                return NetworkManager.getInterfaceNames()
            }

            /// Returns true if any interface has connectivity.
            public static func isConnected() -> Bool {
                return NetworkManager.isConnected()
            }

            /// Returns detailed info for all interfaces.
            public static func getAllInterfaces() -> [NetworkManager.InterfaceInfo] {
                return NetworkManager.getAllInterfaces()
            }
        }

        /// Raw input queries (for pre-display-server console mode).
        public struct input {
            public static func readKey() -> Character? {
                return InputManager.readKeyStroke()
            }
        }
    }
}

// ── Command ID Constants ──────────────────────────────────────────

/// All supported IPC command identifiers.
public enum CommandID: UInt16 {
    case getTime        = 101
    case getIP          = 102
    case getBattery     = 103
    case getBluetooth   = 104
    case shutdown       = 105
    case dumpLogs       = 106
    case getInterfaces  = 107
    case getServices    = 108
    case restartService = 109
    case getSystemInfo  = 110
}

// ── Command Router ────────────────────────────────────────────────

public struct CommandRouter {

    /// Routes an incoming binary request to the appropriate handler
    /// and returns a binary response frame.
    ///
    /// - Parameter requestBuffer: Raw bytes of the incoming request.
    /// - Returns: Binary response frame with header and payload.
    public static func route(requestBuffer: UnsafeRawBufferPointer) -> Data {
        // Validate minimum header size (2B command + 4B length = 6B)
        guard requestBuffer.count >= 6 else {
            LogManager.log("Router: Invalid header (\(requestBuffer.count) bytes, need >= 6)", level: .warn)
            return makeResponse(cmdId: 0, payload: "ERROR:INVALID_HEADER")
        }

        // Parse header fields (zero-copy, big-endian)
        let rawCmdId = requestBuffer.load(fromByteOffset: 0, as: UInt16.self).bigEndian
        let payloadLen = requestBuffer.load(fromByteOffset: 2, as: UInt32.self).bigEndian

        // Validate payload length
        guard requestBuffer.count >= 6 + Int(payloadLen) else {
            LogManager.log("Router: Payload truncated (declared=\(payloadLen), actual=\(requestBuffer.count - 6))", level: .warn)
            return makeResponse(cmdId: rawCmdId, payload: "ERROR:SIZE_MISMATCH")
        }

        // Extract payload string (zero-copy slice)
        let payloadBytes = UnsafeRawBufferPointer(rebasing: requestBuffer[6..<(6 + Int(payloadLen))])
        let payloadString = String(decoding: payloadBytes, as: UTF8.self)

        LogManager.log("Router: CMD=\(rawCmdId) payload_len=\(payloadLen)")

        // Dispatch to the appropriate handler
        let responseString: String

        if let cmdId = CommandID(rawValue: rawCmdId) {
            switch cmdId {
            case .getTime:
                responseString = ark.system.time.getCurrentTime()

            case .getIP:
                responseString = ark.system.network.getIPAddress()

            case .getBattery:
                let pct = PowerManager.getBatteryPercentage()
                let state = PowerManager.getChargeState()
                let ac = PowerManager.isACConnected() ? "AC" : "Battery"
                responseString = "\(pct)%|\(state.rawValue)|\(ac)"

            case .getBluetooth:
                let enabled = BluetoothManager.isEnabled()
                let adapters = BluetoothManager.getAdapters()
                responseString = enabled ? "ACTIVE|\(adapters.joined(separator: ","))" : "INACTIVE"

            case .shutdown:
                responseString = "SHUTTING_DOWN"
                // Dispatch shutdown asynchronously so the response is sent first
                ResourceController.executeOnCorePool {
                    sleep(1)
                    PowerManager.shutdown()
                }

            case .dumpLogs:
                responseString = LogManager.dumpLogs().joined(separator: "\n")

            case .getInterfaces:
                let interfaces = NetworkManager.getAllInterfaces()
                let lines = interfaces.map { iface in
                    "\(iface.name)|\(iface.isUp ? "UP" : "DOWN")|\(iface.hasCarrier ? "CARRIER" : "NO_CARRIER")|\(iface.ipAddress ?? "none")|\(iface.macAddress ?? "unknown")"
                }
                responseString = lines.joined(separator: "\n")

            case .getServices:
                responseString = ServiceManager.shared.getStatusReport()

            case .restartService:
                if !payloadString.isEmpty {
                    ServiceManager.shared.stopService(name: payloadString)
                    ServiceManager.shared.startService(name: payloadString)
                    responseString = "OK:RESTARTED:\(payloadString)"
                } else {
                    responseString = "ERROR:MISSING_SERVICE_NAME"
                }

            case .getSystemInfo:
                let cores = ResourceController.getCPUCoreCount()
                let totalMem = ResourceController.getTotalMemory() / 1024 / 1024
                let usedMem = ResourceController.checkMemoryUsage() / 1024 / 1024
                let uptime = ark.system.time.getUptimeFormatted()
                let connected = NetworkManager.isConnected() ? "Connected" : "Disconnected"
                responseString = "cores=\(cores)|ram=\(usedMem)/\(totalMem)MB|uptime=\(uptime)|net=\(connected)"
            }
        } else {
            LogManager.log("Router: Unknown command ID \(rawCmdId)", level: .warn)
            responseString = "ERROR:UNKNOWN_COMMAND"
        }

        return makeResponse(cmdId: rawCmdId, payload: responseString)
    }

    // ── Response Builder ──────────────────────────────────────────

    /// Constructs a binary response frame from a command ID and string payload.
    private static func makeResponse(cmdId: UInt16, payload: String) -> Data {
        let payloadData = payload.data(using: .utf8) ?? Data()
        var response = Data()
        response.reserveCapacity(6 + payloadData.count)

        var bigEndianCmd = cmdId.bigEndian
        var bigEndianLen = UInt32(payloadData.count).bigEndian

        withUnsafeBytes(of: &bigEndianCmd) { response.append(contentsOf: $0) }
        withUnsafeBytes(of: &bigEndianLen) { response.append(contentsOf: $0) }
        response.append(payloadData)

        return response
    }
}