import AppKit
import Foundation
import UniformTypeIdentifiers

@MainActor
enum SystemReportExporter {
    static func export(monitor: SystemMonitor, selectedResource: String? = nil) {
        let panel = NSSavePanel()
        panel.title = "Export system report"
        panel.message = "Save the current performance, process, power, battery, and connected-hardware snapshot as JSON."
        panel.prompt = "Export"
        panel.allowedContentTypes = [.json]
        panel.canCreateDirectories = true
        panel.nameFieldStringValue = "Task-Manager-Report-\(filenameDate()).json"

        let data: Data
        do {
            data = try JSONSerialization.data(
                withJSONObject: report(monitor: monitor, selectedResource: selectedResource),
                options: [.prettyPrinted, .sortedKeys]
            )
        } catch {
            monitor.errorMessage = "Could not create the system report: \(error.localizedDescription)"
            return
        }

        panel.begin { response in
            guard response == .OK, let destination = panel.url else { return }
            do {
                try data.write(to: destination, options: .atomic)
            } catch {
                monitor.errorMessage = "Could not export the system report: \(error.localizedDescription)"
            }
        }
    }

    private static func report(monitor: SystemMonitor, selectedResource: String?) -> [String: Any] {
        let snapshot = monitor.snapshot
        let battery = monitor.hardware.battery
        return [
            "generatedAt": ISO8601DateFormatter().string(from: Date()),
            "selectedResource": selectedResource ?? "All",
            "system": [
                "cpuPercent": snapshot.cpuPercent,
                "logicalProcessors": snapshot.corePercents.count,
                "memoryBytes": snapshot.memoryTotal,
                "memoryUsedBytes": snapshot.memoryUsed,
                "memoryType": snapshot.memoryType,
                "memorySpeed": snapshot.memorySpeed,
                "memoryManufacturer": snapshot.memoryManufacturer,
                "diskReadBytesPerSecond": snapshot.diskReadRate,
                "diskWriteBytesPerSecond": snapshot.diskWriteRate,
                "diskActivePercent": snapshot.diskActivePercent,
                "gpuPercent": snapshot.gpuPercent,
                "gpuCoreCount": snapshot.gpuCoreCount,
                "networkInterface": snapshot.networkInterface,
                "networkReceiveBytesPerSecond": snapshot.networkReceiveRate,
                "networkSendBytesPerSecond": snapshot.networkSendRate,
                "processCount": snapshot.processCount,
                "threadCount": snapshot.threadCount,
                "uptimeSeconds": snapshot.uptime
            ],
            "power": [
                "thermalState": monitor.hardware.thermalState,
                "systemPowerWatts": battery.systemPowerWatts,
                "externalPowerConnected": battery.externalPowerConnected,
                "lowPowerMode": ProcessInfo.processInfo.isLowPowerModeEnabled
            ],
            "battery": batteryReport(battery),
            "ports": monitor.hardware.ports.map(portReport),
            "topProcesses": topProcesses(monitor),
            "topUsers": topUsers(monitor)
        ]
    }

    private static func batteryReport(_ battery: BatterySnapshot) -> [String: Any] {
        var result: [String: Any] = [
            "present": battery.isPresent,
            "chargePercent": battery.chargePercent,
            "charging": battery.isCharging,
            "fullyCharged": battery.isFullyCharged,
            "healthPercent": battery.healthPercent,
            "cycleCount": battery.cycleCount,
            "designCycleCount": battery.designCycleCount,
            "temperatureCelsius": battery.temperatureCelsius,
            "voltageVolts": battery.voltageVolts,
            "fullChargeCapacityMAh": battery.fullChargeCapacityMAh,
            "designCapacityMAh": battery.designCapacityMAh
        ]
        if let adapter = battery.adapter {
            result["adapter"] = [
                "name": adapter.name,
                "manufacturer": adapter.manufacturer,
                "ratedWatts": adapter.ratedWatts,
                "negotiatedVoltage": adapter.negotiatedVoltage,
                "negotiatedCurrent": adapter.negotiatedCurrent,
                "negotiatedWatts": adapter.negotiatedWatts,
                "powerProfiles": adapter.profiles.map {
                    ["voltage": $0.voltageVolts, "current": $0.currentAmps, "watts": $0.watts]
                }
            ]
        }
        return result
    }

    private static func portReport(_ port: HardwarePortSnapshot) -> [String: Any] {
        [
            "name": port.name,
            "transport": port.transport,
            "maximumSpeed": port.maximumSpeed,
            "connected": port.isConnected,
            "status": port.status,
            "devices": port.devices.map {
                var device: [String: Any] = ["name": $0.name, "vendor": $0.vendor, "speed": $0.speed]
                if let value = $0.currentAvailableMA { device["currentAvailableMA"] = value }
                if let value = $0.currentRequiredMA { device["currentRequiredMA"] = value }
                return device
            }
        ]
    }

    private static func topProcesses(_ monitor: SystemMonitor) -> [[String: Any]] {
        monitor.processes.sorted { $0.cpu > $1.cpu }.prefix(20).map { process in
            let activity = monitor.processActivity[process.pid] ?? ProcessActivityRate()
            return [
                "name": process.displayName,
                "pid": process.pid,
                "user": process.user,
                "cpuPercent": process.cpu,
                "residentBytes": process.residentBytes,
                "diskBytesPerSecond": activity.diskTotal,
                "networkBytesPerSecond": activity.networkTotal
            ]
        }
    }

    private static func topUsers(_ monitor: SystemMonitor) -> [[String: Any]] {
        struct Totals {
            var processes = 0
            var cpu = 0.0
            var memory: UInt64 = 0
            var disk = 0.0
            var network = 0.0
        }
        var users: [String: Totals] = [:]
        for process in monitor.processes {
            let activity = monitor.processActivity[process.pid] ?? ProcessActivityRate()
            users[process.user, default: Totals()].processes += 1
            users[process.user, default: Totals()].cpu += process.cpu
            users[process.user, default: Totals()].memory += process.residentBytes
            users[process.user, default: Totals()].disk += activity.diskTotal
            users[process.user, default: Totals()].network += activity.networkTotal
        }
        return users.map { user, totals in
            [
                "user": user,
                "processes": totals.processes,
                "cpuPercent": totals.cpu,
                "residentBytes": totals.memory,
                "diskBytesPerSecond": totals.disk,
                "networkBytesPerSecond": totals.network
            ]
        }
        .sorted { ($0["cpuPercent"] as? Double ?? 0) > ($1["cpuPercent"] as? Double ?? 0) }
    }

    private static func filenameDate() -> String {
        let formatter = DateFormatter()
        formatter.dateFormat = "yyyy-MM-dd-HHmmss"
        return formatter.string(from: Date())
    }
}