//
//  DeviceDataUsage.swift
//  Broadcasting
//
//  Created by Uldis Zingis on 28/06/2021.
//

import Foundation

class DeviceDataUsage {
    private static let wwanInterfacePrefix = "pdp_ip"
    private static let wifiInterfacePrefix = "en"

    public static var dataUsed: Int {
        let wifiUsage = getDataUsage().wifiSent + getDataUsage().wifiReceived
        let cellUsage = getDataUsage().wirelessWanDataSent + getDataUsage().wirelessWanDataReceived

        return Int(max(wifiUsage, cellUsage))
    }

    class func getDataUsage() -> DataUsageInfo {
        var ifaddr: UnsafeMutablePointer<ifaddrs>?
        var dataUsageInfo = DataUsageInfo()

        guard getifaddrs(&ifaddr) == 0 else { return dataUsageInfo }
        while let addr = ifaddr {
            guard let info = getDataUsageInfo(from: addr) else {
                ifaddr = addr.pointee.ifa_next
                continue
            }
            dataUsageInfo.updateInfoByAdding(info)
            ifaddr = addr.pointee.ifa_next
        }

        freeifaddrs(ifaddr)

        return dataUsageInfo
    }

    private class func getDataUsageInfo(from infoPointer: UnsafeMutablePointer<ifaddrs>) -> DataUsageInfo? {
        let pointer = infoPointer
        let name: String! = String(cString: pointer.pointee.ifa_name)
        let addr = pointer.pointee.ifa_addr.pointee
        guard addr.sa_family == UInt8(AF_LINK) else { return nil }

        return dataUsageInfo(from: pointer, name: name)
    }

    private class func dataUsageInfo(from pointer: UnsafeMutablePointer<ifaddrs>, name: String) -> DataUsageInfo {
        var networkData: UnsafeMutablePointer<if_data>?
        var dataUsageInfo = DataUsageInfo()

        if name.hasPrefix(wifiInterfacePrefix) {
            networkData = unsafeBitCast(pointer.pointee.ifa_data, to: UnsafeMutablePointer<if_data>.self)
            if let data = networkData {
                dataUsageInfo.wifiSent += UInt64(data.pointee.ifi_obytes)
                dataUsageInfo.wifiReceived += UInt64(data.pointee.ifi_ibytes)
            }

        } else if name.hasPrefix(wwanInterfacePrefix) {
            networkData = unsafeBitCast(pointer.pointee.ifa_data, to: UnsafeMutablePointer<if_data>.self)
            if let data = networkData {
                dataUsageInfo.wirelessWanDataSent += UInt64(data.pointee.ifi_obytes)
                dataUsageInfo.wirelessWanDataReceived += UInt64(data.pointee.ifi_ibytes)
            }
        }
        return dataUsageInfo
    }
}

struct DataUsageInfo {
    var wifiReceived: UInt64 = 0
    var wifiSent: UInt64 = 0
    var wirelessWanDataReceived: UInt64 = 0
    var wirelessWanDataSent: UInt64 = 0

    mutating func updateInfoByAdding(_ info: DataUsageInfo) {
        wifiSent += info.wifiSent
        wifiReceived += info.wifiReceived
        wirelessWanDataSent += info.wirelessWanDataSent
        wirelessWanDataReceived += info.wirelessWanDataReceived
    }
}