package powerreport

/*
#include <ifaddrs.h>
#include <mach/mach_time.h>
#include <net/if.h>
#include <net/if_var.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <unistd.h>

// The iOS SDK does not ship libproc.h; the symbol is exported by libSystem
// on all darwin platforms.
int proc_pid_rusage(int pid, int flavor, rusage_info_t *buffer);
*/
import "C"

import (
	"os"
	"strings"
	"sync"
	"unsafe"
)

var (
	timebaseOnce  sync.Once
	timebaseNumer int64
	timebaseDenom int64
)

func machTimebase() (int64, int64) {
	timebaseOnce.Do(func() {
		var timebase C.struct_mach_timebase_info
		C.mach_timebase_info(&timebase)
		timebaseNumer = int64(timebase.numer)
		timebaseDenom = int64(timebase.denom)
	})
	return timebaseNumer, timebaseDenom
}

func machToNano(value uint64) int64 {
	numer, denom := machTimebase()
	if denom == 0 {
		return int64(value)
	}
	return int64(value) * numer / denom
}

// The time fields of rusage_info are in mach_absolute_time units on arm64,
// not nanoseconds; the header does not document this.
func readSystemUsage() systemUsage {
	var info C.struct_rusage_info_v6
	result := C.proc_pid_rusage(C.int(os.Getpid()), C.RUSAGE_INFO_V6, (*C.rusage_info_t)(unsafe.Pointer(&info)))
	if result == 0 {
		return systemUsage{
			valid:                       true,
			userTime:                    machToNano(uint64(info.ri_user_time)),
			systemTime:                  machToNano(uint64(info.ri_system_time)),
			performanceUserTime:         machToNano(uint64(info.ri_user_ptime)),
			performanceSystemTime:       machToNano(uint64(info.ri_system_ptime)),
			qosDefaultTime:              machToNano(uint64(info.ri_cpu_time_qos_default)),
			qosMaintenanceTime:          machToNano(uint64(info.ri_cpu_time_qos_maintenance)),
			qosBackgroundTime:           machToNano(uint64(info.ri_cpu_time_qos_background)),
			qosUtilityTime:              machToNano(uint64(info.ri_cpu_time_qos_utility)),
			qosLegacyTime:               machToNano(uint64(info.ri_cpu_time_qos_legacy)),
			qosUserInitiatedTime:        machToNano(uint64(info.ri_cpu_time_qos_user_initiated)),
			qosUserInteractiveTime:      machToNano(uint64(info.ri_cpu_time_qos_user_interactive)),
			packageIdleWakeups:          uint64(info.ri_pkg_idle_wkups),
			interruptWakeups:            uint64(info.ri_interrupt_wkups),
			diskBytesWritten:            uint64(info.ri_diskio_byteswritten),
			energyNanojoules:            uint64(info.ri_energy_nj),
			performanceEnergyNanojoules: uint64(info.ri_penergy_nj),
		}
	}
	var infoV4 C.struct_rusage_info_v4
	result = C.proc_pid_rusage(C.int(os.Getpid()), C.RUSAGE_INFO_V4, (*C.rusage_info_t)(unsafe.Pointer(&infoV4)))
	if result != 0 {
		return systemUsage{}
	}
	return systemUsage{
		valid:                  true,
		userTime:               machToNano(uint64(infoV4.ri_user_time)),
		systemTime:             machToNano(uint64(infoV4.ri_system_time)),
		qosDefaultTime:         machToNano(uint64(infoV4.ri_cpu_time_qos_default)),
		qosMaintenanceTime:     machToNano(uint64(infoV4.ri_cpu_time_qos_maintenance)),
		qosBackgroundTime:      machToNano(uint64(infoV4.ri_cpu_time_qos_background)),
		qosUtilityTime:         machToNano(uint64(infoV4.ri_cpu_time_qos_utility)),
		qosLegacyTime:          machToNano(uint64(infoV4.ri_cpu_time_qos_legacy)),
		qosUserInitiatedTime:   machToNano(uint64(infoV4.ri_cpu_time_qos_user_initiated)),
		qosUserInteractiveTime: machToNano(uint64(infoV4.ri_cpu_time_qos_user_interactive)),
		packageIdleWakeups:     uint64(infoV4.ri_pkg_idle_wkups),
		interruptWakeups:       uint64(infoV4.ri_interrupt_wkups),
		diskBytesWritten:       uint64(infoV4.ri_diskio_byteswritten),
	}
}

func readClocks() (absoluteTime int64, continuousTime int64) {
	return machToNano(uint64(C.mach_absolute_time())), machToNano(uint64(C.mach_continuous_time()))
}

func readInterfaceCounters() map[string]interfaceCounters {
	var list *C.struct_ifaddrs
	if C.getifaddrs(&list) != 0 {
		return nil
	}
	defer C.freeifaddrs(list)
	result := make(map[string]interfaceCounters)
	for entry := list; entry != nil; entry = entry.ifa_next {
		if entry.ifa_addr == nil || entry.ifa_addr.sa_family != C.AF_LINK || entry.ifa_data == nil {
			continue
		}
		name := C.GoString(entry.ifa_name)
		if !strings.HasPrefix(name, "en") && !strings.HasPrefix(name, "pdp_ip") {
			continue
		}
		data := (*C.struct_if_data)(entry.ifa_data)
		result[name] = interfaceCounters{
			inPackets:  uint32(data.ifi_ipackets),
			outPackets: uint32(data.ifi_opackets),
		}
	}
	return result
}