// Copyright (c) 2012 VMware, Inc.

package gosigar

import (
	"fmt"
	"os"
	"path/filepath"
	"runtime"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/elastic/gosigar/sys/windows"
	"github.com/pkg/errors"
)

var (
	// version is Windows version of the host OS.
	version = windows.GetWindowsVersion()

	// processQueryLimitedInfoAccess is set to PROCESS_QUERY_INFORMATION for Windows
	// 2003 and XP where PROCESS_QUERY_LIMITED_INFORMATION is unknown. For all newer
	// OS versions it is set to PROCESS_QUERY_LIMITED_INFORMATION.
	processQueryLimitedInfoAccess = windows.PROCESS_QUERY_LIMITED_INFORMATION

	// bootTime is the time when the OS was last booted. This value may be nil
	// on operating systems that do not support the WMI query used to obtain it.
	bootTime     *time.Time
	bootTimeLock sync.Mutex
)

func init() {
	if !version.IsWindowsVistaOrGreater() {
		// PROCESS_QUERY_LIMITED_INFORMATION cannot be used on 2003 or XP.
		processQueryLimitedInfoAccess = syscall.PROCESS_QUERY_INFORMATION
	}
}

func (self *LoadAverage) Get() error {
	return ErrNotImplemented{runtime.GOOS}
}

func (self *FDUsage) Get() error {
	return ErrNotImplemented{runtime.GOOS}
}

func (self *ProcEnv) Get(pid int) error {
	return ErrNotImplemented{runtime.GOOS}
}

func (self *ProcExe) Get(pid int) error {
	return ErrNotImplemented{runtime.GOOS}
}

func (self *ProcFDUsage) Get(pid int) error {
	return ErrNotImplemented{runtime.GOOS}
}

func (self *Uptime) Get() error {
	// Minimum supported OS is Windows Vista.
	if !version.IsWindowsVistaOrGreater() {
		return ErrNotImplemented{runtime.GOOS}
	}

	bootTimeLock.Lock()
	defer bootTimeLock.Unlock()
	if bootTime == nil {
		uptime, err := windows.GetTickCount64()
		if err != nil {
			return errors.Wrap(err, "failed to get boot time using win32 api")
		}
		var boot = time.Unix(int64(uptime), 0)
		bootTime = &boot
	}

	self.Length = time.Since(*bootTime).Seconds()
	return nil
}

func (self *Mem) Get() error {
	memoryStatusEx, err := windows.GlobalMemoryStatusEx()
	if err != nil {
		return errors.Wrap(err, "GlobalMemoryStatusEx failed")
	}

	self.Total = memoryStatusEx.TotalPhys
	self.Free = memoryStatusEx.AvailPhys
	self.Used = self.Total - self.Free
	self.ActualFree = self.Free
	self.ActualUsed = self.Used
	return nil
}

func (self *Swap) Get() error {
	memoryStatusEx, err := windows.GlobalMemoryStatusEx()
	if err != nil {
		return errors.Wrap(err, "GlobalMemoryStatusEx failed")
	}

	self.Total = memoryStatusEx.TotalPageFile
	self.Free = memoryStatusEx.AvailPageFile
	self.Used = self.Total - self.Free
	return nil
}

func (self *HugeTLBPages) Get() error {
	return ErrNotImplemented{runtime.GOOS}
}

func (self *Cpu) Get() error {
	idle, kernel, user, err := windows.GetSystemTimes()
	if err != nil {
		return errors.Wrap(err, "GetSystemTimes failed")
	}

	// CPU times are reported in milliseconds by gosigar.
	self.Idle = uint64(idle / time.Millisecond)
	self.Sys = uint64(kernel / time.Millisecond)
	self.User = uint64(user / time.Millisecond)
	return nil
}

func (self *CpuList) Get() error {
	cpus, err := windows.NtQuerySystemProcessorPerformanceInformation()
	if err != nil {
		return errors.Wrap(err, "NtQuerySystemProcessorPerformanceInformation failed")
	}

	self.List = make([]Cpu, 0, len(cpus))
	for _, cpu := range cpus {
		self.List = append(self.List, Cpu{
			Idle: uint64(cpu.IdleTime / time.Millisecond),
			Sys:  uint64(cpu.KernelTime / time.Millisecond),
			User: uint64(cpu.UserTime / time.Millisecond),
		})
	}
	return nil
}

func (self *FileSystemList) Get() error {
	drives, err := windows.GetAccessPaths()
	if err != nil {
		return errors.Wrap(err, "GetAccessPaths failed")
	}

	for _, drive := range drives {
		dt, err := windows.GetDriveType(drive)
		if err != nil {
			return errors.Wrapf(err, "GetDriveType failed")
		}

		self.List = append(self.List, FileSystem{
			DirName:  drive,
			DevName:  drive,
			TypeName: dt.String(),
		})
	}
	return nil
}

// Get retrieves a list of all process identifiers (PIDs) in the system.
func (self *ProcList) Get() error {
	pids, err := windows.EnumProcesses()
	if err != nil {
		return errors.Wrap(err, "EnumProcesses failed")
	}

	// Convert uint32 PIDs to int.
	self.List = make([]int, 0, len(pids))
	for _, pid := range pids {
		self.List = append(self.List, int(pid))
	}
	return nil
}

func (self *ProcState) Get(pid int) error {
	var errs []error

	var err error
	self.Name, err = getProcName(pid)
	if err != nil {
		errs = append(errs, errors.Wrap(err, "getProcName failed"))
	}

	self.State, err = getProcStatus(pid)
	if err != nil {
		errs = append(errs, errors.Wrap(err, "getProcStatus failed"))
	}

	self.Ppid, err = getParentPid(pid)
	if err != nil {
		errs = append(errs, errors.Wrap(err, "getParentPid failed"))
	}

	// getProcCredName will often fail when run as a non-admin user. This is
	// caused by strict ACL of the process token belonging to other users.
	// Instead of failing completely, ignore this error and still return most
	// data with an empty Username.
	self.Username, _ = getProcCredName(pid)

	if len(errs) > 0 {
		errStrs := make([]string, 0, len(errs))
		for _, e := range errs {
			errStrs = append(errStrs, e.Error())
		}
		return errors.New(strings.Join(errStrs, "; "))
	}
	return nil
}

// getProcName returns the process name associated with the PID.
func getProcName(pid int) (string, error) {
	handle, err := syscall.OpenProcess(processQueryLimitedInfoAccess, false, uint32(pid))
	if err != nil {
		return "", errors.Wrapf(err, "OpenProcess failed for pid=%v", pid)
	}
	defer syscall.CloseHandle(handle)

	filename, err := windows.GetProcessImageFileName(handle)
	if err != nil {
		return "", errors.Wrapf(err, "GetProcessImageFileName failed for pid=%v", pid)
	}

	return filepath.Base(filename), nil
}

// getProcStatus returns the status of a process.
func getProcStatus(pid int) (RunState, error) {
	handle, err := syscall.OpenProcess(processQueryLimitedInfoAccess, false, uint32(pid))
	if err != nil {
		return RunStateUnknown, errors.Wrapf(err, "OpenProcess failed for pid=%v", pid)
	}
	defer syscall.CloseHandle(handle)

	var exitCode uint32
	err = syscall.GetExitCodeProcess(handle, &exitCode)
	if err != nil {
		return RunStateUnknown, errors.Wrapf(err, "GetExitCodeProcess failed for pid=%v", pid)
	}

	if exitCode == 259 { //still active
		return RunStateRun, nil
	}
	return RunStateSleep, nil
}

// getParentPid returns the parent process ID of a process.
func getParentPid(pid int) (int, error) {
	handle, err := syscall.OpenProcess(processQueryLimitedInfoAccess, false, uint32(pid))
	if err != nil {
		return RunStateUnknown, errors.Wrapf(err, "OpenProcess failed for pid=%v", pid)
	}
	defer syscall.CloseHandle(handle)

	procInfo, err := windows.NtQueryProcessBasicInformation(handle)
	if err != nil {
		return 0, errors.Wrapf(err, "NtQueryProcessBasicInformation failed for pid=%v", pid)
	}

	return int(procInfo.InheritedFromUniqueProcessID), nil
}

func getProcCredName(pid int) (string, error) {
	handle, err := syscall.OpenProcess(syscall.PROCESS_QUERY_INFORMATION, false, uint32(pid))
	if err != nil {
		return "", errors.Wrapf(err, "OpenProcess failed for pid=%v", pid)
	}
	defer syscall.CloseHandle(handle)

	// Find process token via win32.
	var token syscall.Token
	err = syscall.OpenProcessToken(handle, syscall.TOKEN_QUERY, &token)
	if err != nil {
		return "", errors.Wrapf(err, "OpenProcessToken failed for pid=%v", pid)
	}
	// Close token to prevent handle leaks.
	defer token.Close()

	// Find the token user.
	tokenUser, err := token.GetTokenUser()
	if err != nil {
		return "", errors.Wrapf(err, "GetTokenInformation failed for pid=%v", pid)
	}

	// Look up domain account by SID.
	account, domain, _, err := tokenUser.User.Sid.LookupAccount("")
	if err != nil {
		sid, sidErr := tokenUser.User.Sid.String()
		if sidErr != nil {
			return "", errors.Wrapf(err, "failed while looking up account name for pid=%v", pid)
		}
		return "", errors.Wrapf(err, "failed while looking up account name for SID=%v of pid=%v", sid, pid)
	}

	return fmt.Sprintf(`%s\%s`, domain, account), nil
}

func (self *ProcMem) Get(pid int) error {
	handle, err := syscall.OpenProcess(processQueryLimitedInfoAccess|windows.PROCESS_VM_READ, false, uint32(pid))
	if err != nil {
		return errors.Wrapf(err, "OpenProcess failed for pid=%v", pid)
	}
	defer syscall.CloseHandle(handle)

	counters, err := windows.GetProcessMemoryInfo(handle)
	if err != nil {
		return errors.Wrapf(err, "GetProcessMemoryInfo failed for pid=%v", pid)
	}

	self.Resident = uint64(counters.WorkingSetSize)
	self.Size = uint64(counters.PrivateUsage)
	return nil
}

func (self *ProcTime) Get(pid int) error {
	cpu, err := getProcTimes(pid)
	if err != nil {
		return err
	}

	// Windows epoch times are expressed as time elapsed since midnight on
	// January 1, 1601 at Greenwich, England. This converts the Filetime to
	// unix epoch in milliseconds.
	self.StartTime = uint64(cpu.CreationTime.Nanoseconds() / 1e6)

	// Convert to millis.
	self.User = uint64(windows.FiletimeToDuration(&cpu.UserTime).Nanoseconds() / 1e6)
	self.Sys = uint64(windows.FiletimeToDuration(&cpu.KernelTime).Nanoseconds() / 1e6)
	self.Total = self.User + self.Sys

	return nil
}

func getProcTimes(pid int) (*syscall.Rusage, error) {
	handle, err := syscall.OpenProcess(processQueryLimitedInfoAccess, false, uint32(pid))
	if err != nil {
		return nil, errors.Wrapf(err, "OpenProcess failed for pid=%v", pid)
	}
	defer syscall.CloseHandle(handle)

	var cpu syscall.Rusage
	if err := syscall.GetProcessTimes(handle, &cpu.CreationTime, &cpu.ExitTime, &cpu.KernelTime, &cpu.UserTime); err != nil {
		return nil, errors.Wrapf(err, "GetProcessTimes failed for pid=%v", pid)
	}

	return &cpu, nil
}

func (self *ProcArgs) Get(pid int) error {
	// The minimum supported client for Win32_Process is Windows Vista.
	if !version.IsWindowsVistaOrGreater() {
		return ErrNotImplemented{runtime.GOOS}
	}
	handle, err := syscall.OpenProcess(processQueryLimitedInfoAccess|windows.PROCESS_VM_READ, false, uint32(pid))
	if err != nil {
		return errors.Wrapf(err, "OpenProcess failed for pid=%v", pid)
	}
	defer syscall.CloseHandle(handle)
	pbi, err := windows.NtQueryProcessBasicInformation(handle)
	if err != nil {
		return errors.Wrapf(err, "NtQueryProcessBasicInformation failed for pid=%v", pid)
	}
	if err != nil {
		return nil
	}
	userProcParams, err := windows.GetUserProcessParams(handle, pbi)
	if err != nil {
		return nil
	}
	if argsW, err := windows.ReadProcessUnicodeString(handle, &userProcParams.CommandLine); err == nil {
		self.List, err = windows.ByteSliceToStringSlice(argsW)
		if err != nil {
			return err
		}
	}
	return nil
}

func (self *FileSystemUsage) Get(path string) error {
	freeBytesAvailable, totalNumberOfBytes, totalNumberOfFreeBytes, err := windows.GetDiskFreeSpaceEx(path)
	if err != nil {
		return errors.Wrap(err, "GetDiskFreeSpaceEx failed")
	}

	self.Total = totalNumberOfBytes
	self.Free = totalNumberOfFreeBytes
	self.Used = self.Total - self.Free
	self.Avail = freeBytesAvailable
	return nil
}

func (self *Rusage) Get(who int) error {
	if who != 0 {
		return ErrNotImplemented{runtime.GOOS}
	}

	pid := os.Getpid()
	cpu, err := getProcTimes(pid)
	if err != nil {
		return err
	}

	self.Utime = windows.FiletimeToDuration(&cpu.UserTime)
	self.Stime = windows.FiletimeToDuration(&cpu.KernelTime)

	return nil
}