// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.

package admin

import (
	"errors"
	"os"
	"runtime"
	"runtime/pprof"
)

var (
	errCPUProfilerRunning    = errors.New("cpu profiler already running")
	errCPUProfilerNotRunning = errors.New("cpu profiler doesn't exist")
)

// Performance provides helper methods for measuring the current performance of
// the system
type Performance struct{ cpuProfileFile *os.File }

// StartCPUProfiler starts measuring the cpu utilization of this node
func (p *Performance) StartCPUProfiler(filename string) error {
	if p.cpuProfileFile != nil {
		return errCPUProfilerRunning
	}

	file, err := os.Create(filename)
	if err != nil {
		return err
	}
	if err := pprof.StartCPUProfile(file); err != nil {
		file.Close()
		return err
	}
	runtime.SetMutexProfileFraction(1)

	p.cpuProfileFile = file
	return nil
}

// StopCPUProfiler stops measuring the cpu utilization of this node
func (p *Performance) StopCPUProfiler() error {
	if p.cpuProfileFile == nil {
		return errCPUProfilerNotRunning
	}

	pprof.StopCPUProfile()
	err := p.cpuProfileFile.Close()
	p.cpuProfileFile = nil
	return err
}

// MemoryProfile dumps the current memory utilization of this node
func (p *Performance) MemoryProfile(filename string) error {
	file, err := os.Create(filename)
	if err != nil {
		return err
	}
	runtime.GC() // get up-to-date statistics
	if err := pprof.WriteHeapProfile(file); err != nil {
		file.Close()
		return err
	}
	return file.Close()
}

// LockProfile dumps the current lock statistics of this node
func (p *Performance) LockProfile(filename string) error {
	file, err := os.Create(filename)
	if err != nil {
		return err
	}

	profile := pprof.Lookup("mutex")
	if err := profile.WriteTo(file, 1); err != nil {
		file.Close()
		return err
	}
	return file.Close()
}