package main

import (
	"errors"
	"fmt"
	"io/ioutil"
	"net"
	"os"
	"os/exec"
	"strings"

	"github.com/google/gops/agent"
	"github.com/google/gops/signal"
	ps "github.com/keybase/go-ps"
)

var cmds = map[string](func(pid int) error){
	"stack":      stackTrace,
	"gc":         gc,
	"memstats":   memStats,
	"version":    version,
	"pprof-heap": pprofHeap,
	"pprof-cpu":  pprofCPU,
	"vitals":     vitals,
}

func stackTrace(pid int) error {
	out, err := cmd(pid, signal.StackTrace)
	if err != nil {
		return err
	}
	fmt.Println(out)
	return nil
}

func gc(pid int) error {
	_, err := cmd(pid, signal.GC)
	return err
}

func memStats(pid int) error {
	out, err := cmd(pid, signal.MemStats)
	if err != nil {
		return err
	}
	fmt.Printf(out)
	return nil
}

func version(pid int) error {
	out, err := cmd(pid, signal.Version)
	if err != nil {
		return err
	}
	fmt.Printf(out)
	return nil
}

func pprofHeap(pid int) error {
	return pprof(pid, signal.HeapProfile)
}

func pprofCPU(pid int) error {
	fmt.Println("Profiling CPU now, will take 30 secs...")
	return pprof(pid, signal.CPUProfile)
}

func pprof(pid int, p byte) error {
	out, err := cmd(pid, p)
	if err != nil {
		return err
	}
	if out == "" {
		return errors.New("failed to read the profile")
	}
	tmpfile, err := ioutil.TempFile("", "heap-profile")
	if err != nil {
		return err
	}
	defer os.Remove(tmpfile.Name())
	if err := ioutil.WriteFile(tmpfile.Name(), []byte(out), 0); err != nil {
		return err
	}
	process, err := ps.FindProcess(pid)
	if err != nil {
		// TODO(jbd): add context to the error
		return err
	}
	binary, err := process.Path()
	if err != nil {
		// TODO(jbd): add context to the error
		return err
	}
	cmd := exec.Command("go", "tool", "pprof", binary, tmpfile.Name())
	cmd.Env = os.Environ()
	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	return cmd.Run()
}

func vitals(pid int) error {
	out, err := cmd(pid, signal.Vitals)
	if err != nil {
		return err
	}
	fmt.Printf(out)
	return nil
}

func getPort(pid int) (string, error) {
	gopsdir, err := agent.ConfigDir()
	if err != nil {
		return "", err
	}
	portfile := fmt.Sprintf("%s/%d", gopsdir, pid)
	b, err := ioutil.ReadFile(portfile)
	if err != nil {
		return "", err
	}
	port := strings.TrimSpace(string(b))
	return port, nil
}

func cmd(pid int, c byte) (string, error) {
	port, err := getPort(pid)
	if err != nil {
		return "", err
	}
	conn, err := net.Dial("tcp", "127.0.0.1:"+port)
	if err != nil {
		return "", err
	}
	if _, err := conn.Write([]byte{c}); err != nil {
		return "", err
	}
	all, err := ioutil.ReadAll(conn)
	if err != nil {
		return "", err
	}
	return string(all), nil
}