package gracehttp_test

import (
	"bufio"
	"encoding/json"
	"fmt"
	"github.com/daaku/go.freeport"
	"github.com/daaku/go.tool"
	"io/ioutil"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"sync"
	"syscall"
	"testing"
	"time"
)

const (
	// The amount of time we give a process to become ready.
	processWait = time.Second * 2

	// The amount of time for the long HTTP request. This should be
	// bigger than the value above.
	slowHttpWait = time.Second * 4
)

// The response from the test server.
type response struct {
	Sleep time.Duration
	Pid   int
}

// State for the test run.
type harness struct {
	T                *testing.T     // The test instance.
	ImportPath       string         // The import path for the server command.
	ExeName          string         // The temp binary from the build.
	Addr             []string       // The addresses for the http servers.
	Process          []*os.Process  // The server commands, oldest to newest.
	RequestWaitGroup sync.WaitGroup // The wait group for the HTTP requests.
	newProcess       chan bool      // A bool is sent on restart.
}

// Find 3 free ports and setup addresses.
func (h *harness) SetupAddr() {
	for i := 3; i > 0; i-- {
		port, err := freeport.Get()
		if err != nil {
			h.T.Fatalf("Failed to find a free port: %s", err)
		}
		h.Addr = append(h.Addr, fmt.Sprintf("127.0.0.1:%d", port))
	}
}

// Builds the command line arguments.
func (h *harness) Args() []string {
	if h.Addr == nil {
		h.SetupAddr()
	}
	return []string{
		"-gracehttp.log=false",
		"-a0", h.Addr[0],
		"-a1", h.Addr[1],
		"-a2", h.Addr[2],
	}
}

// Builds the command.
func (h *harness) Build() {
	basename := filepath.Base(h.ImportPath)
	tempFile, err := ioutil.TempFile("", basename+"-")
	if err != nil {
		h.T.Fatalf("Error creating temp file: %s", err)
	}
	h.ExeName = tempFile.Name()
	_ = os.Remove(h.ExeName) // the build tool will create this
	options := tool.Options{
		ImportPaths: []string{h.ImportPath},
		Output:      h.ExeName,
	}
	_, err = options.Command("build")
	if err != nil {
		h.T.Fatal(err)
	}
}

// Start a fresh server and wait for pid updates on restart.
func (h *harness) Start() {
	if h.newProcess == nil {
		h.newProcess = make(chan bool)
	}
	cmd := exec.Command(h.ExeName, h.Args()...)
	stderr, err := cmd.StderrPipe()
	go func() {
		reader := bufio.NewReader(stderr)
		for {
			line, isPrefix, err := reader.ReadLine()
			if err != nil {
				h.T.Fatalf("Failed to read line from server process: %s", err)
			}
			if isPrefix {
				h.T.Fatalf("Deal with isPrefix for line: %s", line)
			}
			res := &response{}
			err = json.Unmarshal([]byte(line), res)
			if err != nil {
				h.T.Fatalf("Could not parse json from stderr %s: %s", line, err)
			}
			process, err := os.FindProcess(res.Pid)
			if err != nil {
				h.T.Fatalf("Could not find process with pid: %d", res.Pid)
			}
			h.Process = append(h.Process, process)
			h.newProcess <- true
		}
	}()
	err = cmd.Start()
	if err != nil {
		h.T.Fatalf("Failed to start command: %s", err)
	}
	h.Process = append(h.Process, cmd.Process)
	<-h.newProcess
	time.Sleep(processWait)
}

// Restart the most recent server.
func (h *harness) Restart() {
	err := h.MostRecentProcess().Signal(syscall.SIGUSR2)
	if err != nil {
		h.T.Fatalf("Failed to send SIGUSR2 and restart process: %s", err)
	}
	<-h.newProcess
	time.Sleep(processWait)
}

// Graceful termination of the most recent server.
func (h *harness) Stop() {
	err := h.MostRecentProcess().Signal(syscall.SIGTERM)
	if err != nil {
		h.T.Fatalf("Failed to send SIGTERM and stop process: %s", err)
	}
}

// Returns the most recent server process.
func (h *harness) MostRecentProcess() *os.Process {
	l := len(h.Process)
	if l == 0 {
		h.T.Fatalf("Most recent command requested before command was created.")
	}
	return h.Process[l-1]
}

// Remove the built executable.
func (h *harness) RemoveExe() {
	err := os.Remove(h.ExeName)
	if err != nil {
		h.T.Fatalf("Failed to RemoveExe: %s", err)
	}
}

// Helper for sending a single request.
func (h *harness) SendOne(duration time.Duration, addr string, pid int) {
	client := &http.Client{
		Transport: &http.Transport{DisableKeepAlives: true},
	}
	url := fmt.Sprintf("http://%s/sleep/?duration=%s", addr, duration.String())
	r, err := client.Get(url)
	if err != nil {
		h.T.Fatalf("Failed request to %s: %s", url, err)
	}
	defer r.Body.Close()
	res := &response{}
	err = json.NewDecoder(r.Body).Decode(res)
	if err != nil {
		h.T.Fatalf("Failed to ready decode json response body: %s", err)
	}
	if pid != res.Pid {
		h.T.Fatalf("Didn't get expected pid %d instead got %d", pid, res.Pid)
	}
	h.RequestWaitGroup.Done()
}

// Send test HTTP request.
func (h *harness) SendRequest() {
	pid := h.MostRecentProcess().Pid
	for _, addr := range h.Addr {
		h.RequestWaitGroup.Add(2)
		go h.SendOne(time.Second*0, addr, pid)
		go h.SendOne(slowHttpWait, addr, pid)
	}
}

// Wait for everything.
func (h *harness) Wait() {
	h.RequestWaitGroup.Wait()
}

// The main test case.
func TestComplex(t *testing.T) {
	h := &harness{
		ImportPath: "github.com/daaku/go.grace/gracehttp/testserver",
		T:          t,
	}
	h.Build()
	h.Start()
	h.SendRequest()
	time.Sleep(processWait)
	h.Restart()
	h.SendRequest()
	time.Sleep(processWait)
	h.Restart()
	h.SendRequest()
	time.Sleep(processWait)
	h.Stop()
	h.Wait()
	h.RemoveExe()
}