package diagnostics

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/sony/gobreaker"
)

// TODO: unique Cluster ID

// Default version check URL.
const (
	DefaultVersionCheckURL = "https://diagnostics.pilosa.com/v0/version"
)

type versionResponse struct {
	Version string `json:"version"`
	Message string `json:"message"`
}

// Diagnostics represents a client to the Pilosa cluster.
type Diagnostics struct {
	mu          sync.Mutex
	wg          sync.WaitGroup
	closing     chan struct{}
	host        string
	VersionURL  string
	version     string
	lastVersion string
	startTime   int64
	start       time.Time

	metrics map[string]interface{}

	client   *http.Client
	interval time.Duration

	cb        *gobreaker.CircuitBreaker
	logOutput io.Writer
}

// New returns a pointer to a new Diagnostics Client given an addr in the format "hostname:port".
func New(host string) *Diagnostics {

	return &Diagnostics{
		closing:    make(chan struct{}),
		host:       host,
		VersionURL: DefaultVersionCheckURL,
		startTime:  time.Now().Unix(),
		start:      time.Now(),
		client:     http.DefaultClient,
		metrics:    make(map[string]interface{}),
		logOutput:  ioutil.Discard,
	}
}

// SetVersion of locally running Pilosa Cluster to check against master.
func (d *Diagnostics) SetVersion(v string) {
	d.version = v
	d.Set("Version", v)
}

// SetInterval of the diagnostic go routine and match with the circuit breaker timeout.
func (d *Diagnostics) SetInterval(i time.Duration) {
	d.interval = i
}

// schedule start the diagnostics service ticker.
func (d *Diagnostics) schedule() {
	ticker := time.NewTicker(d.interval)
	defer ticker.Stop()

	for {
		select {
		case <-d.closing:
			return
		case <-ticker.C:
			d.CheckVersion()
			d.Flush()
		}
	}
}

// Flush sends the current metrics.
func (d *Diagnostics) Flush() error {
	d.mu.Lock()
	d.metrics["uptime"] = (time.Now().Unix() - d.startTime)
	buf, _ := d.Encode()
	d.mu.Unlock()

	_, err := d.cb.Execute(func() (interface{}, error) {
		req, err := http.NewRequest("POST", d.host, bytes.NewReader(buf))
		req.Header.Set("Content-Type", "application/json")
		resp, err := d.client.Do(req)
		if err != nil {
			return nil, err
		}
		defer resp.Body.Close()

		// TODO verify response
		body, err := ioutil.ReadAll(resp.Body)
		if err != nil {
			return nil, err
		}
		return body, nil
	})

	return err
}

// Open configures the circuit breaker used by the HTTP client.
func (d *Diagnostics) Open() {
	var st gobreaker.Settings
	if d.interval > 0 {
		st.Timeout = d.interval * 2
	}
	d.cb = gobreaker.NewCircuitBreaker(st)

	d.logger().Printf("Pilosa is currently configured to send small diagnostics reports to our team every hour. More information here: https://www.pilosa.com/docs/latest/administration/#diagnostics")
}

// Close notify goroutine to stop.
func (d *Diagnostics) Close() error {
	close(d.closing)
	d.wg.Wait()
	return nil
}

// CheckVersion of the local build against Pilosa master.
func (d *Diagnostics) CheckVersion() error {
	var rsp versionResponse
	req, err := http.NewRequest("GET", d.VersionURL, nil)
	resp, err := d.client.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("http: status=%d", resp.StatusCode)
	} else if err := json.NewDecoder(resp.Body).Decode(&rsp); err != nil {
		return fmt.Errorf("json decode: %s", err)
	}

	// Same a version as last test
	if rsp.Version == d.lastVersion {
		return nil
	}

	d.lastVersion = rsp.Version
	if err := d.CompareVersion(rsp.Version); err != nil {
		d.logger().Printf("%s\n", err.Error())
	}

	return nil
}

// CompareVersion check version strings.
func (d *Diagnostics) CompareVersion(value string) error {
	currentVersion := VersionSegments(value)
	localVersion := VersionSegments(d.version)

	if localVersion[0] < currentVersion[0] { //Major
		return fmt.Errorf("Warning: You are running Pilosa %s. A newer version (%s) is available: https://github.com/pilosa/pilosa/releases", d.version, value)
	} else if localVersion[1] < currentVersion[1] && localVersion[0] == currentVersion[0] { // Minor
		return fmt.Errorf("Warning: You are running Pilosa %s. The latest Minor release is %s: https://github.com/pilosa/pilosa/releases", d.version, value)
	} else if localVersion[2] < currentVersion[2] && localVersion[0] == currentVersion[0] && localVersion[1] == currentVersion[1] { // Patch
		return fmt.Errorf("There is a new patch release of Pilosa available: %s: https://github.com/pilosa/pilosa/releases", value)
	}

	return nil
}

// Encode metrics maps into the json message format.
func (d *Diagnostics) Encode() ([]byte, error) {
	return json.Marshal(d.metrics)
}

// Set adds a key value metric.
func (d *Diagnostics) Set(name string, value interface{}) {
	d.mu.Lock()
	defer d.mu.Unlock()
	d.metrics[name] = value
}

// SetLogger Set the logger output type.
func (d *Diagnostics) SetLogger(logger io.Writer) {
	d.logOutput = logger
}

// logger returns a logger that writes to LogOutput.
func (d *Diagnostics) logger() *log.Logger {
	return log.New(d.logOutput, "", log.LstdFlags)
}

// VersionSegments returns the numeric segments of the version as a slice of ints.
func VersionSegments(segments string) []int {
	segments = strings.Trim(segments, "v")
	segments = strings.Split(segments, "-")[0]
	s := strings.Split(segments, ".")
	segmentSlice := make([]int, len(s))
	for i, v := range s {
		segmentSlice[i], _ = strconv.Atoi(v)
	}
	return segmentSlice
}