// Copyright © 2023 Ory Corp
// SPDX-License-Identifier: Apache-2.0

package metricsx

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"math"
	"net/http"
	"net/url"
	"os"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"time"

	"connectrpc.com/connect"
	"google.golang.org/grpc"
	"google.golang.org/grpc/metadata"
	"google.golang.org/grpc/status"

	"github.com/gofrs/uuid"
	"github.com/spf13/cobra"

	"github.com/ory/x/cmdx"
	"github.com/ory/x/configx"
	"github.com/ory/x/httpx"
	"github.com/ory/x/logrusx"
	"github.com/ory/x/resilience"
	"github.com/ory/x/urlx"

	"github.com/ory/analytics-go/v5"
)

const (
	XForwardedHostHeader = "X-Forwarded-Host"
	AuthorityHeader      = ":authority"
)

var (
	instance     *Service
	lock         sync.Mutex
	knownHeaders = []string{AuthorityHeader, XForwardedHostHeader}
)

// Service helps with providing context on metrics.
type Service struct {
	optOut     bool
	instanceId string

	o *Options

	c analytics.Client
	l *logrusx.Logger

	mem *MemoryStatistics
}

// Hash returns a hashed string of the value.
func Hash(value string) string {
	sha := sha256.Sum256([]byte(value))
	return hex.EncodeToString(sha[:])
}

// Options configures the metrics service.
type Options struct {
	// Service represents the service name, for example "ory-hydra".
	Service string

	// DeploymentId represents the cluster id, typically a hash of some unique configuration properties.
	DeploymentId string

	// DBDialect specifies the database dialect in use (e.g., "postgres", "mysql", "sqlite").
	DBDialect string

	// When this instance was started
	StartTime time.Time

	// IsDevelopment should be true if we assume that we're in a development environment.
	IsDevelopment bool

	// WriteKey is the segment API key.
	WriteKey string

	// WhitelistedPaths represents a list of paths that can be transmitted in clear text to segment.
	WhitelistedPaths []string

	// BuildVersion represents the build version.
	BuildVersion string

	// BuildHash represents the build git hash.
	BuildHash string

	// BuildTime represents the build time.
	BuildTime string

	// Hostname is a public URL configured for the service, used to derive hosted name for telemetry.
	Hostname string

	// Config overrides the analytics.Config. If nil, sensible defaults will be used.
	Config *analytics.Config

	// MemoryInterval sets how often memory statistics should be transmitted. Defaults to every 12 hours.
	MemoryInterval time.Duration
}

type void struct{}

func (v *void) Logf(format string, args ...interface{}) {
}

func (v *void) Errorf(format string, args ...interface{}) {
}

// New returns a new metrics service. If one has been instantiated already, no new instance will be created.
func New(
	cmd *cobra.Command,
	l *logrusx.Logger,
	c *configx.Provider,
	o *Options,
) *Service {
	lock.Lock()
	defer lock.Unlock()

	if instance != nil {
		return instance
	}

	o.StartTime = time.Now()

	if o.BuildTime == "" {
		o.BuildTime = "unknown"
	}

	if o.BuildVersion == "" {
		o.BuildVersion = "unknown"
	}

	if o.BuildHash == "" {
		o.BuildHash = "unknown"
	}

	if o.Config == nil {
		o.Config = &analytics.Config{
			Interval: time.Hour * 6,
		}
	}

	o.Config.Logger = new(void)

	if o.MemoryInterval < time.Minute {
		o.MemoryInterval = time.Hour * 12
	}

	segment, err := analytics.NewWithConfig(o.WriteKey, *o.Config)
	if err != nil {
		l.WithError(err).Fatalf("Unable to initialise software quality assurance features.")
		return nil
	}

	optOut, err := cmd.Flags().GetBool("sqa-opt-out")
	if err != nil {
		cmdx.Must(err, `Unable to get command line flag "sqa-opt-out": %s`, err)
	}

	if !optOut {
		optOut = c.Bool("sqa.opt_out")
	}

	if !optOut {
		optOut = c.Bool("sqa_opt_out")
	}

	if !optOut {
		optOut, _ = strconv.ParseBool(os.Getenv("SQA_OPT_OUT"))
	}

	if !optOut {
		optOut, _ = strconv.ParseBool(os.Getenv("SQA-OPT-OUT"))
	}

	if !optOut {
		l.Info("Software quality assurance features are enabled. Learn more at: https://www.ory.com/docs/ecosystem/sqa")
	}

	m := &Service{
		optOut:     optOut,
		instanceId: uuid.Must(uuid.NewV4()).String(),
		o:          o,
		c:          segment,
		l:          l,
		mem:        new(MemoryStatistics),
	}

	instance = m

	go m.Identify()
	go m.Track()

	return m
}

// Identify enables reporting to segment.
func (sw *Service) Identify() {
	IdentifySend(sw, true)

	// User has not opt-out then make identify to be sent every 6 hours
	if !sw.optOut {
		for range time.Tick(time.Hour * 6) {
			IdentifySend(sw, false)
		}
	}
}

func IdentifySend(sw *Service, startup bool) {
	if err := resilience.Retry(sw.l, time.Minute*5, time.Hour*6, func() error {
		return sw.c.Enqueue(analytics.Identify{
			InstanceId:   sw.instanceId,
			DeploymentId: sw.o.DeploymentId,
			Project:      sw.o.Service,

			DatabaseDialect:  sw.o.DBDialect,
			ProductVersion:   sw.o.BuildVersion,
			ProductBuild:     sw.o.BuildHash,
			UptimeDeployment: 0,
			UptimeInstance:   math.Round(time.Since(sw.o.StartTime).Seconds()),
			IsDevelopment:    sw.o.IsDevelopment,
			IsOptOut:         sw.optOut,
			Startup:          startup,
		})
	}); err != nil {
		sw.l.WithError(err).Debug("Could not commit anonymized environment information")
	}
}

// Track commits memory statistics to segment.
func (sw *Service) Track() {
	if sw.optOut {
		return
	}

	for {
		sw.mem.Update()
		if err := sw.c.Enqueue(analytics.Track{
			InstanceId:   sw.instanceId,
			DeploymentId: sw.o.DeploymentId,
			Project:      sw.o.Service,

			CPU:            runtime.NumCPU(),
			OsName:         runtime.GOOS,
			OsArchitecture: runtime.GOARCH,
			Alloc:          sw.mem.Alloc,
			TotalAlloc:     sw.mem.TotalAlloc,
			Frees:          sw.mem.Frees,
			Mallocs:        sw.mem.Mallocs,
			Lookups:        sw.mem.Lookups,
			Sys:            sw.mem.Sys,
			NumGC:          sw.mem.NumGC,
			HeapAlloc:      sw.mem.HeapAlloc,
			HeapInuse:      sw.mem.HeapInuse,
			HeapIdle:       sw.mem.HeapIdle,
			HeapObjects:    sw.mem.HeapObjects,
			HeapReleased:   sw.mem.HeapReleased,
			HeapSys:        sw.mem.HeapSys,
		}); err != nil {
			sw.l.WithError(err).Debug("Could not commit anonymized telemetry data")
		}
		time.Sleep(sw.o.MemoryInterval)
	}
}

// ServeHTTP is a middleware for sending meta information to segment.
func (sw *Service) ServeHTTP(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
	var start time.Time
	if !sw.optOut {
		start = time.Now()
	}

	next(rw, r)

	if sw.optOut {
		return
	}

	latency := time.Since(start).Milliseconds()
	path := sw.anonymizePath(r.URL.Path)
	host := urlx.ExtractPublicAddress(sw.o.Hostname, r.Header.Get(XForwardedHostHeader), r.Host)

	// Collecting request info
	stat, _ := httpx.GetResponseMeta(rw)

	if err := sw.c.Enqueue(analytics.Page{
		InstanceId:     sw.instanceId,
		DeploymentId:   sw.o.DeploymentId,
		Project:        sw.o.Service,
		UrlHost:        host,
		UrlPath:        path,
		RequestCode:    stat,
		RequestLatency: int(latency),
	}); err != nil {
		sw.l.WithError(err).Debug("Could not commit anonymized telemetry data")
		// do nothing...
	}
}

func (sw *Service) UnaryInterceptor(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
	var start time.Time
	if !sw.optOut {
		start = time.Now()
	}

	resp, err := handler(ctx, req)

	if sw.optOut {
		return resp, err
	}

	latency := time.Since(start).Milliseconds()

	hosts := []string{sw.o.Hostname}
	if md, ok := metadata.FromIncomingContext(ctx); ok {
		for _, h := range knownHeaders {
			if v := md.Get(h); len(v) > 0 {
				hosts = append(hosts, v[0])
			}
		}
	}
	host := urlx.ExtractPublicAddress(hosts...)

	if err := sw.c.Enqueue(analytics.Page{
		InstanceId:     sw.instanceId,
		DeploymentId:   sw.o.DeploymentId,
		Project:        sw.o.Service,
		UrlHost:        host,
		UrlPath:        info.FullMethod,
		RequestCode:    int(status.Code(err)),
		RequestLatency: int(latency),
	}); err != nil {
		sw.l.WithError(err).Debug("Could not commit anonymized telemetry data")
		// do nothing...
	}

	return resp, err
}

func (sw *Service) WrapUnary(next connect.UnaryFunc) connect.UnaryFunc {
	return func(ctx context.Context, req connect.AnyRequest) (connect.AnyResponse, error) {
		if sw.optOut {
			return next(ctx, req)
		}

		start := time.Now()
		resp, err := next(ctx, req)
		latency := time.Since(start).Milliseconds()

		hosts := []string{sw.o.Hostname}
		for _, h := range append([]string{"Host"}, knownHeaders...) {
			if v := req.Header().Get(h); len(v) > 0 {
				hosts = append(hosts, v)
			}
		}
		host := urlx.ExtractPublicAddress(hosts...)

		if err := sw.c.Enqueue(analytics.Page{
			InstanceId:     sw.instanceId,
			DeploymentId:   sw.o.DeploymentId,
			Project:        sw.o.Service,
			UrlHost:        host,
			UrlPath:        req.Spec().Procedure,
			RequestCode:    int(status.Code(err)),
			RequestLatency: int(latency),
		}); err != nil {
			sw.l.WithError(err).Debug("Could not commit anonymized telemetry data")
			// do nothing...
		}

		return resp, err
	}
}

func (sw *Service) WrapStreamingClient(next connect.StreamingClientFunc) connect.StreamingClientFunc {
	return next
}
func (sw *Service) WrapStreamingHandler(next connect.StreamingHandlerFunc) connect.StreamingHandlerFunc {
	return next
}

func (sw *Service) StreamInterceptor(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
	// this needs a bit of thought, but we don't have streaming RPCs currently anyway
	sw.l.Info("The telemetry stream interceptor is not yet implemented!")
	return handler(srv, stream)
}

func (sw *Service) Close() error {
	return sw.c.Close()
}

func (sw *Service) anonymizePath(path string) string {
	paths := sw.o.WhitelistedPaths
	path = strings.ToLower(path)

	for _, p := range paths {
		p = strings.ToLower(p)
		if path == p {
			return p
		} else if len(path) > len(p) && path[:len(p)+1] == p+"/" {
			return p
		}
	}

	return "/"
}

func (sw *Service) anonymizeQuery(query url.Values, salt string) string {
	for _, q := range query {
		for i, s := range q {
			if s != "" {
				s = Hash(s + "|" + salt)
				q[i] = s
			}
		}
	}
	return query.Encode()
}