package logging

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"net/http"
	"regexp"
	"strconv"
	"strings"
	"sync"
	"time"
	"unicode/utf8"

	"cloud.google.com/go/compute/metadata"
	"cloud.google.com/go/internal/version"
	vkit "cloud.google.com/go/logging/apiv2"
	"cloud.google.com/go/logging/internal"
	"github.com/golang/protobuf/proto"
	"github.com/golang/protobuf/ptypes"
	structpb "github.com/golang/protobuf/ptypes/struct"
	tspb "github.com/golang/protobuf/ptypes/timestamp"
	"google.golang.org/api/option"
	"google.golang.org/api/support/bundler"
	mrpb "google.golang.org/genproto/googleapis/api/monitoredres"
	logtypepb "google.golang.org/genproto/googleapis/logging/type"
	logpb "google.golang.org/genproto/googleapis/logging/v2"
)

	ReadScope = "https://www.googleapis.com/auth/logging.read"

	WriteScope = "https://www.googleapis.com/auth/logging.write"

	AdminScope = "https://www.googleapis.com/auth/logging.admin"
)

	defaultErrorCapacity = 10

	DefaultDelayThreshold = time.Second

	DefaultEntryCountThreshold = 1000

	DefaultEntryByteThreshold = 1 << 20 // 1MiB

	DefaultBufferedByteLimit = 1 << 30 // 1GiB

	defaultWriteTimeout = 10 * time.Minute
)

var now = time.Now

var ErrOverflow = bundler.ErrOverflow

var ErrOversizedEntry = bundler.ErrOversizedItem

type Client struct {
	client  *vkit.Client   // client for the logging service
	parent  string         // e.g. "projects/proj-id"
	errc    chan error     // should be buffered to minimize dropped errors
	donec   chan struct{}  // closed on Client.Close to close Logger bundlers
	loggers sync.WaitGroup // so we can wait for loggers to close
	closed  bool

	mu      sync.Mutex
	nErrs   int   // number of errors we saw
	lastErr error // last error we saw

	OnError func(err error)
}

func NewClient(ctx context.Context, parent string, opts ...option.ClientOption) (*Client, error) {
	if !strings.ContainsRune(parent, '/') {
		parent = "projects/" + parent
	}
	opts = append([]option.ClientOption{
		option.WithEndpoint(internal.ProdAddr),
		option.WithScopes(WriteScope),
	}, opts...)
	c, err := vkit.NewClient(ctx, opts...)
	if err != nil {
		return nil, err
	}
	c.SetGoogleClientInfo("gccl", version.Repo)
	client := &Client{
		client:  c,
		parent:  parent,
		errc:    make(chan error, defaultErrorCapacity), // create a small buffer for errors
		donec:   make(chan struct{}),
		OnError: func(e error) { log.Printf("logging client: %v", e) },

	go func() {

			if fn := client.OnError; fn != nil {
				fn(err)
			} else {
				log.Printf("logging (parent %q): %v", parent, err)
			}
		}
	}()
	return client, nil
}

var unixZeroTimestamp *tspb.Timestamp

func init() {
	var err error
	unixZeroTimestamp, err = ptypes.TimestampProto(time.Unix(0, 0))
	if err != nil {
		panic(err)
	}
}

func (c *Client) Ping(ctx context.Context) error {
	ent := &logpb.LogEntry{
		Payload:   &logpb.LogEntry_TextPayload{TextPayload: "ping"},
		Timestamp: unixZeroTimestamp, // Identical timestamps and insert IDs are both
		InsertId:  "ping",            // necessary for the service to dedup these entries.
	}
	_, err := c.client.WriteLogEntries(ctx, &logpb.WriteLogEntriesRequest{
		LogName:  internal.LogPath(c.parent, "ping"),
		Resource: monitoredResource(c.parent),
		Entries:  []*logpb.LogEntry{ent},
	})
	return err
}

func (c *Client) error(err error) {
	select {
	case c.errc <- err:
	default:
	}
	c.mu.Lock()
	c.lastErr = err
	c.nErrs++
	c.mu.Unlock()
}

func (c *Client) extractErrorInfo() error {
	var err error
	c.mu.Lock()
	if c.lastErr != nil {
		err = fmt.Errorf("saw %d errors; last: %v", c.nErrs, c.lastErr)
		c.nErrs = 0
		c.lastErr = nil
	}
	c.mu.Unlock()
	return err
}

type Logger struct {
	client     *Client
	logName    string // "projects/{projectID}/logs/{logID}"
	stdLoggers map[Severity]*log.Logger
	bundler    *bundler.Bundler

	commonResource *mrpb.MonitoredResource
	commonLabels   map[string]string
	ctxFunc        func() (context.Context, func())
}

type LoggerOption interface {
	set(*Logger)
}

func CommonResource(r *mrpb.MonitoredResource) LoggerOption { return commonResource{r} }

type commonResource struct{ *mrpb.MonitoredResource }

func (r commonResource) set(l *Logger) { l.commonResource = r.MonitoredResource }

var detectedResource struct {
	pb   *mrpb.MonitoredResource
	once sync.Once
}

func detectResource() *mrpb.MonitoredResource {
	detectedResource.once.Do(func() {
		if !metadata.OnGCE() {
			return
		}
		projectID, err := metadata.ProjectID()
		if err != nil {
			return
		}
		id, err := metadata.InstanceID()
		if err != nil {
			return
		}
		zone, err := metadata.Zone()
		if err != nil {
			return
		}
		name, err := metadata.InstanceName()
		if err != nil {
			return
		}
		detectedResource.pb = &mrpb.MonitoredResource{
			Type: "gce_instance",
			Labels: map[string]string{
				"project_id":    projectID,
				"instance_id":   id,
				"instance_name": name,
				"zone":          zone,
			},
		}
	})
	return detectedResource.pb
}

var resourceInfo = map[string]struct{ rtype, label string }{
	"organizations":   {"organization", "organization_id"},
	"folders":         {"folder", "folder_id"},
	"projects":        {"project", "project_id"},
	"billingAccounts": {"billing_account", "account_id"},
}

func monitoredResource(parent string) *mrpb.MonitoredResource {
	parts := strings.SplitN(parent, "/", 2)
	if len(parts) != 2 {
		return globalResource(parent)
	}
	info, ok := resourceInfo[parts[0]]
	if !ok {
		return globalResource(parts[1])
	}
	return &mrpb.MonitoredResource{
		Type:   info.rtype,
		Labels: map[string]string{info.label: parts[1]},
	}
}

func globalResource(projectID string) *mrpb.MonitoredResource {
	return &mrpb.MonitoredResource{
		Type: "global",
		Labels: map[string]string{
			"project_id": projectID,
		},
	}
}

func CommonLabels(m map[string]string) LoggerOption { return commonLabels(m) }

type commonLabels map[string]string

func (c commonLabels) set(l *Logger) { l.commonLabels = c }

func ConcurrentWriteLimit(n int) LoggerOption { return concurrentWriteLimit(n) }

type concurrentWriteLimit int

func (c concurrentWriteLimit) set(l *Logger) { l.bundler.HandlerLimit = int(c) }

func DelayThreshold(d time.Duration) LoggerOption { return delayThreshold(d) }

type delayThreshold time.Duration

func (d delayThreshold) set(l *Logger) { l.bundler.DelayThreshold = time.Duration(d) }

func EntryCountThreshold(n int) LoggerOption { return entryCountThreshold(n) }

type entryCountThreshold int

func (e entryCountThreshold) set(l *Logger) { l.bundler.BundleCountThreshold = int(e) }

func EntryByteThreshold(n int) LoggerOption { return entryByteThreshold(n) }

type entryByteThreshold int

func (e entryByteThreshold) set(l *Logger) { l.bundler.BundleByteThreshold = int(e) }

func EntryByteLimit(n int) LoggerOption { return entryByteLimit(n) }

type entryByteLimit int

func (e entryByteLimit) set(l *Logger) { l.bundler.BundleByteLimit = int(e) }

func BufferedByteLimit(n int) LoggerOption { return bufferedByteLimit(n) }

type bufferedByteLimit int

func (b bufferedByteLimit) set(l *Logger) { l.bundler.BufferedByteLimit = int(b) }

func ContextFunc(f func() (ctx context.Context, afterCall func())) LoggerOption {
	return contextFunc(f)
}

type contextFunc func() (ctx context.Context, afterCall func())

func (c contextFunc) set(l *Logger) { l.ctxFunc = c }

func (c *Client) Logger(logID string, opts ...LoggerOption) *Logger {
	r := detectResource()
	if r == nil {
		r = monitoredResource(c.parent)
	}
	l := &Logger{
		client:         c,
		logName:        internal.LogPath(c.parent, logID),
		commonResource: r,
		ctxFunc:        func() (context.Context, func()) { return context.Background(), nil },
	}
	l.bundler = bundler.NewBundler(&logpb.LogEntry{}, func(entries interface{}) {
		l.writeLogEntries(entries.([]*logpb.LogEntry))
	})
	l.bundler.DelayThreshold = DefaultDelayThreshold
	l.bundler.BundleCountThreshold = DefaultEntryCountThreshold
	l.bundler.BundleByteThreshold = DefaultEntryByteThreshold
	l.bundler.BufferedByteLimit = DefaultBufferedByteLimit
	for _, opt := range opts {
		opt.set(l)
	}
	l.stdLoggers = map[Severity]*log.Logger{}
	for s := range severityName {
		l.stdLoggers[s] = log.New(severityWriter{l, s}, "", 0)
	}

	go func() {
		defer c.loggers.Done()
		<-c.donec
		l.bundler.Flush()
	}()
	return l
}

type severityWriter struct {
	l *Logger
	s Severity
}

func (w severityWriter) Write(p []byte) (n int, err error) {
	w.l.Log(Entry{
		Severity: w.s,
		Payload:  string(p),
	})
	return len(p), nil
}

func (c *Client) Close() error {
	if c.closed {
		return nil
	}
	close(c.donec)   // close Logger bundlers

	err := c.extractErrorInfo()
	err2 := c.client.Close()
	if err == nil {
		err = err2
	}
	c.closed = true
	return err
}

type Severity int

	Emergency = Severity(logtypepb.LogSeverity_EMERGENCY)
)

var severityName = map[Severity]string{
	Default:   "Default",
	Debug:     "Debug",
	Info:      "Info",
	Notice:    "Notice",
	Warning:   "Warning",
	Error:     "Error",
	Critical:  "Critical",
	Alert:     "Alert",
	Emergency: "Emergency",
}

	s, ok := severityName[v]
	if ok {
		return s
	}
	return strconv.Itoa(int(v))
}

func ParseSeverity(s string) Severity {
	sl := strings.ToLower(s)
	for sev, name := range severityName {
		if strings.ToLower(name) == sl {
			return sev
		}
	}
	return Default
}

	Timestamp time.Time

	Severity Severity

	Payload interface{}

	Labels map[string]string

	InsertID string

	HTTPRequest *HTTPRequest

	Operation *logpb.LogEntryOperation

	LogName string

	Resource *mrpb.MonitoredResource

	Trace string

	SpanID string

	TraceSampled bool

	SourceLocation *logpb.LogEntrySourceLocation
}

	Request *http.Request

	RequestSize int64

	Status int

	ResponseSize int64

	Latency time.Duration

	LocalIP string

	RemoteIP string

	CacheHit bool

	CacheValidatedWithOriginServer bool
}

func fromHTTPRequest(r *HTTPRequest) *logtypepb.HttpRequest {
	if r == nil {
		return nil
	}
	if r.Request == nil {
		panic("HTTPRequest must have a non-nil Request")
	}
	u := *r.Request.URL
	u.Fragment = ""
	pb := &logtypepb.HttpRequest{
		RequestMethod:                  r.Request.Method,
		RequestUrl:                     fixUTF8(u.String()),
		RequestSize:                    r.RequestSize,
		Status:                         int32(r.Status),
		ResponseSize:                   r.ResponseSize,
		UserAgent:                      r.Request.UserAgent(),
		ServerIp:                       r.LocalIP,
		RemoteIp:                       r.RemoteIP, // TODO(jba): attempt to parse http.Request.RemoteAddr?
		Referer:                        r.Request.Referer(),
		CacheHit:                       r.CacheHit,
		CacheValidatedWithOriginServer: r.CacheValidatedWithOriginServer,
	}
	if r.Latency != 0 {
		pb.Latency = ptypes.DurationProto(r.Latency)
	}
	return pb
}

func fixUTF8(s string) string {
	if utf8.ValidString(s) {
		return s
	}

	buf := new(bytes.Buffer)
	buf.Grow(len(s))
	for _, r := range s {
		if utf8.ValidRune(r) {
			buf.WriteRune(r)
		} else {
			buf.WriteRune('\uFFFD')
		}
	}
	return buf.String()
}

	if s, ok := v.(*structpb.Struct); ok {
		return s, nil

	var jb []byte
	var err error
	if raw, ok := v.(json.RawMessage); ok { // needed for Go 1.7 and below
		jb = []byte(raw)
	} else {
		jb, err = json.Marshal(v)
		if err != nil {
			return nil, fmt.Errorf("logging: json.Marshal: %v", err)
		}
	}
	var m map[string]interface{}
	err = json.Unmarshal(jb, &m)
	if err != nil {
		return nil, fmt.Errorf("logging: json.Unmarshal: %v", err)
	}
	return jsonMapToProtoStruct(m), nil
}

func jsonMapToProtoStruct(m map[string]interface{}) *structpb.Struct {
	fields := map[string]*structpb.Value{}
	for k, v := range m {
		fields[k] = jsonValueToStructValue(v)
	}
	return &structpb.Struct{Fields: fields}
}

func jsonValueToStructValue(v interface{}) *structpb.Value {
	switch x := v.(type) {
	case bool:
		return &structpb.Value{Kind: &structpb.Value_BoolValue{BoolValue: x}}
	case float64:
		return &structpb.Value{Kind: &structpb.Value_NumberValue{NumberValue: x}}
	case string:
		return &structpb.Value{Kind: &structpb.Value_StringValue{StringValue: x}}
	case nil:
		return &structpb.Value{Kind: &structpb.Value_NullValue{}}
	case map[string]interface{}:
		return &structpb.Value{Kind: &structpb.Value_StructValue{StructValue: jsonMapToProtoStruct(x)}}
	case []interface{}:
		var vals []*structpb.Value
		for _, e := range x {
			vals = append(vals, jsonValueToStructValue(e))
		}
		return &structpb.Value{Kind: &structpb.Value_ListValue{ListValue: &structpb.ListValue{Values: vals}}}
	default:
		panic(fmt.Sprintf("bad type %T for JSON value", v))
	}
}

func (l *Logger) LogSync(ctx context.Context, e Entry) error {
	ent, err := l.toLogEntry(e)
	if err != nil {
		return err
	}
	_, err = l.client.client.WriteLogEntries(ctx, &logpb.WriteLogEntriesRequest{
		LogName:  l.logName,
		Resource: l.commonResource,
		Labels:   l.commonLabels,
		Entries:  []*logpb.LogEntry{ent},
	})
	return err
}

func (l *Logger) Log(e Entry) {
	ent, err := l.toLogEntry(e)
	if err != nil {
		l.client.error(err)
		return
	}
	if err := l.bundler.Add(ent, proto.Size(ent)); err != nil {
		l.client.error(err)
	}
}

func (l *Logger) Flush() error {
	l.bundler.Flush()
	return l.client.extractErrorInfo()
}

func (l *Logger) writeLogEntries(entries []*logpb.LogEntry) {
	req := &logpb.WriteLogEntriesRequest{
		LogName:  l.logName,
		Resource: l.commonResource,
		Labels:   l.commonLabels,
		Entries:  entries,
	}
	ctx, afterCall := l.ctxFunc()
	ctx, cancel := context.WithTimeout(ctx, defaultWriteTimeout)
	defer cancel()
	_, err := l.client.client.WriteLogEntries(ctx, req)
	if err != nil {
		l.client.error(err)
	}
	if afterCall != nil {
		afterCall()
	}
}

func (l *Logger) StandardLogger(s Severity) *log.Logger { return l.stdLoggers[s] }

var reCloudTraceContext = regexp.MustCompile(`([a-f\d]+)/([a-f\d]+);o=(\d)`)

	matches := reCloudTraceContext.FindAllStringSubmatch(s, -1)
	if len(matches) != 1 {
		return
	}

	sub := matches[0]
	if len(sub) != 4 {
		return
	}

	traceID, spanID = sub[1], sub[2]
	if spanID == "0" {
		spanID = ""
	}
	traceSampled = sub[3] == "1"

	return
}

func (l *Logger) toLogEntry(e Entry) (*logpb.LogEntry, error) {
	if e.LogName != "" {
		return nil, errors.New("logging: Entry.LogName should be not be set when writing")
	}
	t := e.Timestamp
	if t.IsZero() {
		t = now()
	}
	ts, err := ptypes.TimestampProto(t)
	if err != nil {
		return nil, err
	}
	if e.Trace == "" && e.HTTPRequest != nil && e.HTTPRequest.Request != nil {
		traceHeader := e.HTTPRequest.Request.Header.Get("X-Cloud-Trace-Context")

			traceID, spanID, traceSampled := deconstructXCloudTraceContext(traceHeader)
			if traceID != "" {
				e.Trace = fmt.Sprintf("%s/traces/%s", l.client.parent, traceID)
			}
			if e.SpanID == "" {
				e.SpanID = spanID
			}

			e.TraceSampled = e.TraceSampled || traceSampled
		}
	}
	ent := &logpb.LogEntry{
		Timestamp:      ts,
		Severity:       logtypepb.LogSeverity(e.Severity),
		InsertId:       e.InsertID,
		HttpRequest:    fromHTTPRequest(e.HTTPRequest),
		Operation:      e.Operation,
		Labels:         e.Labels,
		Trace:          e.Trace,
		SpanId:         e.SpanID,
		Resource:       e.Resource,
		SourceLocation: e.SourceLocation,
		TraceSampled:   e.TraceSampled,
	}
	switch p := e.Payload.(type) {
	case string:
		ent.Payload = &logpb.LogEntry_TextPayload{TextPayload: p}
	default:
		s, err := toProtoStruct(p)
		if err != nil {
			return nil, err
		}
		ent.Payload = &logpb.LogEntry_JsonPayload{JsonPayload: s}
	}
	return ent, nil