package orm

import (
	context2 "context"
	"fmt"
	"log"
	"reflect"
	"sync"

	"github.com/fatih/structtag"
	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/bson/primitive"
	"go.mongodb.org/mongo-driver/mongo"
	"go.mongodb.org/mongo-driver/mongo/options"
	"golang.org/x/net/context"
)

// Reference stores a typed document reference
type Reference struct {
	// owning model name
	Model string
	// the name of the struct field
	FieldName string
	// index of field in owning struct
	Idx int
	// the type of the referenced object
	HydratedType reflect.Type

	// field kind (struct, slice, ...)
	Kind reflect.Kind

	exists bool
}

type gridFSReference struct {
	BucketName  string
	FilenameFmt string
	LoadType    reflect.Type
	Idx         int
}

type TModelRegistry map[string]*Model

// ModelRegistry - the ModelRegistry stores a map containing
// pointers to Model instances, keyed by an associated
// model name
var ModelRegistry = make(TModelRegistry)

// DB - The mongodb database handle
var DB *mongo.Database

// DBClient - The mongodb client
var DBClient *mongo.Client

// NextStringID - Override this function with your own
// string ID generator!
var NextStringID func() string

var mutex sync.Mutex

func makeGfsRef(tag *structtag.Tag, idx int) gridFSReference {
	opts := tag.Options
	var ffmt string
	if len(opts) < 1 {
		ffmt = "%s"
	} else {
		ffmt = opts[0]
	}
	var typ reflect.Type
	if len(opts) < 2 {
		typ = reflect.TypeOf("")
	} else {
		switch opts[1] {
		case "bytes":
			typ = reflect.TypeOf([]byte{})
		case "string":
			typ = reflect.TypeOf("")
		default:
			typ = reflect.TypeOf("")
		}
	}

	return gridFSReference{
		FilenameFmt: ffmt,
		BucketName:  tag.Name,
		LoadType:    typ,
		Idx:         idx,
	}
}

func makeRef(idx int, modelName string, fieldName string, ht reflect.Type) Reference {
	if modelName != "" {
		if ModelRegistry.Index(modelName) != -1 {
			return Reference{
				Idx:          idx,
				Model:        modelName,
				HydratedType: ht,
				Kind:         ht.Kind(),
				exists:       true,
				FieldName:    fieldName,
			}
		}
		return Reference{
			Idx:          idx,
			Model:        modelName,
			FieldName:    fieldName,
			HydratedType: ht,
			Kind:         ht.Kind(),
			exists:       true,
		}
	}
	panic("model name was empty")
}

func parseTags(t reflect.Type, v reflect.Value) (map[string][]InternalIndex, map[string]Reference, map[string]gridFSReference, string) {
	coll := ""
	refs := make(map[string]Reference)
	idcs := make(map[string][]InternalIndex)
	gfsRefs := make(map[string]gridFSReference)

	for i := 0; i < v.NumField(); i++ {
		sft := t.Field(i)
		ft := sft.Type
		tags, err := structtag.Parse(string(sft.Tag))
		panik(err)
		shouldContinue := true
		for {
			if !shouldContinue {
				break
			}
			switch ft.Kind() {
			case reflect.Slice:
				ft = ft.Elem()
				if _, ok := tags.Get("ref"); ok != nil {
					if ft.Kind() == reflect.Struct {
						ii2, rr2, gg2, _ := parseTags(ft, reflect.New(ft).Elem())
						for k, vv := range ii2 {
							idcs[sft.Name+"."+k] = vv
						}
						for k, vv := range rr2 {
							refs[sft.Name+"."+k] = vv
						}
						for k, vv := range gg2 {
							gfsRefs[sft.Name+"."+k] = vv
						}
					}
				}
				continue
			case reflect.Pointer:
				ft = ft.Elem()
				fallthrough
			case reflect.Struct:
				if ft.ConvertibleTo(reflect.TypeOf(Document{})) {
					collTag, err := tags.Get("coll")
					panik(err)
					coll = collTag.Name
					idxTag, err := tags.Get("idx")
					if err == nil {
						idcs[sft.Type.Name()] = scanIndex(idxTag.Value())
					}
					shouldContinue = false
					break
				}
				if refTag, ok := tags.Get("ref"); ok == nil {
					sname := sft.Name + "@" + refTag.Name
					refs[sname] = makeRef(i, refTag.Name, sft.Name, sft.Type)
				}
				if gtag, ok := tags.Get("gridfs"); ok == nil {
					sname := sft.Name + "@" + gtag.Name
					gfsRefs[sname] = makeGfsRef(gtag, i)
				}
				fallthrough
			default:
				idxTag, err := tags.Get("idx")
				if err == nil {
					idcs[sft.Name] = scanIndex(idxTag.Value())
				}
				if gtag, ok := tags.Get("gridfs"); ok == nil {
					sname := sft.Name + "@" + gtag.Name
					gfsRefs[sname] = makeGfsRef(gtag, i)
				}
				shouldContinue = false
			}

		}
	}
	return idcs, refs, gfsRefs, coll
}

// Has returns the model typename and Model instance corresponding
// to the argument passed, as well as a boolean indicating whether it
// was found. otherwise returns `"", nil, false`
func (r TModelRegistry) Has(i interface{}) (string, *Model, bool) {
	t := reflect.TypeOf(i)
	if t.Kind() == reflect.Ptr {
		t = t.Elem()
	}
	n := t.Name()
	if rT, ok := ModelRegistry[n]; ok {
		return n, rT, true
	}
	return "", nil, false
}

// HasByName functions almost identically to Has,
// except that it takes a string as its argument.
func (r TModelRegistry) HasByName(n string) (string, *Model, bool) {
	if t, ok := ModelRegistry[n]; ok {
		return n, t, true
	}
	return "", nil, false
}

// Index returns the index at which the Document struct is embedded
func (r TModelRegistry) Index(n string) int {
	if v, ok := ModelRegistry[n]; ok {
		return v.idx
	}
	return -1
}

func (r TModelRegistry) new_(n string) interface{} {
	if name, m, ok := ModelRegistry.HasByName(n); ok {
		v := reflect.New(m.Type)
		df := v.Elem().Field(m.idx)
		do := reflect.New(df.Type())
		d := do.Interface().(IDocument)
		//d := df.Interface().(IDocument)
		d.setModel(*m)
		d.getModel().typeName = name
		df.Set(reflect.ValueOf(d).Elem())
		return v.Interface()
	}
	return nil
}

// Model registers models in the ModelRegistry, where
// they can be accessed via a model's struct name
func (r TModelRegistry) Model(mdl ...any) {
	defer mutex.Unlock()
	mutex.Lock()

	for _, m := range mdl {
		t := reflect.TypeOf(m)
		v := reflect.ValueOf(m)
		vp := v
		if vp.Kind() != reflect.Ptr {
			vp = reflect.New(v.Type())
			vp.Elem().Set(v)
		}
		id, ok := vp.Interface().(HasID)
		if !ok {
			panic(fmt.Sprintf("you MUST implement the HasID interface!!! skipping...\n"))
		}
		switch (id).Id().(type) {
		case int, int64, int32, string, primitive.ObjectID, uint, uint32, uint64:
			break
		default:
			log.Printf("invalid ID type specified!!! skipping...\n")
		}

		if t.Kind() == reflect.Ptr {
			t = reflect.Indirect(reflect.ValueOf(m)).Type()
			v = reflect.ValueOf(m).Elem()
		}
		n := t.Name()
		if t.Kind() != reflect.Struct {
			panic(fmt.Sprintf("Only structs can be passed to this function, silly! (passed type: %s)", n))
		}
		idx := -1
		for i := 0; i < v.NumField(); i++ {
			ft := t.Field(i)
			if (ft.Type.ConvertibleTo(reflect.TypeOf(Document{}))) {
				idx = i
				break
			}
		}
		if idx < 0 {
			panic("A model must embed the Document struct!")
		}
		inds, refs, gfs, coll := parseTags(t, v)
		if coll == "" {
			panic(fmt.Sprintf("a Document needs to be given a collection name! (passed type: %s)", n))
		}
		ModelRegistry[n] = &Model{
			idx:              idx,
			Type:             t,
			collection:       coll,
			Indexes:          inds,
			references:       refs,
			gridFSReferences: gfs,
		}
	}
	for k, v := range ModelRegistry {
		for k2, v2 := range v.references {
			if !v2.exists {
				if _, ok := ModelRegistry[v2.FieldName]; ok {
					tmp := ModelRegistry[k].references[k2]
					ModelRegistry[k].references[k2] = Reference{
						Model:        k,
						Idx:          tmp.Idx,
						FieldName:    tmp.FieldName,
						Kind:         tmp.Kind,
						HydratedType: tmp.HydratedType,
						exists:       true,
					}
				}
			}
		}
	}
}

func innerWatch(coll *mongo.Collection) {
	sspipeline := mongo.Pipeline{
		bson.D{{"$match", bson.D{{"$or",
			bson.A{
				bson.D{{
					"operationType", "insert",
				}},
				bson.D{{"operationType", "update"}},
			},
		}},
		}},
	}

	stream, err := coll.Watch(context.TODO(), sspipeline, options.ChangeStream().SetFullDocument(options.UpdateLookup).SetFullDocumentBeforeChange(options.WhenAvailable))
	panik(err)
	defer func(stream *mongo.ChangeStream, ctx context2.Context) {
		err := stream.Close(ctx)
		panik(err)
	}(stream, context.TODO())
	for stream.Next(context.TODO()) {
		var data bson.M
		if err := stream.Decode(&data); err != nil {
			log.Fatal(err)
		}

		var uid = data["documentKey"].(bson.M)["_id"]

		if data["operationType"] == "insert" {
			counterColl := DB.Collection(COUNTER_COL)
			counterColl.UpdateOne(context.TODO(), bson.M{"collection": coll.Name()}, bson.M{"$set": bson.M{
				"current": uid,
			}}, options.Update().SetUpsert(true))
		}

		fmt.Printf("%v\n", data)
	}
}

func Connect(uri string, dbName string) {
	cli, err := mongo.Connect(context.TODO(), options.Client().ApplyURI(uri))
	if err != nil {
		log.Fatal("failed to open database")
	}
	panik(err)
	DB = cli.Database(dbName)
	colls, err := DB.ListCollectionNames(context.TODO(), bson.M{"name": bson.M{"$ne": COUNTER_COL}}, options.ListCollections().SetNameOnly(true))

	for _, c := range colls {
		if c == COUNTER_COL {
			continue
		}
		go innerWatch(DB.Collection(c))
	}

	DBClient = cli
}