package orm

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"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/gridfs"
	"go.mongodb.org/mongo-driver/mongo/options"
	"html/template"
	"io"
	"reflect"
	"strings"
)

type GridFSFile struct {
	ID     primitive.ObjectID `bson:"_id"`
	Name   string             `bson:"filename"`
	Length int                `bson:"length"`
}

func parseFmt(format string, value any) string {
	tmpl, err := template.New("filename").Parse(format)
	panik(err)
	w := new(strings.Builder)
	err = tmpl.Execute(w, value)
	panik(err)
	return w.String()
}

func bucket(gfsRef gridFSReference) *gridfs.Bucket {
	b, _ := gridfs.NewBucket(DB, options.GridFSBucket().SetName(gfsRef.BucketName))
	return b
}

func gridFsLoad(val any, g gridFSReference, field string) any {
	doc := reflect.ValueOf(val)
	rdoc := reflect.ValueOf(val)
	if doc.Kind() != reflect.Pointer {
		doc = reflect.New(reflect.TypeOf(val))
		doc.Elem().Set(reflect.ValueOf(val))
	}
	var next string
	if len(strings.Split(field, ".")) > 1 {
		next = strings.Join(strings.Split(field, ".")[1:], ".")
		field = strings.Split(field, ".")[0]
	} else {
		next = field
	}
	_, rfield, ferr := getNested(field, rdoc)
	if ferr != nil {
		return nil
	}
	switch rfield.Kind() {
	case reflect.Slice:
		for i := 0; i < rfield.Len(); i++ {
			cur := rfield.Index(i)
			if cur.Kind() != reflect.Pointer {
				tmp := reflect.New(cur.Type())
				tmp.Elem().Set(cur)
				cur = tmp
			}
			intermediate := gridFsLoad(cur.Interface(), g, next)
			if intermediate == nil {
				continue
			}
			ival := reflect.ValueOf(intermediate)
			if ival.Kind() == reflect.Pointer {
				ival = ival.Elem()
			}
			rfield.Index(i).Set(ival)
		}
	case reflect.Struct:

		intermediate := gridFsLoad(rfield.Interface(), g, next)
		if intermediate != nil {
			rfield.Set(reflect.ValueOf(intermediate))
		}
	default:
		b := bucket(g)
		var found GridFSFile
		cursor, err := b.Find(bson.M{"filename": parseFmt(g.FilenameFmt, val)})
		if err != nil {
			return nil
		}
		cursor.Next(context.TODO())
		_ = cursor.Decode(&found)
		bb := bytes.NewBuffer(nil)
		_, err = b.DownloadToStream(found.ID, bb)
		if err != nil {
			return nil
		}
		if rfield.Type().AssignableTo(reflect.TypeFor[[]byte]()) {
			rfield.Set(reflect.ValueOf(bb.Bytes()))
		} else if rfield.Type().AssignableTo(reflect.TypeFor[string]()) {
			rfield.Set(reflect.ValueOf(bb.String()))
		}

	}
	if rdoc.Kind() != reflect.Pointer {
		return doc.Elem().Interface()
	}
	return doc.Interface()
}

func gridFsSave(val any, imodel Model) error {
	var rerr error
	v := reflect.ValueOf(val)
	el := v
	if v.Kind() == reflect.Pointer {
		el = el.Elem()
	}

	switch el.Kind() {
	case reflect.Struct:
		for i := 0; i < el.NumField(); i++ {
			ft := el.Type().Field(i)
			fv := el.Field(i)
			if !ft.IsExported() {
				continue
			}
			_, err := structtag.Parse(string(ft.Tag))
			panik(err)
			var gfsRef *gridFSReference
			for kk, vv := range imodel.gridFSReferences {
				if strings.HasPrefix(kk, ft.Name) {
					gfsRef = &vv
					break
				}
			}
			var inner = func(b *gridfs.Bucket, it reflect.Value) error {
				filename := parseFmt(gfsRef.FilenameFmt, it.Interface())
				contents := GridFSFile{}
				curs, err2 := b.Find(bson.M{"filename": filename})

				if !errors.Is(err2, mongo.ErrNoDocuments) {
					_ = curs.Decode(&contents)
					if !reflect.ValueOf(contents).IsZero() {
						_ = b.Delete(contents.ID)
					}
				}
				c := it.Field(gfsRef.Idx)
				var rdr io.Reader

				if c.Type().AssignableTo(reflect.TypeOf([]byte{})) {
					rdr = bytes.NewReader(c.Interface().([]byte))
				} else if c.Type().AssignableTo(reflect.TypeOf("")) {
					rdr = strings.NewReader(c.Interface().(string))
				} else {
					return fmt.Errorf("gridfs loader type '%s' not supported", c.Type().String())
				}
				_, err = b.UploadFromStream(filename, rdr)
				return err
			}

			if gfsRef != nil {
				b := bucket(*gfsRef)
				if fv.Kind() == reflect.Slice {
					for j := 0; j < fv.Len(); j++ {
						lerr := inner(b, fv.Index(j))
						if lerr != nil {
							return lerr
						}
					}
				} else if fv.Kind() == reflect.Struct {
					lerr := inner(b, fv)
					if lerr != nil {
						return lerr
					}
				} else {
					lerr := inner(b, el)
					if lerr != nil {
						return lerr
					}
				}
			}
			err = gridFsSave(fv.Interface(), imodel)
			if err != nil {
				return err
			}
		}
	case reflect.Slice:
		for i := 0; i < el.Len(); i++ {
			rerr = gridFsSave(el.Index(i).Interface(), imodel)
			if rerr != nil {
				return rerr
			}
		}
	default:
		break
	}
	return rerr
}