package mgocrud

import (
	"fmt"
	"reflect"
	"runtime/debug"
	"strings"
	"time"

	mgo "gopkg.in/mgo.v2"
	"gopkg.in/mgo.v2/bson"
)

// ErrorWithStack is error which stored its stack trace
type ErrorWithStack struct {
	Message    string
	StackTrace string
}

// Error returns error message
func (e *ErrorWithStack) Error() string {
	return e.Message
}

// Stack returns strack trace to error origin
func (e *ErrorWithStack) Stack() string {
	return e.StackTrace
}

// CreateDocument creates a document from specified model
func CreateDocument(db *mgo.Database, m ModelInterface) error {
	m.PrepareInsert()

	c := db.C(GetCollectionName(m))
	err := c.Insert(m)

	return err
}

// ReadDocument gets one document via its id
func ReadDocument(db *mgo.Database, m ModelInterface, selector bson.M) error {
	c := db.C(GetCollectionName(m))

	q := c.FindId(m.GetID())
	if selector != nil {
		q = q.Select(selector)
	}
	err := q.One(m)

	return err
}

// PipelineModifierFunction is a function to modify mongodb query
type PipelineModifierFunction func(pipeline []bson.M) []bson.M

func convertIDValue(v reflect.Value) reflect.Value {
	v = reflect.ValueOf(v.Interface())
	vKind := v.Kind() // mapVal.Kind() does not work, no idea why ;(
	//spew.Dump(v.Interface())
	//spew.Dump(vKind)

	switch vKind {
	case reflect.String:
		if hex, ok := v.Interface().(string); ok {
			return reflect.ValueOf(bson.ObjectIdHex(hex))
		}
	case reflect.Map:
		for _, key := range v.MapKeys() {
			v.SetMapIndex(key, convertIDValue(v.MapIndex(key)))
		}
	case reflect.Slice:
		for i := 0; i < v.Len(); i++ {
			v.Index(i).Set(convertIDValue(v.Index(i)))
		}
	}

	return v
}

func idToObjectID(filter interface{}) {
	if filter == nil {
		return
	}
	//spew.Dump(filter)
	val := reflect.ValueOf(filter)
	switch reflect.TypeOf(filter).Kind() {
	case reflect.Slice:
		for i := 0; i < val.Len(); i++ {
			idToObjectID(val.Index(i).Interface())
		}
	case reflect.Ptr:
		idToObjectID(reflect.Indirect(val).Interface())
	case reflect.Map:
		for _, key := range val.MapKeys() {
			if k, ok := key.Interface().(string); ok {
				mapVal := val.MapIndex(key)
				if mapVal.Type().Kind() == reflect.Ptr {
					mapVal = reflect.Indirect(mapVal)
				}
				if k == "_id" {
					val.SetMapIndex(key, convertIDValue(mapVal))
				} else {
					idToObjectID(mapVal.Interface())
				}
			}
		}
	}

	/*
		for key, data := range filter {
			if key == "_id" {
				if hex, ok := data.(string); ok {
					filter[key] = bson.ObjectIdHex(hex)
				}
			} else {
				switch d := data.(type) {
				case map[string]interface{}:
					idToObjectID(d)
				case bson.M:
					idToObjectID(d)
				case []map[string]interface{}:
					for _, s := range d {
						idToObjectID(s)
					}
				case []bson.M:
					for _, s := range d {
						idToObjectID(s)
					}
				case []interface{}:
					for _, s := range d {
						isToObjectID(s)
					}
				}
			}
		}
	*/
}

// ReadCollection gets the filtered collection of the model
func ReadCollection(db *mgo.Database, results interface{}, filter bson.M, selector bson.M, offset int, limit int, sort []string, pipelineModifier PipelineModifierFunction) (err error) {
	defer func() {
		if r := recover(); r != nil {
			err = &ErrorWithStack{Message: fmt.Sprintf("%v", r), StackTrace: string(debug.Stack())}
		}
	}()

	mSlice := reflect.Indirect(reflect.ValueOf(results)) // results is *[]ModelInterface, so we need to indirect
	var m ModelInterface
	if mSlice.Len() > 0 {
		// use existing first element
		m = mSlice.Index(0).Interface().(ModelInterface)
	} else {
		// create new element to get collection name
		m = reflect.New(reflect.TypeOf(mSlice.Interface()).Elem()).Interface().(ModelInterface)
	}

	/*
		// get pointer to model (element of slice in results) to get collection name
		m := reflect.New(reflect.TypeOf(
			reflect.Indirect(reflect.ValueOf(results)).Interface(), // get indirection of slice pointer
		).Elem()).Interface().(ModelInterface) // it must be a ModelInterface here
	*/

	c := db.C(GetCollectionName(m))

	var _err error

	if pipelineModifier != nil {
		// search via pipeline

		pipeline := []bson.M{}

		if filter != nil {
			pipeline = append(pipeline, bson.M{
				"$match": filter,
			})
		}

		if len(sort) > 0 {
			sortM := bson.M{}
			for _, s := range sort {
				if strings.HasPrefix(s, "-") {
					s = s[1:]
					sortM[s] = -1
				} else {
					sortM[s] = 1
				}
			}
			// spew.Dump(sortM)
			pipeline = append(pipeline, bson.M{
				"$sort": sortM,
			})
		}

		if offset > 0 {
			pipeline = append(pipeline, bson.M{
				"$skip": offset,
			})
		}
		if limit > 0 {
			pipeline = append(pipeline, bson.M{
				"$limit": limit,
			})
		}
		if selector != nil {
			pipeline = append(pipeline, bson.M{
				"$project": selector,
			})
		}

		if pipelineModifier != nil {
			pipeline = pipelineModifier(pipeline)
		}

		q := c.Pipe(pipeline).AllowDiskUse().Iter()
		_err = q.All(results)
	} else {
		// search without pipe is faster

		idToObjectID(filter)

		// spew.Dump(filter)

		q := c.Find(filter)
		if selector != nil {
			q = q.Select(selector)
		}
		if len(sort) > 0 {
			q = q.Sort(sort...)
		}
		if offset > 0 {
			q = q.Skip(offset)
		}
		if limit > 0 {
			q = q.Limit(limit)
		}

		_err = q.All(results)
	}

	if _err != nil {
		return &ErrorWithStack{Message: _err.Error(), StackTrace: string(debug.Stack())}
	}
	return nil
}

// ReadCollectionCount gets the count of elements in filtered collection
func ReadCollectionCount(db *mgo.Database, m ModelInterface, filter bson.M) (count int, err error) {
	defer func() {
		if r := recover(); r != nil {
			err = fmt.Errorf("%v", r)
		}
	}()

	c := db.C(GetCollectionName(m))
	return c.Find(filter).Count()
}

// UpdateDocument updates a document from specified model
func UpdateDocument(db *mgo.Database, m ModelInterface, changes bson.M) error {
	m.PrepareUpdate()
	changes["updateTime"] = time.Now()

	c := db.C(GetCollectionName(m))
	err := c.UpdateId(m.GetID(), bson.M{"$set": changes})

	return err
}

// UpsertDocument updates a document from specified model or inserts it, of not found
func UpsertDocument(db *mgo.Database, m ModelInterface, changes bson.M) error {
	m.PrepareUpdate()
	changes["updateTime"] = time.Now()

	c := db.C(GetCollectionName(m))
	_, err := c.Upsert(m, bson.M{"$set": changes})

	return err
}

// DeleteDocument deletes one document via its id
func DeleteDocument(db *mgo.Database, m ModelInterface) error {
	c := db.C(GetCollectionName(m))

	err := c.RemoveId(m.GetID())

	return err
}

// DeleteDocuments deletes documents found by filter
func DeleteDocuments(db *mgo.Database, m ModelInterface, filter bson.M) (removed int, err error) {
	c := db.C(GetCollectionName(m))

	info, err := c.RemoveAll(filter)
	if info != nil {
		removed = info.Removed
	}

	return removed, err
}