package dbAccess

import (
	"context"
	"errors"
	"time"

	"git.fjla.uk/owlboard/go-types/pkg/database"
	"git.fjla.uk/owlboard/timetable-mgr/log"
	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/mongo"
	"go.mongodb.org/mongo-driver/mongo/options"
	"go.uber.org/zap"
)

const Doctype = "CifMetadata"

// The type describing the CifMetadata 'type' in the database.
// This type will be moved to owlboard/go-types
type CifMetadata struct {
	Doctype        string    `bson:"type"`
	LastUpdate     time.Time `bson:"lastUpdate"`
	LastTimestamp  int64     `bson:"lastTimestamp"`
	LastSequence   int64     `bson:"lastSequence"`
	LastUpdateType string    `bson:"lastUpdateType"`
}

// Fetches the CifMetadata from the database, returns nil if no metadata exists - before first initialisation for example.
func GetCifMetadata() (*CifMetadata, error) {
	database := MongoClient.Database(DatabaseName)
	collection := database.Collection(MetaCollection)
	filter := bson.M{"type": Doctype}
	var result CifMetadata
	err := collection.FindOne(context.Background(), filter).Decode(&result)
	if err != nil {
		if errors.Is(err, mongo.ErrNoDocuments) {
			return nil, nil
		}
		return nil, err
	}

	log.Debug("Fetched CIF Metadata from database", zap.Any("Metadata", result))

	return &result, nil
}

// Uses upsert to Insert/Update the CifMetadata in the database
func PutCifMetadata(metadata *CifMetadata, lastUpdateType string) bool {
	database := MongoClient.Database(DatabaseName)
	collection := database.Collection(MetaCollection)
	options := options.Update().SetUpsert(true)
	filter := bson.M{"type": Doctype}
	update := bson.M{
		"$set": bson.M{
			"type":           Doctype,
			"lastUpdate":     metadata.LastUpdate,
			"lastTimestamp":  metadata.LastTimestamp,
			"lastSequence":   metadata.LastSequence,
			"lastUpdateType": lastUpdateType,
		},
	}

	_, err := collection.UpdateOne(context.Background(), filter, update, options)

	if err != nil {
		log.Error("Error updating CIF Metadata", zap.Error(err))
		return false
	}

	log.Info("New CIF Metadata written", zap.Time("Update time", metadata.LastUpdate))
	return true
}

// Handles 'Delete' tasks from CIF Schedule updates, accepts DeleteQuery types and batches deletions.
func DeleteCifEntries(deletions []database.DeleteQuery) error {
	defer func() {
		if r := recover(); r != nil {
			log.Panic("Panic:", zap.Any("panic", r))
		}
	}()
	// Skip if deletions is empty
	if len(deletions) == 0 {
		log.Info("No deletions required")
		return nil
	}
	log.Debug("Running deletions against database", zap.Int("count", len(deletions)))

	// Prepare deletion tasks
	collection := MongoClient.Database(DatabaseName).Collection(TimetableCollection)
	bulkDeletions := make([]mongo.WriteModel, 0, len(deletions))

	for _, deleteQuery := range deletions {
		filter := bson.M{
			"trainUid":          deleteQuery.TrainUid,
			"scheduleStartDate": deleteQuery.ScheduleStartDate,
			"stpIndicator":      deleteQuery.StpIndicator,
		}
		bulkDeletions = append(bulkDeletions, mongo.NewDeleteManyModel().SetFilter(filter))
	}

	bulkWriteOptions := options.BulkWrite().SetOrdered(false)

	_, err := collection.BulkWrite(context.Background(), bulkDeletions, bulkWriteOptions)
	if err != nil {
		return err
	}

	return nil
}

// Clears all non-vstp services from the database.  Used when a CIF full download is required.
func PurgeNonVstp() (int64, error) {
	coll := MongoClient.Database(DatabaseName).Collection(TimetableCollection)
	filter := bson.M{"serviceDetail.vstp": false}

	result, err := coll.DeleteMany(context.Background(), filter)
	if err != nil {
		return result.DeletedCount, err
	}

	return result.DeletedCount, nil
}

// Handles 'Create' tasks for CIF Schedule updates, accepts Service structs and batches their creation.
func CreateCifEntries(schedules []database.Service) error {
	// Skip if deletions is empty
	if len(schedules) == 0 {
		log.Info("No creations required")
		return nil
	}
	log.Debug("Running creations against database", zap.Int("count", len(schedules)))

	collection := MongoClient.Database(DatabaseName).Collection(TimetableCollection)

	models := make([]mongo.WriteModel, 0, len(schedules))

	for _, s := range schedules {
		model := mongo.NewInsertOneModel().SetDocument(s)
		models = append(models, model)
	}

	bulkWriteOptions := options.BulkWrite().SetOrdered(false)

	_, err := collection.BulkWrite(context.Background(), models, bulkWriteOptions)
	if err != nil {
		return err
	}

	return nil
}

// Removes any schedules which ended before 'cutoff'
func RemoveOutdatedServices(cutoff time.Time) (count int64, err error) {
	// Define filter
	filter := bson.M{"scheduleEndDate": bson.M{"$lt": cutoff}}

	collection := MongoClient.Database(DatabaseName).Collection(TimetableCollection)

	res, err := collection.DeleteMany(context.Background(), filter)
	if err != nil {
		return // Automatically returns named values
	}

	count = res.DeletedCount
	return // Automatically returns names values
}

// Creates indexes on the Timetable collection... Index suitability needs checking.
func CreateTimetableIndexes() error {
	log.Info("Creating timetable indexes")
	coll := MongoClient.Database(DatabaseName).Collection(TimetableCollection)
	indexModels := []mongo.IndexModel{
		{
			Keys: bson.D{
				{Key: "trainUid", Value: 1},
				{Key: "stpIndicator", Value: 1},
				{Key: "scheduleStartDate", Value: 1},
			},
			Options: options.Index().SetName("delete_query"),
		}, // The find by UID Query can make use of the delete_query index
		{
			Keys: bson.D{
				{Key: "headcode", Value: 1},
				{Key: "daysRun", Value: 1},
				{Key: "scheduleStartDate", Value: 1},
				{Key: "scheduleEndDate", Value: 1},
			},
			Options: options.Index().SetName("find_by_headcode"),
		},
		{
			Keys: bson.D{
				{Key: "serviceDetail.vstp", Value: 1},
			},
			Options: options.Index().SetName("vstp"),
		},
	}

	_, err := coll.Indexes().CreateMany(context.Background(), indexModels)
	if err != nil {
		return err
	}

	return nil
}