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"`
}

// 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
		}
		log.Msg.Error("Error fetching CIF Metadata")
		return nil, err
	}

	log.Msg.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) 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,
		},
	}

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

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

	log.Msg.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 {
	// Skip if deletions is empty
	if len(deletions) == 0 {
		log.Msg.Info("No deletions required")
		return nil
	}

	// 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))
	}

	_, err := collection.BulkWrite(context.Background(), bulkDeletions)
	if err != nil {
		log.Msg.Error("Error deleting documents", zap.Error(err))
		return err
	}

	return 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.Msg.Info("No creations required")
		return nil
	}

	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 {
		log.Msg.Error("Error inserting documents", zap.Error(err))
		return err
	}

	return nil
}