package db

import (
	"htwkalender/model"

	"github.com/pocketbase/dbx"
	"github.com/pocketbase/pocketbase"
)

func SaveEvents(seminarGroup []model.SeminarGroup, app *pocketbase.PocketBase) ([]model.Event, error) {
	var toBeSavedEvents model.Events
	var savedRecords model.Events

	// check if event is already in database and add to toBeSavedEvents if not
	for _, seminarGroup := range seminarGroup {
		for _, event := range seminarGroup.Events {
			event = event.SetCourse(seminarGroup.Course)
			existsInDatabase, err := findEventByDayWeekStartEndNameCourse(event, seminarGroup.Course, app)
			alreadyAddedToSave := toBeSavedEvents.Contains(event)

			if err != nil {
				return nil, err
			}

			if !existsInDatabase && !alreadyAddedToSave {
				toBeSavedEvents = append(toBeSavedEvents, event)
			}
		}
	}

	// create record for each event that's not already in the database
	for _, event := range toBeSavedEvents {
		event.MarkAsNew()
		// auto mapping for event fields to record fields
		err := app.Dao().Save(&event)
		if err != nil {
			return nil, err
		} else {
			savedRecords = append(savedRecords, event)
		}
	}

	return savedRecords, nil
}

// check if event is already in database and return true if it is and false if it's not
func findEventByDayWeekStartEndNameCourse(event model.Event, course string, app *pocketbase.PocketBase) (bool, error) {

	var dbEvent model.Event

	err := app.Dao().DB().Select("*").From("events").
		Where(dbx.NewExp(
			"Day = {:day} AND "+
				"Week = {:week} AND "+
				"Start = {:start} AND "+
				"End = {:end} AND "+
				"Name = {:name} AND "+
				"course = {:course} AND "+
				"Prof = {:prof} AND "+
				"Rooms = {:rooms} AND "+
				"EventType = {:eventType}",
			dbx.Params{
				"day":       event.Day,
				"week":      event.Week,
				"start":     event.Start,
				"end":       event.End,
				"name":      event.Name,
				"course":    course,
				"prof":      event.Prof,
				"rooms":     event.Rooms,
				"eventType": event.EventType}),
		).One(&dbEvent)

	if err != nil {
		if err.Error() == "sql: no rows in result set" {
			return false, nil
		}
		return false, err
	} else {
		return true, nil
	}
}

func buildIcalQueryForModules(modules []model.FeedCollection) dbx.Expression {

	// build where conditions for each module

	//first check if modules is empty
	if len(modules) == 0 {
		return dbx.HashExp{}
	}

	//second check if modules has only one element
	if len(modules) == 1 {
		return dbx.And(
			dbx.HashExp{"Name": modules[0].Name},
			dbx.HashExp{"course": modules[0].Course},
		)
	}

	//third check if modules has more than one element
	var wheres []dbx.Expression

	for _, module := range modules {
		where := dbx.And(
			dbx.HashExp{"Name": module.Name},
			dbx.HashExp{"course": module.Course},
		)
		wheres = append(wheres, where)
	}

	// Use dbx.And or dbx.Or to combine the where conditions as needed
	where := dbx.Or(wheres...)

	return where

}

// GetPlanForModules returns all events for the given modules with the given course
// used for the ical feed
func GetPlanForModules(app *pocketbase.PocketBase, modules []model.FeedCollection) model.Events {

	var events model.Events

	// iterate over modules in 100 batch sizes
	for i := 0; i < len(modules); i += 100 {
		var moduleBatch []model.FeedCollection

		if i+100 > len(modules) {
			moduleBatch = modules[i:]
		} else {
			moduleBatch = modules[i : i+100]
		}

		var selectedModulesQuery = buildIcalQueryForModules(moduleBatch)
		// get all events from event records in the events collection
		err := app.Dao().DB().Select("*").From("events").Where(selectedModulesQuery).All(&events)
		if err != nil {
			print("Error while getting events from database: ", err)
			return nil
		}
	}

	return events
}

func GetAllModulesForCourse(app *pocketbase.PocketBase, course string, semester string) (model.Events, error) {
	var events model.Events

	// get all events from event records in the events collection
	err := app.Dao().DB().Select("*").From("events").Where(dbx.NewExp("course = {:course} AND semester = {:semester}", dbx.Params{"course": course, "semester": semester})).GroupBy("Name").Distinct(true).All(&events)
	if err != nil {
		print("Error while getting events from database: ", err)
		return nil, err
	}

	return events, nil
}

func GetAllModulesDistinctByNameAndCourse(app *pocketbase.PocketBase) (model.Events, error) {
	var events model.Events

	err := app.Dao().DB().Select("*").From("events").GroupBy("Name", "course").Distinct(true).All(&events)
	if err != nil {
		print("Error while getting events from database: ", err)
		return nil, err
	}

	return events, nil
}

func DeleteAllEventsForCourse(app *pocketbase.PocketBase, course string, semester string) error {
	_, err := app.Dao().DB().Delete("events", dbx.NewExp("course = {:course} AND semester = {:semester}", dbx.Params{"course": course, "semester": semester})).Execute()

	if err != nil {
		print("Error while deleting events from database: ", err)
		return err
	}

	return nil
}

func DeleteAllEvents(app *pocketbase.PocketBase) error {

	_, err := app.Dao().DB().Delete("events", dbx.NewExp("1=1")).Execute()

	if err != nil {
		return err
	}

	return nil
}

func FindAllEventsByModule(app *pocketbase.PocketBase, module model.Module) (model.Events, error) {
	var events model.Events

	err := app.Dao().DB().Select("*").From("events").Where(dbx.NewExp("Name = {:moduleName} AND course = {:course}", dbx.Params{"moduleName": module.Name, "course": module.Course})).All(&events)
	if err != nil {
		print("Error while getting events from database: ", err)
		return nil, err
	}

	return events, nil
}