package events

import (
	"github.com/labstack/echo/v5"
	"github.com/pocketbase/pocketbase"
	"github.com/pocketbase/pocketbase/apis"
	"htwkalender/model"
	"htwkalender/service/db"
	"htwkalender/service/fetch"
	"htwkalender/service/functions"
)

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

	modules, err := db.GetAllModulesForCourse(app, course, semester)
	replaceEmptyEntry(modules, "Sonderveranstaltungen")
	return modules, err
}

// replaceEmptyEntry replaces an empty entry in a module with a replacement string
// If the module is not empty, nothing happens
func replaceEmptyEntry(modules model.Events, replacement string) {

	for i, module := range modules {
		if functions.OnlyWhitespace(module.Name) {
			modules[i].Name = replacement
		}
	}
}

// GetAllModulesDistinct returns all modules distinct by name and course from the database
// That means you get all modules with duplicates if they have different courses
func GetAllModulesDistinct(app *pocketbase.PocketBase, c echo.Context) error {
	modules, err := db.GetAllModulesDistinctByNameAndCourse(app)

	replaceEmptyEntry(modules, "Sonderveranstaltungen")

	if err != nil {
		return c.JSON(400, err)
	} else {
		return c.JSON(200, modules)
	}
}

// GetModuleByName returns a module by its name
// If the module does not exist, an error is returned
// If the module exists, the module is returned
// Module is a struct that exists in database as events
func GetModuleByName(app *pocketbase.PocketBase, name string) (model.Module, error) {
	events, err := db.FindAllEventsByModule(app, name)

	if err != nil || len(events) == 0 {
		return model.Module{}, err
	} else {
		return model.Module{
			UUID:     events[0].UUID,
			Name:     name,
			Events:   events,
			Prof:     events[0].Prof,
			Course:   events[0].Course,
			Semester: events[0].Semester,
		}, nil
	}
}

// DeleteAllEventsByCourseAndSemester deletes all events for a course and a semester
// If the deletion was successful, nil is returned
// If the deletion was not successful, an error is returned
func DeleteAllEventsByCourseAndSemester(app *pocketbase.PocketBase, course string, semester string) error {
	err := db.DeleteAllEventsForCourse(app, course, semester)
	if err != nil {
		return err
	} else {
		return nil
	}
}

// UpdateModulesForCourse updates all modules for a course
// Does Updates for ws and ss semester sequentially
// Update runs through the following steps:
// 1. Delete all events for the course and the semester
// 2. Fetch all events for the course and the semester
// 3. Save all events for the course and the semester
// If the update was successful, nil is returned
// If the update was not successful, an error is returned
func UpdateModulesForCourse(app *pocketbase.PocketBase, course string) error {

	//new string array with one element (course)
	var courses []string
	courses = append(courses, course)

	seminarGroups := fetch.GetSeminarGroupsEventsFromHTML(courses)

	seminarGroups = fetch.ClearEmptySeminarGroups(seminarGroups)

	seminarGroups = fetch.ReplaceEmptyEventNames(seminarGroups)

	//check if events in the seminarGroups Events are already in the database
	//if yes, keep the database as it is
	//if no, delete all events for the course and the semester and save the new events
	//if there are no events in the database, save the new events

	//get all events for the course and the semester
	events, err := db.GetAllModulesForCourse(app, course, "ws")
	if err != nil {
		return apis.NewNotFoundError("Events for winter semester could not be found", err)
	}

	// append all events for the course and the semester to the events array for ss
	summerEvents, err := db.GetAllModulesForCourse(app, course, "ss")
	if err != nil {
		return apis.NewNotFoundError("Events for summer semester could not be found", err)
	}

	events = append(events, summerEvents...)

	//if there are no events in the database, save the new events
	if len(events) == 0 {
		_, dbError := db.SaveEvents(seminarGroups, app)
		if dbError != nil {
			return apis.NewNotFoundError("Events could not be saved", dbError)
		}
		return nil
	}

	//check if events in the seminarGroups Events are already in the database
	//if yes, keep the database as it is
	//if no, delete all events for the course and the semester and save the new events
	for _, seminarGroup := range seminarGroups {
		for _, event := range seminarGroup.Events {
			// if the event is not in the database, delete all events for the course and the semester and save the new events
			if !ContainsEvent(events, event) {

				err = DeleteAllEventsByCourseAndSemester(app, course, "ws")
				if err != nil {
					return err
				}

				err = DeleteAllEventsByCourseAndSemester(app, course, "ss")
				if err != nil {
					return err
				}

				//save the new events
				_, dbError := db.SaveEvents(seminarGroups, app)
				if dbError != nil {
					return apis.NewNotFoundError("Events could not be saved", dbError)
				}
				return nil
			}
		}
	}

	return nil
}

func ContainsEvent(events model.Events, event model.Event) bool {
	for _, e := range events {
		if e.Name == event.Name &&
			e.Prof == event.Prof &&
			e.Rooms == event.Rooms &&
			e.Semester == event.Semester &&
			e.Start == event.Start &&
			e.End == event.End &&
			e.Course == event.Course {
			return true
		}
	}
	return false
}