// Package application is the base of a stateful application, storing loaded data in memory.
package application

import (
	"slices"
	"strings"
	"sync"
	"time"

	"suruatoel.xyz/timefiles/lib"
)

// Application represents a stateful time-tracker application.
//
// jobLock is a mutual-exclusive lock to limit the execution of asynchronous jobs.
//
// jobWait is a wait group to wait for asynchronous jobs to finished.
//
// ui represents the user interface allowing the application to call callbacks.
//
// projectsByID stores projects by their ID
//
// projectsByTitle stores projects by their title
//
// activitiesByID stores activities by the ID of the project they belong to and their ID
//
// activitiesByTitle stores activities by the ID of the project they belong to and their title
type Application struct {
	jobLock           sync.Mutex
	jobWait           sync.WaitGroup
	ui                UserInterface
	projectsByID      map[string]*lib.Project
	projectsByTitle   map[string]*lib.Project
	activitiesByID    map[string]map[string]*lib.Activity
	activitiesByTitle map[string]map[string]*lib.Activity
}

// UserInterface is the representation of a user interface with callback functions.
//
// SetTimerStart notifies the user interface that the update of the time has started.
//
// SetTimer sends an updated timer to the user interface. If the timer was stopped, nil will be passed.
//
// SetSummaryStart notifies the user interface that calculating the summary has started.
//
// SetSummary sends the calculated summary to the user interface.
//
// SetTotalsStart notifies the user interface that calculating the totals has started.
//
// SetTotals sends the calculated totals to the user interface.
type UserInterface interface {
	SetTimerStart()
	SetTimer(timer *lib.Time, err error)
	SetSummaryStart()
	SetSummary(summary []*lib.Time, err error)
	SetTotalsStart()
	SetTotals(totals lib.TotalTime, err error)
}

// NewApplication creates a new application for a user interface.
func NewApplication(ui UserInterface) *Application {
	app := Application{
		ui:                ui,
		projectsByID:      make(map[string]*lib.Project),
		projectsByTitle:   make(map[string]*lib.Project),
		activitiesByID:    make(map[string]map[string]*lib.Activity),
		activitiesByTitle: make(map[string]map[string]*lib.Activity),
	}

	return &app
}

// Load loads initial application data like projects and activities.
func (app *Application) Load() {
	projects, err := lib.GetProjects()
	if err != nil {
		return
	}

	for _, project := range projects {
		app.projectsByID[project.ID] = project
		app.projectsByTitle[project.Title] = project

		activities, activitiesErr := lib.GetActivities(project)
		if activitiesErr != nil {
			return
		}

		activitiesByID := make(map[string]*lib.Activity)
		activitiesByTitle := make(map[string]*lib.Activity)
		for _, activity := range activities {
			activitiesByID[activity.ID] = activity
			activitiesByTitle[activity.Title] = activity
		}
		app.activitiesByID[project.ID] = activitiesByID
		app.activitiesByTitle[project.ID] = activitiesByTitle
	}
}

// GetProject returns a project by its ID.
func (app *Application) GetProject(projectID string) *lib.Project {
	return app.projectsByID[projectID]
}

// GetActivity returns an activity by its ID.
func (app *Application) GetActivity(project *lib.Project, activityID string) *lib.Activity {
	activities, found := app.activitiesByID[project.ID]
	if !found {
		return nil
	}

	return activities[activityID]
}

// SearchProjects searches for projects by comparing their title with a given query. The comparison is case-insensitive
// and finds any project which title contains the query string.
func (app *Application) SearchProjects(query string) (projects []*lib.Project) {
	for _, project := range app.projectsByTitle {
		if strings.Contains(strings.ToLower(project.Title), strings.ToLower(query)) {
			projects = append(projects, project)
		}
	}

	return
}

// SearchActivities searches for activities of a projects by comparing their title with a given query. The comparison is
// case-insensitive and finds any activity which title contains the query string.
func (app *Application) SearchActivities(projectTitle string, query string) (activities []*lib.Activity) {
	project, projectFound := app.projectsByTitle[projectTitle]
	if !projectFound {
		return
	}
	projectActivities, found := app.activitiesByTitle[project.ID]
	if !found {
		return
	}
	for _, activity := range projectActivities {
		if strings.Contains(strings.ToLower(activity.Title), strings.ToLower(query)) {
			activities = append(activities, activity)
		}
	}

	return
}

// GetTimer loads the current timer. This function queues the job and returns immediately. When the job is done,
// UserInterface.SetTimer is called.
func (app *Application) GetTimer() {
	app.runJob(app.getTimer)
}

// StartTimer starts a new timer. This function queues the job and returns immediately. When the job is done,
// UserInterface.SetTimer is called.
func (app *Application) StartTimer() {
	app.runJob(app.startTimer)
}

// UpdateTimer updates the current timer. This function queues the job and returns immediately. When the job is done,
// UserInterface.SetTimer is called.
func (app *Application) UpdateTimer(project string, activity string) {
	app.runJob(func() {
		app.updateTimer(project, activity)
	})
}

// StopTimer stops the current timer. This function queues the job and returns immediately. When the job is done,
// UserInterface.SetTimer is called.
// Additionally, it gathers the time summary and calculates time totals, which will call UserInterface.SetSummary and
// UserInterface.SetTotals.
func (app *Application) StopTimer() {
	app.runJob(app.stopTimer)
	app.runJob(app.getTimeSummary)
	app.runJob(app.getTimeTotals)
}

// GetTimeSummary gathers a list of time entries for the current day. This function queues the job and returns
// immediately. When the job is done, UserInterface.SetSummary is called.
func (app *Application) GetTimeSummary() {
	app.runJob(app.getTimeSummary)
}

// GetTimeTotals collects the time spent per project and activity for the current day. This function queues the job and
// returns immediately. When the job is done, UserInterface.SetTotals is called.
func (app *Application) GetTimeTotals() {
	app.runJob(app.getTimeTotals)
}

// Wait blocks until all asynchronous jobs have been completed.
func (app *Application) Wait() {
	app.jobWait.Wait()
}

// runJob runs a job in a separate go-routine.
func (app *Application) runJob(job func()) {
	app.jobWait.Add(1)
	go func() {
		job()
		app.jobWait.Done()
	}()
}

// getTimer loads the current timer. It calls the corresponding callback functions on the application.
func (app *Application) getTimer() {
	app.ui.SetTimerStart()
	timer, err := lib.GetTimer()
	app.ui.SetTimer(timer, err)
}

// startTimer starts a new timer. It calls the corresponding callback functions on the application.
func (app *Application) startTimer() {
	app.ui.SetTimerStart()
	timer, err := lib.StartTimer()
	app.ui.SetTimer(timer, err)
}

// updateTimer updates the current timer. It calls the corresponding callback functions on the application.
func (app *Application) updateTimer(projectTitle string, activityTitle string) {
	app.ui.SetTimerStart()
	timer, err := app.updateTimerInternal(projectTitle, activityTitle)
	app.ui.SetTimer(timer, err)
}

// updateTimerInternal updates the current timer.
func (app *Application) updateTimerInternal(projectTitle string, activityTitle string) (*lib.Time, error) {
	project, projectErr := app.getProjectByTitle(projectTitle)
	if projectErr != nil {
		return nil, projectErr
	}

	activity, activityErr := app.getActivityByTitle(project, activityTitle)
	if activityErr != nil {
		return nil, activityErr
	}

	return lib.UpdateTimer(project, activity)
}

// stopTimer stops the current timer.
func (app *Application) stopTimer() {
	app.ui.SetTimerStart()
	timer, err := lib.StopTimer()
	app.ui.SetTimer(timer, err)
}

// getTimeSummary gathers a list of time entries for the current day.
func (app *Application) getTimeSummary() {
	app.ui.SetSummaryStart()
	summary, err := lib.GetTimeSummary()

	app.ui.SetSummary(summary, err)
}

// getTimeTotals collects the time spent per project and activity for the current day.
func (app *Application) getTimeTotals() {
	app.ui.SetTotalsStart()
	totalTime, totalTimeErr := lib.GetTimeTotals(
		time.Now().Truncate(24*time.Hour),
		time.Now().Truncate(24*time.Hour).AddDate(0, 0, 1).Add(-1*time.Second),
	)

	// Resolve IDs to labels
	for _, entry := range totalTime.Totals {
		project := app.GetProject(entry.ProjectID)
		if project != nil {
			entry.Project = project.Title
			activity := app.GetActivity(project, entry.ActivityID)
			if activity != nil {
				entry.Activity = activity.Title
			}
		}
	}

	// Sort entries alphabetically
	slices.SortFunc(totalTime.Totals, func(a, b *lib.TotalTimeEntry) int {
		return strings.Compare(a.Project, b.Project)
	})

	app.ui.SetTotals(totalTime, totalTimeErr)
}

// getProjectByTitle gets a project by its title. If no project with the given title exists, it creates a new project.
func (app *Application) getProjectByTitle(title string) (*lib.Project, error) {
	project, found := app.projectsByTitle[title]
	if found {
		return project, nil
	}

	// Create new project
	project = lib.NewProject()
	project.Title = title
	err := lib.SetProject(project)
	if err != nil {
		return nil, err
	}

	// Update in-memory storage
	app.projectsByID[project.ID] = project
	app.projectsByTitle[project.Title] = project
	app.activitiesByID[project.ID] = make(map[string]*lib.Activity)
	app.activitiesByTitle[project.ID] = make(map[string]*lib.Activity)

	return project, nil
}

// getActivityByTitle gets an activity by its title. If no activity with the given title exists, it creates a new
// activity.
func (app *Application) getActivityByTitle(project *lib.Project, title string) (*lib.Activity, error) {
	activitiesByTitle, activitiesFound := app.activitiesByTitle[project.ID]
	if !activitiesFound {
		// This should never happen
		return nil, nil
	}

	activity, found := activitiesByTitle[title]
	if found {
		return activity, nil
	}

	// Create new activity
	activity = &lib.Activity{
		Title: title,
	}
	err := lib.SetActivity(project, activity)
	if err != nil {
		return nil, err
	}

	// Update in-memory storage
	app.activitiesByID[project.ID][activity.ID] = activity
	app.activitiesByTitle[project.ID][activity.Title] = activity

	return activity, nil
}