package services

import (
	"errors"
	"fmt"
	"math"
	"sort"
	"time"

	"github.com/jinzhu/gorm"
	"github.com/n1try/wakapi/models"
)

type SummaryService struct {
	Config           *models.Config
	Db               *gorm.DB
	HeartbeatService *HeartbeatService
	AliasService     *AliasService
}

type Interval struct {
	Start time.Time
	End   time.Time
}

func (srv *SummaryService) GetSummary(from, to time.Time, user *models.User) (*models.Summary, error) {
	existingSummaries, err := srv.GetByUserWithin(user, from, to)
	if err != nil {
		return nil, err
	}

	missingIntervals := getMissingIntervals(from, to, existingSummaries)

	heartbeats := make([]*models.Heartbeat, 0)
	for _, interval := range missingIntervals {
		hb, err := srv.HeartbeatService.GetAllWithin(interval.Start, interval.End, user)
		if err != nil {
			return nil, err
		}
		heartbeats = append(heartbeats, hb...)
	}

	types := []uint8{models.SummaryProject, models.SummaryLanguage, models.SummaryEditor, models.SummaryOS}

	var projectItems []models.SummaryItem
	var languageItems []models.SummaryItem
	var editorItems []models.SummaryItem
	var osItems []models.SummaryItem

	if err := srv.AliasService.LoadUserAliases(user.ID); err != nil {
		return nil, err
	}

	c := make(chan models.SummaryItemContainer)
	for _, t := range types {
		go srv.aggregateBy(heartbeats, t, user, c)
	}

	for i := 0; i < len(types); i++ {
		item := <-c
		switch item.Type {
		case models.SummaryProject:
			projectItems = item.Items
		case models.SummaryLanguage:
			languageItems = item.Items
		case models.SummaryEditor:
			editorItems = item.Items
		case models.SummaryOS:
			osItems = item.Items
		}
	}
	close(c)

	aggregatedSummary := &models.Summary{
		UserID:           user.ID,
		FromTime:         &from,
		ToTime:           &to,
		Projects:         projectItems,
		Languages:        languageItems,
		Editors:          editorItems,
		OperatingSystems: osItems,
	}

	allSummaries := []*models.Summary{aggregatedSummary}
	allSummaries = append(allSummaries, existingSummaries...)

	summary, err := mergeSummaries(allSummaries)
	if err != nil {
		return nil, err
	}

	return summary, nil
}

func mergeSummaries(summaries []*models.Summary) (*models.Summary, error) {
	if len(summaries) < 1 {
		return nil, errors.New("no summaries given")
	}

	var minTime, maxTime time.Time
	minTime = time.Now()

	finalSummary := &models.Summary{
		UserID:           summaries[0].UserID,
		Projects:         make([]models.SummaryItem, 0),
		Languages:        make([]models.SummaryItem, 0),
		Editors:          make([]models.SummaryItem, 0),
		OperatingSystems: make([]models.SummaryItem, 0),
	}

	for _, s := range summaries {
		if s.UserID != finalSummary.UserID {
			return nil, errors.New("users don't match")
		}

		if s.FromTime.Before(minTime) {
			minTime = *(s.FromTime)
		}

		if s.ToTime.After(maxTime) {
			maxTime = *(s.ToTime)
		}

		// TODO: Multi-thread ?
		finalSummary.Projects = mergeSummaryItems(&(finalSummary.Projects), &(s.Projects))
		finalSummary.Languages = mergeSummaryItems(&(finalSummary.Languages), &(s.Languages))
		finalSummary.Editors = mergeSummaryItems(&(finalSummary.Editors), &(s.Editors))
		finalSummary.OperatingSystems = mergeSummaryItems(&(finalSummary.OperatingSystems), &(s.OperatingSystems))
	}

	finalSummary.FromTime = &minTime
	finalSummary.ToTime = &maxTime

	return finalSummary, nil
}

func mergeSummaryItems(existing *[]models.SummaryItem, new *[]models.SummaryItem) []models.SummaryItem {
	items := make(map[string]time.Duration)

	// Build map from existing
	for _, item := range *existing {
		items[item.Key] = item.Total
	}

	for _, item := range *new {
		if _, ok := items[item.Key]; !ok {
			items[item.Key] = item.Total
		} else {
			items[item.Key] += item.Total
		}
	}

	var i int
	itemList := make([]models.SummaryItem, len(items))
	for k, v := range items {
		itemList[i] = models.SummaryItem{Key: k, Total: v}
		i++
	}

	sort.Slice(itemList, func(i, j int) bool {
		return itemList[i].Total > itemList[j].Total
	})

	return itemList
}

func (srv *SummaryService) SaveSummary(summary *models.Summary) error {
	fmt.Println("Saving summary", summary)
	if err := srv.Db.Create(summary).Error; err != nil {
		return err
	}
	return nil
}

func (srv *SummaryService) GetByUserWithin(user *models.User, from, to time.Time) ([]*models.Summary, error) {
	var summaries []*models.Summary
	if err := srv.Db.
		Where(&models.Summary{UserID: user.ID}).
		Where("from_time >= ?", from).
		Where("to_time <= ?", to).
		Find(&summaries).Error; err != nil {
		return nil, err
	}
	return summaries, nil
}

func (srv *SummaryService) GetLatestUserSummaries() ([]*models.Summary, error) {
	var summaries []*models.Summary
	if err := srv.Db.
		Table("summaries").
		Select("user_id, max(to_time) as to_time").
		Group("user_id").
		Scan(&summaries).Error; err != nil {
		return nil, err
	}
	return summaries, nil
}

func (srv *SummaryService) aggregateBy(heartbeats []*models.Heartbeat, summaryType uint8, user *models.User, c chan models.SummaryItemContainer) {
	durations := make(map[string]time.Duration)

	for i, h := range heartbeats {
		var key string
		switch summaryType {
		case models.SummaryProject:
			key = h.Project
		case models.SummaryEditor:
			key = h.Editor
		case models.SummaryLanguage:
			key = h.Language
		case models.SummaryOS:
			key = h.OperatingSystem
		}

		if key == "" {
			key = "unknown"
		}

		if aliasedKey, err := srv.AliasService.GetAliasOrDefault(user.ID, summaryType, key); err == nil {
			key = aliasedKey
		}

		if _, ok := durations[key]; !ok {
			durations[key] = time.Duration(0)
		}

		if i == 0 {
			continue
		}

		timePassed := h.Time.Time().Sub(heartbeats[i-1].Time.Time())
		timeThresholded := math.Min(float64(timePassed), float64(time.Duration(2)*time.Minute))
		durations[key] += time.Duration(int64(timeThresholded))
	}

	items := make([]models.SummaryItem, 0)
	for k, v := range durations {
		items = append(items, models.SummaryItem{
			Key:   k,
			Total: v / time.Second,
		})
	}

	sort.Slice(items, func(i, j int) bool {
		return items[i].Total > items[j].Total
	})

	c <- models.SummaryItemContainer{Type: summaryType, Items: items}
}

func getMissingIntervals(from, to time.Time, existingSummaries []*models.Summary) []*Interval {
	if len(existingSummaries) == 0 {
		return []*Interval{&Interval{from, to}}
	}

	intervals := make([]*Interval, 0)

	// Pre
	if from.Before(*(existingSummaries[0].FromTime)) {
		intervals = append(intervals, &Interval{from, *(existingSummaries[0].FromTime)})
	}

	// Between
	for i := 0; i < len(existingSummaries)-1; i++ {
		if existingSummaries[i].ToTime.Before(*(existingSummaries[i+1].FromTime)) {
			intervals = append(intervals, &Interval{*(existingSummaries[i].ToTime), *(existingSummaries[i+1].FromTime)})
		}
	}

	// Post
	if to.After(*(existingSummaries[len(existingSummaries)-1].ToTime)) {
		intervals = append(intervals, &Interval{to, *(existingSummaries[len(existingSummaries)-1].ToTime)})
	}

	return intervals
}