package services

import (
	"context"
	"github.com/AchievementNetwork/stringset"
	"github.com/gissleh/stufflog/database"
	"github.com/gissleh/stufflog/internal/auth"
	"github.com/gissleh/stufflog/internal/slerrors"
	"github.com/gissleh/stufflog/models"
	"golang.org/x/sync/errgroup"
)

// Loader loads the stuff.
type Loader struct {
	DB database.Database
}

func (l *Loader) FindGroup(ctx context.Context, id string) (*models.GroupResult, error) {
	group, err := l.DB.Groups().Find(ctx, id)
	if err != nil {
		return nil, err
	}
	if group.UserID != auth.UserID(ctx) {
		return nil, slerrors.NotFound("Goal")
	}

	result := &models.GroupResult{Group: *group}
	result.Items, err = l.DB.Items().List(ctx, models.ItemFilter{
		UserID:   auth.UserID(ctx),
		GroupIDs: []string{group.ID},
	})
	if err != nil {
		return nil, err
	}

	return result, nil
}

func (l *Loader) ListGroups(ctx context.Context, filter models.GroupFilter) ([]*models.GroupResult, error) {
	filter.UserID = auth.UserID(ctx)
	groups, err := l.DB.Groups().List(ctx, filter)
	if err != nil {
		return nil, err
	}

	groupIDs := make([]string, 0, len(groups))
	for _, group := range groups {
		groupIDs = append(groupIDs, group.ID)
	}
	items, err := l.DB.Items().List(ctx, models.ItemFilter{
		UserID:   auth.UserID(ctx),
		GroupIDs: groupIDs,
	})

	results := make([]*models.GroupResult, len(groups))
	for i, group := range groups {
		results[i] = &models.GroupResult{Group: *group, Items: []*models.Item{}}
		for _, item := range items {
			if item.GroupID == group.ID {
				results[i].Items = append(results[i].Items, item)
			}
		}
	}

	return results, nil
}

func (l *Loader) FindItem(ctx context.Context, id string) (*models.ItemResult, error) {
	item, err := l.DB.Items().Find(ctx, id)
	if err != nil {
		return nil, err
	}
	if item.UserID != auth.UserID(ctx) {
		return nil, slerrors.NotFound("Item")
	}

	result := &models.ItemResult{Item: *item}
	result.Group, err = l.DB.Groups().Find(ctx, item.GroupID)
	if err != nil {
		return nil, err
	}

	return result, nil
}

func (l *Loader) ListItems(ctx context.Context, filter models.ItemFilter) ([]*models.ItemResult, error) {
	filter.UserID = auth.UserID(ctx)
	items, err := l.DB.Items().List(ctx, filter)
	if err != nil {
		return nil, err
	}

	groupIDs := make([]string, 0, len(items))
	for _, item := range items {
		groupIDs = append(groupIDs, item.GroupID)
	}
	groups, err := l.DB.Groups().List(ctx, models.GroupFilter{
		UserID: auth.UserID(ctx),
		IDs:    groupIDs,
	})

	results := make([]*models.ItemResult, len(items))
	for i, item := range items {
		results[i] = &models.ItemResult{Item: *item}
		for _, group := range groups {
			if item.GroupID == group.ID {
				results[i].Group = group
				break
			}
		}
	}

	return results, nil
}

func (l *Loader) FindLog(ctx context.Context, id string) (*models.LogResult, error) {
	log, err := l.DB.Logs().Find(ctx, id)
	if err != nil {
		return nil, err
	}
	if log.UserID != auth.UserID(ctx) {
		return nil, slerrors.NotFound("Goal")
	}
	result := &models.LogResult{
		Log:  *log,
		Task: nil,
	}

	result.Task, _ = l.DB.Tasks().Find(ctx, id)
	result.Item, _ = l.DB.Items().Find(ctx, log.ItemID)

	return result, nil
}

func (l *Loader) ListLogs(ctx context.Context, filter models.LogFilter) ([]*models.LogResult, error) {
	filter.UserID = auth.UserID(ctx)
	logs, err := l.DB.Logs().List(ctx, filter)
	if err != nil {
		return nil, err
	}

	taskIDs := stringset.New()
	itemIDs := stringset.New()
	for _, log := range logs {
		taskIDs.Add(log.TaskID)
		itemIDs.Add(log.ItemID)
	}
	tasks, err := l.DB.Tasks().List(ctx, models.TaskFilter{
		UserID: auth.UserID(ctx),
		IDs:    taskIDs.Strings(),
	})
	if err != nil {
		return nil, err
	}
	items, err := l.DB.Items().List(ctx, models.ItemFilter{
		UserID: auth.UserID(ctx),
		IDs:    itemIDs.Strings(),
	})
	if err != nil {
		return nil, err
	}

	results := make([]*models.LogResult, len(logs))
	for i, log := range logs {
		results[i] = &models.LogResult{
			Log:  *log,
			Task: nil,
		}

		for _, task := range tasks {
			if task.ID == log.TaskID {
				results[i].Task = task
				break
			}
		}

		for _, item := range items {
			if item.ID == log.ItemID {
				results[i].Item = item
				break
			}
		}
	}

	return results, nil
}

func (l *Loader) FindProject(ctx context.Context, id string) (*models.ProjectResult, error) {
	project, err := l.DB.Projects().Find(ctx, id)
	if err != nil {
		return nil, err
	}
	if project.UserID != auth.UserID(ctx) {
		return nil, slerrors.NotFound("Goal")
	}
	result := &models.ProjectResult{Project: *project}

	tasks, err := l.DB.Tasks().List(ctx, models.TaskFilter{
		UserID:     auth.UserID(ctx),
		ProjectIDs: []string{project.ID},
	})
	taskIDs := make([]string, 0, len(tasks))
	itemIDs := stringset.New()
	for _, task := range tasks {
		taskIDs = append(taskIDs, task.ID)
		itemIDs.Add(task.ItemID)
	}

	logs, err := l.DB.Logs().List(ctx, models.LogFilter{
		UserID:  auth.UserID(ctx),
		TaskIDs: taskIDs,
	})
	if err != nil {
		return nil, err
	}
	items, err := l.DB.Items().List(ctx, models.ItemFilter{
		UserID: auth.UserID(ctx),
		IDs:    itemIDs.Strings(),
	})
	if err != nil {
		return nil, err
	}

	result.Tasks = make([]*models.TaskResult, len(tasks))
	for i, task := range tasks {
		result.Tasks[i] = &models.TaskResult{
			Logs: []*models.Log{},
		}
		result.Tasks[i].Task = *task
		for _, log := range logs {
			if log.TaskID == task.ID {
				result.Tasks[i].Logs = append(result.Tasks[i].Logs, log)
			}
		}
		for _, item := range items {
			if item.ID == task.ItemID {
				result.Tasks[i].Item = item
				break
			}
		}
		result.Tasks[i].CompletedAmount = len(result.Tasks[i].Logs)
	}

	return result, nil
}

func (l *Loader) ListProjects(ctx context.Context, filter models.ProjectFilter) ([]*models.ProjectResult, error) {
	filter.UserID = auth.UserID(ctx)
	projects, err := l.DB.Projects().List(ctx, filter)
	if err != nil {
		return nil, err
	}
	projectIDs := make([]string, 0, len(projects))
	for _, project := range projects {
		projectIDs = append(projectIDs, project.ID)
	}

	tasks, err := l.DB.Tasks().List(ctx, models.TaskFilter{
		UserID:     auth.UserID(ctx),
		ProjectIDs: projectIDs,
	})
	if err != nil {
		return nil, err
	}
	taskIDs := make([]string, 0, len(tasks))
	itemIDs := stringset.New()
	for _, task := range tasks {
		taskIDs = append(taskIDs, task.ID)
		itemIDs.Add(task.ItemID)
	}

	logs, err := l.DB.Logs().List(ctx, models.LogFilter{
		UserID:  auth.UserID(ctx),
		TaskIDs: taskIDs,
	})
	if err != nil {
		return nil, err
	}

	items, err := l.DB.Items().List(ctx, models.ItemFilter{
		UserID: auth.UserID(ctx),
		IDs:    itemIDs.Strings(),
	})
	if err != nil {
		return nil, err
	}

	results := make([]*models.ProjectResult, len(projects))
	for i, project := range projects {
		results[i] = &models.ProjectResult{Project: *project}
		results[i].Tasks = make([]*models.TaskResult, 0, 16)
		for _, task := range tasks {
			if task.ProjectID != project.ID {
				continue
			}

			taskResult := &models.TaskResult{
				Task: *task,
				Logs: []*models.Log{},
			}
			for _, log := range logs {
				if log.TaskID == task.ID {
					taskResult.Logs = append(taskResult.Logs, log)
				}
			}
			for _, item := range items {
				if item.ID == task.ItemID {
					taskResult.Item = item
					break
				}
			}
			taskResult.CompletedAmount = len(taskResult.Logs)

			results[i].Tasks = append(results[i].Tasks, taskResult)
		}
	}

	return results, nil
}

func (l *Loader) FindTask(ctx context.Context, id string) (*models.TaskResult, error) {
	task, err := l.DB.Tasks().Find(ctx, id)
	if err != nil {
		return nil, err
	}
	if task.UserID != auth.UserID(ctx) {
		return nil, slerrors.NotFound("Goal")
	}
	result := &models.TaskResult{Task: *task}

	result.Item, _ = l.DB.Items().Find(ctx, task.ItemID)
	result.Project, _ = l.DB.Projects().Find(ctx, task.ProjectID)
	result.Logs, err = l.DB.Logs().List(ctx, models.LogFilter{
		UserID:  task.UserID,
		TaskIDs: []string{task.ID},
	})
	if err != nil {
		return nil, err
	}

	result.CompletedAmount = len(result.Logs)

	return result, nil
}

func (l *Loader) ListTasks(ctx context.Context, filter models.TaskFilter) ([]*models.TaskResult, error) {
	filter.UserID = auth.UserID(ctx)
	tasks, err := l.DB.Tasks().List(ctx, filter)
	if err != nil {
		return nil, err
	}
	if len(tasks) == 0 {
		return []*models.TaskResult{}, nil
	}

	taskIDs := make([]string, 0, len(tasks))
	itemIDs := stringset.New()
	projectIDs := stringset.New()
	for _, task := range tasks {
		taskIDs = append(taskIDs, task.ID)
		itemIDs.Add(task.ItemID)
		projectIDs.Add(task.ProjectID)
	}

	logs, err := l.DB.Logs().List(ctx, models.LogFilter{
		UserID:  auth.UserID(ctx),
		TaskIDs: taskIDs,
	})
	if err != nil {
		return nil, err
	}

	items, err := l.DB.Items().List(ctx, models.ItemFilter{
		UserID: auth.UserID(ctx),
		IDs:    itemIDs.Strings(),
	})
	if err != nil {
		return nil, err
	}

	projects, err := l.DB.Projects().List(ctx, models.ProjectFilter{
		UserID: auth.UserID(ctx),
		IDs:    projectIDs.Strings(),
	})
	if err != nil {
		return nil, err
	}

	results := make([]*models.TaskResult, 0, len(tasks))
	for _, task := range tasks {
		result := &models.TaskResult{
			Task: *task,
			Logs: []*models.Log{},
		}

		for _, log := range logs {
			if log.TaskID == task.ID {
				result.Logs = append(result.Logs, log)
			}
		}

		for _, item := range items {
			if item.ID == task.ItemID {
				result.Item = item
				break
			}
		}

		for _, project := range projects {
			if project.ID == task.ProjectID {
				result.Project = project
				break
			}
		}

		result.CompletedAmount = len(result.Logs)

		results = append(results, result)
	}

	return results, nil
}

func (l *Loader) FindGoal(ctx context.Context, id string) (*models.GoalResult, error) {
	goal, err := l.DB.Goals().Find(ctx, id)
	if err != nil {
		return nil, err
	}
	if goal.UserID != auth.UserID(ctx) {
		return nil, slerrors.NotFound("Goal")
	}

	return l.populateGoals(ctx, goal)
}

func (l *Loader) ListGoals(ctx context.Context, filter models.GoalFilter) ([]*models.GoalResult, error) {
	filter.UserID = auth.UserID(ctx)

	goals, err := l.DB.Goals().List(ctx, filter)
	if err != nil {
		return nil, err
	}

	results := make([]*models.GoalResult, len(goals))
	eg := errgroup.Group{}
	for i := range results {
		index := i // Required to avoid race condition.

		eg.Go(func() error {
			res, err := l.populateGoals(ctx, goals[index])
			if err != nil {
				return err
			}

			results[index] = res

			return nil
		})
	}
	err = eg.Wait()
	if err != nil {
		return nil, err
	}

	return results, nil
}

func (l *Loader) populateGoals(ctx context.Context, goal *models.Goal) (*models.GoalResult, error) {
	userID := auth.UserID(ctx)
	result := &models.GoalResult{
		Goal:            *goal,
		Group:           nil,
		Items:           nil,
		Logs:            nil,
		CompletedAmount: 0,
	}

	result.Group, _ = l.DB.Groups().Find(ctx, goal.GroupID)
	if result.Group != nil {
		// Get items
		items, err := l.DB.Items().List(ctx, models.ItemFilter{
			UserID:   userID,
			GroupIDs: []string{goal.GroupID},
		})
		if err != nil {
			return nil, err
		}
		itemIDs := make([]string, 0, len(items))
		for _, item := range items {
			result.Items = append(result.Items, &models.GoalResultItem{
				Item:            *item,
				CompletedAmount: 0,
			})

			itemIDs = append(itemIDs, item.ID)
		}

		// Get logs
		logs, err := l.DB.Logs().List(ctx, models.LogFilter{
			UserID:  userID,
			ItemIDs: itemIDs,
			MinTime: &goal.StartTime,
			MaxTime: &goal.EndTime,
		})

		// Get tasks
		taskIDs := make([]string, 0, len(result.Logs))
		for _, log := range logs {
			taskIDs = append(taskIDs, log.TaskID)
		}
		tasks, err := l.DB.Tasks().List(ctx, models.TaskFilter{
			UserID: userID,
			IDs:    taskIDs,
		})

		// Apply logs
		result.Logs = make([]*models.LogResult, 0, len(logs))
		for _, log := range logs {
			resultLog := &models.LogResult{
				Log: *log,
			}

			for _, task := range tasks {
				if task.ID == log.TaskID {
					resultLog.Task = task

					for _, item := range result.Items {
						if task.ItemID == item.ID {
							item.CompletedAmount += 1
							result.CompletedAmount += item.GroupWeight
							break
						}

						resultLog.Item = &item.Item
					}

					break
				}
			}
			result.Logs = append(result.Logs, resultLog)
		}
	}

	return result, nil
}