package service

import (
	"database/sql"
	"time"

	"github.com/daniil/homelab-api/internal/model"
	"github.com/daniil/homelab-api/internal/repository"
)

type TaskService struct {
	taskRepo *repository.TaskRepository
}

func NewTaskService(taskRepo *repository.TaskRepository) *TaskService {
	return &TaskService{taskRepo: taskRepo}
}

func (s *TaskService) Create(userID int64, req *model.CreateTaskRequest) (*model.Task, error) {
	task := &model.Task{
		UserID:             userID,
		Title:              req.Title,
		Description:        req.Description,
		Icon:               defaultString(req.Icon, "📋"),
		Color:              defaultString(req.Color, "#6B7280"),
		Priority:           req.Priority,
		IsRecurring:        req.IsRecurring,
		RecurrenceInterval: defaultInt(req.RecurrenceInterval, 1),
	}

	if req.DueDate != nil && *req.DueDate != "" {
		parsed, err := time.Parse("2006-01-02", *req.DueDate)
		if err == nil {
			task.DueDate = sql.NullTime{Time: parsed, Valid: true}
		}
	}

	if req.ReminderTime != nil && *req.ReminderTime != "" {
		task.ReminderTime = sql.NullString{String: *req.ReminderTime, Valid: true}
	}

	if req.RecurrenceType != nil && *req.RecurrenceType != "" {
		task.RecurrenceType = sql.NullString{String: *req.RecurrenceType, Valid: true}
	}

	if req.RecurrenceEndDate != nil && *req.RecurrenceEndDate != "" {
		parsed, err := time.Parse("2006-01-02", *req.RecurrenceEndDate)
		if err == nil {
			task.RecurrenceEndDate = sql.NullTime{Time: parsed, Valid: true}
		}
	}

	if err := s.taskRepo.Create(task); err != nil {
		return nil, err
	}

	task.ProcessForJSON()
	return task, nil
}

func (s *TaskService) Get(id, userID int64) (*model.Task, error) {
	return s.taskRepo.GetByID(id, userID)
}

func (s *TaskService) List(userID int64, completed *bool) ([]model.Task, error) {
	tasks, err := s.taskRepo.ListByUser(userID, completed)
	if err != nil {
		return nil, err
	}
	if tasks == nil {
		tasks = []model.Task{}
	}
	return tasks, nil
}

func (s *TaskService) GetTodayTasks(userID int64) ([]model.Task, error) {
	tasks, err := s.taskRepo.GetTodayTasks(userID)
	if err != nil {
		return nil, err
	}
	if tasks == nil {
		tasks = []model.Task{}
	}
	return tasks, nil
}

func (s *TaskService) Update(id, userID int64, req *model.UpdateTaskRequest) (*model.Task, error) {
	task, err := s.taskRepo.GetByID(id, userID)
	if err != nil {
		return nil, err
	}

	if req.Title != nil {
		task.Title = *req.Title
	}
	if req.Description != nil {
		task.Description = *req.Description
	}
	if req.Icon != nil {
		task.Icon = *req.Icon
	}
	if req.Color != nil {
		task.Color = *req.Color
	}
	if req.Priority != nil {
		task.Priority = *req.Priority
	}
	if req.DueDate != nil {
		if *req.DueDate == "" {
			task.DueDate = sql.NullTime{Valid: false}
		} else {
			parsed, err := time.Parse("2006-01-02", *req.DueDate)
			if err == nil {
				task.DueDate = sql.NullTime{Time: parsed, Valid: true}
			}
		}
	}
	if req.ReminderTime != nil {
		if *req.ReminderTime == "" {
			task.ReminderTime = sql.NullString{Valid: false}
		} else {
			task.ReminderTime = sql.NullString{String: *req.ReminderTime, Valid: true}
		}
	}

	// Handle recurring fields
	if req.IsRecurring != nil {
		task.IsRecurring = *req.IsRecurring
	}
	if req.RecurrenceType != nil {
		if *req.RecurrenceType == "" {
			task.RecurrenceType = sql.NullString{Valid: false}
		} else {
			task.RecurrenceType = sql.NullString{String: *req.RecurrenceType, Valid: true}
		}
	}
	if req.RecurrenceInterval != nil {
		task.RecurrenceInterval = *req.RecurrenceInterval
	}
	if req.RecurrenceEndDate != nil {
		if *req.RecurrenceEndDate == "" {
			task.RecurrenceEndDate = sql.NullTime{Valid: false}
		} else {
			parsed, err := time.Parse("2006-01-02", *req.RecurrenceEndDate)
			if err == nil {
				task.RecurrenceEndDate = sql.NullTime{Time: parsed, Valid: true}
			}
		}
	}

	if err := s.taskRepo.Update(task); err != nil {
		return nil, err
	}

	task.ProcessForJSON()
	return task, nil
}

func (s *TaskService) Delete(id, userID int64) error {
	return s.taskRepo.Delete(id, userID)
}

func (s *TaskService) Complete(id, userID int64) (*model.Task, error) {
	// First, get the task to check if it's recurring
	task, err := s.taskRepo.GetByID(id, userID)
	if err != nil {
		return nil, err
	}

	// Complete the current task
	if err := s.taskRepo.Complete(id, userID); err != nil {
		return nil, err
	}

	// If task is recurring, create the next occurrence
	if task.IsRecurring && task.RecurrenceType.Valid && task.DueDate.Valid {
		s.createNextRecurrence(task)
	}

	return s.taskRepo.GetByID(id, userID)
}

func (s *TaskService) createNextRecurrence(task *model.Task) {
	// Calculate next due date based on recurrence type
	var nextDueDate time.Time
	interval := task.RecurrenceInterval
	if interval < 1 {
		interval = 1
	}

	currentDue := task.DueDate.Time
	
	switch task.RecurrenceType.String {
	case "daily":
		nextDueDate = currentDue.AddDate(0, 0, interval)
	case "weekly":
		nextDueDate = currentDue.AddDate(0, 0, 7*interval)
	case "monthly":
		nextDueDate = currentDue.AddDate(0, interval, 0)
	case "custom":
		nextDueDate = currentDue.AddDate(0, 0, interval)
	default:
		return // Unknown recurrence type, don't create
	}

	// Check if next date is past the end date
	if task.RecurrenceEndDate.Valid && nextDueDate.After(task.RecurrenceEndDate.Time) {
		return // Don't create task past end date
	}

	// Create the next task
	nextTask := &model.Task{
		UserID:             task.UserID,
		Title:              task.Title,
		Description:        task.Description,
		Icon:               task.Icon,
		Color:              task.Color,
		Priority:           task.Priority,
		DueDate:            sql.NullTime{Time: nextDueDate, Valid: true},
		ReminderTime:       task.ReminderTime,
		IsRecurring:        true,
		RecurrenceType:     task.RecurrenceType,
		RecurrenceInterval: task.RecurrenceInterval,
		RecurrenceEndDate:  task.RecurrenceEndDate,
		ParentTaskID:       sql.NullInt64{Int64: task.ID, Valid: true},
	}

	// Silently create, ignore errors
	s.taskRepo.Create(nextTask)
}

func (s *TaskService) Uncomplete(id, userID int64) (*model.Task, error) {
	if err := s.taskRepo.Uncomplete(id, userID); err != nil {
		return nil, err
	}
	return s.taskRepo.GetByID(id, userID)
}