// Package task_service implements the shared developer board.
package task_service

import (
	"context"
	"strings"
	"time"
	"unicode/utf8"

	"evening_detective_server/internal/repos/tasks_repo"
)

var (
	ErrInvalidTask     = tasks_repo.ErrInvalidTask
	ErrNotFound        = tasks_repo.ErrNotFound
	ErrConflict        = tasks_repo.ErrConflict
	ErrInvalidAssignee = tasks_repo.ErrInvalidAssignee
)

type Task = tasks_repo.Task
type Assignee = tasks_repo.Assignee

type ITasksRepo interface {
	List(context.Context) ([]*Task, error)
	ListAssignees(context.Context) ([]Assignee, error)
	Create(context.Context, Task) (*Task, error)
	Update(context.Context, Task) (*Task, error)
	SetStatus(context.Context, int, int, string) (*Task, error)
	Delete(context.Context, int, int) error
}

type TaskService struct{ repo ITasksRepo }

func NewTaskService(repo ITasksRepo) *TaskService { return &TaskService{repo: repo} }

func (s *TaskService) List(ctx context.Context) ([]*Task, error) { return s.repo.List(ctx) }
func (s *TaskService) ListAssignees(ctx context.Context) ([]Assignee, error) {
	return s.repo.ListAssignees(ctx)
}

// ParseDueDate preserves calendar dates without a local time zone conversion.
func ParseDueDate(value string) (*time.Time, error) {
	if value == "" {
		return nil, nil
	}
	date, err := time.Parse("2006-01-02", value)
	if err != nil || date.Year() < 1 {
		return nil, ErrInvalidTask
	}
	return &date, nil
}

func validStatus(status string) bool {
	return status == "new" || status == "in_progress" || status == "review" || status == "done"
}

func validate(task *Task) error {
	task.Title = strings.TrimSpace(task.Title)
	if task.Title == "" || strings.ContainsRune(task.Title, 0) || strings.ContainsRune(task.Description, 0) ||
		utf8.RuneCountInString(task.Title) > 255 ||
		utf8.RuneCountInString(task.Description) > 10000 || !validStatus(task.Status) ||
		(task.AssigneeID != nil && *task.AssigneeID <= 0) {
		return ErrInvalidTask
	}
	return nil
}

func (s *TaskService) Create(ctx context.Context, task Task) (*Task, error) {
	if task.Status == "" {
		task.Status = "new"
	}
	if err := validate(&task); err != nil {
		return nil, err
	}
	return s.repo.Create(ctx, task)
}

func (s *TaskService) Update(ctx context.Context, task Task) (*Task, error) {
	if task.ID <= 0 || task.Version <= 0 {
		return nil, ErrInvalidTask
	}
	if err := validate(&task); err != nil {
		return nil, err
	}
	return s.repo.Update(ctx, task)
}

func (s *TaskService) SetStatus(ctx context.Context, id, version int, status string) (*Task, error) {
	if id <= 0 || version <= 0 || !validStatus(status) {
		return nil, ErrInvalidTask
	}
	return s.repo.SetStatus(ctx, id, version, status)
}

func (s *TaskService) Delete(ctx context.Context, id, version int) error {
	if id <= 0 || version <= 0 {
		return ErrInvalidTask
	}
	return s.repo.Delete(ctx, id, version)
}