package model

import (
	"errors"
	"strings"

	"gorm.io/gorm"
)

// TaskStatus represents the status of a task
type TaskStatus string

const (
	TaskStatusTodo       TaskStatus = "todo"
	TaskStatusInProgress TaskStatus = "in_progress"
	TaskStatusDone       TaskStatus = "done"
	TaskStatusCanceled   TaskStatus = "canceled"
)

// TaskPriority represents the priority of a task
type TaskPriority string

const (
	TaskPriorityLow    TaskPriority = "low"
	TaskPriorityMedium TaskPriority = "medium"
	TaskPriorityHigh   TaskPriority = "high"
)

// Task represents a task in the system
type Task struct {
	BaseModel
	Title       string       `json:"title" gorm:"not null;type:varchar(255)"`
	Description string       `json:"description" gorm:"type:text"`
	Status      TaskStatus   `json:"status" gorm:"not null;default:'todo';type:varchar(20)"`
	Priority    TaskPriority `json:"priority" gorm:"not null;default:'medium';type:varchar(20)"`
	ProjectID   string       `json:"project_id" gorm:"not null;type:uuid;index;references:projects(id);onDelete:CASCADE"`
	DueDate     *string      `json:"due_date" gorm:"type:date"`
	Project     Project      `json:"project,omitempty" gorm:"foreignKey:ProjectID"`
	Assignees   []User       `json:"assignees,omitempty" gorm:"many2many:task_assignees;"`
}

// TaskCreateRequest represents the request to create a new task
type TaskCreateRequest struct {
	Title       string       `json:"title" validate:"required,min=1,max=255"`
	Description string       `json:"description" validate:"max=1000"`
	Status      TaskStatus   `json:"status" validate:"omitempty,oneof=todo in_progress done canceled"`
	Priority    TaskPriority `json:"priority" validate:"omitempty,oneof=low medium high"`
	ProjectID   string       `json:"project_id" validate:"required,uuid"`
	DueDate     *string      `json:"due_date"`
	AssigneeIDs []string     `json:"assignee_ids"`
}

// TaskUpdateRequest represents the request to update a task
type TaskUpdateRequest struct {
	Title       *string       `json:"title,omitempty" validate:"omitempty,min=1,max=255"`
	Description *string       `json:"description,omitempty" validate:"omitempty,max=1000"`
	Status      *TaskStatus   `json:"status,omitempty" validate:"omitempty,oneof=todo in_progress done canceled"`
	Priority    *TaskPriority `json:"priority,omitempty" validate:"omitempty,oneof=low medium high"`
	DueDate     *string       `json:"due_date,omitempty"`
	AssigneeIDs []string      `json:"assignee_ids,omitempty"`
}

// TaskInfo represents public task information
type TaskInfo struct {
	ID          string       `json:"id"`
	Title       string       `json:"title"`
	Description string       `json:"description"`
	Status      TaskStatus   `json:"status"`
	Priority    TaskPriority `json:"priority"`
	ProjectID   string       `json:"project_id"`
	DueDate     *string      `json:"due_date"`
	Project     ProjectInfo  `json:"project,omitempty"`
	Assignees   []UserInfo   `json:"assignees,omitempty"`
	CreatedAt   string       `json:"created_at"`
	UpdatedAt   string       `json:"updated_at"`
}

// TaskAssignee represents the many-to-many relationship between tasks and users
type TaskAssignee struct {
	TaskID string `json:"task_id" gorm:"type:uuid;primaryKey"`
	UserID string `json:"user_id" gorm:"type:uuid;primaryKey"`
	Task   Task   `json:"task,omitempty" gorm:"foreignKey:TaskID"`
	User   User   `json:"user,omitempty" gorm:"foreignKey:UserID"`
}

// BeforeCreate is called before creating a task
func (t *Task) BeforeCreate(tx *gorm.DB) error {
	t.BaseModel.BeforeCreate()

	// Normalize title and description
	t.Title = strings.TrimSpace(t.Title)
	t.Description = strings.TrimSpace(t.Description)

	// Set default values
	if t.Status == "" {
		t.Status = TaskStatusTodo
	}
	if t.Priority == "" {
		t.Priority = TaskPriorityMedium
	}

	return t.Validate()
}

// BeforeUpdate is called before updating a task
func (t *Task) BeforeUpdate(tx *gorm.DB) error {
	t.BaseModel.BeforeUpdate()

	// Normalize fields if they're being updated
	if t.Title != "" {
		t.Title = strings.TrimSpace(t.Title)
	}
	if t.Description != "" {
		t.Description = strings.TrimSpace(t.Description)
	}

	return t.Validate()
}

// Validate validates task data
func (t *Task) Validate() error {
	if t.Title == "" {
		return errors.New("title is required")
	}

	if len(t.Title) > 255 {
		return errors.New("title must not exceed 255 characters")
	}

	if t.ProjectID == "" {
		return errors.New("project_id is required")
	}

	// Validate status
	if t.Status != "" {
		switch t.Status {
		case TaskStatusTodo, TaskStatusInProgress, TaskStatusDone, TaskStatusCanceled:
			// Valid status
		default:
			return errors.New("invalid status")
		}
	}

	// Validate priority
	if t.Priority != "" {
		switch t.Priority {
		case TaskPriorityLow, TaskPriorityMedium, TaskPriorityHigh:
			// Valid priority
		default:
			return errors.New("invalid priority")
		}
	}

	return nil
}

// ToTaskInfo converts Task to TaskInfo (public information)
func (t *Task) ToTaskInfo() TaskInfo {
	taskInfo := TaskInfo{
		ID:          t.ID,
		Title:       t.Title,
		Description: t.Description,
		Status:      t.Status,
		Priority:    t.Priority,
		ProjectID:   t.ProjectID,
		DueDate:     t.DueDate,
		CreatedAt:   t.CreatedAt.Format("2006-01-02T15:04:05Z07:00"),
		UpdatedAt:   t.UpdatedAt.Format("2006-01-02T15:04:05Z07:00"),
		Assignees:   make([]UserInfo, len(t.Assignees)),
	}

	// Add project info if loaded
	if t.Project.ID != "" {
		taskInfo.Project = t.Project.ToProjectInfo()
	}

	// Add assignee info if loaded
	for i, assignee := range t.Assignees {
		taskInfo.Assignees[i] = assignee.ToUserInfo()
	}

	return taskInfo
}

// IsAssignedTo checks if a user is assigned to this task
func (t *Task) IsAssignedTo(userID string) bool {
	for _, assignee := range t.Assignees {
		if assignee.ID == userID {
			return true
		}
	}
	return false
}

// IsCompleted checks if the task is completed
func (t *Task) IsCompleted() bool {
	return t.Status == TaskStatusDone
}

// IsCanceled checks if the task is canceled
func (t *Task) IsCanceled() bool {
	return t.Status == TaskStatusCanceled
}

// IsInProgress checks if the task is in progress
func (t *Task) IsInProgress() bool {
	return t.Status == TaskStatusInProgress
}

// IsTodo checks if the task is todo
func (t *Task) IsTodo() bool {
	return t.Status == TaskStatusTodo
}