// Package story provides database access for the Story resource.
// It defines the DBStory struct and StoryTranslator to convert between
// the API format (api.pb.go) and the database format (schema.sql).
package story

import (
	"database/sql"
	"errors"
	"fmt"
	"regexp"
	"strings"
	"time"

	v1 "git.tipsy.codes/charles/webstory/pkg/api/webstory/v1"
	"github.com/google/uuid"
	"google.golang.org/protobuf/types/known/timestamppb"
)

var (
	// ErrStoryIDInvalid is returned when the story_id format is invalid.
	ErrStoryIDInvalid = errors.New("invalid story_id format: must be 4-63 characters, matching pattern /[a-z][0-9-]/")

	// storyIDPattern validates the story_id format.
	// Must start with a lowercase letter, end with a letter or number,
	// and contain only lowercase letters, numbers, and hyphens.
	storyIDPattern = regexp.MustCompile(`^[a-z][0-9a-z-]{2,61}[0-9a-z]$`)
)

// DBStory represents a story in the PostgreSQL database.
// This is the database model that corresponds to the schema.sql structure.
type DBStory struct {
	// Database-generated unique identifier
	ID int64

	// StoryID is the resource identifier used in the story's resource name.
	// Format: stories/{story_id}
	StoryID string

	// Title of the story.
	Title string

	// Content of the story.
	Content string

	// Description or summary of the story.
	Description string

	// Labels for organizing and categorizing the story.
	Labels []string

	// CreatedAt is when the story was created.
	CreatedAt time.Time

	// UpdatedAt is when the story was last updated.
	UpdatedAt time.Time

	// Etag is used for concurrency control.
	Etag string
}

// StoryTranslator provides conversion methods between API and database formats.
type StoryTranslator struct{}

// NewStoryTranslator creates a new StoryTranslator instance.
func NewStoryTranslator() *StoryTranslator {
	return &StoryTranslator{}
}

// FromAPI converts an API Story message to a DBStory struct.
// This handles the conversion from the protobuf-generated type to the database model.
func (t *StoryTranslator) FromAPI(apiStory *v1.Story) (*DBStory, error) {
	if apiStory == nil {
		return nil, errors.New("api story cannot be nil")
	}

	// Validate story_id if provided (required for create operations)
	if apiStory.StoryId != "" {
		if err := validateStoryID(apiStory.StoryId); err != nil {
			return nil, err
		}
	}

	// Validate title (required field)
	if apiStory.Title == "" {
		return nil, errors.New("title is required")
	}

	// Convert labels (may be nil)
	labels := apiStory.GetLabels()
	if labels == nil {
		labels = []string{}
	}

	// Build resource name if not set
	name := apiStory.GetName()
	if name == "" && apiStory.StoryId != "" {
		name = fmt.Sprintf("stories/%s", apiStory.StoryId)
	}

	// Convert timestamps if provided
	var createdAt, updatedAt time.Time
	if apiStory.GetCreateTime() != nil {
		createdAt = apiStory.CreateTime.AsTime()
	}
	if apiStory.GetUpdateTime() != nil {
		updatedAt = apiStory.UpdateTime.AsTime()
	}

	return &DBStory{
		ID:          0, // Will be generated by database
		StoryID:     apiStory.StoryId,
		Title:       apiStory.Title,
		Content:     apiStory.Content,
		Description: apiStory.Description,
		Labels:      labels,
		CreatedAt:   createdAt,
		UpdatedAt:   updatedAt,
		Etag:        apiStory.Etag,
	}, nil
}

// ToAPI converts a DBStory struct to an API Story message.
// This prepares the database model for response serialization.
func (t *StoryTranslator) ToAPI(dbStory *DBStory) *v1.Story {
	if dbStory == nil {
		return nil
	}

	// Build scenes list from the story
	scenes := make([]*v1.Scene, 0)

	// Build actors list from the story
	actors := make([]*v1.Actor, 0)

	// Build resource name
	name := fmt.Sprintf("stories/%s", dbStory.StoryID)

	return &v1.Story{
		Name:        name,
		StoryId:     dbStory.StoryID,
		Title:       dbStory.Title,
		Content:     dbStory.Content,
		Description: dbStory.Description,
		Labels:      dbStory.Labels,
		CreateTime:  timestamppb.New(dbStory.CreatedAt),
		UpdateTime:  timestamppb.New(dbStory.UpdatedAt),
		Etag:        dbStory.Etag,
		Scenes:      scenes,
		Actors:      actors,
	}
}

// ToAPIDetailed converts a DBStory to an API Story with nested scenes and actors.
// This is used when loading stories with their related resources.
func (t *StoryTranslator) ToAPIDetailed(dbStory *DBStory, scenes []*v1.Scene, actors []*v1.Actor) *v1.Story {
	apiStory := t.ToAPI(dbStory)
	apiStory.Scenes = scenes
	apiStory.Actors = actors
	return apiStory
}

// Validate validates the DBStory struct.
func (s *DBStory) Validate() error {
	if s.StoryID == "" {
		return errors.New("story_id is required")
	}

	if err := validateStoryID(s.StoryID); err != nil {
		return err
	}

	if s.Title == "" {
		return errors.New("title is required")
	}

	return nil
}

// validateStoryID validates the story_id format.
func validateStoryID(storyID string) error {
	if storyID == "" {
		return ErrStoryIDInvalid
	}

	if len(storyID) < 4 || len(storyID) > 63 {
		return ErrStoryIDInvalid
	}

	if !storyIDPattern.MatchString(storyID) {
		return ErrStoryIDInvalid
	}

	return nil
}

// Save saves the DBStory to the database.
// If the story has an ID, it performs an UPDATE; otherwise, it performs an INSERT.
func (s *DBStory) Save(db *sql.DB) error {
	if err := s.Validate(); err != nil {
		return err
	}

	// Check if this is an update (has ID from database) or insert
	if s.ID > 0 {
		return s.update(db)
	}

	return s.insert(db)
}

// insert inserts a new story into the database.
func (s *DBStory) insert(db *sql.DB) error {
	query := `
		INSERT INTO stories (story_id, title, content, description, labels, created_at, updated_at, etag)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
		RETURNING id, created_at, updated_at, etag
	`

	labels := make([]string, len(s.Labels))
	copy(labels, s.Labels)

	now := time.Now()
	if s.CreatedAt.IsZero() {
		s.CreatedAt = now
	}
	if s.UpdatedAt.IsZero() {
		s.UpdatedAt = now
	}

	// Generate etag if not provided
	etag := s.Etag
	if etag == "" {
		etag = generateEtag()
	}

	var createdID int64
	var createdAt, updatedAt time.Time
	var returnedEtag string

	err := db.QueryRow(
		query,
		s.StoryID,
		s.Title,
		s.Content,
		s.Description,
		labels,
		s.CreatedAt,
		s.UpdatedAt,
		etag,
	).Scan(&createdID, &createdAt, &updatedAt, &returnedEtag)

	if err != nil {
		return fmt.Errorf("failed to insert story: %w", err)
	}

	s.ID = createdID
	s.CreatedAt = createdAt
	s.UpdatedAt = updatedAt
	s.Etag = returnedEtag

	return nil
}

// update updates an existing story in the database.
func (s *DBStory) update(db *sql.DB) error {
	query := `
		UPDATE stories
		SET title = $1,
		    content = $2,
		    description = $3,
		    labels = $4,
		    updated_at = $5,
		    etag = $6
		WHERE id = $7
		RETURNING created_at, updated_at, etag
	`

	labels := make([]string, len(s.Labels))
	copy(labels, s.Labels)

	now := time.Now()
	if s.UpdatedAt.IsZero() {
		s.UpdatedAt = now
	}

	etag := s.Etag
	if etag == "" {
		etag = generateEtag()
	}

	var createdAt, updatedAt time.Time
	var returnedEtag string

	err := db.QueryRow(
		query,
		s.Title,
		s.Content,
		s.Description,
		labels,
		s.UpdatedAt,
		etag,
		s.ID,
	).Scan(&createdAt, &updatedAt, &returnedEtag)

	if err != nil {
		return fmt.Errorf("failed to update story: %w", err)
	}

	s.CreatedAt = createdAt
	s.UpdatedAt = updatedAt
	s.Etag = returnedEtag

	return nil
}

// generateEtag generates a unique etag for the story.
func generateEtag() string {
	return uuid.New().String()
}

// GetByID retrieves a story by its primary key ID.
func GetByID(db *sql.DB, id int64) (*DBStory, error) {
	query := `
		SELECT id, story_id, title, content, description, labels, created_at, updated_at, etag
		FROM stories
		WHERE id = $1
	`

	story := &DBStory{}
	err := db.QueryRow(query, id).Scan(
		&story.ID,
		&story.StoryID,
		&story.Title,
		&story.Content,
		&story.Description,
		&story.Labels,
		&story.CreatedAt,
		&story.UpdatedAt,
		&story.Etag,
	)

	if err != nil {
		if err == sql.ErrNoRows {
			return nil, fmt.Errorf("story with id %d not found", id)
		}
		return nil, fmt.Errorf("failed to get story: %w", err)
	}

	return story, nil
}

// GetByStoryID retrieves a story by its story_id.
func GetByStoryID(db *sql.DB, storyID string) (*DBStory, error) {
	if err := validateStoryID(storyID); err != nil {
		return nil, err
	}

	query := `
		SELECT id, story_id, title, content, description, labels, created_at, updated_at, etag
		FROM stories
		WHERE story_id = $1
	`

	story := &DBStory{}
	err := db.QueryRow(query, storyID).Scan(
		&story.ID,
		&story.StoryID,
		&story.Title,
		&story.Content,
		&story.Description,
		&story.Labels,
		&story.CreatedAt,
		&story.UpdatedAt,
		&story.Etag,
	)

	if err != nil {
		if err == sql.ErrNoRows {
			return nil, fmt.Errorf("story with story_id '%s' not found", storyID)
		}
		return nil, fmt.Errorf("failed to get story: %w", err)
	}

	return story, nil
}

// List returns a paginated list of stories.
func List(db *sql.DB, pageSize int, pageToken string, filter string, orderBy string) ([]*DBStory, string, error) {
	if pageSize <= 0 || pageSize > 1000 {
		pageSize = 50
	}

	var query string
	var args []interface{}

	switch orderBy {
	case "title":
		query = `
			SELECT id, story_id, title, content, description, labels, created_at, updated_at, etag
			FROM stories
			WHERE 1=1
		`
	case "create_time":
		fallthrough
	default:
		query = `
			SELECT id, story_id, title, content, description, labels, created_at, updated_at, etag
			FROM stories
			WHERE 1=1
		`
	}

	// Parse page token for pagination
	if pageToken != "" {
		query += " AND id > " + pageToken
	}

	query += " ORDER BY id DESC"
	query += fmt.Sprintf(" LIMIT %d", pageSize)

	rows, err := db.Query(query, args...)
	if err != nil {
		return nil, "", fmt.Errorf("failed to list stories: %w", err)
	}
	defer rows.Close()

	stories := make([]*DBStory, 0)
	for rows.Next() {
		var id int64
		var storyID string
		var title, content, description, etag string
		var labels []string
		var createdAt, updatedAt time.Time

		err := rows.Scan(&id, &storyID, &title, &content, &description, &labels, &createdAt, &updatedAt, &etag)
		if err != nil {
			return nil, "", fmt.Errorf("failed to scan story: %w", err)
		}

		stories = append(stories, &DBStory{
			ID:          id,
			StoryID:     storyID,
			Title:       title,
			Content:     content,
			Description: description,
			Labels:      labels,
			CreatedAt:   createdAt,
			UpdatedAt:   updatedAt,
			Etag:        etag,
		})
	}

	if err := rows.Err(); err != nil {
		return nil, "", fmt.Errorf("error iterating stories: %w", err)
	}

	var nextPageToken string
	if len(stories) == pageSize {
		// Use the last story's ID as the next page token
		nextPageToken = fmt.Sprintf("%d", stories[len(stories)-1].ID)
	}

	return stories, nextPageToken, nil
}

// Delete removes a story from the database.
func Delete(db *sql.DB, id int64) error {
	query := `
		DELETE FROM stories
		WHERE id = $1
	`

	result, err := db.Exec(query, id)
	if err != nil {
		return fmt.Errorf("failed to delete story: %w", err)
	}

	rowsAffected, err := result.RowsAffected()
	if err != nil {
		return fmt.Errorf("failed to get rows affected: %w", err)
	}

	if rowsAffected == 0 {
		return fmt.Errorf("story with id %d not found", id)
	}

	return nil
}

// GetStoryIDForResourceName extracts the story_id from a resource name.
// Resource name format: stories/{story_id}
func GetStoryIDForResourceName(resourceName string) (string, error) {
	prefix := "stories/"
	if !strings.HasPrefix(resourceName, prefix) {
		return "", fmt.Errorf("invalid resource name: must start with '%s', got '%s'", prefix, resourceName)
	}

	storyID := strings.TrimPrefix(resourceName, prefix)
	if storyID == "" {
		return "", errors.New("story_id is empty in resource name")
	}

	if err := validateStoryID(storyID); err != nil {
		return "", fmt.Errorf("invalid story_id in resource name: %w", err)
	}

	return storyID, nil
}