// SPDX-License-Identifier: AGPL-3.0-or-later

package store

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

	"kode.naiv.no/olemd/favoritter/internal/model"
)

var ErrFaveNotFound = errors.New("fave not found")

type FaveStore struct {
	db *sql.DB
}

func NewFaveStore(db *sql.DB) *FaveStore {
	return &FaveStore{db: db}
}

// Create inserts a new fave and returns it with its ID populated.
func (s *FaveStore) Create(userID int64, description, url, imagePath, notes, privacy string) (*model.Fave, error) {
	result, err := s.db.Exec(
		`INSERT INTO faves (user_id, description, url, image_path, notes, privacy)
		VALUES (?, ?, ?, ?, ?, ?)`,
		userID, description, url, imagePath, notes, privacy,
	)
	if err != nil {
		return nil, fmt.Errorf("insert fave: %w", err)
	}

	id, _ := result.LastInsertId()
	return s.GetByID(id)
}

// GetByID returns a fave by its ID, including joined user info.
func (s *FaveStore) GetByID(id int64) (*model.Fave, error) {
	f := &model.Fave{}
	var createdAt, updatedAt string
	err := s.db.QueryRow(
		`SELECT f.id, f.user_id, f.description, f.url, f.image_path, f.notes, f.privacy,
			f.created_at, f.updated_at, u.username, COALESCE(NULLIF(u.display_name, ''), u.username)
		FROM faves f
		JOIN users u ON u.id = f.user_id
		WHERE f.id = ?`, id,
	).Scan(
		&f.ID, &f.UserID, &f.Description, &f.URL, &f.ImagePath, &f.Notes, &f.Privacy,
		&createdAt, &updatedAt, &f.Username, &f.DisplayName,
	)
	if errors.Is(err, sql.ErrNoRows) {
		return nil, ErrFaveNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("query fave: %w", err)
	}
	f.CreatedAt, _ = time.Parse(time.RFC3339, createdAt)
	f.UpdatedAt, _ = time.Parse(time.RFC3339, updatedAt)
	return f, nil
}

// Update modifies an existing fave's fields.
func (s *FaveStore) Update(id int64, description, url, imagePath, notes, privacy string) error {
	_, err := s.db.Exec(
		`UPDATE faves SET description = ?, url = ?, image_path = ?, notes = ?, privacy = ?,
			updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
		WHERE id = ?`,
		description, url, imagePath, notes, privacy, id,
	)
	return err
}

// Delete removes a fave by its ID. The cascade will clean up fave_tags.
func (s *FaveStore) Delete(id int64) error {
	result, err := s.db.Exec("DELETE FROM faves WHERE id = ?", id)
	if err != nil {
		return err
	}
	n, _ := result.RowsAffected()
	if n == 0 {
		return ErrFaveNotFound
	}
	return nil
}

// ListByUser returns all faves for a user (both public and private),
// ordered by newest first, with pagination.
func (s *FaveStore) ListByUser(userID int64, limit, offset int) ([]*model.Fave, int, error) {
	var total int
	err := s.db.QueryRow("SELECT COUNT(*) FROM faves WHERE user_id = ?", userID).Scan(&total)
	if err != nil {
		return nil, 0, err
	}

	rows, err := s.db.Query(
		`SELECT f.id, f.user_id, f.description, f.url, f.image_path, f.notes, f.privacy,
			f.created_at, f.updated_at, u.username, COALESCE(NULLIF(u.display_name, ''), u.username)
		FROM faves f
		JOIN users u ON u.id = f.user_id
		WHERE f.user_id = ?
		ORDER BY f.created_at DESC
		LIMIT ? OFFSET ?`,
		userID, limit, offset,
	)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()

	faves, err := s.scanFaves(rows)
	return faves, total, err
}

// ListPublicByUser returns only public faves for a user, with pagination.
func (s *FaveStore) ListPublicByUser(userID int64, limit, offset int) ([]*model.Fave, int, error) {
	var total int
	err := s.db.QueryRow(
		"SELECT COUNT(*) FROM faves WHERE user_id = ? AND privacy = 'public'", userID,
	).Scan(&total)
	if err != nil {
		return nil, 0, err
	}

	rows, err := s.db.Query(
		`SELECT f.id, f.user_id, f.description, f.url, f.image_path, f.notes, f.privacy,
			f.created_at, f.updated_at, u.username, COALESCE(NULLIF(u.display_name, ''), u.username)
		FROM faves f
		JOIN users u ON u.id = f.user_id
		WHERE f.user_id = ? AND f.privacy = 'public'
		ORDER BY f.created_at DESC
		LIMIT ? OFFSET ?`,
		userID, limit, offset,
	)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()

	faves, err := s.scanFaves(rows)
	return faves, total, err
}

// ListPublic returns all public faves across all users, with pagination.
func (s *FaveStore) ListPublic(limit, offset int) ([]*model.Fave, int, error) {
	var total int
	err := s.db.QueryRow("SELECT COUNT(*) FROM faves WHERE privacy = 'public'").Scan(&total)
	if err != nil {
		return nil, 0, err
	}

	rows, err := s.db.Query(
		`SELECT f.id, f.user_id, f.description, f.url, f.image_path, f.notes, f.privacy,
			f.created_at, f.updated_at, u.username, COALESCE(NULLIF(u.display_name, ''), u.username)
		FROM faves f
		JOIN users u ON u.id = f.user_id
		WHERE f.privacy = 'public'
		ORDER BY f.created_at DESC
		LIMIT ? OFFSET ?`,
		limit, offset,
	)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()

	faves, err := s.scanFaves(rows)
	return faves, total, err
}

// ListByTag returns all public faves with a given tag, with pagination.
func (s *FaveStore) ListByTag(tagName string, limit, offset int) ([]*model.Fave, int, error) {
	var total int
	err := s.db.QueryRow(
		`SELECT COUNT(*) FROM faves f
		JOIN fave_tags ft ON ft.fave_id = f.id
		JOIN tags t ON t.id = ft.tag_id
		WHERE t.name = ? AND f.privacy = 'public'`, tagName,
	).Scan(&total)
	if err != nil {
		return nil, 0, err
	}

	rows, err := s.db.Query(
		`SELECT f.id, f.user_id, f.description, f.url, f.image_path, f.notes, f.privacy,
			f.created_at, f.updated_at, u.username, COALESCE(NULLIF(u.display_name, ''), u.username)
		FROM faves f
		JOIN users u ON u.id = f.user_id
		JOIN fave_tags ft ON ft.fave_id = f.id
		JOIN tags t ON t.id = ft.tag_id
		WHERE t.name = ? AND f.privacy = 'public'
		ORDER BY f.created_at DESC
		LIMIT ? OFFSET ?`,
		tagName, limit, offset,
	)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()

	faves, err := s.scanFaves(rows)
	return faves, total, err
}

// Count returns the total number of faves.
func (s *FaveStore) Count() (int, error) {
	var n int
	err := s.db.QueryRow("SELECT COUNT(*) FROM faves").Scan(&n)
	return n, err
}

// LoadTags populates the Tags field on each fave.
func (s *FaveStore) LoadTags(faves []*model.Fave) error {
	if len(faves) == 0 {
		return nil
	}

	// Build a map for fast lookup.
	faveMap := make(map[int64]*model.Fave, len(faves))
	ids := make([]any, len(faves))
	placeholders := make([]string, len(faves))
	for i, f := range faves {
		faveMap[f.ID] = f
		ids[i] = f.ID
		placeholders[i] = "?"
	}

	query := fmt.Sprintf(
		`SELECT ft.fave_id, t.id, t.name
		FROM fave_tags ft
		JOIN tags t ON t.id = ft.tag_id
		WHERE ft.fave_id IN (%s)
		ORDER BY t.name COLLATE NOCASE`,
		strings.Join(placeholders, ","),
	)

	rows, err := s.db.Query(query, ids...)
	if err != nil {
		return fmt.Errorf("load tags: %w", err)
	}
	defer rows.Close()

	for rows.Next() {
		var faveID int64
		var tag model.Tag
		if err := rows.Scan(&faveID, &tag.ID, &tag.Name); err != nil {
			return fmt.Errorf("scan tag: %w", err)
		}
		if f, ok := faveMap[faveID]; ok {
			f.Tags = append(f.Tags, tag)
		}
	}
	return rows.Err()
}

func (s *FaveStore) scanFaves(rows *sql.Rows) ([]*model.Fave, error) {
	var faves []*model.Fave
	for rows.Next() {
		f := &model.Fave{}
		var createdAt, updatedAt string
		err := rows.Scan(
			&f.ID, &f.UserID, &f.Description, &f.URL, &f.ImagePath, &f.Notes, &f.Privacy,
			&createdAt, &updatedAt, &f.Username, &f.DisplayName,
		)
		if err != nil {
			return nil, fmt.Errorf("scan fave: %w", err)
		}
		f.CreatedAt, _ = time.Parse(time.RFC3339, createdAt)
		f.UpdatedAt, _ = time.Parse(time.RFC3339, updatedAt)
		faves = append(faves, f)
	}
	return faves, rows.Err()
}