package store

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"strings"
)

type Item struct {
	ID          int64             `json:"id"`
	ListID      int64             `json:"listId"`
	Rank        int               `json:"rank"`
	Title       string            `json:"title"`
	Subtitle    string            `json:"subtitle"`
	Year        string            `json:"year"`
	Image       string            `json:"image"`       // cached file name under /images/
	ImageSource string            `json:"imageSource"` // where the image came from
	CustomArt   bool              `json:"customArt"`   // chosen by the owner, not the source
	Provider    string            `json:"provider"`
	ProviderID  string            `json:"providerId"`
	ExternalURL string            `json:"externalUrl"`
	Description string            `json:"description"` // from the source, editable
	Note        string            `json:"note"`        // the owner's "why it's here"
	Extra       map[string]string `json:"extra"`
}

const itemColumns = `id, list_id, rank, title, subtitle, year, image, image_source, image_custom, provider, provider_id, external_url, description, note, extra`

func scanItem(row interface{ Scan(...any) error }) (Item, error) {
	var it Item
	var extra string
	err := row.Scan(&it.ID, &it.ListID, &it.Rank, &it.Title, &it.Subtitle, &it.Year, &it.Image, &it.ImageSource, &it.CustomArt,
		&it.Provider, &it.ProviderID, &it.ExternalURL, &it.Description, &it.Note, &extra)
	if errors.Is(err, sql.ErrNoRows) {
		return it, ErrNotFound
	}
	if err != nil {
		return it, err
	}
	it.Extra = map[string]string{}
	_ = json.Unmarshal([]byte(extra), &it.Extra)
	return it, nil
}

// Items returns a page of a list's items in rank order. limit <= 0 means all.
func (s *Store) Items(ctx context.Context, listID int64, offset, limit int) ([]Item, error) {
	if limit <= 0 {
		limit = -1
	}
	rows, err := s.db.QueryContext(ctx, `SELECT `+itemColumns+` FROM items WHERE list_id = ? ORDER BY rank LIMIT ? OFFSET ?`, listID, limit, offset)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []Item{}
	for rows.Next() {
		it, err := scanItem(rows)
		if err != nil {
			return nil, err
		}
		out = append(out, it)
	}
	return out, rows.Err()
}

func (s *Store) ItemByID(ctx context.Context, id int64) (Item, error) {
	return scanItem(s.db.QueryRowContext(ctx, `SELECT `+itemColumns+` FROM items WHERE id = ?`, id))
}

// FindItemByProvider returns an item in the list that came from the same
// provider entry, if any.
func (s *Store) FindItemByProvider(ctx context.Context, listID int64, provider, providerID string) (Item, error) {
	if provider == "" || providerID == "" {
		return Item{}, ErrNotFound
	}
	return scanItem(s.db.QueryRowContext(ctx, `SELECT `+itemColumns+` FROM items WHERE list_id = ? AND provider = ? AND provider_id = ? LIMIT 1`,
		listID, provider, providerID))
}

func (it *Item) normalize() error {
	it.Title = strings.TrimSpace(it.Title)
	it.Subtitle = strings.TrimSpace(it.Subtitle)
	it.Year = strings.TrimSpace(it.Year)
	it.Note = strings.TrimSpace(it.Note)
	it.Description = strings.TrimSpace(it.Description)
	it.ExternalURL = strings.TrimSpace(it.ExternalURL)
	if it.Title == "" {
		return invalid("Title is required")
	}
	if len(it.Title) > 500 || len(it.Subtitle) > 500 || len(it.Year) > 20 || len(it.Note) > 10000 || len(it.Description) > 10000 || len(it.ExternalURL) > 2000 {
		return invalid("One of the fields is too long")
	}
	if it.ExternalURL != "" && !strings.HasPrefix(it.ExternalURL, "https://") && !strings.HasPrefix(it.ExternalURL, "http://") {
		return invalid("Links must start with http:// or https://")
	}
	clean := map[string]string{}
	for k, v := range it.Extra {
		if v = strings.TrimSpace(v); v != "" && len(k) <= 50 && len(v) <= 500 {
			clean[k] = v
		}
	}
	it.Extra = clean
	return nil
}

func extraJSON(m map[string]string) string {
	b, _ := json.Marshal(m)
	return string(b)
}

// AddItem inserts it into the list at rank (1-based); rank <= 0 or beyond the
// end appends. Items at or below the rank shift down by one.
func (s *Store) AddItem(ctx context.Context, it Item, rank int) (Item, error) {
	if err := it.normalize(); err != nil {
		return it, err
	}
	tx, err := s.db.BeginTx(ctx, nil)
	if err != nil {
		return it, err
	}
	defer tx.Rollback()

	var maxItems, count int
	err = tx.QueryRowContext(ctx, `SELECT max_items, (SELECT COUNT(*) FROM items WHERE list_id = lists.id) FROM lists WHERE id = ?`, it.ListID).Scan(&maxItems, &count)
	if errors.Is(err, sql.ErrNoRows) {
		return it, ErrNotFound
	}
	if err != nil {
		return it, err
	}
	if count >= maxItems {
		return it, invalid("This list is full (%d of %d). Increase its size or remove an item first.", count, maxItems)
	}
	if rank <= 0 || rank > count+1 {
		rank = count + 1
	}
	if _, err := tx.ExecContext(ctx, `UPDATE items SET rank = rank + 1 WHERE list_id = ? AND rank >= ?`, it.ListID, rank); err != nil {
		return it, err
	}
	res, err := tx.ExecContext(ctx, `INSERT INTO items (list_id, rank, title, subtitle, year, image, image_source, image_custom, provider, provider_id, external_url, description, note, extra)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
		it.ListID, rank, it.Title, it.Subtitle, it.Year, it.Image, it.ImageSource, it.CustomArt, it.Provider, it.ProviderID, it.ExternalURL, it.Description, it.Note, extraJSON(it.Extra))
	if err != nil {
		return it, err
	}
	if err := touchList(ctx, tx, it.ListID); err != nil {
		return it, err
	}
	if err := tx.Commit(); err != nil {
		return it, err
	}
	id, _ := res.LastInsertId()
	return s.ItemByID(ctx, id)
}

// UpdateItem saves everything except rank and list.
func (s *Store) UpdateItem(ctx context.Context, it Item) (Item, error) {
	if err := it.normalize(); err != nil {
		return it, err
	}
	res, err := s.db.ExecContext(ctx, `UPDATE items SET title=?, subtitle=?, year=?, image=?, image_source=?, image_custom=?, external_url=?, description=?, note=?, extra=?, updated_at=unixepoch() WHERE id=?`,
		it.Title, it.Subtitle, it.Year, it.Image, it.ImageSource, it.CustomArt, it.ExternalURL, it.Description, it.Note, extraJSON(it.Extra), it.ID)
	if err != nil {
		return it, err
	}
	if n, _ := res.RowsAffected(); n == 0 {
		return it, ErrNotFound
	}
	cur, err := s.ItemByID(ctx, it.ID)
	if err == nil {
		_, err = s.db.ExecContext(ctx, `UPDATE lists SET updated_at = unixepoch() WHERE id = ?`, cur.ListID)
	}
	return cur, err
}

// MoveItem moves an item to a new 1-based rank, shifting the items between.
func (s *Store) MoveItem(ctx context.Context, id int64, newRank int) error {
	tx, err := s.db.BeginTx(ctx, nil)
	if err != nil {
		return err
	}
	defer tx.Rollback()
	var listID int64
	var oldRank, count int
	err = tx.QueryRowContext(ctx, `SELECT list_id, rank, (SELECT COUNT(*) FROM items x WHERE x.list_id = items.list_id) FROM items WHERE id = ?`, id).Scan(&listID, &oldRank, &count)
	if errors.Is(err, sql.ErrNoRows) {
		return ErrNotFound
	}
	if err != nil {
		return err
	}
	if newRank < 1 {
		newRank = 1
	}
	if newRank > count {
		newRank = count
	}
	if newRank == oldRank {
		return nil
	}
	if newRank < oldRank {
		_, err = tx.ExecContext(ctx, `UPDATE items SET rank = rank + 1 WHERE list_id = ? AND rank >= ? AND rank < ?`, listID, newRank, oldRank)
	} else {
		_, err = tx.ExecContext(ctx, `UPDATE items SET rank = rank - 1 WHERE list_id = ? AND rank > ? AND rank <= ?`, listID, oldRank, newRank)
	}
	if err != nil {
		return err
	}
	if _, err := tx.ExecContext(ctx, `UPDATE items SET rank = ? WHERE id = ?`, newRank, id); err != nil {
		return err
	}
	if err := touchList(ctx, tx, listID); err != nil {
		return err
	}
	return tx.Commit()
}

func (s *Store) DeleteItem(ctx context.Context, id int64) (Item, error) {
	it, err := s.ItemByID(ctx, id)
	if err != nil {
		return it, err
	}
	tx, err := s.db.BeginTx(ctx, nil)
	if err != nil {
		return it, err
	}
	defer tx.Rollback()
	if _, err := tx.ExecContext(ctx, `DELETE FROM items WHERE id = ?`, id); err != nil {
		return it, err
	}
	if _, err := tx.ExecContext(ctx, `UPDATE items SET rank = rank - 1 WHERE list_id = ? AND rank > ?`, it.ListID, it.Rank); err != nil {
		return it, err
	}
	if err := touchList(ctx, tx, it.ListID); err != nil {
		return it, err
	}
	return it, tx.Commit()
}

// ImageInUse reports whether any item or setting still references a cached
// image file.
func (s *Store) ImageInUse(ctx context.Context, name string) (bool, error) {
	var n int
	err := s.db.QueryRowContext(ctx, `SELECT (SELECT COUNT(*) FROM items WHERE image = ?) + (SELECT COUNT(*) FROM settings WHERE value = ?)`, name, name).Scan(&n)
	return n > 0, err
}

// ListImages returns the image file names used by a list's items.
func (s *Store) ListImages(ctx context.Context, listID int64) ([]string, error) {
	rows, err := s.db.QueryContext(ctx, `SELECT DISTINCT image FROM items WHERE list_id = ? AND image != ''`, listID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []string
	for rows.Next() {
		var n string
		if err := rows.Scan(&n); err != nil {
			return nil, err
		}
		out = append(out, n)
	}
	return out, rows.Err()
}

func touchList(ctx context.Context, tx *sql.Tx, listID int64) error {
	_, err := tx.ExecContext(ctx, `UPDATE lists SET updated_at = unixepoch() WHERE id = ?`, listID)
	return err
}