package store

import (
	"context"
	"database/sql"
	"fmt"
	"strings"

	_ "modernc.org/sqlite"
)

type SQLiteCounterStore struct {
	db *sql.DB
}

func NewSQLiteCounterStore(path string) (*SQLiteCounterStore, error) {
	db, err := sql.Open("sqlite", path)
	if err != nil {
		return nil, err
	}
	db.SetMaxOpenConns(1)
	return &SQLiteCounterStore{db: db}, nil
}

func (s *SQLiteCounterStore) Init(ctx context.Context) error {
	_, err := s.db.ExecContext(ctx, `
		CREATE TABLE IF NOT EXISTS ticks (
			slug TEXT PRIMARY KEY,
			count INTEGER NOT NULL DEFAULT 0,
			created_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP,
			updated_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
		);
	`)
	return err
}

func (s *SQLiteCounterStore) Increment(ctx context.Context, slug string) (int64, error) {
	if slug == "" {
		return 0, fmt.Errorf("empty slug")
	}

	_, err := s.db.ExecContext(ctx, `
		INSERT INTO ticks(slug, count) VALUES(?, 1)
		ON CONFLICT(slug) DO UPDATE SET
			count = count + 1,
			updated_at = CURRENT_TIMESTAMP;
	`, slug)
	if err != nil {
		return 0, err
	}
	return s.Get(ctx, slug)
}

func (s *SQLiteCounterStore) Get(ctx context.Context, slug string) (int64, error) {
	var count int64
	err := s.db.QueryRowContext(ctx, `SELECT count FROM ticks WHERE slug = ?`, slug).Scan(&count)
	if err == sql.ErrNoRows {
		return 0, nil
	}
	return count, err
}

func (s *SQLiteCounterStore) GetMany(ctx context.Context, slugs []string) (map[string]int64, error) {
	out := make(map[string]int64, len(slugs))
	if len(slugs) == 0 {
		return out, nil
	}

	placeholders := strings.TrimRight(strings.Repeat("?,", len(slugs)), ",")
	args := make([]any, len(slugs))
	for i, slug := range slugs {
		args[i] = slug
		out[slug] = 0
	}

	rows, err := s.db.QueryContext(ctx, `SELECT slug, count FROM ticks WHERE slug IN (`+placeholders+`)`, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	for rows.Next() {
		var slug string
		var count int64
		if err := rows.Scan(&slug, &count); err != nil {
			return nil, err
		}
		out[slug] = count
	}
	return out, rows.Err()
}

func (s *SQLiteCounterStore) Close() error {
	return s.db.Close()
}