package database

import (
	"context"
	"database/sql"
	"errors"
	"net/url"
	"os"
	"path/filepath"
	"strings"

	_ "github.com/mattn/go-sqlite3"
)

const busyTimeoutMilliseconds = 5000

type safeError struct {
	message string
	cause   error
}

func (e safeError) Error() string {
	return e.message
}

func (e safeError) Unwrap() error {
	return e.cause
}

func Open(ctx context.Context, path string) (*sql.DB, error) {
	absolutePath, err := filepath.Abs(path)
	if err != nil {
		return nil, errors.New("resolve SQLite path")
	}
	if err := os.MkdirAll(filepath.Dir(absolutePath), 0o700); err != nil {
		return nil, errors.New("create SQLite directory")
	}
	if info, err := os.Stat(absolutePath); err == nil && info.IsDir() {
		return nil, errors.New("SQLite path is a directory")
	} else if err != nil && !errors.Is(err, os.ErrNotExist) {
		return nil, errors.New("inspect SQLite path")
	}

	db, err := sql.Open("sqlite3", dataSourceName(absolutePath))
	if err != nil {
		return nil, errors.New("initialize SQLite driver")
	}
	db.SetMaxOpenConns(1)
	db.SetMaxIdleConns(1)

	if err := db.PingContext(ctx); err != nil {
		_ = db.Close()
		return nil, safeError{
			message: "connect to SQLite",
			cause:   err,
		}
	}
	return db, nil
}

func dataSourceName(absolutePath string) string {
	slashPath := filepath.ToSlash(absolutePath)
	if filepath.VolumeName(absolutePath) != "" &&
		!strings.HasPrefix(slashPath, "/") {
		slashPath = "/" + slashPath
	}
	dsnURL := &url.URL{
		Scheme: "file",
		Path:   slashPath,
	}
	query := dsnURL.Query()
	query.Set("_busy_timeout", "5000")
	query.Set("_foreign_keys", "on")
	query.Set("_journal_mode", "WAL")
	query.Set("_txlock", "immediate")
	dsnURL.RawQuery = query.Encode()
	return dsnURL.String()
}

func isSafeDataSourceName(value string) bool {
	lowerValue := strings.ToLower(value)
	return strings.HasPrefix(lowerValue, "file:") &&
		strings.Contains(lowerValue, "_busy_timeout=") &&
		strings.Contains(lowerValue, "_foreign_keys=") &&
		strings.Contains(lowerValue, "_journal_mode=wal") &&
		strings.Contains(lowerValue, "_txlock=immediate")
}