package sqlite

import (
	"context"
	"database/sql"
	"strings"
	"sync"
	"time"

	"github.com/pkg/errors"
	"gitlab.com/wpetit/goweb/logger"

	"modernc.org/sqlite"
	_ "modernc.org/sqlite"
	sqlite3 "modernc.org/sqlite/lib"
)

func Open(path string) (*sql.DB, error) {
	db, err := sql.Open("sqlite", path)
	if err != nil {
		return nil, errors.Wrapf(err, "could not open database with path '%s'", path)
	}

	return db, nil
}

func WithRetry(ctx context.Context, db *sql.DB, max int, fn func(*sql.Tx) error) error {
	attempts := 0

	ctx = logger.With(ctx, logger.F("max", max))

	var err error
	for {
		ctx = logger.With(ctx)

		if attempts >= max {
			logger.Debug(ctx, "transaction retrying failed", logger.F("attempts", attempts))

			return errors.Wrapf(err, "transaction failed after %d attempts", max)
		}

		err = WithTx(ctx, db, fn)
		if err != nil {
			if !strings.Contains(err.Error(), "(5) (SQLITE_BUSY)") {
				return errors.WithStack(err)
			}

			err = errors.WithStack(err)

			logger.Warn(ctx, "database is busy", logger.E(err))

			wait := time.Duration(8<<(attempts+1)) * time.Millisecond

			logger.Debug(
				ctx, "database is busy, waiting before retrying transaction",
				logger.F("wait", wait.String()),
				logger.F("attempts", attempts),
			)

			timer := time.NewTimer(wait)
			select {
			case <-timer.C:
				attempts++
				continue

			case <-ctx.Done():
				if err := ctx.Err(); err != nil {
					return errors.WithStack(err)
				}

				return nil
			}
		}

		return nil
	}
}

func WithTx(ctx context.Context, db *sql.DB, fn func(tx *sql.Tx) error) error {
	var tx *sql.Tx

	tx, err := db.BeginTx(ctx, nil)
	if err != nil {
		return errors.WithStack(err)
	}

	defer func() {
		if err := tx.Rollback(); err != nil {
			if errors.Is(err, sql.ErrTxDone) {
				return
			}

			panic(errors.WithStack(err))
		}
	}()

	for {
		if err = fn(tx); err != nil {
			var sqlErr *sqlite.Error
			if errors.As(err, &sqlErr) {
				if sqlErr.Code() == sqlite3.SQLITE_BUSY {
					logger.Warn(ctx, "database busy, retrying transaction")

					if err := ctx.Err(); err != nil {
						logger.Error(ctx, "could not execute transaction", logger.CapturedE(errors.WithStack(err)))

						return errors.WithStack(err)
					}

					continue
				}
			}

			return errors.WithStack(err)
		}

		break
	}

	if err = tx.Commit(); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

type GetDBFunc func(ctx context.Context) (*sql.DB, error)

func NewGetDBFunc(dsn string, initFunc func(ctx context.Context, db *sql.DB) error) GetDBFunc {
	var (
		db    *sql.DB
		mutex sync.RWMutex
	)

	return func(ctx context.Context) (*sql.DB, error) {
		mutex.RLock()
		if db != nil {
			defer mutex.RUnlock()

			return db, nil
		}

		mutex.RUnlock()

		mutex.Lock()
		defer mutex.Unlock()

		logger.Debug(ctx, "opening database", logger.F("dsn", dsn))

		newDB, err := sql.Open("sqlite", dsn)
		if err != nil {
			return nil, errors.WithStack(err)
		}

		logger.Debug(ctx, "initializing database")

		if err = initFunc(ctx, newDB); err != nil {
			return nil, errors.WithStack(err)
		}

		db = newDB

		return db, nil
	}
}

func NewGetDBFuncFromDB(db *sql.DB, initFunc func(ctx context.Context, db *sql.DB) error) GetDBFunc {
	var err error

	initOnce := &sync.Once{}

	return func(ctx context.Context) (*sql.DB, error) {
		initOnce.Do(func() {
			logger.Debug(ctx, "initializing database")

			err = initFunc(ctx, db)
		})

		if err != nil {
			return nil, errors.WithStack(err)
		}

		return db, nil
	}
}