package db

import (
	"context"
	"errors"
	"time"

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

const defaultSQLiteRetryBudget = 20 * time.Second

func isSQLiteBusy(err error) bool {
	var sqliteErr sqlite3.Error
	if !errors.As(err, &sqliteErr) {
		return false
	}
	return sqliteErr.Code == sqlite3.ErrBusy || sqliteErr.Code == sqlite3.ErrLocked
}

func retrySQLite(fn func() error) error {
	return retrySQLiteCtx(context.Background(), defaultSQLiteRetryBudget, fn)
}

func retrySQLiteCtx(ctx context.Context, budget time.Duration, fn func() error) error {
	if budget <= 0 {
		budget = defaultSQLiteRetryBudget
	}
	deadline := time.Now().Add(budget)
	backoff := 10 * time.Millisecond
	const maxBackoff = 100 * time.Millisecond

	for {
		if err := ctx.Err(); err != nil {
			return err
		}
		err := fn()
		if err == nil || !isSQLiteBusy(err) {
			return err
		}
		if time.Now().After(deadline) {
			return err
		}

		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-time.After(backoff):
		}
		backoff = min(backoff*2, maxBackoff)
	}
}