// Copyright 2024 Patial Tech (Ankit Patial).
//
// This file is part of code.patial.tech/go/appcore, which is MIT licensed.
// See http://opensource.org/licenses/MIT

package uid

import (
	"sync"

	"github.com/sqids/sqids-go"
)

type Service interface {
	SquiOptions() sqids.Options
}

var (
	mu       sync.Mutex
	sqidInst *sqids.Sqids
	sqidOpts *sqids.Options
)

func getSqids(svc Service) (*sqids.Sqids, error) {
	opts := svc.SquiOptions()

	mu.Lock()
	defer mu.Unlock()

	if sqidInst != nil && sqidOpts != nil && opts.Alphabet == sqidOpts.Alphabet && opts.MinLength == sqidOpts.MinLength {
		return sqidInst, nil
	}

	s, err := sqids.New(opts)
	if err != nil {
		return nil, err
	}

	sqidInst = s
	sqidOpts = &opts
	return s, nil
}

// Encode a slice of IDs into one unique ID
func Encode(svc Service, ids ...uint64) (string, error) {
	s, err := getSqids(svc)
	if err != nil {
		return "", err
	}

	return s.Encode(ids) // "86Rf07"
}

// Decode an ID back to slice of IDs
func Decode(svc Service, id string) ([]uint64, error) {
	s, err := getSqids(svc)
	if err != nil {
		return nil, err
	}

	return s.Decode(id), nil
}