package redisqueue

import (
	"context"
	"fmt"
	"regexp"
	"strconv"
	"strings"

	"github.com/pkg/errors"
	"github.com/redis/go-redis/v9"
)

var redisVersionRE = regexp.MustCompile(`redis_version:(.+)`)

// RedisOptions is an alias to redis.Options so that users can this instead of
// having to import go-redis directly.
type RedisOptions = redis.Options

// newRedisClient creates a new Redis client with the given options. If options
// is nil, it will use default options.
func newRedisClient(options *RedisOptions) *redis.Client {
	if options == nil {
		options = &RedisOptions{}
	}
	return redis.NewClient(options)
}

// redisPreflightChecks makes sure the Redis instance backing the *redis.Client
// offers the functionality we need. Specifically, it also that it can connect
// to the actual instance and that the instance supports Redis streams (i.e.
// it's at least v5).
func redisPreflightChecks(client redis.UniversalClient) error {
	info, err := client.Info(context.TODO(), "server").Result()
	if err != nil {
		return err
	}

	match := redisVersionRE.FindAllStringSubmatch(info, -1)
	if len(match) < 1 {
		return fmt.Errorf("could not extract redis version")
	}
	version := strings.TrimSpace(match[0][1])
	parts := strings.Split(version, ".")
	major, err := strconv.Atoi(parts[0])
	if err != nil {
		return err
	}
	if major < 5 {
		return fmt.Errorf("redis streams are not supported in version %q", version)
	}

	return nil
}

// incrementMessageID takes in a message Id (e.g. 1564886140363-0) and
// increments the index section (e.g. 1564886140363-1). This is the next valid
// Id value, and it can be used for paging through messages.
func incrementMessageID(id string) (string, error) {
	parts := strings.Split(id, "-")
	index := parts[1]
	parsed, err := strconv.ParseInt(index, 10, 64)
	if err != nil {
		return "", errors.Wrapf(err, "error parsing message Id %q", id)
	}
	return fmt.Sprintf("%s-%d", parts[0], parsed+1), nil
}