package service

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"os"
	"time"

	"github.com/go-redis/redis/v8"
)

const (
	worksmobileRelayLeaderLockKey = "baron:worksmobile:relay:leader"
	worksmobileRelayLeaderLockTTL = 30 * time.Second
)

const worksmobileRelayLeaderRenewScript = `
if redis.call("GET", KEYS[1]) == ARGV[1] then
	return redis.call("EXPIRE", KEYS[1], ARGV[2])
end
return 0
`

type WorksmobileRedisRelayLeaderLock struct {
	client  *redis.Client
	key     string
	ttl     time.Duration
	ownerID string
}

func NewWorksmobileRedisRelayLeaderLock(redisService *RedisService) *WorksmobileRedisRelayLeaderLock {
	if redisService == nil || redisService.Client == nil {
		return nil
	}
	return &WorksmobileRedisRelayLeaderLock{
		client:  redisService.Client,
		key:     worksmobileRelayLeaderLockKey,
		ttl:     worksmobileRelayLeaderLockTTL,
		ownerID: newWorksmobileRelayLeaderOwnerID(),
	}
}

func (l *WorksmobileRedisRelayLeaderLock) EnsureLeadership(ctx context.Context) (bool, error) {
	if l == nil || l.client == nil {
		return true, nil
	}

	acquired, err := l.client.SetNX(ctx, l.key, l.ownerID, l.ttl).Result()
	if err != nil {
		return false, err
	}
	if acquired {
		return true, nil
	}

	ttlSeconds := int64(l.ttl / time.Second)
	if ttlSeconds <= 0 {
		ttlSeconds = 30
	}
	result, err := l.client.Eval(ctx, worksmobileRelayLeaderRenewScript, []string{l.key}, l.ownerID, ttlSeconds).Int()
	if err != nil {
		return false, err
	}
	return result == 1, nil
}

func newWorksmobileRelayLeaderOwnerID() string {
	hostname, _ := os.Hostname()
	if hostname == "" {
		hostname = "unknown-host"
	}
	randomBytes := make([]byte, 8)
	if _, err := rand.Read(randomBytes); err != nil {
		return fmt.Sprintf("%s:%d:%d", hostname, os.Getpid(), time.Now().UnixNano())
	}
	return fmt.Sprintf("%s:%d:%s", hostname, os.Getpid(), hex.EncodeToString(randomBytes))
}