package utils

import (
	"context"
	"errors"
	"time"
)

var ErrRedisNotInitialized = errors.New("redis client is not initialized, set redis_enable=true and restart")

const redisLockReleaseScript = `
if redis.call("GET", KEYS[1]) == ARGV[1] then
	return redis.call("DEL", KEYS[1])
else
	return 0
end
`

// AcquireRedisLock tries to create a distributed lock with key and value.
// It returns true when lock is acquired, false when lock already exists.
func AcquireRedisLock(key, value string) (bool, error) {
	if RedisClient == nil {
		return false, ErrRedisNotInitialized
	}
	if key == "" || value == "" {
		return false, errors.New("key and value must not be empty")
	}

	lockTTLMS := redisInt("redis_lock_ttl_ms", 30000)
	opTimeoutMS := redisInt("redis_lock_op_timeout_ms", 1000)
	ctx, cancel := context.WithTimeout(context.Background(), time.Duration(opTimeoutMS)*time.Millisecond)
	defer cancel()

	return RedisClient.SetNX(ctx, key, value, time.Duration(lockTTLMS)*time.Millisecond).Result()
}

// ReleaseRedisLock releases lock only when key currently matches value.
// It returns true when released successfully.
func ReleaseRedisLock(key, value string) (bool, error) {
	if RedisClient == nil {
		return false, ErrRedisNotInitialized
	}
	if key == "" || value == "" {
		return false, errors.New("key and value must not be empty")
	}

	opTimeoutMS := redisInt("redis_lock_op_timeout_ms", 1000)
	ctx, cancel := context.WithTimeout(context.Background(), time.Duration(opTimeoutMS)*time.Millisecond)
	defer cancel()

	n, err := RedisClient.Eval(ctx, redisLockReleaseScript, []string{key}, value).Int64()
	if err != nil {
		return false, err
	}
	return n == 1, nil
}