using System;
using System.Collections.Generic;
using System.Collections.Concurrent;
using System.Linq;
using System.Text;
using System.Threading.Tasks;


using StackExchange.Redis;


namespace ServerCore;

//=============================================================================================
// Server-side transactional scripting in Redis
//
//=============================================================================================
public abstract class RedisWithLuaScriptExecutorBase
{
    private readonly RedisConnectorBase m_connector;

    private readonly ConcurrentDictionary<string, LoadedLuaScript> m_loaded_lua_scripts = new();

    public RedisWithLuaScriptExecutorBase(RedisConnectorBase connector)
    {
        m_connector = connector;
    }

    public async Task<bool> tryLoadLuaScriptToRedisServer(string scriptName, string luaScript)
    {
        var err_msg = string.Empty;

        try
        {
            if (true == m_loaded_lua_scripts.ContainsKey(scriptName))
            {
                return true;
            }

            var multiplexer = m_connector.getConnectionMultiplexer();
            NullReferenceCheckHelper.throwIfNull(multiplexer, () => $"multiplexer is null !!!");

            var end_points = multiplexer.GetEndPoints();
            NullReferenceCheckHelper.throwIfNull(end_points, () => $"end_points is null !!!");

            var curr_server = multiplexer.GetServer(end_points[0]);
            NullReferenceCheckHelper.throwIfNull(curr_server, () => $"curr_server is null !!!");

            var prepared_lug_script = LuaScript.Prepare(luaScript);
            NullReferenceCheckHelper.throwIfNull(prepared_lug_script, () => $"prepared_lug_script is null !!!");

            var uploaded_lua_script = await prepared_lug_script.LoadAsync(curr_server);
            NullReferenceCheckHelper.throwIfNull(uploaded_lua_script, () => $"uploaded_lua_script is null !!!");

            m_loaded_lua_scripts[scriptName] = uploaded_lua_script;
        }
        catch (Exception e)
        {
            err_msg = $"Exception !!!, Failed to function in tryLoadScriptAsync() !!! : exception:{e}";
            Log.getLogger().error(err_msg);

            return false;
        }

        return true;
    }

    public async Task<(bool, RedisResult?)> tryExecuteLuaScriptAsync(string scriptName, RedisKey[] keys, RedisValue[]? args = null)
    {
        RedisResult? redis_result = null;
        var err_msg = string.Empty;

        try
        {
            var connected_redis_db = m_connector.getDatabase();
            NullReferenceCheckHelper.throwIfNull(connected_redis_db, () => $"connected_redis_db is null !!!");

            if (false == m_loaded_lua_scripts.TryGetValue(scriptName, out var found_lua_script))
            {
                err_msg = $"Not found LuaScript !!! : scriptName:{scriptName}";
                return (false, null);
            }

            var script = found_lua_script.ExecutableScript;

            redis_result = await connected_redis_db.ScriptEvaluateAsync(script, keys, args);
        }
        catch (Exception e)
        {
            err_msg = $"Exception !!!, Failed to ScriptEvaluateAsync() !!! : exception:{e} - LuaScriptName:{scriptName}";
            Log.getLogger().error(err_msg);

            return (false, null);
        }

        return (true, redis_result);
    }
}