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


using Amazon.DynamoDBv2;
using Amazon.DynamoDBv2.Model;


using ServerCore; using ServerBase;


namespace ServerBase;

//==============================================================================================
// 쿼리 내용을 작성하는 기반 클래스
//==============================================================================================    
public abstract partial class QueryExecutorBase
{
    private readonly string m_query_name;

    public delegate Task<QueryBatchBase.QueryResultType> FnCommit(QueryExecutorBase query);
    public delegate Task<QueryBatchBase.QueryResultType> FnRollback(QueryExecutorBase query, Result errorResult);

    private FnCommit? m_fn_commit;        // 쿼리 성공시 호출될 콜백함수
    private FnRollback? m_fn_rollback;    // 쿼리 실패시 호출될 콜백함수

    private QueryBatchBase? m_parent;         // 배치쿼리


    public QueryExecutorBase(string queryName)
    {
        m_query_name = queryName;
    }

    public void bindCallback(FnCommit? fnCommit, FnRollback? fnRollback)
    {
        m_fn_commit = fnCommit;
        m_fn_rollback = fnRollback;
    }

    //=====================================================================================
    // DB 쿼리를 작성한다.
    //=====================================================================================
    public virtual bool onAddQueryRequests() => true;

    //=====================================================================================
    // DB 쿼리 직전에 준비해야 할 로직들을 작성한다.
    //=====================================================================================
    public abstract Task<Result> onPrepareQuery();

    //=====================================================================================
    // onPrepareQuery()를 성공할 경우 호출된다.
    //=====================================================================================
    public abstract Task<Result> onQuery();

    //=====================================================================================
    // DB 쿼리를 성공하고, doFnCommit()가 QueryResultType.NotCalledQueryFunc를 반환할 경우 호출된다.
    //=====================================================================================
    public abstract Task onQueryResponseCommit();

    //=====================================================================================
    // DB 쿼리를 실패하고, doFnRollback()가 QueryResultType.NotCalledQueryFunc를 반환할 경우 호출된다.
    //=====================================================================================
    public abstract Task onQueryResponseRollback(Result errorResult);


    //=====================================================================================
    // DB commit 성공후 호출된다.
    //=====================================================================================
    public async Task<QueryBatchBase.QueryResultType> doFnCommit()
    {
        if (null != m_fn_commit)
        {
            await m_fn_commit(this);
            return QueryBatchBase.QueryResultType.CalledQueryFunc;
        }

        return QueryBatchBase.QueryResultType.NotCalledQueryFunc;
    }

    //=====================================================================================
    // DB commit 실패후 호출된다.
    //=====================================================================================
    public async Task<QueryBatchBase.QueryResultType> doFnRollback(Result errorResult)
    {
        if (null != m_fn_rollback)
        {
            await m_fn_rollback(this, errorResult);
            return QueryBatchBase.QueryResultType.CalledQueryFunc;
        }

        return QueryBatchBase.QueryResultType.NotCalledQueryFunc;
    }

    public void appendBusinessLog(ILogInvoker log)
    {
        if(null == m_parent)
        {
            var err_msg = $"Failed to QueryContextBase.appendBusinessLog() !!!, m_parent is null - {log.toBasicString()}, {toBasicString()}";
            Log.getLogger().error(err_msg);
            return;
        }

        m_parent?.appendBusinessLog(log);
    }

    public TQuery? getQuery<TQuery>() 
        where TQuery : QueryExecutorBase
    {
        if (this is TQuery query)
        {
            return query;
        }

        if (null == m_parent)
        {
            var err_msg = $"Failed to QueryContextBase.getQuery<{nameof(TQuery)}>() !!!, m_parent is null - {toBasicString()}";
            Log.getLogger().error(err_msg);
            return null;
        }

        return m_parent.getQuery<TQuery>();
    }

    public List<TQuery>? getQuerys<TQuery>() 
        where TQuery : QueryExecutorBase
    {
        if (null == m_parent)
        {
            var err_msg = $"Failed to QueryContextBase.getQuerys<{nameof(TQuery)}>() !!!, m_parent is null - {toBasicString()}";
            Log.getLogger().error(err_msg);
            return null;
        }

        return m_parent.getQuerys<TQuery>();
    }

    public virtual EntityBase getOwner()
    {
        var query_batch = getQueryBatch();
        NullReferenceCheckHelper.throwIfNull(query_batch, () => $"query_batch is null !!!");
        var owner = query_batch.getLogActor() as EntityBase;
        NullReferenceCheckHelper.throwIfNull(owner, () => $"owner is null !!!");
        return owner;
    }

    public virtual string toBasicString()
    {
        return $"QueryName:{getQueryName()}, ";
    }
}

//==============================================================================================
// 배치 쿼리시 마지막 스텝의 콜백을 받기 위한 empty 쿼리
//==============================================================================================
public class QueryFinal : QueryExecutorBase
{

    public QueryFinal()
        : base(nameof(QueryFinal))
    { }

    public override async Task<Result> onPrepareQuery()
    {
        await Task.CompletedTask;
        var result = new Result();
        return result;
    }

    public override async Task<Result> onQuery()
    {
        await Task.CompletedTask;
        var result = new Result();
        return result;
    }

    public override async Task onQueryResponseCommit()
    {
        await Task.CompletedTask;
    }

    public override async Task onQueryResponseRollback(Result errorResult)
    {
        await Task.CompletedTask;
    }
}//QueryFinal