#include "fielddb/request.h"
#include <cassert>
#include "leveldb/slice.h"
#include "leveldb/status.h"
#include "leveldb/write_batch.h"
#include "util/mutexlock.h"
#include "util/serialize_value.h"
#include "fielddb/encode_index.h"
#include "fielddb/field_db.h"
#include "fielddb/meta.h"
#include "request.h"
namespace fielddb {
using namespace leveldb;

//为虚函数提供最基本的实现
void Request::PendReq(Request *req) {
    assert(0);
}

//为虚函数提供最基本的实现
void Request::ConstructBatch(WriteBatch &KVBatch,WriteBatch &IndexBatch,
                WriteBatch &MetaBatch,fielddb::FieldDB *DB,std::unordered_set<std::string *> &batchKeySet)
{
    assert(0);
}

void Request::Prepare(FieldDB *DB) {
    assert(0);
}

void Request::Finalize(FieldDB *DB) {
    assert(0);
}

//为虚函数提供最基本的实现
bool Request::isPending() {
    //pending中的请求的parent会指向所等待的请求（iCreate/iDelete）
    return parent != this; 
}


/*******FieldsReq*******/
void FieldsReq::ConstructBatch(WriteBatch &KVBatch,WriteBatch &IndexBatch,
                    WriteBatch &MetaBatch,fielddb::FieldDB *DB,std::unordered_set<std::string *> &batchKeySet)
{
    if (batchKeySet.find(Key) != batchKeySet.end()){
        return;//并发的被合并的put/delete请求只处理一次
    } else {
        batchKeySet.insert(Key);
    }
    std::string val_str;
    Status s = DB->kvDB_->Get(ReadOptions(), *Key, &val_str);
    FieldArray *oldFields;
    if (s.IsNotFound()){
        oldFields = nullptr;
    } else if (s.ok()) { //得到数据库之前key的fields, 判断需不需要删除其中潜在的索引
        oldFields = ParseValue(val_str);        
    } else {
        assert(0);
    }


    KVBatch.Put(Slice(*Key), Slice(SerializeValue(*Fields)));
    bool HasIndex = false;
    bool HasOldIndex = false;
    {
        // MutexLock L(&DB->index_mu); //互斥访问索引状态表
        DB->index_mu.AssertHeld();
        //1.将存在冲突的put pend到对应的请求
        for(auto [field_name,field_value] : *Fields) {
            if(field_name == "") break;
            if(DB->index_.count(field_name)) {
                auto [index_status,parent_req] = DB->index_[field_name];
                if(index_status == IndexStatus::Creating || index_status == IndexStatus::Deleting) {
                    parent_req->PendReq(this);
                    return;
                } else if(index_status == IndexStatus::Exist) {
                    HasIndex = true;
                }
                //assert(0);
            }
        }
        //冲突也可能存在于，需要删除旧数据的索引，但该索引正在创删中
        if (oldFields != nullptr){
            for(auto [field_name,field_value] : *oldFields) {
                if(field_name == "") break;
                if(DB->index_.count(field_name)) {
                    auto [index_status,parent_req] = DB->index_[field_name];
                    if(index_status == IndexStatus::Creating || index_status == IndexStatus::Deleting) {
                        parent_req->PendReq(this);
                        return;
                    } else if(index_status == IndexStatus::Exist) {
                        HasOldIndex = true;
                    }
                    //assert(0);
                }
            }
        }

        //2.对于没有冲突但含有索引操作的put，构建metaKV，这里直接将KV对简单编码后写入metaDB
        if(HasIndex || HasOldIndex) {
            Slice MetaKey,MetaValue;
            std::string serialized = SerializeValue(*Fields);
            MetaKV MKV = MetaKV(Key,&serialized);
            MKV.TransPut(MetaKey, MetaValue);
            MetaBatch.Put(MetaKey, MetaValue);
            
        
        //3.1对于含有索引的oldfield删除索引
            if (HasOldIndex) {
                for(auto [field_name,field_value] : *oldFields) {
                    if(field_name == "") continue;
                    if(DB->index_.count(field_name)) {
                        std::string indexKey;
                        AppendIndexKey(&indexKey, ParsedInternalIndexKey(
                                                    *Key,field_name,field_value));
                        IndexBatch.Delete(indexKey);
                    }
                }
            }

        //3.2对于含有索引的field建立索引
            if (HasIndex) {
                for(auto [field_name,field_value] : *Fields) {
                    if(field_name == "") continue;
                    if(DB->index_.count(field_name)) {
                        std::string indexKey;
                        AppendIndexKey(&indexKey, ParsedInternalIndexKey(
                                                    *Key,field_name,field_value));
                        IndexBatch.Put(indexKey, Slice());
                    }
                }
            }
            
        }
        //优化：对于3.1，3.2中都有的索引只写一次
    }
}


/*******DeleteReq*******/
void DeleteReq::ConstructBatch(WriteBatch &KVBatch,WriteBatch &IndexBatch,
        WriteBatch &MetaBatch,fielddb::FieldDB *DB,std::unordered_set<std::string *> &batchKeySet)
{
    if (batchKeySet.find(Key) != batchKeySet.end()){
        return;//并发的被合并的put/delete请求只处理一次
    } else {
        batchKeySet.insert(Key);
    }
    //1. 读取当前的最新的键值对，判断是否存在含有键值对的field
    //2.1 如果无，则正常构造delete
    //2.2 如果是有的field的索引状态都是exist，则在meta中写KV_Deleting类型的记录
    //在kvDB和metaDB中写入对应的delete
    //2.3 如果存在field的索引状态是Creating或者Deleting，那么在那个队列上面进行等待
    std::string val_str;
    DB->kvDB_->Get(ReadOptions(), *Key, &val_str);
    FieldArray *Fields = ParseValue(val_str);
    KVBatch.Delete(Slice(*Key));
    bool HasIndex = false;
    {
        // MutexLock L(&DB->index_mu); //互斥访问索引状态表
        DB->index_mu.AssertHeld();
        //1.将存在冲突的delete pend到对应的请求
        for(auto [field_name,field_value] : *Fields) {
            if(field_name == "") break;
            if(DB->index_.count(field_name)) {
                auto [index_status,parent_req] = DB->index_[field_name];
                if(index_status == IndexStatus::Creating || index_status == IndexStatus::Deleting) {
                    parent_req->PendReq(this);
                    return;
                } else if(index_status == IndexStatus::Exist) {
                    HasIndex = true;
                }
                //assert(0);
            }
        }
        //2.对于没有冲突但含有索引操作的delete，构建metaKV，这里直接将KV对简单编码后写入metaDB
        if(HasIndex) {
            Slice MetaKey;
            MetaKV MKV = MetaKV(Key);
            MKV.TransDelete(MetaKey); //meta中写入一个delete不需要value
            MetaBatch.Put(MetaKey, Slice());
        //3.对于含有索引的field删除索引
            for(auto [field_name,field_value] : *Fields) {
                if(field_name == "") continue;
                if(DB->index_.count(field_name)) {
                    std::string indexKey;
                    AppendIndexKey(&indexKey, ParsedInternalIndexKey(
                                                *Key,field_name,field_value));
                    IndexBatch.Delete(indexKey);
                }
            }
        }
    }
}

/*******iCreateReq*******/
void iCreateReq::Prepare(FieldDB *DB) {
    //在index_中完成索引状态更新,在这里可以避免重复创建
    DB->index_mu.AssertHeld();
    if(DB->index_.count(*Field)) {
        auto [istatus,parent] = DB->index_[*Field];
        if(istatus == IndexStatus::Exist) {
            //如果已经完成建立索引，则返回成功
            done = true;
            Existed = true;
            s = Status::OK();
        } else {
            //如果正在创建或删除，那么进行等待
            parent->PendReq(this);
        }
        return;
    }
    //如果索引状态表中没有，则表示尚未创建，更新相应的状态
    //这里将done设置为true表示在taskqueue中需要完成的部分已经完成，不需要pend
    DB->index_[*Field] = {IndexStatus::Creating,this};
    done = true;
}

void iCreateReq::PendReq(Request *req) {
    req->parent = this;
    pending_list.push_back(req);
}

void iCreateReq::ConstructBatch(WriteBatch &KVBatch,WriteBatch &IndexBatch,
        WriteBatch &MetaBatch,fielddb::FieldDB *DB,std::unordered_set<std::string *> &batchKeySet)
{
    //遍历数据库，构建二级索引到indexbatch，(更新metaDB中的元数据为Index类型的（Field,Creating）)
    //一个indexwritebatch写入，那么索引创建删除应该和metadb没有交互
    std::vector<std::pair<std::string, std::string>> keysAndVal = 
                                            DB->FindKeysAndValByFieldName(*Field);
    Slice value = Slice();   
    for (auto &kvPair : keysAndVal){
        std::string indexKey;
        AppendIndexKey(&indexKey, 
                        ParsedInternalIndexKey(kvPair.first, *Field, kvPair.second));
        IndexBatch.Put(indexKey, value);
    }
}

void iCreateReq::Finalize(FieldDB *DB) {
    //1. 写入完成后，更新index状态表，(并将metaDB的值改为Index类型的（Field，Existing）)
    MutexLock iL(&DB->index_mu);
    DB->index_[*Field] = {IndexStatus::Exist, nullptr};   
    DB->index_mu.Unlock(); 

    if (pending_list.empty())   return;
    //2. 将所有的pendinglist重新入队    
    MutexLock L(&DB->mutex_);
    for (auto req : pending_list){
        DB->taskqueue_.push_back(req);
        req->parent = req; //解绑
    }
    if (pending_list[0] == DB->taskqueue_.front()) {
        pending_list[0]->cond_.Signal();
    }
    this->s = Status::OK();
}

/*******iDeleteReq*******/
void iDeleteReq::Prepare(FieldDB *DB) {
    DB->index_mu.AssertHeld();
    if(DB->index_.count(*Field) == 0) {
        done = true;
        Deleted = true;
        s = Status::OK();
        return ;
    }
    auto [istatus,parent] = DB->index_[*Field];
    if(istatus == IndexStatus::Exist) {
        DB->index_[*Field] = {IndexStatus::Deleting,this};
        done = true;
    } else {
        //如果正在创建或者删除，那么pend到对应的请求上
        parent->PendReq(this);
    }
}

void iDeleteReq::PendReq(Request* req) {
    req->parent = this;
    pending_list.push_back(req);
}

void iDeleteReq::ConstructBatch(WriteBatch &KVBatch,WriteBatch &IndexBatch,
        WriteBatch &MetaBatch,fielddb::FieldDB *DB,std::unordered_set<std::string *> &batchKeySet)
{
    std::vector<std::pair<std::string, std::string>> keysAndVal = 
                                            DB->FindKeysAndValByFieldName(*Field);
    Slice value = Slice();   
    for (auto &kvPair : keysAndVal){
        std::string indexKey;
        AppendIndexKey(&indexKey, 
                        ParsedInternalIndexKey(kvPair.first, *Field, kvPair.second));
        IndexBatch.Delete(indexKey);
    }
}

void iDeleteReq::Finalize(FieldDB *DB) {
    MutexLock iL(&DB->index_mu);
    DB->index_.erase(*Field);   
    DB->index_mu.Unlock(); 

    if (pending_list.empty())   return;
    //2. 将所有的pendinglist重新入队    
    MutexLock L(&DB->mutex_);
    for (auto req : pending_list){
        DB->taskqueue_.push_back(req);
        req->parent = req; //解绑
    }
    if (pending_list[0] == DB->taskqueue_.front()) {
        pending_list[0]->cond_.Signal();
    }
    this->s = Status::OK();
}


}  // namespace fielddb