#include "bs_util.h"
#include "MySQLTransaction.h"
using namespace std;

int main()
{
    Request req;
    Session se(req);
    Response res;
    json j;

    auto jsonfail=[&](int errcode,const std::string& dtl="")
    {
        jsonfail_func(j,errcode,dtl);
    };

    do
    {
        if(!se.isReady())
        {
            jsonfail(err_session);
            break;
        }

        if(se.getUser().empty())
        {
            jsonfail(err_need_login);
            break;
        }

        if(req.requestMethod!="POST")
        {
            jsonfail(err_method_not_supported);
            break;
        }

        postval(bid);

        int bid_real=ParseInt(bid);
        if(bid_real<0)
        {
            jsonfail(err_parameter,"Failed to parse bid");
            break;
        }

        startdb();

        /// Start transaction
        Transaction ts(conn);
        if(!ts.isReady())
        {
            jsonfail(err_sql_logic,"Failed to start transaction.");
            break;
        }

        /// Check if user can borrow...
        int cntval;
        if(conn.exec(make_str("select count(username) from bs_reader where username='",
                              se.getUser(),
                              "'"),
                     SQLParseInt(cntval))<0)
        {
            jsonfail(err_sql,"Step 1");
            break;
        }

        if(cntval!=1)
        {
            jsonfail(err_permission_denied,"You are not in reader list!");
            break;
        }

        int borrow_limit,borrow_used,borrow_time_limit;
        if(conn.exec(make_str("select borrow_limit,borrow_used,borrow_time_limit from bs_reader where username='",
                              se.getUser(),
                              "'"),
                     [&](MySQLResult& res)
                     {
                         res.stepRow([&](char** val,unsigned long* len)
                                     {
                                         borrow_limit=ParseInt(val[0]);
                                         borrow_used=ParseInt(val[1]);
                                         borrow_time_limit=ParseInt(val[2]);
                                     });
                     })<0)
        {
            jsonfail(err_sql,"Step 2");
            break;
        }

        if(borrow_limit-borrow_used<=0)
        {
            jsonfail(err_general,"Reach Borrow Limit");
            break;
        }

        /// Verify bid
        if(conn.exec(make_str("select count(book_id) from bs_bookstatus where book_id=",
                              bid_real),
                     SQLParseInt(cntval))<0)
        {
            jsonfail(err_sql,"Step 3");
            break;
        }

        if(cntval!=1)
        {
            jsonfail(err_parameter,"Failed to verify bid");
            break;
        }

        /// Check if bid is allowed to be borrowed.
        int book_status;
        if(conn.exec(make_str("select status from bs_bookstatus where book_id=",bid_real),
                     SQLParseInt(book_status))<0)
        {
            jsonfail(err_sql,"Step 4");
            break;
        }

        if(book_status!=2)
        {
            jsonfail(err_data,"Book is not allowed to borrow");
            break;
        }

        /// DO UPDATE
        if(conn.exec(make_str("update bs_reader set borrow_used=borrow_used+1 where username='",
                              se.getUser(),
                              "'"),nullptr)<0)
        {
            jsonfail(err_sql,"Update 1");
            break;
        }

        if(conn.exec(make_str("update bs_bookstatus set status=0 where book_id=",bid_real),nullptr)<0)
        {
            jsonfail(err_sql,"Update 2");
            break;
        }

        if(conn.exec(make_str("insert into bs_borrow values ('",
                              se.getUser(),
                              "',",
                              bid_real,
                              ",curdate(),date_add(curdate(),interval ",
                              borrow_time_limit,
                              " day),null)"),nullptr)<0)
        {
            jsonfail(err_sql,"Update 3");
            break;
        }

        /// Commit it
        ts.commit();

        j["success"]=1;
    }
    while(0);

    se.writeToResponse(res);
    res.content.append(j.dump());

    return 0;
}