#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(id);
        int id_real=ParseInt(id);
        if(id_real<0)
        {
            jsonfail(err_parameter,"Failed to parse id");
            break;
        }

        startdb();

        Transaction ts(conn);

        /// Check Permission
        int permission_level=-1;
        if(conn.exec(make_str("select permission_level from bs_user where username='",
                              se.getUser(),
                              "'"),
                     SQLParseInt(permission_level))<0)
        {
            jsonfail(err_sql,"Step 1");
            break;
        }

        if(permission_level<0)
        {
            jsonfail(err_general,"Failed to check Permission");
            break;
        }

        if(permission_level>=3)
        {
            jsonfail(err_permission_denied);
            break;
        }

        /// Check if the book info can be removed.
        /// count_val: Count of books with class_id={ID} and status is borrowed (0)
        int count_val=-1;
        if(conn.exec(make_str("select count(book_id) from bs_bookstatus where class_id=",
                              id_real,
                              " and status=0"),
                     SQLParseInt(count_val))<0)
        {
            jsonfail(err_sql,"Step 2");
            break;
        }

        if(count_val<0)
        {
            jsonfail(err_data,"Failed to get book id data");
            break;
        }

        if(count_val!=0)
        {
            jsonfail(err_data,make_str("Cannot remove book. Still ",count_val," books borrowed."));
            break;
        }

        if(conn.exec(make_str("delete from bs_borrow where book_id in (select book_id from bs_bookstatus where class_id=",id_real),nullptr)<0)
        {
            jsonfail(err_sql,"Step 3");
        }

        if(conn.exec(make_str("delete from bs_bookstatus where class_id=",id_real),nullptr)<0)
        {
            jsonfail(err_sql,"Step 4");
            break;
        }

        if(conn.exec(make_str("delete from bs_book where class_id=",id_real),nullptr)<0)
        {
            jsonfail(err_sql,"Step 5");
            break;
        }

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

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

    return 0;
}