#include <postgres.h>
#include <commands/explain.h>
#include <nodes/nodeFuncs.h>
#include <optimizer/optimizer.h>
#include <access/heapam.h>
#include <access/xact.h>
#include "db2_fdw.h"
#include "DB2FdwState.h"

/** external prototypes */
extern DB2Session*  db2GetSession             (const char* connectstring, char* user, char* password, char* jwt_token, int curlevel);
extern DB2FdwState* deserializePlanData       (List* list);

/** local prototypes */
        void  db2BeginForeignScan (ForeignScanState* node, int eflags);
static  void  addExprParams       (ForeignScanState* node);

/* db2BeginForeignScan
 * Recover ("deserialize") connection information, remote query, DB2 table description and parameter list from the plan's "fdw_private" field.
 * Reestablish a connection to DB2.
 */
void db2BeginForeignScan(ForeignScanState* node, int eflags) {
  ForeignScan* fsplan      = (ForeignScan*) node->ss.ps.plan;
  DB2FdwState* fdw_state   = NULL;

  db2Entry1();
  /* deserialize private plan data */
  fdw_state       = deserializePlanData(fsplan->fdw_private);
  node->fdw_state = (void *) fdw_state;

  addExprParams(node);

  /* add a fake parameter "if that string appears in the query */
  if (strstr (fdw_state->query, "?/*:now*/") != NULL) {
    ParamDesc*  paramDesc = (ParamDesc*) db2alloc (sizeof (ParamDesc), "fdw_state->paramList->next");
    paramDesc->type      = TIMESTAMPTZOID;
    paramDesc->bindType  = BIND_STRING;
    paramDesc->value     = NULL;
    paramDesc->node      = NULL;
    paramDesc->colnum    = -1;
    paramDesc->txts      = 1;
    paramDesc->next      = fdw_state->paramList;
    fdw_state->paramList = paramDesc;
  }

  if (node->ss.ss_currentRelation)
    db2Debug3("begin foreign table scan on relid: %d", RelationGetRelid (node->ss.ss_currentRelation));
  else
    db2Debug3("begin foreign join");

  /* connect to DB2 database */
  fdw_state->session = db2GetSession (fdw_state->dbserver
                                     ,fdw_state->user
                                     ,fdw_state->password
                                     ,fdw_state->jwt_token
                                     ,GetCurrentTransactionNestLevel()
    );

  /* initialize row count to zero */
  fdw_state->rowcount = 0;
  db2Exit1();
}

static void addExprParams(ForeignScanState* node){
  DB2FdwState* fdw_state   = node->fdw_state;
  ForeignScan* fsplan      = (ForeignScan*) node->ss.ps.plan;
  List*        exec_exprs  = NIL;
  ParamDesc*   paramDesc   = NULL;
  ListCell*    cell        = NULL;

  db2Entry1();
  /* create an ExprState tree for the parameter expressions */
  exec_exprs = (List*) ExecInitExprList (fsplan->fdw_exprs, (PlanState*) node);
  db2Debug2("exec_expr: %x[%d]",exec_exprs, list_length(exec_exprs));
  /* create the list of parameters */
  foreach (cell, exec_exprs) {
    ExprState* expr = (ExprState*) lfirst (cell);

    /* count, but skip deleted entries */
    if (expr == NULL)
      continue;

    /* create a new entry in the parameter list */
    paramDesc       = (ParamDesc*) db2alloc(sizeof (ParamDesc), "fdw_state->paramList->next");
    paramDesc->type = exprType ((Node*) (expr->expr));

    if (paramDesc->type == TEXTOID
    ||  paramDesc->type == VARCHAROID
    ||  paramDesc->type == BPCHAROID
    ||  paramDesc->type == CHAROID
    ||  paramDesc->type == DATEOID
    ||  paramDesc->type == TIMESTAMPOID
    ||  paramDesc->type == TIMESTAMPTZOID
    ||  paramDesc->type == TIMEOID
    ||  paramDesc->type == TIMETZOID)
      paramDesc->bindType = BIND_STRING;
    else
      paramDesc->bindType = BIND_NUMBER;

    paramDesc->value     = NULL;
    paramDesc->node      = expr;
    paramDesc->colnum    = -1;
    paramDesc->txts      = 0;
    paramDesc->next      = fdw_state->paramList;
    db2Debug2("paramDesc->colnum: %d  ",paramDesc->colnum);
    fdw_state->paramList = paramDesc;
  }
  db2Exit1();
}