#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

#if (PERL_VERSION < 5) || ((PERL_VERSION == 5) && (PERL_SUBVERSION <= 6))
# define get_sv      perl_get_sv
# define call_method perl_call_method
# define call_sv     perl_call_sv
#endif

#if (PERL_VERSION < 5) || ((PERL_VERSION == 5) && (PERL_SUBVERSION <= 5))
# define CAN_UTF8 1
#endif

static SV *
sql_upgrade_utf8 (SV *sv)
{
#if CAN_UTF8
  if (SvPOK (sv))
    sv_utf8_upgrade (sv);
#endif
  return sv;
}

static SV *
sql_force_utf8 (SV *sv)
{
#if CAN_UTF8
  if (SvPOK (sv))
    SvUTF8_on (sv);
#endif
  return sv;
}

#define maybe_upgrade_utf8(utf8,sv) ((utf8) ? sql_upgrade_utf8 (sv) : (sv))
#define maybe_force_utf8(utf8,sv)   ((utf8) ? sql_force_utf8   (sv) : (sv))

#define is_dbh(sv) ((sv) && sv_isobject (sv) && sv_derived_from ((sv), "DBI::db"))

typedef struct lru_node {
  struct lru_node *next;
  struct lru_node *prev;
  U32 hash;
  SV *dbh;
  SV *sql;

  SV *sth;
#if 0 /* method cache */
  GV *execute;
  GV *bind_columns;
  GV *fetch;
  GV *finish;
#endif
} lru_node;

static lru_node lru_list;
static int lru_size;
static int lru_maxsize;

#define lru_init lru_list.next = &lru_list; lru_list.prev = &lru_list /* other fields are zero */

/* this is primitive, yet effective */
/* the returned value must never be zero (or bad things will happen) */
#define lru_hash do {	\
	hash = (((U32)dbh)>>2);	\
        hash += *statement;\
        hash += len;		\
} while (0)

/* fetch and "use" */
/* could be done using a single call (we could call prepare!) */
static SV *lru_fetch(SV *dbh, SV *sql)
{
  lru_node *n;

  U32 hash;
  STRLEN len;
  char *statement = SvPV (sql, len);

  dbh = SvRV (dbh);

  lru_hash;

  /*fprintf (stderr, "F: %08lx %s\n", hash, SvPV_nolen (sql));/*D*/

  n = &lru_list;
  do {
    n = n->next;
    if (!n->hash)
      return 0;
  } while (n->hash != hash
           || !sv_eq (n->sql, sql)
           || n->dbh != dbh);

  /* found, so return to the start of the list */
  n->prev->next = n->next;
  n->next->prev = n->prev;

  n->next = lru_list.next;
  n->prev = &lru_list;
  lru_list.next->prev = n;
  lru_list.next = n;

  return n->sth;
}

static void lru_nukeone(void)
{
  lru_node *n;
  /* nuke at the end */

  n = lru_list.prev;

  lru_list.prev = n->prev;
  n->prev->next = &lru_list;

  /*fprintf (stderr, "N: %s\n", SvPV_nolen (n->sql));/*D*/

  SvREFCNT_dec (n->dbh);
  SvREFCNT_dec (n->sql);
  SvREFCNT_dec (n->sth);
  Safefree (n);
  
  lru_size--;
}

/* store a not-yet existing entry(!) */
static void lru_store(SV *dbh, SV *sql, SV *sth)
{
  lru_node *n;

  U32 hash;
  STRLEN len;
  char *statement = SvPV (sql, len);

  dbh = SvRV (dbh);

  lru_hash;

  /*fprintf (stderr, "S: %08lx %s\n", hash, SvPV_nolen (sql));/*D*/

  lru_size++;
  if (lru_size > lru_maxsize)
    lru_nukeone ();

  New (0, n, 1, lru_node);

  n->hash = hash;
  n->dbh = dbh; SvREFCNT_inc (dbh); /* note: this is the dbi hash itself, not the reference */
  n->sql = newSVsv (sql);
  n->sth = sth; SvREFCNT_inc (sth);

  n->next = lru_list.next;
  n->prev = &lru_list;
  lru_list.next->prev = n;
  lru_list.next = n;
}

static void lru_cachesize (int size)
{
  if (size >= 0)
    {
      lru_maxsize = size;
      while (lru_size > lru_maxsize)
        lru_nukeone ();
    }
}

static GV *sql_exec;
static GV *DBH;
static SV *sv_prepare, *sv_execute, *sv_bind_columns, *sv_fetchrow_arrayref, *sv_finish;

#define newconstpv(str) newSVpvn ((str), sizeof (str))

MODULE = PApp::SQL		PACKAGE = PApp::SQL

PROTOTYPES: DISABLE

BOOT:
{
   sql_exec = gv_fetchpv ("PApp::SQL::sql_exec", TRUE, SVt_PV);
   DBH      = gv_fetchpv ("PApp::SQL::DBH"     , TRUE, SVt_PV);

   if (!sv_prepare)
     {
       sv_prepare           = newconstpv ("prepare");
       sv_execute           = newconstpv ("execute");
       sv_bind_columns      = newconstpv ("bind_columns");
       sv_fetchrow_arrayref = newconstpv ("fetchrow_arrayref");
       sv_finish            = newconstpv ("finish");
     }

   /* apache might BOOT: twice :( */
   if (lru_size)
     lru_cachesize (0);

   lru_init;
   lru_cachesize (50);
}

int
cachesize(size = -1)
	int	size
	CODE:
        RETVAL = lru_maxsize;
        lru_cachesize (size);
        OUTPUT:
        RETVAL

void
sql_exec(...)
	ALIAS:
                sql_uexec     = 1
        	sql_fetch     = 2
                sql_ufetch    = 3
                sql_fetchall  = 4
                sql_ufetchall = 5
                sql_exists    = 6
                sql_uexists   = 7
	PPCODE:
{
	if (items == 0)
          croak ("Usage: sql_exec [database-handle,] [bind-var-refs,... ] \"sql-statement\", [arguments, ...]");
        else
          {
            int arg = 0;
            int bind_first, bind_last;
            int count;
            SV *dbh = ST(0);
            SV *sth;
            SV *sql;
            SV *execute;
            STRLEN dc;

            /* save our arguments against destruction through function calls */
            SP += items;
            
            /* first check wether we should use an explicit db handle */
            if (!is_dbh (dbh))
              {
                dbh = get_sv ("DBH", FALSE);
                if (!is_dbh (dbh))
                  {
                    dbh = GvSV(DBH);
                    if (!is_dbh (dbh))
                      croak ("sql_exec: no $DBH found in current package or in PApp::SQL::");
                  }
              }
            else
              arg++; /* we consumed one argument */

            /* count the remaining references (for bind_columns) */
            bind_first = arg;
            while (items > arg && SvROK (ST(arg)))
              arg++;

            bind_last = arg;

            /* consume the sql-statement itself */
            if (items <= arg)
              croak ("sql_exec: required argument \"sql-statement\" missing");

            if (!SvPOK (ST(arg)))
              croak ("sql_exec: sql-statement must be a string");

            sql = ST(arg); arg++;

            if ((ix & ~1) == 6)
              {
                SV *neu = sv_2mortal (newSVpv ("select count(*) > 0 from ", 0));
                sv_catsv (neu, sql);
                sv_catpv (neu, " limit 1");
                sql = neu;
                ix -= 6; /* sql_fetch */
              }

            /* check cache for existing statement handle */
            sth = lru_fetch (dbh, sql);
            if (!sth)
              {
                PUSHMARK (SP);
                EXTEND (SP, 2);
                PUSHs (dbh);
                PUSHs (sql);
                PUTBACK;
                count = call_sv (sv_prepare, G_METHOD | G_SCALAR);
                SPAGAIN;

                if (count != 1)
                  croak ("sql_exec: unable to prepare() statement '%s': %s",
                         SvPV (sql, dc),
                         SvPV (get_sv ("DBI::errstr", TRUE), dc));

                sth = POPs;

                lru_store (dbh, sql, sth);
              }

            PUSHMARK (SP);
            EXTEND (SP, items - arg + 1);
            PUSHs (sth);
            while (items > arg)
              {
                PUSHs (maybe_upgrade_utf8 (ix & 1, ST(arg)));
                arg++;
              }

            PUTBACK;
            /* { static GV *execute;
              if (!execute) execute = gv_fetchmethod_autoload(SvSTASH(SvRV(sth)), "execute", 0);
              count = call_sv(GvCV(execute), G_SCALAR);
             }*/
            count = call_sv (sv_execute, G_METHOD | G_SCALAR);
            SPAGAIN;

            if (count != 1)
              croak ("sql_exec: execute() didn't return any value ('%s'): %s",
                     SvPV (sql, dc),
                     SvPV (get_sv ("DBI::errstr", TRUE), dc));

            execute = POPs;

            if (!SvTRUE (execute))
              croak ("sql_exec: unable to execute statement '%s' (%s)",
                     SvPV (sql, dc),
                     SvPV (get_sv ("DBI::errstr", TRUE), dc));

            sv_setsv (GvSV(sql_exec), execute);

            if (bind_first != bind_last)
              {
                PUSHMARK (SP);
                EXTEND (SP, bind_last - bind_first + 2);
                PUSHs (sth);
                do {
                  PUSHs (ST(bind_first));
                  bind_first++;
                } while (bind_first != bind_last);

                PUTBACK;
                count = call_sv (sv_bind_columns, G_METHOD | G_SCALAR);
                SPAGAIN;

                if (count != 1)
                  croak ("sql_exec: bind_columns() didn't return any value ('%s'): %s",
                         SvPV (sql, dc),
                         SvPV (get_sv ("DBI::errstr", TRUE), dc));

                if (!SvOK (POPs))
                  croak ("sql_exec: bind_columns() didn't return a true ('%s'): %s",
                         SvPV (sql, dc),
                         SvPV (get_sv ("DBI::errstr", TRUE), dc));
              }

            /* free our arguments from the stack */
            SP -= items;

            if ((ix & ~1) == 2)
              { /* sql_fetch */
                SV *row;

                PUSHMARK (SP);
                XPUSHs (sth);
                PUTBACK;
                count = call_sv (sv_fetchrow_arrayref, G_METHOD | G_SCALAR);
                SPAGAIN;

                if (count != 1)
                  abort ();

                row = POPs;

                if (SvROK (row))
                  {
                    AV *av;

                    switch (GIMME_V)
                      {
                        case G_VOID:
                          /* no thing */
                          break;
                        case G_SCALAR:
                          /* the first element */
                          XPUSHs (maybe_force_utf8 (ix & 1, *av_fetch ((AV *)SvRV (row), 0, 1)));
                          break;
                        case G_ARRAY:
                          av = (AV *)SvRV (row);
                          count = AvFILL (av) + 1;
                          EXTEND (SP, count);
                          for (arg = 0; arg < count; arg++)
                            PUSHs (maybe_force_utf8 (ix & 1, AvARRAY (av)[arg]));

                          break;
                        default:
                          abort ();
                      }
                 }
              }
            else if ((ix & ~1) == 4)
              { /* sql_fetchall */
                SV *rows;

                PUSHMARK (SP);
                XPUSHs (sth);
                PUTBACK;
                count = call_sv (sv_fetchrow_arrayref, G_METHOD | G_SCALAR);
                SPAGAIN;

                if (count != 1)
                  abort ();

                rows = POPs;

                if (SvROK (rows))
                  {
                    AV *av = (AV *)SvRV (rows);
                    count = AvFILL (av) + 1;

                    if (count)
                      {
                        int columns = AvFILL ((AV *)SvRV (AvARRAY(av)[0])) + 1; /* columns? */

                        EXTEND (SP, count);
                        if (columns == 1)
                          for (arg = 0; arg < count; arg++)
                            PUSHs (maybe_force_utf8 (ix & 1, AvARRAY ((AV *)SvRV (AvARRAY (av)[arg]))[0]));
                        else
                          for (arg = 0; arg < count; arg++)
                            PUSHs (maybe_force_utf8 (ix & 1, AvARRAY (av)[arg]));
                      }
                 }
              }
            else
              XPUSHs (sth);

            if (ix > 1 || GIMME_V == G_VOID)
              {
                PUSHMARK (SP);
                XPUSHs (sth);
                PUTBACK;
                (void) call_sv (sv_finish, G_METHOD | G_DISCARD);
                SPAGAIN;
              }
          }
}