/*
** 2020-03-27
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
******************************************************************************
**
** Implement a collating sequence that sorts (unsigned) integers embedded 
** in the middle of text in numeric order.
*/
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#include <ctype.h>

/*
** Collating function that compares text byte-by-byte but compares
** digits in numeric order.
*/
static int mixedCollFunc(
  void *notUsed,
  int nKey1, const void *pKey1,
  int nKey2, const void *pKey2
){
  const unsigned char *zA = (const unsigned char*)pKey1;
  const unsigned char *zB = (const unsigned char*)pKey2;
  int i, x;
  for(i=0; i<nKey1 && i<nKey2; i++){
    x = zA[i] - zB[i];
    if( x!=0 ){
      int j;
      for(j=i; j<nKey1 && j<nKey2 && isdigit(zA[j]) && isdigit(zB[j]); j++){}
      if( j<nKey1 && isdigit(zA[j]) ){
        return +1;
      }else if( j<nKey2 && isdigit(zB[j]) ){
        return -1;
      }else{
        return x;
      }
    }
  }
  return nKey1 - nKey2;
}


#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_mixedcoll_init(
  sqlite3 *db, 
  char **pzErrMsg, 
  const sqlite3_api_routines *pApi
){
  int rc = SQLITE_OK;
  SQLITE_EXTENSION_INIT2(pApi);
  (void)pzErrMsg;  /* Unused parameter */
  rc = sqlite3_create_collation(db, "mixed", SQLITE_UTF8, 0, mixedCollFunc);
  return rc;
}