/*
 * JavaToODBC.c
 *
 * Copyright (c) 1999 Karl Moss. All Rights Reserved.
 *
 * You may study, use, modify, and distribute this software for any
 * purpose provided that this copyright notice appears in all copies.
 *
 * This software is provided WITHOUT WARRANTY either expressed or
 * implied.
 *
 * author  Karl Moss
 * version 1.0
 * date    16Feb99
 *
 * This module contains functions that expose ODBC functions
 * to Java applications using JNI (the Java Native Interface)
 */

#include <windows.h>
#include <jni.h>
#include "sql.h"
#include "sqlext.h"
#include "javaservlets_nativeCode_JavaToODBC.h"

/**
  * Helper function to throw an exception.
  * @param env JNIEnv interface pointer
  * @param cls The exception class name
  * @param desc The exception description
  */
void throwException(JNIEnv *env, char* cls, char* desc)
{
    jclass c;
    
    // Clear any pending exceptions
    (*env)->ExceptionDescribe(env);
    (*env)->ExceptionClear(env);

    // Load the exception class
    c = (*env)->FindClass(env, cls);

    // Make sure the class was found
    if (c) {

        // Throw the exception
        (*env)->ThrowNew(env, c, desc);
    }
}

/*
 * Class:     javaservlets_nativeCode_JavaToODBC
 * Method:    SQLAllocEnv
 * Signature: ()I
 */
JNIEXPORT jint JNICALL
  Java_javaservlets_nativeCode_JavaToODBC_SQLAllocEnv
    (JNIEnv *env, jclass cls)
{
    // The environment handle
    HENV henv;

    // The return code
    RETCODE retcode;

    // Allocate an environment handle
    retcode = SQLAllocEnv(&henv);

    // Throw an exception if the environment cannot be allocated
    if (retcode == SQL_ERROR) {
        throwException(env, "java/lang/Exception",
                       "Environment handle cannot be allocated");
        return 0;
    }
    
    return (jint) henv;
}

/*
 * Class:     javaservlets_nativeCode_JavaToODBC
 * Method:    SQLFreeEnv
 * Signature: ()I
 */
JNIEXPORT void JNICALL
  Java_javaservlets_nativeCode_JavaToODBC_SQLFreeEnv
    (JNIEnv *env, jclass cls, jint henv)
{
    // The return code
    RETCODE retcode;

    // Free the handle
    retcode = SQLFreeEnv((HENV) henv);

    // Check for errors
    if (retcode == SQL_ERROR) {
        throwException(env, "java/lang/Exception",
                       "Unable to free environment handle");
        return;
    }
    else if (retcode == SQL_INVALID_HANDLE) {
        throwException(env, "java/lang/Exception",
                       "Invalid environment handle");
        return;
    }
    return;
}

/*
 * Class:     javaservlets_nativeCode_JavaToODBC
 * Method:    SQLDataSources
 * Signature: (Ljavaservlets/nativeCode/DataSource;)Z
 */
JNIEXPORT jboolean JNICALL
  Java_javaservlets_nativeCode_JavaToODBC_SQLDataSources
    (JNIEnv *env, jclass cls, jint henv, jobject dataSource)
{
    // Return code
    RETCODE retcode;

    // Storage for the name and description
    UCHAR szDSN[SQL_MAX_DSN_LENGTH + 1];
    UCHAR szDesc[255];

    // Actual length of name and description
    SWORD cbDSN;
    SWORD cbDesc;

    // A java class
    jclass jcls;

    // A java method ID
    jmethodID jmid;
        
    // Make sure we've got a DataSource object to work with
    if (!dataSource) {
        throwException(env, "java/lang/Exception",
                       "DataSource object is null");
        return FALSE;
    }
    
    // Get the next data source entry
    retcode = SQLDataSources((HENV) henv, SQL_FETCH_NEXT,
                             &szDSN[0], (SWORD) sizeof(szDSN),
                             &cbDSN, &szDesc[0],
                             (SWORD) sizeof(szDesc), &cbDesc);

    // Check for errors
    if (retcode == SQL_ERROR) {
        throwException(env, "java/lang/Exception",
                       "Unable to get data source information");
        return FALSE;
    }
    else if (retcode == SQL_INVALID_HANDLE) {
        throwException(env, "java/lang/Exception",
                       "Invalid environment handle");
        return FALSE;
    }
    else if (retcode == SQL_NO_DATA_FOUND) {

        // End of data sources
        return FALSE;
    }

    // Get the DataSource class and find the setName method
    jcls = (*env)->GetObjectClass(env, dataSource);
    if (!jcls) {
        throwException(env, "java/lang/Exception",
                       "Unable to find DataSource class");
        return FALSE;
    }
    jmid = (*env)->GetMethodID(env, jcls, "setName",
                               "(Ljava/lang/String;)V");
    if (!jmid) {
        throwException(env, "java/lang/Exception",
                       "Unable to find DataSource.setName");
        return FALSE;
    }

    // Invoke the setName method on the DataSource object
    (*env)->CallVoidMethod(env, dataSource, jmid,
                           (*env)->NewStringUTF(env, szDSN));

    // Find the setDescription method
    jmid = (*env)->GetMethodID(env, jcls, "setDescription",
                               "(Ljava/lang/String;)V");
    if (!jmid) {
        throwException(env, "java/lang/Exception",
                       "Unable to find DataSource.setDescription");
        return FALSE;
    }

    // Invoke the setDescription method on the DataSource object
    (*env)->CallVoidMethod(env, dataSource, jmid,
                           (*env)->NewStringUTF(env, szDesc));

    return TRUE;
}