/** 
 * section: 	XPath
 * synopsis: 	Evaluate XPath expression and prints result node set.
 * purpose: 	Shows how to evaluate XPath expression and register 
 *          	known namespaces in XPath context.
 * usage:	xpath1 <xml-file> <xpath-expr> [<known-ns-list>]
 * test: ./xpath1 test3.xml '//child2' > xpath1.tmp ; diff xpath1.tmp xpath1.res ; rm xpath1.tmp
 * author: 	Aleksey Sanin
 * copy: 	see Copyright for the status of this software.
 */
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>

#include <libxml/tree.h>
#include <libxml/parser.h>
#include <libxml/xpath.h>
#include <libxml/xpathInternals.h>

#ifdef LIBXML_XPATH_ENABLED


void usage(const char *name);
int  execute_xpath_expression(const char* filename, const xmlChar* xpathExpr, const xmlChar* nsList);

void
LibXML_serror_handler(void *userData, xmlErrorPtr err) {
  printf("ERROR occured\n");
}

int 
main(int argc, char **argv) {
    /* Parse command line and process file */
    if((argc < 2) || (argc > 3)) {
	fprintf(stderr, "Error: wrong number of arguments.\n");
	usage(argv[0]);
	return(-1);
    } 
    
    /* Init libxml */     
    xmlInitParser();
    LIBXML_TEST_VERSION

    xmlSetStructuredErrorFunc(NULL,
			      (xmlStructuredErrorFunc)LibXML_serror_handler);

    /* Do the main job */
    execute_xpath_expression(argv[1], BAD_CAST argv[2], (argc > 3) ? BAD_CAST argv[3] : NULL);

    /* Shutdown libxml */
    xmlCleanupParser();
    
    /*
     * this is to debug memory for regression tests
     */
    xmlMemoryDump();
    return 0;
}

/**
 * usage:
 * @name:		the program name.
 *
 * Prints usage information.
 */
void 
usage(const char *name) {
    assert(name);
    
    fprintf(stderr, "Usage: %s <xml-file> <xpath-expr> [<known-ns-list>]\n", name);
    fprintf(stderr, "where <known-ns-list> is a list of known namespaces\n");
    fprintf(stderr, "in \"<prefix1>=<href1> <prefix2>=href2> ...\" format\n");
}

/**
 * execute_xpath_expression:
 * @filename:		the input XML filename.
 * @xpathExpr:		the xpath expression for evaluation.
 * @nsList:		the optional list of known namespaces in 
 *			"<prefix1>=<href1> <prefix2>=href2> ..." format.
 *
 * Parses input XML file, evaluates XPath expression and prints results.
 *
 * Returns 0 on success and a negative value otherwise.
 */
int 
execute_xpath_expression(const char* filename, const xmlChar* xpathExpr, const xmlChar* nsList) {
    xmlDocPtr doc;
    xmlXPathContextPtr xpathCtx; 
    xmlXPathObjectPtr xpathObj; 
    xmlXPathCompExprPtr comp;
    
    assert(filename);
    assert(xpathExpr);

    /* Load XML document */
    doc = xmlParseFile(filename);
    if (doc == NULL) {
	fprintf(stderr, "Error: unable to parse file \"%s\"\n", filename);
	return(-1);
    }

    /* Create xpath evaluation context */
    xpathCtx = xmlXPathNewContext(doc);
    if(xpathCtx == NULL) {
        fprintf(stderr,"Error: unable to create new XPath context\n");
        xmlFreeDoc(doc); 
        return(-1);
    }

    comp = xmlXPathCompile( xpathExpr );
    if ( comp == NULL ) {
        fprintf(stderr,"Error: unable to compile XPath expression\n");
        xmlFreeDoc(doc); 
	return (-1);
    }
    
    /* Evaluate xpath expression */
    xpathObj = xmlXPathCompiledEval(comp, xpathCtx);
    if(xpathObj == NULL) {
        fprintf(stderr,"Error: unable to evaluate xpath expression \"%s\"\n", xpathExpr);
        xmlXPathFreeCompExpr(comp);
        xmlXPathFreeContext(xpathCtx); 
        xmlFreeDoc(doc); 
        return(-1);
    }

    /* Cleanup */
    xmlXPathFreeCompExpr(comp);
    xmlXPathFreeObject(xpathObj);
    xmlXPathFreeContext(xpathCtx); 
    xmlFreeDoc(doc); 
    
    return(0);
}

#else
int main(void) {
    fprintf(stderr, "XPath support not compiled in\n");
    exit(1);
}
#endif