#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>


#define BUFFER_LENGTH 256
#define ATTR_LENGTH 64
#define TAG_LENGTH 64
#define URL_LENGTH 1024

char buff[BUFFER_LENGTH];
int offset = 0;
int end = 0;
int last_char = -1;

int my_get_char(){
	if( last_char > -1 ){
		int temp = last_char;
		last_char = -1;
		return temp;	
	}
    if( offset < end ){
        return buff[offset++];
    }
    else {
        end = read( STDIN_FILENO, buff, BUFFER_LENGTH );
        if( !end )
            exit(EXIT_SUCCESS);
        if( end == -1 ){
            printf("Echec de la lecture sur l'entrée standard %d !\n", errno);
            perror("");
            exit(EXIT_FAILURE);
        }
        offset = 1;
        return buff[0];
    }
}

void my_put_back(char c){
	last_char = c;
} 

int cur = 0;
int lineno = 1;

char last_attr[ATTR_LENGTH+1];
char last_tag[TAG_LENGTH+1];
char url[URL_LENGTH + 1];

void newline(){
	lineno++;
}

void ignore_ws(){
	while( isspace(cur) ) {
		if( cur == '\n' )
			newline();
		cur = my_get_char();
	}
}

int expect(char *s){
	for( ; *s ; s++ ){
		if( (cur = my_get_char()) != *s ){
			if( cur == '\n' )
				newline();
			return 0;
		}
	}
	return 1;
}

void go_char(char c){
	while( (cur = my_get_char()) != c ){
		if( cur == '\n' )
			newline();
	}
}

// tokens :
void _document();
void _out();
void _tag();
void _tag_name(); // set last_tag
void _tag_content();
void _comment_content();
int _attr_name(); // set last_attr
void _attr_content();


void _document(){
	go_char('<');
	if( (cur = my_get_char()) == '!' ){
		go_char('>');
		_out();
	}
	else {
		my_put_back(cur);
		_tag();
		_out();
	}
}


void _out(){
	for(;;){
		go_char('<');
    	_tag();
	}
}

void _tag(){
	cur = my_get_char();
	// end tag
	if( cur == '/' ){
		cur = my_get_char();
		_tag_name();
		ignore_ws();
		if( ! (cur = my_get_char()) == '>' ){
			fprintf(stderr, "Le tag fermant de %s à la ligne %d contient des caractères"
				"innattendus !\n", last_tag, lineno);
			go_char('>');
		}
		return;
	}
	// comment case
	else if( cur == '!' ){
		if( ! expect("--" ) ){
			fprintf(stderr, "Le tag commençant par ! à la ligne %d semble ne pas être "
				"un commentaire, tentative de récupération.\n", lineno);
			go_char('>');
		}
		_comment_content();
		return;
	}
	// start tag
	else {
		_tag_name();
		_tag_content();
		
		// start-end tag
		if( cur == '/' ){
			go_char('>');
		}
		
		if( ! cur == '>' ){
			fprintf(stderr, "Le tag ouvrant de %s à la ligne %d contient des caractères"
				"innattendus !\n", last_tag, lineno);
			go_char('>');
		}
		return;
	}
}

void _tag_name(){
	int i = 0;
	while( isalpha(cur) ){
		if( i < TAG_LENGTH ){
			last_tag[i++] = cur;
		}
		else {
			last_tag[i] = 0;
			fprintf(stderr, "Tag trop long à la ligne %d : %s\n", 
				lineno, last_tag);
			return;
		}
		cur = my_get_char();
	}
	last_tag[i] = 0;
	return;
}


void _tag_content(){
	for(;;){
		ignore_ws();
		int i = _attr_name();
		if( ! i )
			return;
		if( i == -1 ){
			go_char('>');
			return;
		}
		ignore_ws();
		if( cur == '=' ){
			cur = my_get_char();
			ignore_ws();
			_attr_content();
		}	
	}
}


void _comment_content(){
	for(;;){
		go_char('-');
		if( expect("->") ){
			return;
		}
	}
}


int _attr_name(){
	int i = 0;
	while( isalpha(cur) ){
		if( i < ATTR_LENGTH ){
			last_attr[i++] = cur;
		}
		else {
			last_attr[i] = 0;
			fprintf(stderr, "Attr trop long à la ligne %d : %s\n", 
				lineno, last_attr);
			return -1;
		}
		cur = my_get_char();
	}
	last_attr[i] = 0;
	return i;
}


void _attr_content(){
    int i = 0;
	if( cur == '"' ){
		cur = my_get_char();
		while( cur != '"' ) {
			if( i < URL_LENGTH ){
				url[i++] = cur;
			}
			else {
				url[i] = 0;
				fprintf(stderr, "URL trop longue à la ligne %d : %s\n", 
					lineno, url);
				return;
			}
			if( cur == '\\' ){
				cur = my_get_char();
				if( i < URL_LENGTH ){
					url[i++] = cur;
				}
				else {
					url[i] = 0;
					fprintf(stderr, "URL trop longue à la ligne %d : %s\n", 
						lineno, url);
					return;
				}
			}
			cur = my_get_char();
		}
	}
	else {
		while( ! isspace(cur) || cur == '>' ) {
			if( i < URL_LENGTH ){
				url[i++] = cur;
			}
			else {
				url[i] = 0;
				fprintf(stderr, "URL trop longue à la ligne %d : %s\n", 
					lineno, url);
				return;
			}
			if( cur == '\\' ){
				cur = my_get_char();
				if( i < URL_LENGTH ){
					url[i++] = cur;
				}
				else {
					url[i] = 0;
					fprintf(stderr, "URL trop longue à la ligne %d : %s\n", 
						lineno, url);
					return;
				}
			}
			cur = my_get_char();
		}
	}
			
	url[i] = 0;
	
	if( (!strcmp( last_tag, "a" ) || !strcmp( last_tag, "A" ) )
		&& (!strcmp( last_attr, "href" ) || !strcmp( last_attr, "HREF" ) )
		) {
			printf("%s\n", url);
	}
	else if( (!strcmp( last_tag, "img" ) || !strcmp( last_tag, "IMG" ) )
		&& (!strcmp( last_attr, "src" ) || !strcmp( last_attr, "SRC" ) )
		) {
			printf("%s\n", url);
	}
	
	return;
}


int main()
{
    _document();
    return EXIT_SUCCESS;
}