#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "cforum.h"

/* Return an allocated string containing the next cookie ("name=value"). */
char *
nextcookie(int max)
{
	char *buf;
	int n;
	static char *cs = NULL;

	if(!(buf = malloc(max)))
		err(1, "malloc");

	if(!cs)
		cs = getenv("HTTP_COOKIE");

	if(!cs || !*cs)
		return NULL;

	if(*cs == ' ')
		cs++;

	n = strcspn(cs, ";");
	snprintf(buf, max, "%.*s", n, cs);
	cs += n + (n != strlen(cs));

	return buf;
}

/*
 * Return an allocated string containing the next parameter ("key=value").
 * The method argument decides which data (GET or POST) to read from.
 * 
 * If len is NULL, the string will be NUL-terminated; if len is non-NULL,
 * the string will not be NUL-terminated, and len will be pointed to the
 * length of the string.
 * 
 * The string is truncated to max characters. If truncation occurred, the
 * -1th character of the string is set to 1. 
 */
char *
nextparam(enum method method, int *len, int max)
{
	char *buf;
	int i, sz;
	static int j = 0;

	/* Return NULL if at end of parameter string. */
	if(method == GET && !query.string[j-1])
		return NULL;

#define STEP 256

	sz = STEP;
	if(!(buf = malloc(1+sz))) /* Leave space for -1th character. */
		err(1, "malloc");

	/*
	 * buf's -1th character is set to 1 if the string
	 * has been truncated (i.e. if input exceeded max).
	 */
	buf++;
	TRUNCATED(buf) = 0;

#define READ(b) (method == GET? \
	(*(b) = query.string[j++]): \
	fread(b, 1, 1, stdin))

	/*
	 * The parameter is read in a rather lopsided loop, treating
	 * the first character specially.
	 */
first:	
	/* Return NULL if at end of parameter string. */
	if(!READ(buf))
		return NULL;

	/* Skip empty parameters. */
	if(*buf == '&')
		goto first;

	i = 0;
	goto rest;

	for(; READ(buf+i); i++){
rest:
		if(buf[i] == '&'){
			buf[i] = 0;
			break;
		}
		if(i+1 > max){
			TRUNCATED(buf) = 1;
			/* Skip ahead to next parameter. */
			while(READ(buf+i+1) && buf[i+1] != '&') ;
			break;
		}
		if(i+1 >= sz){
			sz += STEP;
			/* Remember to adjust for -1th character. */
			if(buf--, buf = realloc(buf, 1+sz), !buf++)
				err(1, "realloc");
		}
	}
	if(len) *len = i;
	else buf[i] = 0;

	return buf;
}

/* Fill global query structure from CGI environment variables. */
void
setquery()
{
	query.string = getenv("QUERY_STRING");
	if(!query.string){
		fprintf(stderr, "no QUERY_STRING\n");
		exit(1);
	}
	query.method = strcmp(getenv("REQUEST_METHOD"), "POST")? GET: POST;
	if(query.method == POST)
		query.length = atoi(getenv("CONTENT_LENGTH"));
}

/*
 * Split parameter string on equals sign and return value portion;
 * return NULL if none found. For example, v = split(p) results in
 * p pointing to the parameter key and v pointing to the value.
 */
char *
split(char *param)
{
	int n;

	n = strcspn(param, "=");
	if(!param[n])
		return NULL;
	param[n] = 0;
	return param+n+1;
}

/*
 * Decode a URL-encoded string in place. If len is negative, the string
 * is assumed to be NUL-terminated. The length of the new string is
 * returned. Note that the new string is NOT NUL-terminated! To produce
 * a NUL-terminated string, use s[urldecode(s, -1)] = 0.
 */
int
urldecode(char *s, int len)
{
	unsigned int code, i, j;

	if(len < 0)
		len = strlen(s);

	for(i = j = 0; i < len; i++, j++){
		if(s[i] == '+')
			s[j] = ' ';
		else if(s[i] == '%'){
			if(!sscanf(s+i+1, "%2x", &code))
				code = '?';
			s[j] = code;
			i += 2;
		}else
			s[j] = s[i];
	}

	return j;
}