/********************************************************************\
  * BitlBee -- An IRC to other IM-networks gateway                     *
  *                                                                    *
  * Copyright 2002-2013 Wilmer van der Gaast and others                *
  \********************************************************************/

/* HTTP(S) module                                                       */

/*
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License with
  the Debian GNU/Linux distribution in /usr/share/common-licenses/GPL;
  if not, write to the Free Software Foundation, Inc., 51 Franklin St.,
  Fifth Floor, Boston, MA  02110-1301  USA
*/

#include <string.h>
#include <stdio.h>

#include "http_client.h"
#include "url.h"
#include "sock.h"


static gboolean http_connected( gpointer data, int source, b_input_condition cond );
static gboolean http_ssl_connected( gpointer data, int returncode, void *source, b_input_condition cond );
static gboolean http_incoming_data( gpointer data, int source, b_input_condition cond );
static void http_free( struct http_request *req );


struct http_request *http_dorequest( char *host, int port, int ssl, char *request, http_input_function func, gpointer data )
{
	struct http_request *req;
	int error = 0;
	
	req = g_new0( struct http_request, 1 );
	
	if( ssl )
	{
		req->ssl = ssl_connect( host, port, TRUE, http_ssl_connected, req );
		if( req->ssl == NULL )
			error = 1;
	}
	else
	{
		req->fd = proxy_connect( host, port, http_connected, req );
		if( req->fd < 0 )
			error = 1;
	}
	
	if( error )
	{
		http_free( req );
		return NULL;
	}
	
	req->func = func;
	req->data = data;
	req->request = g_strdup( request );
	req->request_length = strlen( request );
	req->redir_ttl = 3;
	req->content_length = -1;
	
	if( getenv( "BITLBEE_DEBUG" ) )
		printf( "About to send HTTP request:\n%s\n", req->request );
	
	return req;
}

struct http_request *http_dorequest_url( char *url_string, http_input_function func, gpointer data )
{
	url_t *url = g_new0( url_t, 1 );
	char *request;
	void *ret;
	
	if( !url_set( url, url_string ) )
	{
		g_free( url );
		return NULL;
	}
	
	if( url->proto != PROTO_HTTP && url->proto != PROTO_HTTPS )
	{
		g_free( url );
		return NULL;
	}
	
	request = g_strdup_printf( "GET %s HTTP/1.0\r\n"
	                           "Host: %s\r\n"
	                           "User-Agent: BitlBee " BITLBEE_VERSION " " ARCH "/" CPU "\r\n"
	                           "\r\n", url->file, url->host );
	
	ret = http_dorequest( url->host, url->port,
	                      url->proto == PROTO_HTTPS, request, func, data );
	
	g_free( url );
	g_free( request );
	return ret;
}

/* This one is actually pretty simple... Might get more calls if we can't write 
   the whole request at once. */
static gboolean http_connected( gpointer data, int source, b_input_condition cond )
{
	struct http_request *req = data;
	int st;
	
	if( source < 0 )
		goto error;
	
	if( req->inpa > 0 )
		b_event_remove( req->inpa );
	
	sock_make_nonblocking( req->fd );
	
	if( req->ssl )
	{
		st = ssl_write( req->ssl, req->request + req->bytes_written,
		                req->request_length - req->bytes_written );
		if( st < 0 )
		{
			if( ssl_errno != SSL_AGAIN )
			{
				ssl_disconnect( req->ssl );
				goto error;
			}
		}
	}
	else
	{
		st = write( source, req->request + req->bytes_written,
		                    req->request_length - req->bytes_written );
		if( st < 0 )
		{
			if( !sockerr_again() )
			{
				closesocket( req->fd );
				goto error;
			}
		}
	}
	
	if( st > 0 )
		req->bytes_written += st;
	
	if( req->bytes_written < req->request_length )
		req->inpa = b_input_add( source,
		                         req->ssl ? ssl_getdirection( req->ssl ) : B_EV_IO_WRITE,
	        	                 http_connected, req );
	else
		req->inpa = b_input_add( source, B_EV_IO_READ, http_incoming_data, req );
	
	return FALSE;
	
error:
	if( req->status_string == NULL )
		req->status_string = g_strdup( "Error while writing HTTP request" );
	
	req->func( req );
	http_free( req );
	return FALSE;
}

static gboolean http_ssl_connected( gpointer data, int returncode, void *source, b_input_condition cond )
{
	struct http_request *req = data;
	
	if( source == NULL )
	{
		if( returncode != 0 )
		{
			char *err = ssl_verify_strerror( returncode );
			req->status_string = g_strdup_printf(
				"Certificate verification problem 0x%x: %s",
				returncode, err ? err : "Unknown" );
			g_free( err );
		}
		return http_connected( data, -1, cond );
	}
	
	req->fd = ssl_getfd( source );
	
	return http_connected( data, req->fd, cond );
}

typedef enum {
	CR_OK,
	CR_EOF,
	CR_ERROR,
	CR_ABORT,
} http_ret_t;

static gboolean http_handle_headers( struct http_request *req );
static http_ret_t http_process_chunked_data( struct http_request *req, const char *buffer, int len );
static http_ret_t http_process_data( struct http_request *req, const char *buffer, int len );

static gboolean http_incoming_data( gpointer data, int source, b_input_condition cond )
{
	struct http_request *req = data;
	char buffer[4096];
	int st;
	
	if( req->inpa > 0 )
	{
		b_event_remove( req->inpa );
		req->inpa = 0;
	}
	
	if( req->ssl )
	{
		st = ssl_read( req->ssl, buffer, sizeof( buffer ) );
		if( st < 0 )
		{
			if( ssl_errno != SSL_AGAIN )
			{
				/* goto cleanup; */
				
				/* YAY! We have to deal with crappy Microsoft
				   servers that LOVE to send invalid TLS
				   packets that abort connections! \o/ */
				
				goto eof;
			}
		}
		else if( st == 0 )
		{
			goto eof;
		}
	}
	else
	{
		st = read( req->fd, buffer, sizeof( buffer ) );
		if( st < 0 )
		{
			if( !sockerr_again() )
			{
				req->status_string = g_strdup( strerror( errno ) );
				goto cleanup;
			}
		}
		else if( st == 0 )
		{
			goto eof;
		}
	}
	
	if( st > 0 )
	{
		http_ret_t c;
		
		if( req->flags & HTTPC_CHUNKED )
			c = http_process_chunked_data( req, buffer, st );
		else
			c = http_process_data( req, buffer, st );
		
		if( c == CR_EOF )
			goto eof;
		else if( c == CR_ERROR || c == CR_ABORT )
			return FALSE;
	}
	
	if( req->content_length != -1 &&
	    req->body_size >= req->content_length )
		goto eof;
	
	if( ssl_pending( req->ssl ) )
		return http_incoming_data( data, source, cond );
	
	/* There will be more! */
	req->inpa = b_input_add( req->fd,
	                         req->ssl ? ssl_getdirection( req->ssl ) : B_EV_IO_READ,
	                         http_incoming_data, req );
	
	return FALSE;

eof:
	req->flags |= HTTPC_EOF;
	
	/* Maybe if the webserver is overloaded, or when there's bad SSL
	   support... */
	if( req->bytes_read == 0 )
	{
		req->status_string = g_strdup( "Empty HTTP reply" );
		goto cleanup;
	}

cleanup:
	/* Avoid g_source_remove warnings */
	req->inpa = 0;

	if( req->ssl )
		ssl_disconnect( req->ssl );
	else
		closesocket( req->fd );
	
	if( req->body_size < req->content_length )
	{
		req->status_code = -1;
		g_free( req->status_string );
		req->status_string = g_strdup( "Response truncated" );
	}
	
	if( getenv( "BITLBEE_DEBUG" ) && req )
		printf( "Finishing HTTP request with status: %s\n",
		        req->status_string ? req->status_string : "NULL" );
	
	req->func( req );
	http_free( req );
	return FALSE;
}

static http_ret_t http_process_chunked_data( struct http_request *req, const char *buffer, int len )
{
	char *chunk, *eos, *s;
	
	if( len < 0 )
		return TRUE;
	
	if( len > 0 )
	{
		req->cbuf = g_realloc( req->cbuf, req->cblen + len + 1 );
		memcpy( req->cbuf + req->cblen, buffer, len );
		req->cblen += len;
		req->cbuf[req->cblen] = '\0';
	}
	
	/* Turns out writing a proper chunked-encoding state machine is not
	   that simple. :-( I've tested this one feeding it byte by byte so
	   I hope it's solid now. */
	chunk = req->cbuf;
	eos = req->cbuf + req->cblen;
	while( TRUE )
	{
		int clen = 0;
		
		/* Might be a \r\n from the last chunk. */
		s = chunk;
		while( g_ascii_isspace( *s ) )
			s ++;
		/* Chunk length. Might be incomplete. */
		if( s < eos && sscanf( s, "%x", &clen ) != 1 )
			return CR_ERROR;
		while( g_ascii_isxdigit( *s ) )
			s ++;
		
		/* If we read anything here, it *must* be \r\n. */
		if( strncmp( s, "\r\n", MIN( 2, eos - s ) ) != 0 )
			return CR_ERROR;
		s += 2;
		
		if( s >= eos )
			break;
		
		/* 0-length chunk means end of response. */	
		if( clen == 0 )
			return CR_EOF;
		
		/* Wait for the whole chunk to arrive. */
		if( s + clen > eos )
			break;
		if( http_process_data( req, s, clen ) != CR_OK )
			return CR_ABORT;
		
		chunk = s + clen;
	}
	
	if( chunk != req->cbuf )
	{
		req->cblen = eos - chunk;
		s = g_memdup( chunk, req->cblen + 1 );
		g_free( req->cbuf );
		req->cbuf = s;
	}
	
	return CR_OK;
}

static http_ret_t http_process_data( struct http_request *req, const char *buffer, int len )
{
	if( len <= 0 )
		return CR_OK;
	
	if( !req->reply_body )
	{
		req->reply_headers = g_realloc( req->reply_headers, req->bytes_read + len + 1 );
		memcpy( req->reply_headers + req->bytes_read, buffer, len );
		req->bytes_read += len;
		req->reply_headers[req->bytes_read] = '\0';
		
		if( strstr( req->reply_headers, "\r\n\r\n" ) ||
		    strstr( req->reply_headers, "\n\n" ) )
		{
			/* We've now received all headers. Look for something
			   interesting. */
			if( !http_handle_headers( req ) )
				return CR_ABORT;
			
			/* Start parsing the body as chunked if required. */
			if( req->flags & HTTPC_CHUNKED )
				return http_process_chunked_data( req, NULL, 0 );
		}
	}
	else
	{
		int pos = req->reply_body - req->sbuf;
		req->sbuf = g_realloc( req->sbuf, req->sblen + len + 1 );
		memcpy( req->sbuf + req->sblen, buffer, len );
		req->bytes_read += len;
		req->sblen += len;
		req->sbuf[req->sblen] = '\0';
		req->reply_body = req->sbuf + pos;
		req->body_size = req->sblen - pos;
	}
	
	if( ( req->flags & HTTPC_STREAMING ) && req->reply_body )
		req->func( req );
	
	return CR_OK;
}

/* Splits headers and body. Checks result code, in case of 300s it'll handle
   redirects. If this returns FALSE, don't call any callbacks! */
static gboolean http_handle_headers( struct http_request *req )
{
	char *end1, *end2, *s;
	int evil_server = 0;
	
	/* Zero termination is very convenient. */
	req->reply_headers[req->bytes_read] = '\0';
	
	/* Find the separation between headers and body, and keep stupid
	   webservers in mind. */
	end1 = strstr( req->reply_headers, "\r\n\r\n" );
	end2 = strstr( req->reply_headers, "\n\n" );
	
	if( end2 && end2 < end1 )
	{
		end1 = end2 + 1;
		evil_server = 1;
	}
	else if( end1 )
	{
		end1 += 2;
	}
	else
	{
		req->status_string = g_strdup( "Malformed HTTP reply" );
		return TRUE;
	}
	
	*end1 = '\0';
	
	if( getenv( "BITLBEE_DEBUG" ) )
		printf( "HTTP response headers:\n%s\n", req->reply_headers );
	
	if( evil_server )
		req->reply_body = end1 + 1;
	else
		req->reply_body = end1 + 2;
	
	/* Separately allocated space for headers and body. */
	req->sblen = req->body_size = req->reply_headers + req->bytes_read - req->reply_body;
	req->sbuf = req->reply_body = g_memdup( req->reply_body, req->body_size + 1 );
	req->reply_headers = g_realloc( req->reply_headers, end1 - req->reply_headers + 1 );
	
	if( ( end1 = strchr( req->reply_headers, ' ' ) ) != NULL )
	{
		if( sscanf( end1 + 1, "%hd", &req->status_code ) != 1 )
		{
			req->status_string = g_strdup( "Can't parse status code" );
			req->status_code = -1;
		}
		else
		{
			char *eol;
			
			if( evil_server )
				eol = strchr( end1, '\n' );
			else
				eol = strchr( end1, '\r' );
			
			req->status_string = g_strndup( end1 + 1, eol - end1 - 1 );
			
			/* Just to be sure... */
			if( ( eol = strchr( req->status_string, '\r' ) ) )
				*eol = 0;
			if( ( eol = strchr( req->status_string, '\n' ) ) )
				*eol = 0;
		}
	}
	else
	{
		req->status_string = g_strdup( "Can't locate status code" );
		req->status_code = -1;
	}
	
	if( ( ( req->status_code >= 301 && req->status_code <= 303 ) ||
	      req->status_code == 307 ) && req->redir_ttl-- > 0 )
	{
		char *loc, *new_request, *new_host;
		int error = 0, new_port, new_proto;
		
		/* We might fill it again, so let's not leak any memory. */
		g_free( req->status_string );
		req->status_string = NULL;
		
		loc = strstr( req->reply_headers, "\nLocation: " );
		if( loc == NULL ) /* We can't handle this redirect... */
		{
			req->status_string = g_strdup( "Can't locate Location: header" );
			return TRUE;
		}
		
		loc += 11;
		while( *loc == ' ' )
			loc ++;
		
		/* TODO/FIXME: Possibly have to handle relative redirections,
		   and rewrite Host: headers. Not necessary for now, it's
		   enough for passport authentication like this. */
		
		if( *loc == '/' )
		{
			/* Just a different pathname... */
			
			/* Since we don't cache the servername, and since we
			   don't need this yet anyway, I won't implement it. */
			
			req->status_string = g_strdup( "Can't handle relative redirects" );
			
			return TRUE;
		}
		else
		{
			/* A whole URL */
			url_t *url;
			char *s, *version, *headers;
			const char *new_method;
			
			s = strstr( loc, "\r\n" );
			if( s == NULL )
				return TRUE;
			
			url = g_new0( url_t, 1 );
			*s = 0;
			
			if( !url_set( url, loc ) )
			{
				req->status_string = g_strdup( "Malformed redirect URL" );
				g_free( url );
				return TRUE;
			}
			
			/* Find all headers and, if necessary, the POST request contents.
			   Skip the old Host: header though. This crappy code here means
			   anything using this http_client MUST put the Host: header at
			   the top. */
			if( !( ( s = strstr( req->request, "\r\nHost: " ) ) &&
			       ( s = strstr( s + strlen( "\r\nHost: " ), "\r\n" ) ) ) )
			{
				req->status_string = g_strdup( "Error while rebuilding request string" );
				g_free( url );
				return TRUE;
			}
			headers = s;
			
			/* More or less HTTP/1.0 compliant, from my reading of RFC 2616.
			   Always perform a GET request unless we received a 301. 303 was
			   meant for this but it's HTTP/1.1-only and we're specifically
			   speaking HTTP/1.0. ...
			   
			   Well except someone at identi.ca's didn't bother reading any
			   RFCs and just return HTTP/1.1-specific status codes to HTTP/1.0
			   requests. Fuckers. So here we are, handle 301..303,307. */
			if( strncmp( req->request, "GET", 3 ) == 0 )
				/* GETs never become POSTs. */
				new_method = "GET";
			else if( req->status_code == 302 || req->status_code == 303 )
				/* 302 de-facto becomes GET, 303 as specified by RFC 2616#10.3.3 */
				new_method = "GET";
			else
				/* 301 de-facto should stay POST, 307 specifally RFC 2616#10.3.8 */
				new_method = "POST";
			
			if( ( version = strstr( req->request, " HTTP/" ) ) &&
			    ( s = strstr( version, "\r\n" ) ) )
			{
				version ++;
				version = g_strndup( version, s - version );
			}
			else
				version = g_strdup( "HTTP/1.0" );
			
			/* Okay, this isn't fun! We have to rebuild the request... :-( */
			new_request = g_strdup_printf( "%s %s %s\r\nHost: %s%s",
			                               new_method, url->file, version,
			                               url->host, headers );
			
			new_host = g_strdup( url->host );
			new_port = url->port;
			new_proto = url->proto;
			
			/* If we went from POST to GET, truncate the request content. */
			if( new_request[0] != req->request[0] && new_request[0] == 'G' &&
			    ( s = strstr( new_request, "\r\n\r\n" ) ) )
				s[4] = '\0';
			
			g_free( url );
			g_free( version );
		}
		
		if( req->ssl )
			ssl_disconnect( req->ssl );
		else
			closesocket( req->fd );
		
		req->fd = -1;
		req->ssl = NULL;
		
		if( getenv( "BITLBEE_DEBUG" ) )
			printf( "New headers for redirected HTTP request:\n%s\n", new_request );
	
		if( new_proto == PROTO_HTTPS )
		{
			req->ssl = ssl_connect( new_host, new_port, TRUE, http_ssl_connected, req );
			if( req->ssl == NULL )
				error = 1;
		}
		else
		{
			req->fd = proxy_connect( new_host, new_port, http_connected, req );
			if( req->fd < 0 )
				error = 1;
		}
		g_free( new_host );
		
		if( error )
		{
			req->status_string = g_strdup( "Connection problem during redirect" );
			g_free( new_request );
			return TRUE;
		}
		
		g_free( req->request );
		g_free( req->reply_headers );
		g_free( req->sbuf );
		req->request = new_request;
		req->request_length = strlen( new_request );
		req->bytes_read = req->bytes_written = req->inpa = 0;
		req->reply_headers = req->reply_body = NULL;
		req->sbuf = req->cbuf = NULL;
		req->sblen = req->cblen = 0;
		
		return FALSE;
	}

	if( ( s = get_rfc822_header( req->reply_headers, "Content-Length", 0 ) ) &&
	    sscanf( s, "%d", &req->content_length ) != 1 )
		req->content_length = -1;
	g_free( s );
	
	if( ( s = get_rfc822_header( req->reply_headers, "Transfer-Encoding", 0 ) ) )
	{
		if( strcasestr( s, "chunked" ) )
		{
			req->flags |= HTTPC_CHUNKED;
			req->cbuf = req->sbuf;
			req->cblen = req->sblen;
			
			req->reply_body = req->sbuf = g_strdup( "" );
			req->body_size = req->sblen = 0;
		}
		g_free( s );
	}
	
	return TRUE;
}

void http_flush_bytes( struct http_request *req, size_t len )
{
	if( len <= 0 || len > req->body_size || !( req->flags & HTTPC_STREAMING ) )
		return;
	
	req->reply_body += len;
	req->body_size -= len;
	
	if( req->reply_body - req->sbuf >= 512 )
	{
		char *new = g_memdup( req->reply_body, req->body_size + 1 );
		g_free( req->sbuf );
		req->reply_body = req->sbuf = new;
		req->sblen = req->body_size;
	}
}

void http_close( struct http_request *req )
{
	if( !req )
		return;
	
	if( req->inpa > 0 )
		b_event_remove( req->inpa );
	
	if( req->ssl )
		ssl_disconnect( req->ssl );
	else
		closesocket( req->fd );
	
	http_free( req );
}

static void http_free( struct http_request *req )
{
	g_free( req->request );
	g_free( req->reply_headers );
	g_free( req->status_string );
	g_free( req->sbuf );
	g_free( req->cbuf );
	g_free( req );
}