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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2026 Olaf Wintermann. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "proxy.h"

#include <sys/socket.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <string.h>

#include "../util/pblock.h"
#include "../util/util.h"
#include "../proxy/httpclient.h"


typedef struct ProxyRequest {
    Session *sn;
    Request *rq;
    
    /*
     * request header rewrite map
     * name: header name
     * value: header value or an empty string, if the header should be removed
     */
    pblock *request_header_rewrite;
    
    /*
     * response header rewrite map
     * name: header name
     * value: header value or an empty string, if the header should be removed
     */
    pblock  *response_header_rewrite;
    
    /*
     * Has the response started (proxy_response_start called)
     */
    int response_started;
} ProxyRequest;

static int proxy_response_start(HttpClient *client, int status, char *message, void *userdata) {
    ProxyRequest *proxy = userdata;
    
    HeaderArray *headers = client->response_headers;
    while(headers) {
        for(int i=0;i<headers->len;i++) {
            cxmutstr name = headers->headers[i].name;
            cxmutstr value = headers->headers[i].value;
            // NSAPI uses lower case header names internally
            for(int c=0;c<name.length;c++) {
                name.ptr[c] = tolower(name.ptr[c]);
            }
            // HttpClient does not 0-terminate strings
            name.ptr[name.length] = 0;
            // check if this header should be modified
            char *rewrite = pblock_findval(name.ptr, proxy->response_header_rewrite);
            if(rewrite) {
                value = cx_mutstr(rewrite);
                if(value.length == 0) {
                    // empty header value -> skip
                    continue;
                }
            }
            
            // add header to response
            pblock_nvlinsert(name.ptr, name.length, value.ptr, value.length, proxy->rq->srvhdrs);
        }
        headers = headers->next;
    }
    
    protocol_status(proxy->sn, proxy->rq, status, message);
    protocol_start_response(proxy->sn, proxy->rq);
    proxy->response_started = 1;
    
    return 0;
}

static void proxy_response_finished(HttpClient *client, void *userdata) {
    ProxyRequest *proxy = userdata;
    
    int ret = REQ_PROCEED;
    if(!proxy->response_started) {
        protocol_status(proxy->sn, proxy->rq, 502, NULL);
        ret = REQ_ABORTED;
    }
    
    http_client_free(client);
    
    nsapi_function_return(proxy->sn, proxy->rq, ret);
}

static ssize_t proxy_request_read(HttpClient *client, void *buf, size_t nbytes, void *userdata) {
    ProxyRequest *proxy = userdata;
    int ret = netbuf_getbytes(proxy->sn->inbuf, buf, nbytes);
    if(ret == NETBUF_EOF) {
        ret = 0;
    }
    // TODO: handle errors
    return ret;
}

static ssize_t proxy_response_write(HttpClient *client, void *buf, size_t nbytes, void *userdata) {
    ProxyRequest *proxy = userdata;
    ssize_t ret = net_write(proxy->sn->csd, buf, nbytes);
    // TODO: handle errors
    return ret;
}

static void proxy_request_finished(HttpClient *client, void *userdata) {
    ProxyRequest *proxy = userdata;
    net_setnonblock(proxy->sn->csd, 0);
    nsapi_saf_return(proxy->sn, proxy->rq, REQ_PROCEED);
}

int http_reverse_proxy_service(pblock *param, Session *sn, Request *rq) {
    EventHandler *ev = sn->ev;
    const char *method = pblock_findkeyval(pb_key_method, rq->reqpb);
    const char *uri = pblock_findkeyval(pb_key_uri, rq->reqpb);
    const char *query = pblock_findkeyval(pb_key_query, rq->reqpb);
    
    cxmutstr new_uri = CX_NULLSTR;
    size_t uri_len = strlen(uri);
    size_t query_len = query ? strlen(query) : 0;
    size_t new_uri_alloc = ((uri_len + query_len) * 3) + 2;
    new_uri.ptr = pool_malloc(sn->pool, new_uri_alloc);
    new_uri.length = util_uri_escape_s(new_uri.ptr, new_uri_alloc, uri);
    if(new_uri.length > 0 && query_len > 0) {
        new_uri.ptr[new_uri.length] = '?';
        memcpy(new_uri.ptr + new_uri.length + 1, query, query_len + 1);
        new_uri.length = new_uri.length + 1 + query_len;
    }
    
    // remove some response headers, that were previously set by ObjectType
    // or other SAFs
    pblock_removekey(pb_key_content_type, rq->srvhdrs);
    
    ProxyRequest *proxy = pool_malloc(sn->pool, sizeof(ProxyRequest));
    proxy->sn = sn;
    proxy->rq = rq;
    proxy->request_header_rewrite = pblock_create_pool(sn->pool, 16);
    proxy->response_header_rewrite = pblock_create_pool(sn->pool, 16);
    proxy->response_started = 0;
    
    // Some request/response headers should be removed or altered
    // An empty string means, the header should be removed
    pblock_nvinsert("host", "", proxy->request_header_rewrite);
    pblock_nvinsert("connection", "", proxy->request_header_rewrite);
    pblock_nvinsert("transfer-encoding", "", proxy->request_header_rewrite);
    pblock_nvinsert("content-length", "", proxy->request_header_rewrite);
    pblock_nvinsert("server", "", proxy->response_header_rewrite);
    pblock_nvinsert("connection", "", proxy->response_header_rewrite);
    
    // setup HttpClient
    HttpClient *client = http_client_new(ev);
    if(!client) {
        return REQ_ABORTED;
    }
    
    if(http_client_set_method(client, method)) {
        http_client_free(client);
        return REQ_ABORTED;
    }
    
    if(http_client_set_uri_len(client, new_uri.ptr, new_uri.length)) {
        http_client_free(client);
        return REQ_ABORTED;
    }
    
    // test address
    struct sockaddr_in address;
    inet_pton(AF_INET, "127.0.0.1", &address.sin_addr);
    address.sin_family = AF_INET;
    address.sin_port = htons(8080);
    http_client_set_addr(client, (struct sockaddr*)&address, sizeof(address));    
    http_client_add_request_header(client, cx_mutstr("host"), cx_mutstr("localhost:8080"));
    
    // add request headers to the client
    CxIterator i = pblock_iterator(rq->headers);
    cx_foreach(pb_entry*, entry, i) {
        cxmutstr header_value;
        char *rewrite_header = pblock_findval(entry->param->name, proxy->request_header_rewrite);
        if(rewrite_header) {
            if(!strcmp(entry->param->name, "transfer-encoding")) {
                if(!strcmp(entry->param->value, "chunked")) {
                    // enable chunked transfer encoding
                    if(http_client_enable_chunked_transfer_encoding(client)) {
                        http_client_free(client);
                        return REQ_ABORTED;
                    }
                    continue;
                }
            } else if(!strcmp(entry->param->name, "content-length")) {
                long long contentlength;
                if(!cx_strtoll(cx_str(entry->param->value), &contentlength, 10)) {
                    if(http_client_set_content_length(client, contentlength)) {
                        http_client_free(client);
                        return REQ_ABORTED;
                    }
                } else {
                    // illegal content-length
                    protocol_status(sn, rq, 400, NULL);
                    http_client_free(client);
                    return REQ_ABORTED;
                }
                continue;
            } else {
                // static header rewrite or remove header if it is empty
                header_value = cx_mutstr(rewrite_header);
                if(header_value.length == 0) {
                    continue;
                }
            }
        } else {
            header_value = cx_mutstr(entry->param->value);
        }
        
        if(http_client_add_request_header(client, cx_mutstr(entry->param->name), header_value)) {
            http_client_free(client);
            return REQ_ABORTED;
        }
    }
    
    client->request_body_read = proxy_request_read;
    client->request_body_read_userdata = proxy;
    client->response_start = proxy_response_start;
    client->response_start_userdata = proxy;
    client->response_body_write = proxy_response_write;
    client->response_body_write_userdata = proxy;
    client->response_finished = proxy_request_finished;
    client->response_finished_userdata = proxy;
    
    net_setnonblock(sn->csd, 1);
    if(http_client_start(client)) {
        net_setnonblock(sn->csd, 0);
        http_client_free(client);
        return REQ_ABORTED;
    }
    
    return REQ_PROCESSING;
}