/*
 * This file Copyright (C) 2008 Charles Kerr <charles@rebelbase.com>
 *
 * This file is licensed by the GPL version 2.  Works owned by the
 * Transmission project are granted a special exemption to clause 2(b)
 * so that the bulk of its code can remain under the MIT license. 
 * This exemption does not extend to derived works not owned by
 * the Transmission project.
 *
 * $Id$
 */

#include <assert.h>
#include <stdlib.h> /* bsearch */

#include <event.h>
#include <curl/curl.h>

#include "transmission.h"
#include "list.h"
#include "trevent.h"
#include "utils.h"
#include "web.h"

#define MAX_CONCURRENT_TASKS 16

#if LIBCURL_VERSION_NUM < 0x071003
#define curl_multi_socket_action(m,fd,mask,i) curl_multi_socket((m),(fd),(i))
#endif

#define DEFAULT_TIMER_MSEC 2000

#define dbgmsg( ... )  tr_deepLog( __FILE__, __LINE__, "web", __VA_ARGS__ )
/* #define dbgmsg(...)  do { fprintf( stderr, __VA_ARGS__ ); fprintf( stderr, "\n" ); } while( 0 ) */

struct tr_web
{
    unsigned int dying : 1;
    int prev_running;
    int still_running;
    long timer_ms;
    CURLM * multi;
    tr_session * session;
    tr_list * easy_queue;
    struct event timer_event;
};

/***
****
***/

struct tr_web_task
{
    unsigned long tag;
    struct evbuffer * response;
    char * url;
    char * range;
    tr_session * session;
    tr_web_done_func * done_func;
    void * done_func_user_data;
    long timer_ms;
};

static size_t
writeFunc( void * ptr, size_t size, size_t nmemb, void * task )
{
    const size_t byteCount = size * nmemb;
    evbuffer_add( ((struct tr_web_task*)task)->response, ptr, byteCount );
    dbgmsg( "wrote %zu bytes to task %p's buffer", byteCount, task );
    return byteCount;
}

static int
getCurlProxyType( tr_proxy_type t )
{
    switch( t )
    {
        case TR_PROXY_SOCKS4: return CURLPROXY_SOCKS4;
        case TR_PROXY_SOCKS5: return CURLPROXY_SOCKS5;
        default:              return CURLPROXY_HTTP;
    }
}

static void
addTask( void * vtask )
{
    struct tr_web_task * task = vtask;
    const tr_handle * session = task->session;

    if( session && session->web )
    {
        struct tr_web * web = session->web;
        CURL * easy;

        dbgmsg( "adding task #%lu [%s]", task->tag, task->url );

        easy = curl_easy_init( );

        if( !task->range && session->isProxyEnabled ) {
            curl_easy_setopt( easy, CURLOPT_PROXY, session->proxy );
            curl_easy_setopt( easy, CURLOPT_PROXYPORT, session->proxyPort );
            curl_easy_setopt( easy, CURLOPT_PROXYTYPE,
                                      getCurlProxyType( session->proxyType ) );
            curl_easy_setopt( easy, CURLOPT_PROXYAUTH, CURLAUTH_ANY );
        }
        if( !task->range && session->isProxyAuthEnabled ) {
            char * str = tr_strdup_printf( "%s:%s", session->proxyUsername,
                                                    session->proxyPassword );
            curl_easy_setopt( easy, CURLOPT_PROXYUSERPWD, str );
            tr_free( str );
        }

        curl_easy_setopt( easy, CURLOPT_PRIVATE, task );
        curl_easy_setopt( easy, CURLOPT_URL, task->url );
        curl_easy_setopt( easy, CURLOPT_WRITEFUNCTION, writeFunc );
        curl_easy_setopt( easy, CURLOPT_WRITEDATA, task );
        curl_easy_setopt( easy, CURLOPT_USERAGENT,
                                             TR_NAME "/" LONG_VERSION_STRING );
        curl_easy_setopt( easy, CURLOPT_SSL_VERIFYHOST, 0 );
        curl_easy_setopt( easy, CURLOPT_SSL_VERIFYPEER, 0 );
        //curl_easy_setopt( easy, CURLOPT_FORBID_REUSE, 1 );
        curl_easy_setopt( easy, CURLOPT_NOSIGNAL, 1 );
        curl_easy_setopt( easy, CURLOPT_FOLLOWLOCATION, 1 );
        curl_easy_setopt( easy, CURLOPT_MAXREDIRS, 5 );
        curl_easy_setopt( easy, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4 );
        curl_easy_setopt( easy, CURLOPT_VERBOSE,
                                         getenv( "TR_CURL_VERBOSE" ) != NULL );
        if( task->range )
            curl_easy_setopt( easy, CURLOPT_RANGE, task->range );
        else /* don't set encoding on webseeds; it messes up binary data */
            curl_easy_setopt( easy, CURLOPT_ENCODING, "" );

        if( web->still_running >= MAX_CONCURRENT_TASKS ) {
            tr_list_append( &web->easy_queue, easy );
            dbgmsg( " >> adding a task to the curl queue... size is now %d",
                                             tr_list_size( web->easy_queue ) );
        } else {
            CURLMcode rc = curl_multi_add_handle( web->multi, easy );
            if( rc == CURLM_OK )
                ++web->still_running;
            else
                tr_err( "%s", curl_multi_strerror( rc ) );
        }
    }
}

/***
****
***/

struct tr_web_sockinfo
{
    struct event ev;
    int evset;
};

static void
finish_task( struct tr_web_task * task, long response_code )
{
    dbgmsg( "finished a web task... response code is %ld", response_code );
    dbgmsg( "===================================================" );
    task->done_func( task->session,
                     response_code,
                     EVBUFFER_DATA( task->response ),
                     EVBUFFER_LENGTH( task->response ),
                     task->done_func_user_data );
    evbuffer_free( task->response );
    tr_free( task->range );
    tr_free( task->url );
    tr_free( task );
}

static void
webDestroy( tr_web * web )
{
    timeout_del( &web->timer_event );
    curl_multi_cleanup( web->multi );
    tr_free( web );
}

/* note: this function can free the tr_web if it's been flagged for deletion
   and there are no more tasks remaining.  so, callers need to make sure to
   not reference their g pointer after calling this function */
static void
check_run_count( tr_web * g )
{
    int added_from_queue = FALSE;

    dbgmsg( "check_run_count: prev_running %d, still_running %d",
            g->prev_running, g->still_running );

    if( 1 )
    {
        CURLMsg * msg;
        int msgs_left;
        CURL * easy;
        CURLcode res;

        do{
            easy = NULL;
            while(( msg = curl_multi_info_read( g->multi, &msgs_left ))) {
                if( msg->msg == CURLMSG_DONE ) {
                    easy = msg->easy_handle;
                    res = msg->data.result;
                    break;
                }
            }
            if( easy ) {
                long code;
                struct tr_web_task * task;
                curl_easy_getinfo( easy, CURLINFO_PRIVATE, (void*)&task );
                curl_easy_getinfo( easy, CURLINFO_RESPONSE_CODE, &code );
                curl_multi_remove_handle( g->multi, easy );
                curl_easy_cleanup( easy );
                finish_task( task, code );
            }
        } while ( easy );
    }

    g->prev_running = g->still_running;

dbgmsg( "--> still running: %d ... max: %d ... queue size: %d", g->still_running, MAX_CONCURRENT_TASKS, tr_list_size( g->easy_queue ) );

    while( ( g->still_running < MAX_CONCURRENT_TASKS ) 
        && ( tr_list_size( g->easy_queue ) > 0 ) )
    {
        CURL * easy = tr_list_pop_front( &g->easy_queue );
        if( easy )
        {
            const CURLMcode rc = curl_multi_add_handle( g->multi, easy );
            if( rc != CURLM_OK ) {
                tr_err( "%s", curl_multi_strerror( rc ) );
            } else {
                dbgmsg( "pumped a task out of the curl queue... %d remain", tr_list_size( g->easy_queue ) );
                added_from_queue = TRUE;
                ++g->still_running;
            }
        }
    }

    if( !added_from_queue )
    {
        if( g->still_running <= 0 ) {
            if( evtimer_pending( &g->timer_event, NULL ) ) {
                dbgmsg( "deleting the pending global timer" );
                evtimer_del( &g->timer_event );
            }
        }

        if( g->dying && ( g->still_running < 1 ) ) {
            dbgmsg( "destroying the web global now that all the tasks are done" );
            webDestroy( g );
        }
    }
}


static void
reset_timer( tr_web * g )
{
    struct timeval timeout;

    if( evtimer_pending( &g->timer_event, NULL ) )
        evtimer_del( &g->timer_event );

    dbgmsg( "adding a timeout for %ld seconds from now", g->timer_ms/1000l );
    tr_timevalMsec( g->timer_ms, &timeout );
    timeout_add( &g->timer_event, &timeout );
}

/* libevent says that sock is ready to be processed, so wake up libcurl */
static void
event_cb( int fd, short kind, void * vg )
{
    tr_web * g = vg;
    CURLMcode rc;
    int error = 0;
    int mask;
    socklen_t errsz = sizeof( error );

    getsockopt( fd, SOL_SOCKET, SO_ERROR, &error, &errsz );
    if( error )
        mask = CURL_CSELECT_ERR;
    else {
        mask = 0;
        if( kind & EV_READ  ) mask |= CURL_CSELECT_IN;
        if( kind & EV_WRITE ) mask |= CURL_CSELECT_OUT;
    }

    do {
        dbgmsg( "event_cb calling socket_action fd %d, mask %d", fd, mask );
        rc = curl_multi_socket_action( g->multi, fd, mask, &g->still_running );
        dbgmsg( "event_cb(): still_running is %d", g->still_running );
    } while( rc == CURLM_CALL_MULTI_PERFORM );
    if( rc != CURLM_OK )
        tr_err( "%s", curl_multi_strerror( rc ) );

    reset_timer( g );
    check_run_count( g );
}

/* libevent says that timer_ms have passed, so wake up libcurl */
static void
timer_cb( int socket UNUSED, short action UNUSED, void * vg )
{
    tr_web * g = vg;
    CURLMcode rc;
    dbgmsg( "libevent timer is done" );

    do {
        dbgmsg( "timer_cb calling CURL_SOCKET_TIMEOUT" );
        rc = curl_multi_socket_action( g->multi, CURL_SOCKET_TIMEOUT, 0,
                                       &g->still_running );
        dbgmsg( "timer_cb(): still_running is %d", g->still_running );
    } while( rc == CURLM_CALL_MULTI_PERFORM );

    if( rc != CURLM_OK )
        tr_err( "%s", curl_multi_strerror( rc ) );

    reset_timer( g );
    check_run_count( g );
}

static void
remsock( struct tr_web_sockinfo * f )
{
    if( f ) {
        dbgmsg( "deleting sockinfo %p", f );
        if( f->evset )
            event_del( &f->ev );
        tr_free( f );
    }
}

static void
setsock( curl_socket_t            sockfd,
         int                      action,
         struct tr_web          * g,
         struct tr_web_sockinfo * f )
{
    const int kind = EV_PERSIST
                   | (action & CURL_POLL_IN ? EV_READ : 0)
                   | (action & CURL_POLL_OUT ? EV_WRITE : 0);
    dbgmsg( "setsock: fd is %d, curl action is %d, libevent action is %d", sockfd, action, kind );
    if( f->evset )
        event_del( &f->ev );
    event_set( &f->ev, sockfd, kind, event_cb, g );
    f->evset = 1;
    event_add( &f->ev, NULL );
}

static void
addsock( curl_socket_t    sockfd,
         int              action,
         struct tr_web  * g )
{
    struct tr_web_sockinfo * f = tr_new0( struct tr_web_sockinfo, 1 );
    dbgmsg( "creating a sockinfo %p for fd %d", f, sockfd );
    setsock( sockfd, action, g, f );
    curl_multi_assign( g->multi, sockfd, f );
}

/* CURLMOPT_SOCKETFUNCTION */
static int
sock_cb( CURL            * e UNUSED,
         curl_socket_t     s,
         int               what,
         void            * vg,
         void            * vf)
{
    struct tr_web * g = vg;
    struct tr_web_sockinfo * f = vf;
    dbgmsg( "sock_cb: what is %d, sockinfo is %p", what, f );

    if( what == CURL_POLL_REMOVE )
        remsock( f );
    else if( !f )
        addsock( s, what, g );
    else
        setsock( s, what, g, f );

    return 0;
}


/* from libcurl documentation: "The timeout value returned in the long timeout
   points to, is in number of milliseconds at this very moment. If 0, it means
   you should proceed immediately without waiting for anything. If it
   returns -1, there's no timeout at all set.  Note: if libcurl returns a -1
   timeout here, it just means that libcurl currently has no stored timeout
   value. You must not wait too long (more than a few seconds perhaps) before
   you call curl_multi_perform() again."  */
static void
multi_timer_cb( CURLM *multi UNUSED, long timer_ms, void * g )
{
    if( timer_ms < 1 ) {
        if( timer_ms == 0 ) /* call it immediately */
            timer_cb( 0, 0, g );
        timer_ms = DEFAULT_TIMER_MSEC;
    }
    reset_timer( g );
}

/****
*****
****/

void
tr_webRun( tr_session         * session,
           const char         * url,
           const char         * range,
           tr_web_done_func     done_func,
           void               * done_func_user_data )
{
    if( session->web )
    {
        static unsigned long tag = 0;
        struct tr_web_task * task;

        task = tr_new0( struct tr_web_task, 1 );
        task->session = session;
        task->url = tr_strdup( url );
        task->range = tr_strdup( range );
        task->done_func = done_func;
        task->done_func_user_data = done_func_user_data;
        task->tag = ++tag;
        task->response = evbuffer_new( );

        tr_runInEventThread( session, addTask, task );
    }
}

tr_web*
tr_webInit( tr_session * session )
{
    static int curlInited = FALSE;
    tr_web * web;

    /* call curl_global_init if we haven't done it already.
     * try to enable ssl for https support; but if that fails,
     * try a plain vanilla init */ 
    if( curlInited == FALSE ) {
        curlInited = TRUE;
        if( curl_global_init( CURL_GLOBAL_SSL ) )
            curl_global_init( 0 );
    }
   
    web = tr_new0( struct tr_web, 1 );
    web->multi = curl_multi_init( );
    web->session = session;
    web->timer_ms = DEFAULT_TIMER_MSEC; /* default value to overwrite in multi_timer_cb() */

    timeout_set( &web->timer_event, timer_cb, web );
    curl_multi_setopt( web->multi, CURLMOPT_SOCKETDATA, web );
    curl_multi_setopt( web->multi, CURLMOPT_SOCKETFUNCTION, sock_cb );
    curl_multi_setopt( web->multi, CURLMOPT_TIMERDATA, web );
    curl_multi_setopt( web->multi, CURLMOPT_TIMERFUNCTION, multi_timer_cb );

    return web;
}

void
tr_webClose( tr_web ** web_in )
{
    tr_web * web = *web_in;
    *web_in = NULL;
    if( web->still_running < 1 )
        webDestroy( web );
    else
        web->dying = 1;
}

/*****
******
******
*****/

static struct http_msg {
    long code;
    const char * text;
} http_msg[] = {
    { 101, "Switching Protocols" },
    { 200, "OK" },
    { 201, "Created" },
    { 202, "Accepted" },
    { 203, "Non-Authoritative Information" },
    { 204, "No Content" },
    { 205, "Reset Content" },
    { 206, "Partial Content" },
    { 300, "Multiple Choices" },
    { 301, "Moved Permanently" },
    { 302, "Found" },
    { 303, "See Other" },
    { 304, "Not Modified" },
    { 305, "Use Proxy" },
    { 306, "(Unused)" },
    { 307, "Temporary Redirect" },
    { 400, "Bad Request" },
    { 401, "Unauthorized" },
    { 402, "Payment Required" },
    { 403, "Forbidden" },
    { 404, "Not Found" },
    { 405, "Method Not Allowed" },
    { 406, "Not Acceptable" },
    { 407, "Proxy Authentication Required" },
    { 408, "Request Timeout" },
    { 409, "Conflict" },
    { 410, "Gone" },
    { 411, "Length Required" },
    { 412, "Precondition Failed" },
    { 413, "Request Entity Too Large" },
    { 414, "Request-URI Too Long" },
    { 415, "Unsupported Media Type" },
    { 416, "Requested Range Not Satisfiable" },
    { 417, "Expectation Failed" },
    { 500, "Internal Server Error" },
    { 501, "Not Implemented" },
    { 502, "Bad Gateway" },
    { 503, "Service Unavailable" },
    { 504, "Gateway Timeout" },
    { 505, "HTTP Version Not Supported" },
    { 0, NULL }
};

static int
compareResponseCodes( const void * va, const void * vb )
{
    const long a = *(const long*) va;
    const struct http_msg * b = vb;
    return a - b->code;
}

const char *
tr_webGetResponseStr( long code )
{
    struct http_msg * msg = bsearch( &code,
                                     http_msg, 
                                     sizeof( http_msg ) / sizeof( http_msg[0] ),
                                     sizeof( http_msg[0] ),
                                     compareResponseCodes );
    return msg ? msg->text : "Unknown Error";
}