/*
 * Copyright (C) 2015 "IoT.bzh"
 * Author "Fulup Ar Foll"
 *
 * 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 3 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
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 * 
 * Reference: 
 * https://github.com/json-c/json-c/blob/master/linkhash.c
 * https://github.com/json-c/json-c/blob/master/linkhash.h
 */


#include "local-def.h"
#include <dirent.h>
#include <string.h>
#include <time.h>
#include <sys/stat.h>
#include <sys/types.h>

#define AFB_SESSION_JTYPE "AFB_session"
#define AFB_SESSION_JLIST "AFB_sessions"
#define AFB_SESSION_JINFO "AFB_infos"


#define AFB_CURRENT_SESSION "active-session"  // file link name within sndcard dir
#define AFB_DEFAULT_SESSION "current-session" // should be in sync with UI


static struct lh_table *clientCtxs=NULL;    // let's use JsonObject Hashtable to Store Sessions


// verify we can read/write in session dir
PUBLIC AFB_error sessionCheckdir (AFB_session *session) {

   int err;

   // in case session dir would not exist create one
   if (verbose) fprintf (stderr, "AFB:notice checking session dir [%s]\n", session->config->sessiondir);
   mkdir(session->config->sessiondir, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);

   // change for session directory
   err = chdir(session->config->sessiondir);
   if (err) {
     fprintf(stderr,"AFB: Fail to chdir to %s error=%s\n", session->config->sessiondir, strerror(err));
     return err;
   }

   // verify we can write session in directory
   json_object *dummy= json_object_new_object();
   json_object_object_add (dummy, "checked"  , json_object_new_int (getppid()));
   err = json_object_to_file ("./AFB-probe.json", dummy);
   if (err < 0) return err;

   return AFB_SUCCESS;
}

// let's return only sessions files
STATIC int fileSelect (const struct dirent *entry) {
   return (strstr (entry->d_name, ".afb") != NULL);
}

STATIC  json_object *checkCardDirExit (AFB_session *session, AFB_request *request ) {
    int  sessionDir, cardDir;

    // card name should be more than 3 character long !!!!
    if (strlen (request->plugin) < 3) {
       return (jsonNewMessage (AFB_FAIL,"Fail invalid plugin=%s", request->plugin));
    }

    // open session directory
    sessionDir = open (session->config->sessiondir, O_DIRECTORY);
    if (sessionDir < 0) {
          return (jsonNewMessage (AFB_FAIL,"Fail to open directory [%s] error=%s", session->config->sessiondir, strerror(sessionDir)));
    }

   // create session sndcard directory if it does not exit
    cardDir = openat (sessionDir, request->plugin,  O_DIRECTORY);
    if (cardDir < 0) {
          cardDir  = mkdirat (sessionDir, request->plugin, O_RDWR | S_IRWXU | S_IRGRP);
          if (cardDir < 0) {
              return (jsonNewMessage (AFB_FAIL,"Fail to create directory [%s/%s] error=%s", session->config->sessiondir, request->plugin, strerror(cardDir)));
          }
    }
    close (sessionDir);
    return NULL;
}

// create a session in current directory
PUBLIC json_object *sessionList (AFB_session *session, AFB_request *request) {
    json_object *sessionsJ, *ajgResponse;
    struct stat fstat;
    struct dirent **namelist;
    int  count, sessionDir;

    // if directory for card's sessions does not exist create it
    ajgResponse = checkCardDirExit (session, request);
    if (ajgResponse != NULL) return ajgResponse;

    // open session directory
    sessionDir = open (session->config->sessiondir, O_DIRECTORY);
    if (sessionDir < 0) {
          return (jsonNewMessage (AFB_FAIL,"Fail to open directory [%s] error=%s", session->config->sessiondir, strerror(sessionDir)));
    }

    count = scandirat (sessionDir, request->plugin, &namelist, fileSelect, alphasort);
    close (sessionDir);

    if (count < 0) {
        return (jsonNewMessage (AFB_FAIL,"Fail to scan sessions directory [%s/%s] error=%s", session->config->sessiondir, request->plugin, strerror(sessionDir)));
    }
    if (count == 0) return (jsonNewMessage (AFB_EMPTY,"[%s] no session at [%s]", request->plugin, session->config->sessiondir));

    // loop on each session file, retrieve its date and push it into json response object
    sessionsJ = json_object_new_array();
    while (count--) {
         json_object *sessioninfo;
         char timestamp [64];
         char *filename;

         // extract file name and last modification date
         filename = namelist[count]->d_name;
         printf("%s\n", filename);
         stat(filename,&fstat);
         strftime (timestamp, sizeof(timestamp), "%c", localtime (&fstat.st_mtime));
         filename[strlen(filename)-4] = '\0'; // remove .afb extension from filename

         // create an object by session with last update date
         sessioninfo = json_object_new_object();
         json_object_object_add (sessioninfo, "date" , json_object_new_string (timestamp));
         json_object_object_add (sessioninfo, "session" , json_object_new_string (filename));
         json_object_array_add (sessionsJ, sessioninfo);

         free(namelist[count]);
    }

    // free scandir structure
    free(namelist);

    // everything is OK let's build final response
    ajgResponse = json_object_new_object();
    json_object_object_add (ajgResponse, "jtype" , json_object_new_string (AFB_SESSION_JLIST));
    json_object_object_add (ajgResponse, "status"  , jsonNewStatus(AFB_SUCCESS));
    json_object_object_add (ajgResponse, "data"    , sessionsJ);

    return (ajgResponse);
}

// Create a link toward last used sessionname within sndcard directory
STATIC void makeSessionLink (const char *cardname, const char *sessionname) {
   char linkname [256], filename [256];
   int err;
   // create a link to keep track of last uploaded sessionname for this card
   strncpy (filename, sessionname, sizeof(filename));
   strncat (filename, ".afb", sizeof(filename));

   strncpy (linkname, cardname, sizeof(linkname));
   strncat (linkname, "/", sizeof(filename));
   strncat (linkname, AFB_CURRENT_SESSION, sizeof(linkname));
   strncat (linkname, ".afb", sizeof(filename));
   unlink (linkname); // remove previous link if any
   err = symlink (filename, linkname);
   if (err < 0) fprintf (stderr, "Fail to create link %s->%s error=%s\n", linkname, filename, strerror(errno));
}

// Load Json session object from disk
PUBLIC json_object *sessionFromDisk (AFB_session *session, AFB_request *request, char *name) {
    json_object *jsonSession, *jtype, *response;
    const char *ajglabel;
    char filename [256];
    int defsession;

    if (name == NULL) {
        return  (jsonNewMessage (AFB_FATAL,"session name missing &session=MySessionName"));
    }

    // check for current session request
    defsession = (strcmp (name, AFB_DEFAULT_SESSION) ==0);

    // if directory for card's sessions does not exist create it
    response = checkCardDirExit (session, request);
    if (response != NULL) return response;

    // add name and file extension to session name
    strncpy (filename, request->plugin, sizeof(filename));
    strncat (filename, "/", sizeof(filename));
    if (defsession) strncat (filename, AFB_CURRENT_SESSION, sizeof(filename)-1);
    else strncat (filename, name, sizeof(filename)-1);
    strncat (filename, ".afb", sizeof(filename));

    // just upload json object and return without any further processing
    jsonSession = json_object_from_file (filename);

    if (jsonSession == NULL)  return (jsonNewMessage (AFB_EMPTY,"File [%s] not found", filename));

    // verify that file is a JSON ALSA session type
    if (!json_object_object_get_ex (jsonSession, "jtype", &jtype)) {
        json_object_put   (jsonSession);
        return  (jsonNewMessage (AFB_EMPTY,"File [%s] 'jtype' descriptor not found", filename));
    }

    // check type value is AFB_SESSION_JTYPE
    ajglabel = json_object_get_string (jtype);
    if (strcmp (AFB_SESSION_JTYPE, ajglabel)) {
       json_object_put   (jsonSession);
       return  (jsonNewMessage (AFB_FATAL,"File [%s] jtype=[%s] != [%s]", filename, ajglabel, AFB_SESSION_JTYPE));
    }

    // create a link to keep track of last uploaded session for this card
    if (!defsession) makeSessionLink (request->plugin, name);

    return (jsonSession);
}

// push Json session object to disk
PUBLIC json_object * sessionToDisk (AFB_session *session, AFB_request *request, char *name, json_object *jsonSession) {
   char filename [256];
   time_t rawtime;
   struct tm * timeinfo;
   int err, defsession;
   static json_object *response;

   // we should have a session name
   if (name == NULL) return (jsonNewMessage (AFB_FATAL,"session name missing &session=MySessionName"));

   // check for current session request
   defsession = (strcmp (name, AFB_DEFAULT_SESSION) ==0);

   // if directory for card's sessions does not exist create it
   response = checkCardDirExit (session, request);
   if (response != NULL) return response;

   // add cardname and file extension to session name
   strncpy (filename, request->plugin, sizeof(filename));
   strncat (filename, "/", sizeof(filename));
   if (defsession) strncat (filename, AFB_CURRENT_SESSION, sizeof(filename)-1);
   else strncat (filename, name, sizeof(filename)-1);
   strncat (filename, ".afb", sizeof(filename)-1);


   json_object_object_add(jsonSession, "jtype", json_object_new_string (AFB_SESSION_JTYPE));

   // add a timestamp and store session on disk
   time ( &rawtime );  timeinfo = localtime ( &rawtime );
   // A copy of the string is made and the memory is managed by the json_object
   json_object_object_add (jsonSession, "timestamp", json_object_new_string (asctime (timeinfo)));


   // do we have extra session info ?
   if (request->post) {
       static json_object *info, *jtype;
       const char  *ajglabel;

       // extract session info from args
       info = json_tokener_parse (request->post);
       if (!info) {
            response = jsonNewMessage (AFB_FATAL,"sndcard=%s session=%s invalid json args=%s", request->plugin, name, request->post);
            goto OnErrorExit;
       }

       // info is a valid AFB_info type
       if (!json_object_object_get_ex (info, "jtype", &jtype)) {
            response = jsonNewMessage (AFB_EMPTY,"sndcard=%s session=%s No 'AFB_type' args=%s", request->plugin, name, request->post);
            goto OnErrorExit;
       }

       // check type value is AFB_INFO_JTYPE
       ajglabel = json_object_get_string (jtype);
       if (strcmp (AFB_SESSION_JINFO, ajglabel)) {
              json_object_put   (info); // release info json object
              response = jsonNewMessage (AFB_FATAL,"File [%s] jtype=[%s] != [%s] data=%s", filename, ajglabel, AFB_SESSION_JTYPE, request->post);
              goto OnErrorExit;
       }

       // this is valid info data for our session
       json_object_object_add (jsonSession, "info", info);
   }

   // Finally save session on disk
   err = json_object_to_file (filename, jsonSession);
   if (err < 0) {
        response = jsonNewMessage (AFB_FATAL,"Fail save session = [%s] to disk", filename);
        goto OnErrorExit;
   }


   // create a link to keep track of last uploaded session for this card
   if (!defsession) makeSessionLink (request->plugin, name);

   // we're donne let's return status message
   response = jsonNewMessage (AFB_SUCCESS,"Session= [%s] saved on disk", filename);
   json_object_put (jsonSession);
   return (response);

OnErrorExit:
   json_object_put (jsonSession);
   return response;
}


// Function to handle Cookies and Client session context it relies on json low level
// linked list functionalities https://github.com/json-c/json-c/blob/master/linkhash.c

// Hash client UUID before storing in table
STATIC unsigned long ctxUuidHashCB (const void *k1) {
    unsigned long hash;
    
    AFB_clientCtx *ctx = (AFB_clientCtx*) k1;
    hash = lh_char_hash(ctx->uuid);
    return (hash);    
}

// Compare client UUIDs within table
STATIC int ctxUuidCompCB (const void *k1, const void *k2) {
    int res;    
    AFB_clientCtx *ctx1 = (AFB_clientCtx*) k1;
    AFB_clientCtx *ctx2 = (AFB_clientCtx*) k2;
    
    res = lh_char_equal(ctx1->uuid, ctx2->uuid);
    return (res);    
}

// Free context [XXXX Should be protected again memory abort XXXX]
STATIC void ctxUuidFreeCB (struct lh_entry *entry) {
    AFB_clientCtx *ctx = (AFB_clientCtx*) entry->v;

    // If application add a handle let's free it now
    if (ctx->handle != NULL) {
        
        // Free client handle with a standard Free function, with app callback or ignore it
        if (ctx->freeHandleCB == NULL) free (ctx->handle); 
        else if (ctx->freeHandleCB != (void*)-1) ctx->freeHandleCB(ctx->handle); 
    }
    free ((void*)entry->v);
}

// Create a new store in RAM, not that is too small it will be automatically extended
STATIC struct lh_table *ctxStoreCreate (int nbSession) {
   lh_table *table; 
    
   // function will exit process in case of error !!! 
   table=lh_table_new (nbSession, "CtxClient", ctxUuidFreeCB, ctxUuidHashCB, ctxUuidCompCB);
   return (table);
}

// Check if context timeout or not
STATIC int ctxStoreToOld (const void *k1, int timeout) {
    int res;    
    AFB_clientCtx *ctx = (AFB_clientCtx*) k1;

    res = ((ctx->timeStamp + timeout) < time(NULL));
    return (res);    
}

// Loop on every entry and remove old context sessions
PUBLIC int ctxStoreGarbage (struct lh_table *lht, const int timeout) {
    struct lh_entry *c;
    
    // Loop on every entry within table
    for(c = lht->head; c != NULL; c = c->next) {
        if(lht->free_fn) {
            if(c->k == LH_EMPTY) return lht->count;
            if(c->k != LH_FREED &&  ctxStoreToOld(c->v, timeout)) lh_table_delete_entry (lht, c);
	}
    }
  
    // return current size after cleanup
    return (lht->count);
}

// This function will return exiting client context or newly created client context
PUBLIC int ctxClientGet (AFB_request *request) {
  static int cid=0;
  AFB_clientCtx *clientCtx=NULL;
  const char *uuid;
  uuid_t newuuid;
  int ret;
  
   // if client session store is null create it
   if (clientCtxs == NULL) {
       clientCtxs= ctxStoreCreate(CTX_NBCLIENTS);
   }

    // Check if client as a context or not inside the URL
    uuid  = MHD_lookup_connection_value(request->connection, MHD_GET_ARGUMENT_KIND, "uuid");
       
    // if UUID in query we're restfull with no cookies otherwise check for cookie
    if (uuid != NULL) request->restfull = TRUE;
    else {
        request->restfull = FALSE;
        uuid = MHD_lookup_connection_value (request->connection, MHD_COOKIE_KIND, COOKIE_NAME);  
    };
    
    
    if (uuid != NULL)   {
        // search if client context exist and it not timeout let's use it
	if ((lh_table_lookup_ex (clientCtxs, uuid, (void**) &clientCtx)) 
                && ! ctxStoreToOld (clientCtx, request->config->cntxTimeout)) {
                request->client=clientCtx;
                if (verbose) fprintf (stderr, "ctxClientGet Old uuid=[%s] token=[%s] timestamp=%d\n"
                             ,request->client->uuid, request->client->token, request->client->timeStamp);
                return;            
        }
    }

    
    // we have no session let's create one otherwise let's clean any exiting values
    if (clientCtx == NULL) clientCtx = calloc(1, sizeof(AFB_clientCtx)); // init NULL clientContext
    uuid_generate(newuuid);         // create a new UUID
    uuid_unparse_lower(newuuid, clientCtx->uuid);
    clientCtx->cid=cid++;
        
    // if table is full at 50% let's clean it up
    if(clientCtxs->count > (clientCtxs->size*0.5)) ctxStoreGarbage(clientCtxs, request->config->cntxTimeout);
    
    // finally add uuid into hashtable
    ret= lh_table_insert (clientCtxs, (void*)clientCtx->uuid, clientCtx);
    
    if (verbose) fprintf (stderr, "ctxClientGet New uuid=[%s] token=[%s] timestamp=%d\n", clientCtx->uuid, clientCtx->token, clientCtx->timeStamp);
       
    request->client = clientCtx;
    return (ret);
}

// Sample Generic Ping Debug API
PUBLIC AFB_error ctxTokenCheck (AFB_request *request) {
    const char *token;
    
    // this time have to extract token from query list
    token = MHD_lookup_connection_value(request->connection, MHD_GET_ARGUMENT_KIND, "token");
    
    // if not token is providing we refuse the exchange
    if ((token == NULL) || (request->client->token == NULL)) return (AFB_FALSE);
    
    // compare current token with previous one
    if ((0 == strcmp (token, request->client->token)) && (!ctxStoreToOld (request->client, request->config->cntxTimeout))) {
       return (AFB_TRUE);
    }
    
    // Token is not valid let move level of assurance to zero and free attached client handle
    return (AFB_FALSE);
}

// Free Client Session Context
PUBLIC int ctxTokenReset (AFB_request *request) {
    struct lh_entry* entry;
    int ret;
        
    entry = lh_table_lookup_entry (clientCtxs, request->client->uuid);
    if (entry == NULL) return FALSE;
    
    lh_table_delete_entry (clientCtxs, entry);
 
    return (TRUE);
}

// generate a new token
PUBLIC char* ctxTokenCreate (AFB_request *request) {
    int oldTnkValid;
    const char *ornew;
    uuid_t newuuid;

    // create a UUID as token value
    uuid_generate(newuuid); 
    uuid_unparse_lower(newuuid, request->client->token);
    
    // keep track of time for session timeout and further clean up
    request->client->timeStamp=time(NULL); 
    
    // Token is also store in context but it might be convenient for plugin to access it directly
    return (request->client->token);
}


// generate a new token and update client context
PUBLIC char* ctxTokenRefresh (AFB_request *request) {
    int oldTnkValid;
    const char *oldornew;
    uuid_t newuuid;
    
    // Check if the old token is valid
    oldTnkValid= ctxTokenCheck (request);
    
    // if token is not valid let check for query argument "oldornew"
    if (!oldTnkValid) {
        oldornew = MHD_lookup_connection_value(request->connection, MHD_GET_ARGUMENT_KIND, "oldornew");
        if (oldornew != NULL) oldTnkValid= TRUE;
    }
   
    // No existing token and no request to create one
    if (oldTnkValid != TRUE) return NULL;

    return (ctxTokenCreate (request));
}