#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <fcntl.h>
#include <sys/time.h>
#include <time.h>
#include "util.h"
#include <stdbool.h>
#include <unistd.h>
#include <signal.h>

#define MAX_THREADS 100
#define MAX_queue_len 100
#define MAX_CE 100
#define INVALID -1
#define BUFF_SIZE 1024

// Global variables
int port, workers, dispatchers, dynFlag, qLen, cSiz, cacheLength, wIndex = 0;
pthread_t *wID;
char *path;
pthread_mutex_t Qlock, logLock, cacheLock;
clock_t start_t, end_t, total_t;
void *worker(void *arg);

/*
  THE CODE STRUCTURE GIVEN BELOW IS JUST A SUGGESTION. FEEL FREE TO MODIFY AS NEEDED
*/

// structs:
typedef struct request_queue
{
  int fd;
  char *request;
  struct request_queue *next;
} request_t;
request_t *Q = NULL; // The request queue

typedef struct cache_entry
{
  int len;
  char *request;
  char *content;
  struct cache_entry *next;
} cache_entry_t;
cache_entry_t *dynQ = NULL; //The cache queue

/* ******************** Dynamic Pool Code  [Extra Credit A] **********************/
// Extra Credit: This function implements the policy to change the worker thread pool dynamically
// depending on the number of requests
void *dynamic_pool_size_update(void *arg) {
  while (1)
  {
    // Run at regular intervals
    usleep(1000000);
    // Increase / decrease dynamically based on your policy
    // Policy: Have clock tracking how long the whole process takes
    //         If above maxProcessTime -> spawn X workers
    //         Else if below mostEfficientTime kill all unnecessary threads leaving 1(or 2) of each
    if(total_t > 30) {
      // Threads must be detachable
      wID = realloc(wID, (++wIndex) * sizeof(pthread_t));
      pthread_attr_t attr;
      pthread_attr_init(&attr);
      pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
      
      // Spawn worker threads
      pthread_create(&wID[wIndex-1], &attr, worker, (void *)&wIndex); // Squeaky clean windows!
      char threadName[16];
      sprintf(threadName, "Worker %d", wIndex); 
      pthread_setname_np(wID[wIndex-1], threadName);
    }
    else if (total_t < 6) {
      //TODO: Make sure thread isn't doing anything before killing it
      pthread_cancel(wID[--wIndex]);
      // Need dynamically allocated array of thread ID's so we can cancel the necessary threads
      wID = realloc(wID, wIndex * sizeof(pthread_t));
    }
  }
}
/**********************************************************************************/

/* ************************ Cache Code [Extra Credit B] **************************/

// Function to check whether the given request is present in cache
int isInCache(char *request) {
  /// return the index if the request is present in the cache
  cache_entry_t *traverse = dynQ;
  if (dynQ == NULL)
    return -2;
  int index = 0;
  pthread_mutex_lock(&cacheLock);
  while (traverse != NULL) {
    if (traverse->request == NULL)
      break;
    if (!strcmp(request, traverse->request)) {
      pthread_mutex_unlock(&cacheLock);
      return index;
    }
    traverse = traverse->next;
    index++;
  }
  pthread_mutex_unlock(&cacheLock);
  return -1;
}

// Function to traverse cache queue to find cache
int readFromCache(int index, char *buffer) {
  cache_entry_t *traverse = dynQ;
  pthread_mutex_lock(&cacheLock);
  for (int i = 0; i < index; i++) {
    if (traverse == NULL) {
      pthread_mutex_unlock(&cacheLock);
      return -1;
    }
    traverse = traverse->next;
  }
  memcpy(buffer, traverse->content, traverse->len);
  pthread_mutex_unlock(&cacheLock);
  return 0;
}

// Function to add the request and its file content into the cache
void addIntoCache(char *mybuf, char *memory, int memory_size) {
  // It should add the request at an index according to the cache replacement policy
  // Make sure to allocate/free memory when adding or replacing cache entries
  
  cache_entry_t *traverse = dynQ;
  if (dynQ == NULL)
    return;
  bool fullCache = false;
  while (traverse->next != NULL) {
    if (cacheLength > cSiz) {
      fullCache = true;
      break;
    }
    traverse = traverse->next;
  }
  pthread_mutex_lock(&cacheLock);
  char *silence = (char *)malloc(memory_size + 1);
  memcpy(silence, memory, memory_size);
  if (fullCache) {
    cache_entry_t *temp = dynQ;
    dynQ = dynQ->next;
    free(temp->content);
    free(temp->request);
    free(temp);
    cacheLength--;
    pthread_mutex_unlock(&cacheLock);
    addIntoCache(mybuf, silence, memory_size);
  } else {
    cache_entry_t *temp = (cache_entry_t*) calloc(1, sizeof(cache_entry_t));
    temp->request = mybuf;
    temp->content = silence;
    temp->len = memory_size;
    if (cacheLength == 0) {
      dynQ = temp;
    } else {
      traverse->next = temp;
    }
    cacheLength++;;
    pthread_mutex_unlock(&cacheLock);
  }
}

// clear the memory allocated to the cache
void deleteCache() {
  request_t *tempReq = NULL;
  while (Q != NULL)
  {
    tempReq = Q;
    Q = Q->next;
    free(tempReq->request);
    free(tempReq);
  }
  // De-allocate/free the cache memory
  cache_entry_t *tempCache = NULL;
  while (dynQ != NULL)
  {
    tempCache = dynQ;
    dynQ = dynQ->next;
    free(tempCache->content);
    free(tempCache->request);
    free(tempCache);
  }
  free(wID);
}

// Function to initialize the cache

void initCache() {
  // Allocating memory and initializing the cache array
  dynQ = (cache_entry_t *)calloc(1, sizeof(cache_entry_t));
  cacheLength = 0;
}

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

/* ************************************ Utilities ********************************/
// Function to get the content type from the request
char *getContentType(char *mybuf) {
  // Should return the content type based on the file type in the request
  // (See Section 5 in Project description for more details)
  char *ext = strrchr(mybuf, '.');

  if (ext == NULL)
  {
    printf("Filetype not found. Exiting\n");
    exit(-1);
  }
  else if ((strcmp((ext + 1), "htm") == 0) || (strcmp((ext + 1), "html") == 0))
  {
    return "text/html";
  }
  else if (strcmp((ext + 1), "jpg") == 0)
  {
    return "image/jpeg";
  }
  else if (strcmp((ext + 1), "gif") == 0)
  {
    return "image/gif";
  }
  else
  {
    return "text/plain";
  }
}

// Function to get the size of the file in the queue
// (Thanks Matt from stackOverflow)
long getFileSize(char *file)
{
  char *temp = (char *)malloc(BUFF_SIZE);
  sprintf(temp, ".%s", file);
  FILE *f = fopen(temp, "r");
  free(temp);
  if (f == NULL)
    return 0;
  fseek(f, 0, SEEK_END);
  long len = (long)ftell(f);
  fclose(f);
  return len;
}

// Function to open and read the file from the disk into the memory
// Add necessary arguments as needed
int readFromDisk(char *fileName, char *buffer, long fileSize)
{
  char *temp = (char *)malloc(BUFF_SIZE);
  sprintf(temp, ".%s", fileName);
  // Open and read the contents of file given the request
  int requestFile = open(temp, O_RDONLY);
  free(temp);
  if (requestFile == -1)
  {
    return -1; // Error handle
  }
  read(requestFile, buffer, fileSize);
  close(requestFile);
  return 0;
}

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

// Function to receive the request from the client and add to the queue
void *dispatch(void *arg)
{

  while (1)
  {
    // Accept client connection and get the fd
    int newReq = accept_connection();
    if (newReq > INVALID)
    {
      pthread_mutex_lock(&Qlock);
      request_t *traverse = Q;

      // Get request from the client
      // Add the request into the queue
      for (int i = 0; i < qLen; i++)
      {
        if (traverse == NULL || traverse->next == NULL)
        {
          //Add things to queue. Lock & unlock to prevent a deadlock

          request_t *tempNode = (request_t *)calloc(1, sizeof(request_t));
          char *dispatchBuf = (char *)malloc(BUFF_SIZE); // Buffer to store the requested filename
          if (get_request(newReq, dispatchBuf) != 0)
          {
            pthread_mutex_unlock(&Qlock);
            free(tempNode);
            free(dispatchBuf);
            continue; // If get_request fails, try again
          }
          tempNode->fd = newReq;
          tempNode->request = dispatchBuf;
          tempNode->next = NULL;
          if (traverse == NULL)
          {
            Q = tempNode;
          }
          else
          {
            traverse->next = tempNode;
          }

          pthread_mutex_unlock(&Qlock);
          break;
        }
        else
        {
          traverse = traverse->next;
        }
      }
    }
  }
  return NULL;
}

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

// Function to retrieve the request from the queue, process it and then return a result to the client
void *worker(void *arg)
{
  int id = *(int *)arg;
  long numbytes;
  unsigned long numReqs = 0;
  while (1)
  {
    // Get the request from the queue
    pthread_mutex_lock(&Qlock);
    if (Q == NULL)
    {
      pthread_mutex_unlock(&Qlock);
      continue;
    }
    //Make copy of request and get rid of old one.
    request_t *request = NULL;
    request = (request_t *) malloc(sizeof(request_t));
    request->fd = Q->fd;
    request->request = Q->request;
    Q = Q->next;
    pthread_mutex_unlock(&Qlock);

    //Get the data from the disk or the cache (extra credit B)
    numbytes = getFileSize(request->request);
    char *workerBuf = (char *)calloc(numbytes+1, sizeof(char));
    char *bytesError = (char *)malloc(BUFF_SIZE);
    bool fail = false;
    if (numbytes != 0) {
      //SUCC
      sprintf(bytesError, "%ld", numbytes);
    } else {
      //ERR
      fail = true;
      sprintf(bytesError, "%s", strerror(errno));
    }
    char *cacheTest; //HIT/MISS only
    if (!fail) {
      //Make sure nothing is fiddling with cache before fiddling with cache
      pthread_mutex_lock(&cacheLock);
      pthread_mutex_unlock(&cacheLock);
      
      int test = isInCache(request->request);
      if (test != -1)
      {
        //In cache, file exists
        cacheTest = "HIT";
        readFromCache(test, workerBuf);
      }
      else
      {
        cacheTest = "MISS";
        if (readFromDisk(request->request, workerBuf, numbytes) == -1)
        {
          //Not in cache, disk read failed
          fail = true;
        }
        else
        {
          //Not in cache, disk read succeeds
          addIntoCache(request->request, workerBuf, numbytes);
        }
      }

    }

    // Log the request into the file and terminal
    pthread_mutex_lock(&logLock);
    FILE *log = fopen("../webserver_log", "a");
    fprintf(log, "[%d][%ld][%d][%s][%s][%s]\n", id, ++numReqs, request->fd, request->request, bytesError, cacheTest);
    printf("[%d][%ld][%d][%s][%s][%s]\n", id, numReqs, request->fd, request->request, bytesError, cacheTest);
    fclose(log);
    pthread_mutex_unlock(&logLock);
    free(bytesError);

    // Return the result
    if (fail)
    {
      //ERR
      return_error(request->fd, request->request);
    }
    else
    {
      //SUCC
      return_result(request->fd, getContentType(request->request), workerBuf, numbytes);
    }
    //Free things no longer needed
    free(request);
    free(workerBuf);
    end_t = clock();
    total_t = (double)(end_t - start_t) / CLOCKS_PER_SEC;
    printf("Total time taken by CPU: %ld\n", total_t);
  }
  return NULL;
}

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

//Flag for when server needs to die nicely
static volatile sig_atomic_t exitFlag = 0;

//Sets e flag so process can die happily and not sad.
static void eggs(int signo)
{
  exitFlag |= 1;
}
int main(int argc, char **argv)
{
  start_t = clock();
  // Error check on number of arguments
  if (argc != 8)
  {
    printf("usage: %s port path num_dispatcher num_workers dynamic_flag queue_length cache_size\n", argv[0]);
    return -1;
  }
  // Get the input args
  //Port
  port = atoi(argv[1]);
  //Webroot path
  path = argv[2];
  //(static) number of dispatchers
  dispatchers = atoi(argv[3]);
  //(static) number of workers
  workers = atoi(argv[4]);
  //Dynamic worker flag
  dynFlag = atoi(argv[5]);
  //Queue Length
  qLen = atoi(argv[6]);
  //Max cache size
  cSiz = atoi(argv[7]);

  /* -- ERROR CHECKING -- */
  if (port < 1025 || port > 65535)
  {
    printf("Invalid port. Port must be greater than 1025 or less than 65535 (inclusive).\n");
    return -1;
  }
  if (dispatchers > MAX_THREADS || dispatchers < 1)
  {
    printf("Number of dispatchers is invalid. It must be greater than 1 or less than %d (inclusive).\n", MAX_THREADS);
    return -1;
  }
  if (workers > MAX_THREADS || workers < 1)
  {
    printf("Number of dispatchers is invalid. It must be greater than 1 or less than %d (inclusive).\n", MAX_THREADS);
    return -1;
  }
  if (qLen > MAX_queue_len || qLen < 1)
  {
    printf("Queue length is invalid It must be greater than 1 or less than %d (inclusive).\n", MAX_queue_len);
    return -1;
  }
  /* -- END ERROR CHECKING -- */

  // Change SIGINT action for graceful termination
  struct sigaction act;
  act.sa_handler = eggs;
  act.sa_flags = 0;
  if (sigemptyset(&act.sa_mask) == -1 ||
      sigaction(SIGINT, &act, NULL) == -1)
  {
    perror("SIGINT Handler Error");
    return -2;
  }
  // Create instance of logfil
  FILE *logfile = fopen("webserver_log", "w");
  fclose(logfile);

  // Change the current working directory to server root directory
  if (chdir(path) == -1)
  {
    perror("Directory Change error");
    return -2;
  }
  // Initialize cache (extra credit B)
  initCache();

  //Make sure threads are all detached
  pthread_attr_t attr;
  pthread_attr_init(&attr);
  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
  // Start the server
  init(port);
  char threadName[16];
  // Create dispatcher threads (make detachable????)
  pthread_t dThreads[dispatchers];
  for (int i = 0; i < dispatchers; i++)
  {
    pthread_create(&dThreads[i], &attr, dispatch, NULL); // DEBUG! figure out last arg
    sprintf(threadName, "Dispatch %d", i);
    pthread_setname_np(dThreads[i], threadName);
  }
  //Create workers (make detachable?????)
  int *Wargs = (int *) malloc(sizeof(int) * workers);
  wID = (pthread_t *) malloc(workers * sizeof(pid_t));
  for (int i = 0; i < workers; i++)
  {
    wIndex++;
    Wargs[i] = i;
    pthread_create(&wID[i], &attr, worker, (void *)&Wargs[i]); //TODO: Worker arguments
    sprintf(threadName, "Worker %d", i);
    pthread_setname_np(wID[i], threadName);
  }
  free(Wargs);
  // Create dynamic pool manager thread (extra credit A)
  if (dynFlag)
  {
    pthread_t pThread;
    pthread_create(&pThread, &attr, dynamic_pool_size_update, NULL); //TODO: possible arguments
    pthread_setname_np(pThread, "Pool Manager");
  }

  //Server loop (RUNS FOREVER)
  while (1)
  {
    //TODO: Add something else?
    // Terminate server gracefully
    if (exitFlag)
    {
      printf("\nSIGINT caught, exiting now.\n");
      // Print the number of pending requests in the request queue
      int pendReqs;
      for (pendReqs = 0; pendReqs < qLen; pendReqs++)
      {
        if (Q == NULL || Q->next == NULL)
          break;
      }
      printf("There are %d pending requests left in the queue.\n", pendReqs);
      // Remove cache (extra credit B)
      deleteCache();
      printf("Cache has been deleted.\n");
      return 0;
    }
  }
  printf("\n\nThis should never be printed.\n\n");
  return 42;
}