// TODO: CHECK/REPLACE/UPDATE OLD CODE (this file is based on xv6)
//
// Support functions for system calls that involve file descriptors.
//

#include "types.h"
#include "riscv.h"
#include "defs.h"
#include "param.h"
#include "fs.h"
#include "sched.h"
#include "file.h"
#include "stat.h"
#include "proc.h"
#include "kprintf.h"

struct devsw devsw[NDEV];
//struct {
  sched_spinlock_t ftable_lock;
  struct file ftable_file[NFILE];
//} ftable;

void
fileinit(void)
{
  initlock(&ftable_lock, "ftable");
}

// Allocate a file structure.
struct file*
filealloc(void)
{
  struct file *f;

  acquire(&ftable_lock);
  for(f = ftable_file; f < ftable_file + NFILE; f++){
    if(f->ref == 0){
      f->ref = 1;
      release(&ftable_lock);
      return f;
    }
  }
  release(&ftable_lock);
  return 0;
}

// Increment ref count for file f.
struct file*
filedup(struct file *f)
{
  // kqueue objects are not duplicated on a call to fork etc.
  if (f->type == FD_KQUEUE) {
    return NULL;
  }
  
  acquire(&ftable_lock);
  if(f->ref < 1)
    panic("filedup");
  f->ref++;
  release(&ftable_lock);
  return f;
}

// Close file f.  (Decrement ref count, close when reaches 0.)
void
fileclose(struct file *f)
{
  struct file ff;

  acquire(&ftable_lock);
  if(f->ref < 1)
    panic("fileclose");
  if(--f->ref > 0){
    release(&ftable_lock);
    return;
  }
  //ff = *f;
  memmove(&ff, f, sizeof(struct file));
  f->ref = 0;
  f->type = FD_NONE;
  release(&ftable_lock);

  if(ff.type == FD_PIPE){
    pipeclose(ff.pipe, ff.writable);
  } else if(ff.type == FD_INODE || ff.type == FD_DEVICE){
    fsinstance_t* instance = ff.ip->instance;
    fsinstance_begin(instance);
    fsinstance_inode_unget(ff.ip);
    fsinstance_end(instance);
  }
}

// Get metadata about file f.
// addr is a user virtual address, pointing to a struct stat.
int
filestat(struct file *f, uint64 addr)
{
  struct proc *p = myproc();
  struct stat st;
  
  if(f->type == FD_INODE || f->type == FD_DEVICE){
    fsinstance_inode_lockandload(f->ip);
    fsinstance_inode_getstatinfo(f->ip, &st);
    fsinstance_inode_unlock(f->ip);
    if(copyout(p->pagetable, addr, (char *)&st, sizeof(st)) < 0)
      return -1;
    return 0;
  }
  return -1;
}

// Read from file f.
// addr is a user virtual address.
int
fileread(struct file *f, uint64 addr, int n)
{
  int (*read)(int, uint64, int);
  int r = 0;

  if(f->readable == 0)
    return -1;

  if(f->type == FD_PIPE){
    r = piperead(f->pipe, addr, n);
  } else if(f->type == FD_DEVICE){
    if(f->major < 0 || f->major >= NDEV || !devsw[f->major].read)
      return -1;
    read = devsw[f->major].read;
    r = read(1, addr, n);
  } else if(f->type == FD_INODE){
    fsinstance_inode_lockandload(f->ip);
    if((r = fsinstance_inode_read(f->ip, 1, addr, f->off, n)) > 0)
      f->off += r;
    fsinstance_inode_unlock(f->ip);
  } else {
    panic("fileread");
  }

  return r;
}

// Write to file f.
// addr is a user virtual address.
int
filewrite(struct file *f, uint64 addr, int n)
{
  int (*write)(int, uint64, int);
  int r, ret = 0;

  if(f->writable == 0)
    return -1;

  if(f->type == FD_PIPE){
    ret = pipewrite(f->pipe, addr, n);
  } else if(f->type == FD_DEVICE){
    if(f->major < 0 || f->major >= NDEV || !devsw[f->major].write)
      return -1;
    write = devsw[f->major].write;
    ret = write(1, addr, n);
  } else if(f->type == FD_INODE){
    // write a few blocks at a time to avoid exceeding
    // the maximum log transaction size, including
    // i-node, indirect block, allocation blocks,
    // and 2 blocks of slop for non-aligned writes.
    // this really belongs lower down, since fsinstance_inode_write()
    // might be writing a device like the console.
    int max = ((MAXOPBLOCKS-1-1-2) / 2) * BSIZE;
    int i = 0;
    while(i < n){
      int n1 = n - i;
      if(n1 > max)
        n1 = max;

      fsinstance_begin(f->ip->instance);
      fsinstance_inode_lockandload(f->ip);
      // Here is where it needs modification for append
      if (f->writable == 2) { // Append
        r = fsinstance_inode_write(f->ip, 1, addr + i, f->ip->size, n1);
      } else if ((r = fsinstance_inode_write(f->ip, 1, addr + i, f->off, n1)) > 0) {
        f->off += r;
      }
      fsinstance_inode_unlock(f->ip);
      fsinstance_end(f->ip->instance);

      if(r != n1){
        // error from writei
        break;
      }
      i += r;
    }
    ret = (i == n ? n : -1);
  } else {
    panic("filewrite");
  }

  return ret;
}