//
// Console input and output, to the uart.
// Reads are line at a time.
// Implements special input characters:
//   newline -- end of line
//   control-h -- backspace
//   control-u -- kill line
//   control-d -- end of file
//   control-p -- print process list
//

#include <stdarg.h>

#include "types.h"
#include "param.h"
#include "spinlock.h"
#include "sleeplock.h"
#include "fs.h"
#include "file.h"
#include "memlayout.h"
#include "riscv.h"
#include "defs.h"
#include "proc.h"

#define BACKSPACE 0x100
#define INPUT_BUF_SIZE 128
#define C(x)  ((x)-'@')  // Control-x

struct console {
  struct spinlock lock;
  
  // input
  char buf[INPUT_BUF_SIZE];
  uint r;  // Read index
  uint w;  // Write index
  uint e;  // Edit index
};

extern struct console cons;
void consputc(int c);
int consolewrite(int user_src, uint64 src, int n);
int consoleread(int user_dst, uint64 dst, int n);

void consoleintr(int c)
{
  acquire(&cons.lock);

  switch(c){
  case C('P'):  // Print process list.
    procdump();
    break;
  case C('U'):  // Kill line.
    while(cons.e != cons.w &&
          cons.buf[(cons.e-1) % INPUT_BUF_SIZE] != '\n'){
      cons.e--;
      consputc(BACKSPACE);
    }
    break;
  case C('H'): // Backspace
  case '\x7f': // Delete key
    if(cons.e != cons.w){
      cons.e--;
      consputc(BACKSPACE);
    }
    break;
  default:
    if(c != 0 && cons.e-cons.r < INPUT_BUF_SIZE){
      c = (c == '\r') ? '\n' : c;

      // echo back to the user.
      consputc(c);

      // store for consumption by consoleread().
      cons.buf[cons.e++ % INPUT_BUF_SIZE] = c;

      if(c == '\n' || c == C('D') || cons.e-cons.r == INPUT_BUF_SIZE){
        // wake up consoleread() if a whole line (or end-of-file)
        // has arrived.
        cons.w = cons.e;
        wakeup(&cons.r);
      }
    }
    break;
  }
  
  release(&cons.lock);
}