typedef struct Opt Opt;

typedef struct Opt Opt;

int debug;
#define DPRINT if(debug)fprint

enum
{
/* control characters */
Se= 240, /* end subnegotiation */
NOP= 241,
Mark= 242, /* data mark */
Break= 243,
Interrupt= 244,
Abort= 245, /* TENEX ^O */
AreYouThere= 246,
Erasechar= 247, /* erase last character */
Eraseline= 248, /* erase line */
GoAhead= 249, /* half duplex clear to send */
Sb= 250, /* start subnegotiation */
Will= 251,
Wont= 252,
Do= 253,
Dont= 254,
Iac= 255,

/* options */
Binary= 0,
Echo,
SGA,
Stat,
Timing,
Det,
Term,
EOR,
Uid,
Outmark,
Ttyloc,
M3270,
Padx3,
Window,
Speed,
Flow,
Line,
Xloc,
Extend,
};

struct Opt
{
char *name;
int code;
char noway;
int (*change)(Biobuf*, int); /* routine for status change */
int (*sub)(Biobuf*, uchar*, int n); /* routine for subnegotiation */
char remote; /* remote value */
char local; /* local value */
};

Opt opt[] =
{
[Binary] { "binary", 0, 0, },
[Echo] { "echo", 1, 0, },
[SGA] { "suppress Go Ahead", 3, 0, },
[Stat] { "status", 5, 1, },
[Timing] { "timing", 6, 1, },
[Det] { "det", 20, 1, },
[Term] { "terminal", 24, 0, },
[EOR] { "end of record", 25, 1, },
[Uid] { "uid", 26, 1, },
[Outmark] { "outmark", 27, 1, },
[Ttyloc] { "ttyloc", 28, 1, },
[M3270] { "3270 mode", 29, 1, },
[Padx3] { "pad x.3", 30, 1, },
[Window] { "window size", 31, 1, },
[Speed] { "speed", 32, 1, },
[Flow] { "flow control", 33, 1, },
[Line] { "line mode", 34, 1, },
[Xloc] { "X display loc", 35, 0, },
[Extend] { "Extended", 255, 1, },
};

int control(Biobuf*, int);
Opt* findopt(int);
int will(Biobuf*);
int wont(Biobuf*);
int doit(Biobuf*);
int dont(Biobuf*);
int sub(Biobuf*);
int send2(int, int, int);
int send3(int, int, int, int);
int sendnote(int, char*);
void fatal(char*, void*, void*);
char* syserr(void);
int wasintr(void);
long iread(int, void*, int);
long iwrite(int, void*, int);
void binit(Biobuf*, int);
void berase(Biobuf*);
void bkill(Biobuf*);

/*
* parse telnet control messages
*/
int
control(Biobuf *bp, int c)
{
if(c < 0)
return -1;
switch(c){
case AreYouThere:
fprint(Bfildes(bp), "Plan 9 telnet, version 1\r\n");
break;
case Sb:
return sub(bp);
case Will:
return will(bp);
case Wont:
return wont(bp);
case Do:
return doit(bp);
case Dont:
return dont(bp);
case Se:
fprint(2, "telnet: SE without an SB\n");
break;
default:
break;
}
return 0;
}

Opt*
findopt(int c)
{
Opt *o;

for(o = opt; o <= &opt[Extend]; o++)
if(o->code == c)
return o;
return 0;
}

int
will(Biobuf *bp)
{
Opt *o;
int c;
int rv = 0;

c = Bgetc(bp);
if(c < 0)
return -1;
DPRINT(2, "will %d\n", c);
o = findopt(c);
if(o == 0){
send3(Bfildes(bp), Iac, Dont, c);
return 0;
}
if(o->noway)
send3(Bfildes(bp), Iac, Dont, c);
else if(o->remote == 0)
rv |= send3(Bfildes(bp), Iac, Do, c);
if(o->remote == 0){
if(o->change)
rv |= (*o->change)(bp, Will);
}
o->remote = 1;
return rv;
}

int
wont(Biobuf *bp)
{
Opt *o;
int c;
int rv = 0;

c = Bgetc(bp);
if(c < 0)
return -1;
DPRINT(2, "wont %d\n", c);
o = findopt(c);
if(o == 0)
return 0;
if(o->remote){
if(o->change)
rv |= (*o->change)(bp, Wont);
rv |= send3(Bfildes(bp), Iac, Dont, c);
}
o->remote = 0;
return rv;
}

int
doit(Biobuf *bp)
{
Opt *o;
int c;
int rv = 0;

c = Bgetc(bp);
if(c < 0)
return -1;
DPRINT(2, "do %d\n", c);
o = findopt(c);
if(o == 0 || o->noway){
send3(Bfildes(bp), Iac, Wont, c);
return 0;
}
if(o->noway)
return 0;
if(o->local == 0){
if(o->change)
rv |= (*o->change)(bp, Do);
rv |= send3(Bfildes(bp), Iac, Will, c);
}
o->local = 1;
return rv;
}

int
dont(Biobuf *bp)
{
Opt *o;
int c;
int rv = 0;

c = Bgetc(bp);
if(c < 0)
return -1;
DPRINT(2, "dont %d\n", c);
o = findopt(c);
if(o == 0)
return 0;
if(o->noway)
return 0;
if(o->local){
o->local = 0;
if(o->change)
rv |= (*o->change)(bp, Dont);
rv |= send3(Bfildes(bp), Iac, Wont, c);
}
o->local = 0;
return rv;
}

/* read in a subnegotiation message and pass it to a routine for that option */
int
sub(Biobuf *bp)
{
uchar subneg[128];
uchar *p;
Opt *o;
int c;

p = subneg;
for(;;){
c = Bgetc(bp);
if(c == Iac){
c = Bgetc(bp);
if(c == Se)
break;
if(p < &subneg[sizeof(subneg)])
*p++ = Iac;
}
if(c < 0)
return -1;
if(p < &subneg[sizeof(subneg)])
*p++ = c;
}
if(p == subneg)
return 0;
DPRINT(2, "sub %d %d n = %d\n", subneg[0], subneg[1], (int)(p - subneg - 1));
o = findopt(subneg[0]);
if(o == 0 || o->sub == 0)
return 0;
return (*o->sub)(bp, subneg+1, p - subneg - 1);
}

void
sendd(int c0, int c1)
{
char *t = 0;

switch(c0){
case Will:
t = "Will";
break;
case Wont:
t = "Wont";
break;
case Do:
t = "Do";
break;
case Dont:
t = "Dont";
break;
}
if(t)
DPRINT(2, "r %s %d\n", t, c1);
}

int
send2(int f, int c0, int c1)
{
uchar buf[2];

buf[0] = c0;
buf[1] = c1;
return iwrite(f, buf, 2) == 2 ? 0 : -1;
}

int
send3(int f, int c0, int c1, int c2)
{
uchar buf[3];

buf[0] = c0;
buf[1] = c1;
buf[2] = c2;
sendd(c1, c2);
return iwrite(f, buf, 3) == 3 ? 0 : -1;
}

int
sendnote(int pid, char *msg)
{
int fd;
char name[128];

sprint(name, "/proc/%d/note", pid);
fd = open(name, OWRITE);
if(fd < 0)
return -1;
if(write(fd, msg, strlen(msg))!=strlen(msg))
return -1;
return close(fd);
}

void
fatal(char *fmt, void *a0, void *a1)
{
char buf[128];

sprint(buf, fmt, a0, a1);
fprint(2, "%s: %s\n", argv0, buf);
exits(buf);
}

char*
syserr(void)
{
static char err[ERRMAX];

errstr(err, sizeof err);
return err;
}

int
wasintr(void)
{
return strcmp(syserr(), "interrupted") == 0;
}

long
iread(int f, void *a, int n)
{
long m;

for(;;){
m = read(f, a, n);
if(m >= 0 || !wasintr())
break;
}
return m;
}

long
iwrite(int f, void *a, int n)
{
long m;

m = write(f, a, n);
if(m < 0 && wasintr())
return n;
return m;
}