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use std::collections::HashMap;

use std::env;

use std::process::exit;

use std::rc::Rc;

use std::io::{self, BufRead, Bytes, Read};

use std::fs::File;

use std::path::Path;

#[derive(Clone)]

enum Term {

I, K, K2(Rc<Term>), S, S2(Rc<Term>), S3(Rc<Term>, Rc<Term>), V, E, Readchar, Printchar(char),

Compchar(char), Reprint, D, D2(Rc<Term>), C, Callcc(Rc<Cont>), App(Rc<Term>, Rc<Term>)

}

#[derive(Clone)]

enum Cont {

Exit, DCheck(Rc<Term>, Rc<Cont>), DDelayed(Rc<Term>, Rc<Cont>), DUndelayed(Rc<Term>, Rc<Cont>)

}

fn eval<B: Read>(k: Rc<Cont>, t: Rc<Term>, c: Option<char>, b: &mut Bytes<B>) -> Result<(Rc<Term>, Rc<Cont>, Option<char>), i32>

{

match *k {

Cont::Exit => Err(0),

Cont::DDelayed(ref right, ref cont) => apply(t, right.clone(), cont.clone(), c, b),

Cont::DUndelayed(ref left, ref cont) => apply(left.clone(), t, cont.clone(), c, b),

Cont::DCheck(ref right, ref cont) => match *t {

Term::D => eval(cont.clone(), Rc::new(Term::D2(right.clone())), c, b),

ref x => descend(Rc::new(Cont::DUndelayed(Rc::new(x.clone()), cont.clone())), right.clone(), c, b)

}

fn descend<B: Read>(k: Rc<Cont>, t: Rc<Term>, c: Option<char>, b: &mut Bytes<B>) -> Result<(Rc<Term>, Rc<Cont>, Option<char>), i32>

{

match *t {

Term::App(ref left,ref right) => descend(Rc::new(Cont::DCheck(right.clone(), k)), left.clone(), c, b),

_ => eval(k, t.clone(), c, b)

}

fn apply<B: Read>(s: Rc<Term>, t: Rc<Term>, k: Rc<Cont>, c: Option<char>, b: &mut Bytes<B>) -> Result<(Rc<Term>, Rc<Cont>, Option<char>), i32>

{

match *s {

Term::I => Ok((t, k, c)),

Term::K => Ok((Rc::new(Term::K2(t)), k, c)),

Term::K2(ref a) => Ok((a.clone(), k, c)),

Term::S => Ok((Rc::new(Term::S2(t)), k, c)),

Term::S2(ref a) => Ok((Rc::new(Term::S3(a.clone(), t)), k, c)),

Term::S3(ref a,ref a2) => descend(k, Rc::new(Term::App(Rc::new(Term::App(a.clone(),t.clone())), Rc::new(Term::App(a2.clone(),t)))), c, b),

Term::V => Ok((Rc::new(Term::V),k,c)),

Term::E => Err(match *t {

Term::I => 0,

_ => 1

}),

Term::D2(ref right) => descend(Rc::new(Cont::DDelayed(t, k)), right.clone(), c, b),

Term::Readchar => match b.next() {

Some(Ok(c)) => descend(k, Rc::new(Term::App(t, Rc::new(Term::I))), Some(c as char), b),

_ => descend(k, Rc::new(Term::App(t, Rc::new(Term::V))), None, b)

Term::Printchar(ch) => {

print!("{}",ch);

Ok((t, k, c))

Term::Compchar(ch) => {

let eq = c.map_or(false, |c| ch == c);

descend(k, Rc::new(Term::App(t, Rc::new((if eq { Term::I } else { Term::V })))), c, b)

Term::Reprint => descend(k, Rc::new(Term::App(t, Rc::new(c.map_or(Term::V, Term::Printchar)))), c, b),

Term::C => descend(k.clone(), Rc::new(Term::App(t, Rc::new(Term::Callcc(k)))), c, b),

Term::Callcc(ref cont) => Ok((t, cont.clone(), c)),

// D and App should never happen here.

_ => Err(-1)

}

enum TermOrApp {

T(Rc<Term>), A

}

fn getch<B: BufRead>(reader: &mut B) -> Result<char, io::Error> {

if let Some(b) = reader.bytes().next() {

b.map(|b| b as char)

} else {

Err(io::Error::new(io::ErrorKind::UnexpectedEof, "getch failed"))

}

fn build<B: BufRead>(reader: &mut B, m: HashMap<char, Rc<Term>>) -> Result<Rc<Term>, io::Error> {

let mut tot = 0;

let mut ticks = 0;

let mut stack = Vec::new();

let mut tree = Vec::new();

while tot != 2*ticks + 1 {

let cur = try!(getch(reader));

tot = tot + 1;

match (cur, m.get(&cur).map(|t| t.clone() )) {

('#',None) => { try!(reader.read_line(&mut String::new())); tot = tot - 1;},

('`', None) => { ticks = ticks + 1; stack.push(TermOrApp::A) },

(_,Some(t)) => stack.push(TermOrApp::T(t)),

('.',_) => stack.push(TermOrApp::T(Rc::new(Term::Printchar(try!(getch(reader)))))),

('?',_) => stack.push(TermOrApp::T(Rc::new(Term::Compchar(try!(getch(reader)))))),

_ => tot = tot - 1

}

};

while let Some(curterm) = stack.pop() {

match curterm {

TermOrApp::A => {

let left = tree.pop().unwrap();

let right = tree.pop().unwrap();

tree.push(Rc::new(Term::App(left,right)))

}

TermOrApp::T(t) => tree.push(t)

}

// can't replace this with tree.pop().unwrap(); type can't be determined!

Ok(tree.pop().unwrap())

}

fn run<B: Read>(t : Rc<Term>, mut b: Bytes<B>) -> i32

{

let mut start = descend(Rc::new(Cont::Exit), t, None, &mut b);

loop {

match start {

Err(i) => {

return i;

Ok((term, cont, c)) => {

start = eval(cont, term, c, &mut b)

}

macro_rules! hashmap {

($($key:expr => $val:expr),*) => ( {

let mut m = HashMap::new();

($(m.insert($key, $val)),*);

})

}

fn main() {

let p = hashmap!{'i' => Rc::new(Term::I),

'v' => Rc::new(Term::V),

'e' => Rc::new(Term::E),

'k' => Rc::new(Term::K),

's' => Rc::new(Term::S),

'|' => Rc::new(Term::Reprint),

'@' => Rc::new(Term::Readchar),

'c' => Rc::new(Term::C),

'r' => Rc::new(Term::Printchar('\n')),

'd' => Rc::new(Term::D)};

let stdin_root = io::stdin();

let mut stdin = stdin_root.lock();

let res = match env::args().nth(1).and_then(|s| File::open(&Path::new(&s)).ok()) {

None => build(&mut stdin, p),

Some(h) => build(&mut io::BufReader::new(h), p),

};

exit(match res {

Err(e) => {

println!("{}",e);

Ok(r) => run(r, stdin.bytes())

});

}