// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.


/*
  A parallel version of fibonacci numbers.

  This version is meant mostly as a way of stressing and benchmarking
  the task system. It supports a lot of old command-line arguments to
  control how it runs.

*/

#![feature(std_misc, rustc_private)]

extern crate getopts;

use std::sync::mpsc::{channel, Sender};
use std::env;
use std::result::Result::{Ok, Err};
use std::thread;
use std::time::Duration;

fn fib(n: isize) -> isize {
    fn pfib(tx: &Sender<isize>, n: isize) {
        if n == 0 {
            tx.send(0).unwrap();
        } else if n <= 2 {
            tx.send(1).unwrap();
        } else {
            let (tx1, rx) = channel();
            let tx2 = tx1.clone();
            thread::spawn(move|| pfib(&tx2, n - 1));
            let tx2 = tx1.clone();
            thread::spawn(move|| pfib(&tx2, n - 2));
            tx.send(rx.recv().unwrap() + rx.recv().unwrap());
        }
    }

    let (tx, rx) = channel();
    thread::spawn(move|| pfib(&tx, n) );
    rx.recv().unwrap()
}

struct Config {
    stress: bool
}

fn parse_opts(argv: Vec<String> ) -> Config {
    let opts = vec!(getopts::optflag("", "stress", ""));

    let argv = argv.iter().map(|x| x.to_string()).collect::<Vec<_>>();
    let opt_args = &argv[1..argv.len()];

    match getopts::getopts(opt_args, &opts) {
      Ok(ref m) => {
          return Config {stress: m.opt_present("stress")}
      }
      Err(_) => { panic!(); }
    }
}

fn stress_task(id: isize) {
    let mut i = 0;
    loop {
        let n = 15;
        assert_eq!(fib(n), fib(n));
        i += 1;
        println!("{}: Completed {} iterations", id, i);
    }
}

fn stress(num_tasks: int) {
    let mut results = Vec::new();
    for i in 0..num_tasks {
        results.push(thread::spawn(move|| {
            stress_task(i);
        }));
    }
    for r in results {
        let _ = r.join();
    }
}

fn main() {
    let args = env::args();
    let args = if env::var_os("RUST_BENCH").is_some() {
        vec!("".to_string(), "20".to_string())
    } else if args.len() <= 1 {
        vec!("".to_string(), "8".to_string())
    } else {
        args.map(|x| x.to_string()).collect()
    };

    let opts = parse_opts(args.clone());

    if opts.stress {
        stress(2);
    } else {
        let max = args[1].parse::<isize>().unwrap();

        let num_trials = 10;

        for n in 1..max + 1 {
            for _ in 0..num_trials {
                let mut fibn = None;
                let dur = Duration::span(|| fibn = Some(fib(n)));
                let fibn = fibn.unwrap();

                println!("{}\t{}\t{}", n, fibn, dur);
            }
        }
    }
}