//! # Super Dense Coding
//!
//! If Alice and Bob share a pair of entangled qubits, then Alice can encode two classical bits into her one entangled qubit,
//! send it to Bob, and Bob can decode it with the help of his entangled qubit.

extern crate failure;
extern crate qcgpu;

use failure::Error;
use qcgpu::Simulator;

fn superdense(input: &str) -> Result<u8, Error> {
    let mut state = Simulator::new_opencl(2)?;
    let input_str = String::from(input);

    // Prepare the bell state
    state.h(0)?;
    state.cx(0, 1)?;

    // Alice prepares her qubit
    let alice = 1;
    if input_str.get(0..1) == Some("1") {
        state.z(alice)?;
    }
    if input_str.get(1..2) == Some("1") {
        state.x(alice)?;
    }

    println!("\nState after Alice prepares her qubit: \n{}", state);

    // Alice sends her qubit to Bob
    let bob = 0;
    state.cx(alice, bob)?;
    state.h(alice)?;

    println!(
        "\nState after Bob receives Alice's qubit and 'decodes' it: \n{}",
        state
    );

    state.measure()
}

fn main() {
    use std::io;

    println!("Two bit string to send:");
    let mut input = String::new();
    match io::stdin().read_line(&mut input) {
        Ok(_n) => {
            let result = superdense(input.as_str()).unwrap();
            println!("\nDecoded string is: {}", result);
        }
        Err(error) => println!("error: {}", error),
    }
}