use std::str::FromStr;
#[derive(Debug, Clone)]
pub struct Program {
    pub commands: Vec<Command>,
}
#[derive(Debug, Clone)]
pub enum Command {
    Input,
    Output,
    Move { spaces: i64 },
    Add { value: i64 },
    Loop { commands: Vec<Self> },
}
#[derive(Debug, Copy, Clone)]
pub enum ProgramParseError {
    MissingLeftBracket,
    MissingRightBracket,
}
impl FromStr for Program {
    type Err = ProgramParseError;
    fn from_str(str: &str) -> Result<Self, Self::Err> {
        use Command as C;
        use ProgramParseError as PPE;
        let mut commands = Vec::new();
        let mut loops = Vec::new();
        for char in str.bytes() {
            let cur_commands = loops.last_mut().unwrap_or(&mut commands);
            match char {
                b',' => cur_commands.push(C::Input),
                b'.' => cur_commands.push(C::Output),
                b'<' => cur_commands.push(C::Move { spaces: -1 }),
                b'>' => cur_commands.push(C::Move { spaces: 1 }),
                b'+' => cur_commands.push(C::Add { value: -1 }),
                b'-' => cur_commands.push(C::Add { value: 1 }),
                b'[' => loops.push(Vec::new()),
                b']' => match loops.pop() {
                    None => return Err(PPE::MissingLeftBracket),
                    Some(loop_commands) => {
                        loops.last_mut().unwrap_or(&mut commands).push(C::Loop {
                            commands: loop_commands,
                        });
                    }
                },
                _ => (),
            }
        }
        if !loops.is_empty() {
            return Err(PPE::MissingRightBracket);
        }
        Ok(Program { commands })
    }
}

use std::io::Read;

mod stage0;

    println!("{args:#?}");

    println!("Opts: {}", if args.opts { "on" } else { "off" });
    let program = read_to_string(args.get_file_reader());
    let program = program.parse::<stage0::Program>().unwrap();
    println!("{program:#?}");
}
fn read_to_string(mut reader: impl Read) -> String {
    let mut buf = String::new();
    reader.read_to_string(&mut buf).unwrap();
    buf

use std::path::PathBuf;

use std::{
    fs::File,
    io::{self, Read},
    path::PathBuf,
};

}
impl Args {
    pub fn get_file_reader(&self) -> Box<dyn Read> {
        if self.file.to_str().is_some_and(|f| f == "-") {
            return Box::new(io::stdin());
        }
        return Box::new(File::open(&self.file).unwrap());
    }

[ This program prints "Hello World!" and a newline to the screen, its
  length is 106 active command characters. [It is not the shortest.]
  This loop is an "initial comment loop", a simple way of adding a comment
  to a BF program such that you don't have to worry about any command
  characters. Any ".", ",", "+", "-", "<" and ">" characters are simply
  ignored, the "[" and "]" characters just have to be balanced. This
  loop and the commands it contains are ignored because the current cell
  defaults to a value of 0; the 0 value causes this loop to be skipped.
]
++++++++               Set Cell #0 to 8
[
    >++++               Add 4 to Cell #1; this will always set Cell #1 to 4
    [                   as the cell will be cleared by the loop
        >++             Add 2 to Cell #2
        >+++            Add 3 to Cell #3
        >+++            Add 3 to Cell #4
        >+              Add 1 to Cell #5
        <<<<-           Decrement the loop counter in Cell #1
    ]                   Loop until Cell #1 is zero; number of iterations is 4
    >+                  Add 1 to Cell #2
    >+                  Add 1 to Cell #3
    >-                  Subtract 1 from Cell #4
    >>+                 Add 1 to Cell #6
    [<]                 Move back to the first zero cell you find; this will
                        be Cell #1 which was cleared by the previous loop
    <-                  Decrement the loop Counter in Cell #0
]                       Loop until Cell #0 is zero; number of iterations is 8
The result of this is:
Cell no :   0   1   2   3   4   5   6
Contents:   0   0  72 104  88  32   8
Pointer :   ^
>>.                     Cell #2 has value 72 which is 'H'
>---.                   Subtract 3 from Cell #3 to get 101 which is 'e'
+++++++..+++.           Likewise for 'llo' from Cell #3
>>.                     Cell #5 is 32 for the space
<-.                     Subtract 1 from Cell #4 for 87 to give a 'W'
<.                      Cell #3 was set to 'o' from the end of 'Hello'
+++.------.--------.    Cell #3 for 'rl' and 'd'
>>+.                    Add 1 to Cell #5 gives us an exclamation point
>++.                    And finally a newline from Cell #6