use std::{
    error,
    fmt,
};

#[cfg(feature = "broken-pipe")]
pub const BROKEN_PIPE: char = '¦';

#[cfg(not(feature = "broken-pipe"))]
pub const BROKEN_PIPE: char = '|';

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct ProcessArgs
{
    pub name: String,
    pub args: Vec<String>,
}

mod proc_args;
pub use proc_args::*;

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Operation
{
    input: ProcessArgs,
    outputs: Vec<ProcessArgs>,
    output_to_tty: bool,
}

#[derive(Clone, Debug)]
pub struct Error(String, String);
impl error::Error for Error{}
impl fmt::Display for Error
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
    {
	write!(f, "<{}>: {}", self.1, self.0)
    }
}
impl Error
{
    pub fn new<T>(message: T) -> Self
	where T: AsRef<str>
    {
	Self(message.as_ref().to_owned(), program())
    }
}
impl<T> From<T> for Error
where T: AsRef<str>
{
    fn from(input: T) -> Self
    {
	Self::new(input)
    }
}

impl Operation
{
    pub fn new(input: ProcessArgs) -> Self
    {
	Self {
	    input,
	    outputs: Vec::new(),
	    output_to_tty: false,
	}
    }

    pub fn parent(&self) -> &ProcessArgs
    {
	&self.input
    }
    pub fn children(&self) -> &Vec<ProcessArgs>
    {
	&self.outputs
    }

    pub fn validate(&self) -> Result<(), String>
    {
	if !self.output_to_tty && self.outputs.len()<1 {
	    return Err("Need at least one output.".to_owned());
	}

	self.input.verify().or_else(|err| Err(format!("bad input <{}>: {}", &self.input, err)))?;
	
	for x in self.outputs.iter()
	{
	    x.verify().or_else(|err| Err(format!("bad output <{}>: {}", &x, err)))?;
	}
	
	Ok(())
    }
}

pub fn program() -> String
{
    std::env::args().next().unwrap()
}

pub fn parse() -> Result<Operation, Error>
{
    let mut iter = std::env::args();

    let this = iter.next().unwrap();
    let mut not_last = false;
    let input = ProcessArgs::parse(&mut iter, &mut not_last).or(Err("Expected at least one input"))?;

    if !not_last {
	return Err(Error::new("Need at least one output."));
    }
    
    let mut output = Operation::new(input);
    while let Ok(op) = ProcessArgs::parse(&mut iter, &mut not_last) {
	output.outputs.push(op);
    }
    
    if not_last {
	output.output_to_tty = true;
    }

    output.validate()?;

    Ok(output)
}