//! For parsing arguments
use super::*;
use std::collections::{HashMap, HashSet};
use std::mem::Discriminant;
use std::fmt;

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum Argument
{
    ModeChangeHelp,
    LimitConcMaxProc,
    LimitConc(NonZeroUsize),
    UnlimitConc,
    
    Save(String),
    SaveStdout,
    SaveRaw(String),
    SaveRawStdout,

    LimitRecurse(NonZeroUsize),
    UnlimitRecurse,

    LogVerbose,
    LogQuiet,
    LogSilent,

    StopReading,

    Input(String),
}

impl fmt::Display for Argument
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
    {
	use Argument::*;
	match self
	{
	    ModeChangeHelp => write!(f, "--help"),
	    LimitConcMaxProc => write!(f, "-m"),
	    LimitConc(limit) => write!(f, "--threads {}", limit),
	    UnlimitConc => write!(f, "-M"),
	    
	    Save(s) => write!(f, "--save {:?}", s),
	    SaveStdout => write!(f, "-D"),
	    SaveRaw(s) => write!(f, "--save-raw {:?}", s),
	    SaveRawStdout => write!(f, "-R"),

	    LimitRecurse(rec) => write!(f, "--recursive {}", rec),
	    UnlimitRecurse => write!(f, "-r"),

	    LogVerbose => write!(f, "-v"),
	    LogQuiet => write!(f, "-q"),
	    LogSilent => write!(f, "-Q"),

	    StopReading => write!(f, "-"),

	    Input(input) => write!(f, "<{}>", input),
	}
    }
}


#[derive(Debug, Clone, PartialEq, Eq, Hash, Copy)]
enum MX
{
    None,
    Itself,
    All,
    Only(Discriminant<Argument>),
    Many(&'static [Discriminant<Argument>]),
}

impl Default for MX
{
    #[inline]
    fn default() -> Self
    {
	Self::Itself
    }
}

impl MX
{
    /// Is this argument discriminant mutually exclusive with this other argument?
    pub fn is_mx(&self, this: Discriminant<Argument>, other: &Argument) -> bool
    {
	use std::mem::discriminant;

	let other = discriminant(other);
	match self
	{
	    Self::Itself if other == this => true,
	    Self::All => true,
	    Self::Only(disc) if other == *disc => true,
	    Self::Many(discs) if discs.contains(&other) => true,
	    _ => false,
	}
    }
}


impl Argument
{
    /// Is this `Argument` mutually exclusive with another?
    pub fn is_mx_with(&self, other: &Self) -> bool
    {
	use std::mem::discriminant;
	lazy_static! {
	    static ref MX_REF: HashMap<Discriminant<Argument>, MaybeVec<MX>> = {
		let mut out = HashMap::new();
		macro_rules! mx {
		    (@) => {
			std::iter::empty()
		    };
		    (@ self $($tt:tt)*) => {
			iter![MX::Itself].chain(mx!(@ $($tt)*))
		    };
		    
		    (@ [$inner:expr] $($tt:tt)*) => {
			iter![MX::Only(discriminant(&$inner))].chain(mx!(@ $($tt)*))
		    };
		    (@ [$($inner:expr),*] $($tt:tt)*) => {
			iter![MX::Many(vec![$(discriminant(&$inner)),*].leak())].chain(mx!(@ $($tt)*))
		    };
		    (@ $ident:ident $($tt:tt)*) => {
			iter![MX::$ident].chain(mx!(@ $($tt)*))
		    };
		    ($disc:expr => $($tt:tt)*) => {
			out.insert(discriminant(&$disc), mx!(@ $($tt)*).collect());
		    };
		}
		
		mx!(Argument::ModeChangeHelp => All);
		
		mx!(Argument::LimitConcMaxProc => self [Argument::UnlimitConc,
							Argument::LimitConc(unsafe{NonZeroUsize::new_unchecked(1)})]);
		mx!(Argument::UnlimitConc => self [Argument::LimitConcMaxProc, Argument::LimitConc(unsafe{NonZeroUsize::new_unchecked(1)})]);
		mx!(Argument::LimitConc(unsafe{NonZeroUsize::new_unchecked(1)}) => self [Argument::LimitConcMaxProc, Argument::UnlimitConc]);

		mx!(Argument::Save(String::default()) => self [Argument::SaveStdout,
							       Argument::SaveRaw(Default::default()),
							       Argument::SaveRawStdout]);
		mx!(Argument::SaveStdout => self [Argument::Save(String::default()), 
						  Argument::SaveRaw(Default::default()),
						  Argument::SaveRawStdout]);
		mx!(Argument::SaveRaw(Default::default()) => self [Argument::Save(String::default()),
								   Argument::SaveStdout,
								   Argument::SaveRawStdout]);
		mx!(Argument::SaveRawStdout => self [Argument::Save(String::default()),
						     Argument::SaveRaw(String::default()),
						     Argument::SaveStdout]);
		mx!(Argument::LimitRecurse(unsafe{NonZeroUsize::new_unchecked(1)}) => self [Argument::UnlimitRecurse]);
		mx!(Argument::UnlimitRecurse => self [Argument::LimitRecurse(unsafe{NonZeroUsize::new_unchecked(1)})]);
		mx!(Argument::LogVerbose => self [Argument::LogQuiet, Argument::LogSilent]);
		mx!(Argument::LogQuiet => self [Argument::LogVerbose, Argument::LogSilent]);
		mx!(Argument::LogSilent => self [Argument::LogQuiet, Argument::LogVerbose]);

		mx!(Argument::StopReading => All);

		mx!(Argument::Input(String::default()) => None);
		out
	    };
	}
	let this = discriminant(self);
	match MX_REF.get(&this) {
	    Some(mx) if mx.iter().filter(|mx| mx.is_mx(this, other)).next().is_some() => true,
	    _ => false,
	}
    }
}

/// Should we continue parsing and/or reading arguments?
#[derive(Debug, Clone, PartialEq, Eq, Hash, Ord, PartialOrd, Copy)]
pub enum Continue
{
    /// Keep parsing the arguments
    Yes,
    /// Stop parsing arguments, add the rest of args as `Input`s
    No,
    /// On mode change, we don't need to parse the rest of the argument. Stop reading entirely.
    Abort,
}

impl Continue
{
    /// Should we keep *parsing* args?
    #[inline] pub fn keep_reading(&self) -> bool
    {
	if let Self::Yes = self {
	    true
	} else {
	    false
	}
    }
}

impl Default for Continue
{
    #[inline]
    fn default() -> Self
    {
	Self::Yes
    }
}

impl From<bool> for Continue
{
    fn from(from: bool) -> Self
    {
	if from {
	    Self::Yes
	} else {
	    Self::No
	}
    }
}



pub type Output = HashSet<Argument>;
#[inline] const fn suggestion_intended_arg() -> &'static str {
    "If this was intended as a path instead of an option, use option `-` before it."
}

fn parse_single<I>(args: &mut I, output: &mut Output, this: char) -> eyre::Result<Continue>
where I: Iterator<Item=String>
    
{
    //TODO: Parse single letter args
    Ok(Continue::Yes)
}

pub fn parse_next<I>(args: &mut I, output: &mut Output, this: String) -> eyre::Result<Continue>
where I: Iterator<Item=String>
{
    let mut keep_reading = Continue::Yes;
    let item = match this.trim()
    {
	"--threads" => {
	    let max = args.next().ok_or(eyre!("`--threads` expects a parameter"))
		.with_suggestion(suggestion_intended_arg.clone())?;
	    match NonZeroUsize::new(max.parse::<usize>()
				    .wrap_err(eyre!("`--threads` expects a non-negative number"))
				    .with_suggestion(suggestion_intended_arg.clone())
				    .with_section(move || max.header("Parameter given was"))?)
	    {
		Some(max) => Argument::LimitConc(max),
		None => Argument::UnlimitConc,
	    }
	},
	"--help" => {
	    keep_reading = Continue::Abort;
	    Argument::ModeChangeHelp
	},
	"-" => {
	    return Ok(Continue::No);
	},
	//TODO: move rest of long args from `mod` to here
	single if single.starts_with("-") => {
	    for ch in single.chars().skip(1) {
		match parse_single(args, output, ch)? {
		    x @ Continue::No |
		    x @ Continue::Abort => keep_reading = x,
		    _ => (),
		}
	    }
	    return Ok(keep_reading);
	},
	_ => {
	    keep_reading = Continue::No;

	    Argument::Input(this)
	}
    };

    if let Some(mx) = output.iter().filter(|arg| item.is_mx_with(arg)).next() {
	return Err(eyre!("Arguments are mutually exclusive"))
	    .with_section(|| item.header("Trying to add"))
	    .with_section(|| mx.to_string().header("Which is mutually exclusive with"));
    }

    output.insert(item); //TODO: Warn when adding duplicate?
    
    Ok(keep_reading)
}