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// TODO: review allow..
use cfg_if::cfg_if;

/// types for use in the WASI filesystem
#[cfg(feature = "enable-serde")]
use serde::{Deserialize, Serialize};

cfg_if! {
    if #[cfg(feature = "host-fs")] {
        pub use virtual_fs::host_fs::{Stderr, Stdin, Stdout};
    } else {
        pub use virtual_fs::mem_fs::{Stderr, Stdin, Stdout};
    }
}

#[derive(Debug, Clone)]
#[allow(clippy::enum_variant_names)]
pub enum PollEvent {
    /// Data available to read
    PollIn = 1,
    /// Data available to write (will still block if data is greater than space available unless
    /// the fd is configured to not block)
    PollOut = 2,
    /// Something didn't work. ignored as input
    PollError = 4,
    /// Connection closed. ignored as input
    PollHangUp = 8,
    /// Invalid request. ignored as input
    PollInvalid = 16,
}

impl PollEvent {
    fn from_i16(raw_num: i16) -> Option<PollEvent> {
        Some(match raw_num {
            1 => PollEvent::PollIn,
            2 => PollEvent::PollOut,
            4 => PollEvent::PollError,
            8 => PollEvent::PollHangUp,
            16 => PollEvent::PollInvalid,
            _ => return None,
        })
    }
}

#[derive(Debug, Clone)]
pub struct PollEventBuilder {
    inner: PollEventSet,
}

pub type PollEventSet = i16;

#[derive(Debug)]
pub struct PollEventIter {
    pes: PollEventSet,
    i: usize,
}

impl Iterator for PollEventIter {
    type Item = PollEvent;

    fn next(&mut self) -> Option<Self::Item> {
        if self.pes == 0 || self.i > 15 {
            None
        } else {
            while self.i < 16 {
                let result = PollEvent::from_i16(self.pes & (1 << self.i));
                self.pes &= !(1 << self.i);
                self.i += 1;
                if let Some(r) = result {
                    return Some(r);
                }
            }
            unreachable!("Internal logic error in PollEventIter");
        }
    }
}

pub fn iterate_poll_events(pes: PollEventSet) -> PollEventIter {
    PollEventIter { pes, i: 0 }
}

#[allow(dead_code)]
impl PollEventBuilder {
    pub fn new() -> PollEventBuilder {
        PollEventBuilder { inner: 0 }
    }

    pub fn add(mut self, event: PollEvent) -> PollEventBuilder {
        self.inner |= event as PollEventSet;
        self
    }

    pub fn build(self) -> PollEventSet {
        self.inner
    }
}

#[allow(dead_code)]
pub trait WasiPath {}

/*
TODO: Think about using this
trait WasiFdBacking: std::fmt::Debug {
    fn get_stat(&self) -> &Filestat;
    fn get_stat_mut(&mut self) -> &mut Filestat;
    fn is_preopened(&self) -> bool;
    fn get_name(&self) -> &str;
}
*/