//! `:input`
//!
//! A seperate scheme is required since all of the input from different input devices is required
//! to be combined into a single stream which is later going to be processed by the "consumer"
//! which usually is Orbital.
//!
//! ## Input Device ("producer")
//! Write events to `input:producer`.
//!
//! ## Input Consumer ("consumer")
//! Read events from `input:consumer`. Optionally, set the `EVENT_READ` flag to be notified when
//! events are available.

use std::collections::BTreeMap;
use std::fs::File;
use std::io::{Read, Write};
use std::os::fd::AsRawFd;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::Arc;

use inputd::{Cmd, VtActivate};

use spin::Mutex;

use orbclient::{Event, EventOption};
use syscall::{Error as SysError, EventFlags, Packet, SchemeMut, EINVAL};

enum Handle {
    Producer,
    Consumer {
        events: EventFlags,
        pending: Vec<u8>,
        notified: bool,
        vt: usize,
    },
    Device {
        device: String,
    },
}

impl Handle {
    pub fn is_producer(&self) -> bool {
        matches!(self, Handle::Producer)
    }
}

/// VT Inner State
///
/// This is *required* to be lazily initialized since opening the handle to the display
/// requires the system call to return first. Otherwise, it will block indefinitely.
struct VtInner {
    handle_file: File,
}

struct Vt {
    display: String,
    index: usize,
    inner: spin::Once<Mutex<VtInner>>,
}

impl Vt {
    pub fn new<D>(display: D, index: usize) -> Arc<Self>
    where
        D: Into<String>,
    {
        Arc::new(Self {
            display: display.into(),
            inner: spin::Once::new(),
            index,
        })
    }

    pub fn inner(&self) -> &Mutex<VtInner> {
        self.inner.call_once(|| {
            let handle_file = File::open(format!("/scheme/{}/handle", self.display)).unwrap();
            Mutex::new(VtInner { handle_file })
        })
    }
}

struct InputScheme {
    handles: BTreeMap<usize, Handle>,

    next_id: AtomicUsize,
    next_vt_id: AtomicUsize,

    vts: BTreeMap<usize, Arc<Vt>>,
    super_key: bool,
    active_vt: Option<Arc<Vt>>,

    todo: Vec<VtActivate>,
}

impl InputScheme {
    pub fn new() -> Self {
        Self {
            next_id: AtomicUsize::new(0),
            next_vt_id: AtomicUsize::new(1),

            handles: BTreeMap::new(),
            vts: BTreeMap::new(),
            super_key: false,
            active_vt: None,

            todo: vec![],
        }
    }
}

impl SchemeMut for InputScheme {
    fn open(&mut self, path: &str, _flags: usize, _uid: u32, _gid: u32) -> syscall::Result<usize> {
        let mut path_parts = path.split('/');

        let command = path_parts.next().ok_or(SysError::new(EINVAL))?;
        let fd = self.next_id.fetch_add(1, Ordering::SeqCst);

        let handle_ty = match command {
            "producer" => Handle::Producer,
            "consumer" => {
                let target = path_parts
                    .next()
                    .and_then(|x| x.parse::<usize>().ok())
                    .ok_or(SysError::new(EINVAL))?;

                Handle::Consumer {
                    events: EventFlags::empty(),
                    pending: Vec::new(),
                    notified: false,
                    vt: target,
                }
            }
            "handle" => {
                let display = path_parts.collect::<Vec<_>>().join(".");
                Handle::Device { device: display }
            }

            _ => {
                log::error!("inputd: invalid path {path}");
                return Err(SysError::new(EINVAL));
            }
        };

        log::info!("inputd: {path} channel has been opened");

        self.handles.insert(fd, handle_ty);
        Ok(fd)
    }

    fn fpath(&mut self, id: usize, buf: &mut [u8]) -> syscall::Result<usize> {
        let handle = self.handles.get(&id).ok_or(SysError::new(EINVAL))?;

        if let Handle::Consumer { vt, .. } = handle {
            let display = self.vts.get(vt).ok_or(SysError::new(EINVAL))?;
            let vt = format!("{}:{vt}", display.display);

            let size = core::cmp::min(vt.len(), buf.len());
            buf[..size].copy_from_slice(&vt.as_bytes()[..size]);

            Ok(size)
        } else {
            Err(SysError::new(EINVAL))
        }
    }

    fn read(&mut self, id: usize, buf: &mut [u8]) -> syscall::Result<usize> {
        let handle = self.handles.get_mut(&id).ok_or(SysError::new(EINVAL))?;

        match handle {
            Handle::Consumer { pending, .. } => {
                let copy = core::cmp::min(pending.len(), buf.len());

                for (i, byte) in pending.drain(..copy).enumerate() {
                    buf[i] = byte;
                }

                Ok(copy)
            }

            Handle::Device { device } => {
                assert!(buf.is_empty());

                let vt = self.next_vt_id.fetch_add(1, Ordering::SeqCst);
                self.vts.insert(vt, Vt::new(device.clone(), vt));
                Ok(vt)
            }

            _ => unreachable!(),
        }
    }

    fn write(&mut self, id: usize, buf: &[u8]) -> syscall::Result<usize> {
        let handle = self.handles.get_mut(&id).ok_or(SysError::new(EINVAL))?;

        match handle {
            Handle::Device { device } => {
                assert!(buf.len() == core::mem::size_of::<VtActivate>());

                // SAFETY: We have verified the size of the buffer above.
                let cmd = unsafe { &*buf.as_ptr().cast::<VtActivate>() };

                self.vts.insert(cmd.vt, Vt::new(device.clone(), cmd.vt));
                self.todo.push(cmd.clone());

                return Ok(buf.len());
            }

            Handle::Consumer { .. } => unreachable!(),
            _ => {}
        }

        if buf.len() == 1 && buf[0] > 0xf4 {
            return Ok(1);
        }

        let events = unsafe {
            core::slice::from_raw_parts(
                buf.as_ptr() as *const Event,
                buf.len() / core::mem::size_of::<Event>(),
            )
        };

        'out: for event in events.iter() {
            let mut new_active_opt = None;
            match event.to_option() {
                EventOption::Key(key_event) => match key_event.scancode {
                    f @ 0x3B..=0x44 if self.super_key => {
                        // F1 through F10
                        new_active_opt = Some((f - 0x3A) as usize);
                    }

                    0x57 if self.super_key => {
                        // F11
                        new_active_opt = Some(11);
                    }

                    0x58 if self.super_key => {
                        // F12
                        new_active_opt = Some(12);
                    }

                    0x5B => {
                        // Super
                        self.super_key = key_event.pressed;
                    }

                    _ => (),
                },

                EventOption::Resize(resize_event) => {
                    let active_vt = self.active_vt.as_ref().unwrap();
                    let mut vt_inner = active_vt.inner().lock();

                    inputd::send_comand(
                        &mut vt_inner.handle_file,
                        Cmd::Resize {
                            vt: active_vt.index,
                            width: resize_event.width,
                            height: resize_event.height,

                            // TODO(andypython): Figure out how to get the stride.
                            stride: resize_event.width,
                        },
                    )?;
                }

                _ => continue,
            }

            if let Some(new_active) = new_active_opt {
                if new_active == self.active_vt.as_ref().unwrap().index {
                    continue 'out;
                }

                if let Some(new_active) = self.vts.get(&new_active).cloned() {
                    {
                        let active_vt = self.active_vt.as_ref().unwrap();
                        let mut vt_inner = active_vt.inner().lock();

                        inputd::send_comand(
                            &mut vt_inner.handle_file,
                            Cmd::Deactivate(active_vt.index),
                        )?;
                    }

                    let mut vt_inner = new_active.inner().lock();

                    inputd::send_comand(
                        &mut vt_inner.handle_file,
                        Cmd::Activate {
                            vt: new_active.index,
                        },
                    )?;
                    self.active_vt = Some(new_active.clone());
                } else {
                    log::warn!("inputd: switch to non-existent VT #{new_active} was requested");
                }
            }
        }

        assert!(handle.is_producer());

        let active_vt = self.active_vt.as_ref().unwrap();
        for handle in self.handles.values_mut() {
            match handle {
                Handle::Consumer {
                    pending,
                    notified,
                    vt,
                    ..
                } => {
                    if *vt != active_vt.index {
                        continue;
                    }

                    pending.extend_from_slice(buf);
                    *notified = false;
                }
                _ => continue,
            }
        }

        Ok(buf.len())
    }

    fn fevent(
        &mut self,
        id: usize,
        flags: syscall::EventFlags,
    ) -> syscall::Result<syscall::EventFlags> {
        let handle = self.handles.get_mut(&id).ok_or(SysError::new(EINVAL))?;

        match handle {
            Handle::Consumer {
                ref mut events,
                ref mut notified,
                ..
            } => {
                *events = flags;
                *notified = false;
            }
            _ => unreachable!(),
        }

        Ok(EventFlags::empty())
    }

    fn close(&mut self, _id: usize) -> syscall::Result<usize> {
        Ok(0)
    }
}

fn deamon(deamon: redox_daemon::Daemon) -> anyhow::Result<()> {
    // Create the ":input" scheme.
    let mut socket_file = File::create(":input")?;
    let mut scheme = InputScheme::new();

    deamon.ready().unwrap();

    loop {
        let mut should_handle = false;
        let mut packet = Packet::default();
        socket_file.read(&mut packet)?;

        // The producer has written to the channel; the consumers should be notified.
        if packet.a == syscall::SYS_WRITE {
            should_handle = true;
        }

        scheme.handle(&mut packet);
        socket_file.write(&packet)?;

        while let Some(cmd) = scheme.todo.pop() {
            let vt = scheme.vts.get_mut(&cmd.vt).unwrap();
            let mut vt_inner = vt.inner().lock();

            // Failing to activate a VT is not a fatal error.
            if let Err(err) =
                inputd::send_comand(&mut vt_inner.handle_file, Cmd::Activate { vt: vt.index })
            {
                log::error!("inputd: failed to activate VT #{}: {err}", vt.index)
            }

            scheme.active_vt = Some(vt.clone());
        }

        if !should_handle {
            continue;
        }

        for (id, handle) in scheme.handles.iter_mut() {
            if let Handle::Consumer {
                events,
                pending,
                ref mut notified,
                vt,
            } = handle
            {
                if pending.is_empty() || *notified || !events.contains(EventFlags::EVENT_READ) {
                    continue;
                }

                let active_vt = scheme.active_vt.as_ref().unwrap();

                // The activate VT is not the same as the VT that the consumer is listening to
                // for events.
                if active_vt.index != *vt {
                    continue;
                }

                // Notify the consumer that we have some events to read. Yum yum.
                let mut event_packet = Packet::default();
                event_packet.a = syscall::SYS_FEVENT;
                event_packet.b = *id;
                event_packet.c = EventFlags::EVENT_READ.bits();
                // Specifies the number of bytes that can be read non-blocking.
                event_packet.d = pending.len();
                socket_file.write(&event_packet)?;

                *notified = true;
            }
        }
    }
}

fn daemon_runner(redox_daemon: redox_daemon::Daemon) -> ! {
    deamon(redox_daemon).unwrap();
    unreachable!();
}

pub fn main() {
    common::setup_logging(
        "misc",
        "inputd",
        "inputd",
        log::LevelFilter::Info,
        log::LevelFilter::Debug,
    );

    let mut args = std::env::args().skip(1);

    if let Some(val) = args.next() {
        match val.as_ref() {
            // Activates a VT.
            "-A" => {
                let vt = args.next().unwrap().parse::<usize>().unwrap();

                let handle = File::open(format!("/scheme/input/consumer/{vt}"))
                    .expect("inputd: failed to open consumer handle");
                let mut display_path = [0; 4096];

                let written = libredox::call::fpath(handle.as_raw_fd() as usize, &mut display_path)
                    .expect("inputd: fpath() failed");

                assert!(written <= display_path.len());
                drop(handle);

                let display_path = std::str::from_utf8(&display_path[..written])
                    .expect("inputd: display path UTF-8 validation failed");
                let display_name = display_path
                    .split('.')
                    .skip(1)
                    .next()
                    .expect("inputd: invalid display path");
                let display_scheme = display_name
                    .split(':')
                    .next()
                    .expect("inputd: invalid display path");

                let mut handle = inputd::Handle::new(display_scheme)
                    .expect("inputd: failed to open display handle");
                handle.activate(vt).expect("inputd: failed to activate VT");
            }

            _ => panic!("inputd: invalid argument: {}", val),
        }
    } else {
        redox_daemon::Daemon::new(daemon_runner).expect("virtio-core: failed to daemonize");
    }
}