// Licensed under the Apache License, Version 2.0 or the MIT License.
// SPDX-License-Identifier: Apache-2.0 OR MIT
// Copyright Tock Contributors 2022.

//! Provides userspace with virtualized access to 9DOF sensors.
//!
//! Usage
//! -----
//!
//! You need a device that provides the `hil::sensors::NineDof` trait.
//!
//! ```rust
//! # use kernel::{hil, static_init};
//!
//! let grant_cap = create_capability!(capabilities::MemoryAllocationCapability);
//! let grant_ninedof = board_kernel.create_grant(&grant_cap);
//!
//! let ninedof = static_init!(
//!     capsules::ninedof::NineDof<'static>,
//!     capsules::ninedof::NineDof::new(grant_ninedof));
//! ninedof.add_driver(fxos8700);
//! hil::sensors::NineDof::set_client(fxos8700, ninedof);
//! ```

use kernel::grant::{AllowRoCount, AllowRwCount, Grant, UpcallCount};
use kernel::hil;
use kernel::syscall::{CommandReturn, SyscallDriver};
use kernel::utilities::cells::OptionalCell;
use kernel::{ErrorCode, ProcessId};

/// Syscall driver number.
use capsules_core::driver;
pub const DRIVER_NUM: usize = driver::NUM::NINEDOF as usize;

#[derive(Clone, Copy, PartialEq)]
pub enum NineDofCommand {
    Exists,
    ReadAccelerometer,
    ReadMagnetometer,
    ReadGyroscope,
}

pub struct App {
    pending_command: bool,
    command: NineDofCommand,
    arg1: usize,
}

impl Default for App {
    fn default() -> App {
        App {
            pending_command: false,
            command: NineDofCommand::Exists,
            arg1: 0,
        }
    }
}

pub struct NineDof<'a> {
    drivers: &'a [&'a dyn hil::sensors::NineDof<'a>],
    apps: Grant<App, UpcallCount<1>, AllowRoCount<0>, AllowRwCount<0>>,
    current_app: OptionalCell<ProcessId>,
}

impl<'a> NineDof<'a> {
    pub fn new(
        drivers: &'a [&'a dyn hil::sensors::NineDof<'a>],
        grant: Grant<App, UpcallCount<1>, AllowRoCount<0>, AllowRwCount<0>>,
    ) -> NineDof<'a> {
        NineDof {
            drivers: drivers,
            apps: grant,
            current_app: OptionalCell::empty(),
        }
    }

    // Check so see if we are doing something. If not,
    // go ahead and do this command. If so, this is queued
    // and will be run when the pending command completes.
    fn enqueue_command(
        &self,
        command: NineDofCommand,
        arg1: usize,
        processid: ProcessId,
    ) -> CommandReturn {
        self.apps
            .enter(processid, |app, _| {
                if self.current_app.is_none() {
                    self.current_app.set(processid);
                    let value = self.call_driver(command, arg1);
                    if value != Ok(()) {
                        self.current_app.clear();
                    }
                    CommandReturn::from(value)
                } else {
                    if app.pending_command {
                        CommandReturn::failure(ErrorCode::BUSY)
                    } else {
                        app.pending_command = true;
                        app.command = command;
                        app.arg1 = arg1;
                        CommandReturn::success()
                    }
                }
            })
            .unwrap_or_else(|err| {
                let rcode: Result<(), ErrorCode> = err.into();
                CommandReturn::from(rcode)
            })
    }

    fn call_driver(&self, command: NineDofCommand, _: usize) -> Result<(), ErrorCode> {
        match command {
            NineDofCommand::ReadAccelerometer => {
                let mut data = Err(ErrorCode::NODEVICE);
                for driver in self.drivers.iter() {
                    data = driver.read_accelerometer();
                    if data == Ok(()) {
                        break;
                    }
                }
                data
            }
            NineDofCommand::ReadMagnetometer => {
                let mut data = Err(ErrorCode::NODEVICE);
                for driver in self.drivers.iter() {
                    data = driver.read_magnetometer();
                    if data == Ok(()) {
                        break;
                    }
                }
                data
            }
            NineDofCommand::ReadGyroscope => {
                let mut data = Err(ErrorCode::NODEVICE);
                for driver in self.drivers.iter() {
                    data = driver.read_gyroscope();
                    if data == Ok(()) {
                        break;
                    }
                }
                data
            }
            _ => Err(ErrorCode::NOSUPPORT),
        }
    }
}

impl hil::sensors::NineDofClient for NineDof<'_> {
    fn callback(&self, arg1: usize, arg2: usize, arg3: usize) {
        // Notify the current application that the command finished.
        // Also keep track of what just finished to see if we can re-use
        // the result.
        let mut finished_command = NineDofCommand::Exists;
        let mut finished_command_arg = 0;
        self.current_app.take().map(|processid| {
            let _ = self.apps.enter(processid, |app, upcalls| {
                app.pending_command = false;
                finished_command = app.command;
                finished_command_arg = app.arg1;
                upcalls.schedule_upcall(0, (arg1, arg2, arg3)).ok();
            });
        });

        // Check if there are any pending events.
        for cntr in self.apps.iter() {
            let processid = cntr.processid();
            let started_command = cntr.enter(|app, upcalls| {
                if app.pending_command
                    && app.command == finished_command
                    && app.arg1 == finished_command_arg
                {
                    // Don't bother re-issuing this command, just use
                    // the existing result.
                    app.pending_command = false;
                    upcalls.schedule_upcall(0, (arg1, arg2, arg3)).ok();
                    false
                } else if app.pending_command {
                    app.pending_command = false;
                    self.current_app.set(processid);
                    self.call_driver(app.command, app.arg1) == Ok(())
                } else {
                    false
                }
            });
            if started_command {
                break;
            }
        }
    }
}

impl SyscallDriver for NineDof<'_> {
    fn command(
        &self,
        command_num: usize,
        arg1: usize,
        _: usize,
        processid: ProcessId,
    ) -> CommandReturn {
        match command_num {
            0 => CommandReturn::success(),
            // Single acceleration reading.
            1 => self.enqueue_command(NineDofCommand::ReadAccelerometer, arg1, processid),

            // Single magnetometer reading.
            100 => self.enqueue_command(NineDofCommand::ReadMagnetometer, arg1, processid),

            // Single gyroscope reading.
            200 => self.enqueue_command(NineDofCommand::ReadGyroscope, arg1, processid),

            _ => CommandReturn::failure(ErrorCode::NOSUPPORT),
        }
    }

    fn allocate_grant(&self, processid: ProcessId) -> Result<(), kernel::process::Error> {
        self.apps.enter(processid, |_, _| {})
    }
}