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// Copyright 2021 UBC Bionics, Ltd.
//
// Licensed under the MIT license
// <LICENSE.md or https://opensource.org/licenses/MIT>.
// This file may not be copied, modified, or
// distributed except according to those terms.

use std::{
    error::Error as StdError,
    fmt::{
        Display,
        Formatter,
        Result as FmtResult,
    },
    io::{
        Error as IoError,
        ErrorKind as IoErrorKind,
    },
};

use rppal::{
    gpio::Error as GpioError,
    uart::Error as UartError,
};

/// The custom `raestro` error type.
///
/// Contains all custom error variants, as well as
/// a wrapper for the `std::io::Error` enum. All
/// `rppal` errors are unwrapped and
/// converted into their underlying
/// `std::io::Error` instances, and then wrapped
/// in the `Error::Io` variant.
#[derive(Debug)]
pub enum Error {
    /// The `maestro` instance is in an
    /// `uninitialized` state.
    ///
    /// Consider calling `Maestro::start` with a
    /// corresponding baudrate to transition
    /// this instance into the `initialized`
    /// state.
    Uninitialized,

    /// An invalid value was passed in as a
    /// parameter.
    ///
    /// Mainly used when an incorrect microsecond
    /// target was passed into `set_target`.
    InvalidValue(u16),

    /// Occurs when the expected number of bytes
    /// received from the Maestro do not
    /// equal `RESPONSE_SIZE`.
    ///
    /// `FaultyRead.0` is the number of bytes
    /// actually read.
    FaultyRead {
        #[allow(missing_docs)]
        actual_count: usize,
    },

    /// Occurs when the expected number of bytes
    /// written to the Maestro were incorrect
    /// (according to the protocol being sent).
    FaultyWrite {
        #[allow(missing_docs)]
        actual_count: usize,

        #[allow(missing_docs)]
        expected_count: usize,
    },

    /// Remaining IO errors as encountered by the
    /// `rppal` library, or something else.
    Io(IoError),
}

#[doc(hidden)]
impl Error {
    /// Constructs a `std::io::Error` from the
    /// given parameters.
    pub(crate) fn new_io_error<E>(err_kind: IoErrorKind, err_msg: E) -> Self
    where
        E: Into<Box<dyn StdError + Send + Sync>>,
    {
        Error::Io(IoError::new(err_kind, err_msg))
    }
}

impl StdError for Error {}

impl Display for Error {
    /// Formatting for `raestro::Error`.
    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
        match self {
            Error::Uninitialized => write!(f, "maestro struct is uninitialized; please consider calling .start() on the instance first"),
            Error::InvalidValue(value) => write!(f, "target must be between 3968 quarter-us (992us) and 8000 quarter-us (2000us) but {} quarter-us was used", value),
            Error::FaultyRead { actual_count, } => write!(f, "2 bytes were expected to be read, but only {} byte(s) were actually read", actual_count),
            Error::FaultyWrite { actual_count, expected_count, } => write!(f, "{} bytes were expected to be written, but only {} byte(s) were actually written", expected_count, actual_count),
            Error::Io(io_error) => io_error.fmt(f),
        }
    }
}

impl From<IoError> for Error {
    /// Wraps a `std::io::Error` in the
    /// `raestro::Error::Io` variant.
    fn from(io_error: IoError) -> Self { Self::Io(io_error) }
}

impl From<UartError> for Error {
    /// Used to convert from an
    /// `rppal::uart::Error` type into the
    /// `raestro::Error`.
    fn from(uart_error: UartError) -> Self {
        match uart_error {
            UartError::Io(std_err) => Error::from(std_err),
            UartError::Gpio(gpio_err) => match gpio_err {
                GpioError::UnknownModel => Error::new_io_error(IoErrorKind::Other, "unknown model"),
                GpioError::PinNotAvailable(pin) => Error::new_io_error(
                    IoErrorKind::AddrNotAvailable,
                    format!("pin number {} is not available", pin),
                ),
                GpioError::PermissionDenied(err_string) => Error::new_io_error(
                    IoErrorKind::PermissionDenied,
                    format!("permission denied: {} ", err_string),
                ),
                GpioError::Io(error) => Error::from(error),
                GpioError::ThreadPanic => Error::new_io_error(IoErrorKind::Other, "thread panic"),
            },
            UartError::InvalidValue => Error::new_io_error(IoErrorKind::Other, "invalid value"),
        }
    }
}