use std::io;
use std::str;

use crate::reflect::error::ReflectError;
use crate::wire_format::WireType;

/// [`Result`] alias for [`Error`].
pub type Result<T> = std::result::Result<T, crate::Error>;

/// Enum values added here for diagnostic purposes.
/// Users should not depend on specific values.
#[derive(Debug, thiserror::Error)]
pub(crate) enum WireError {
    #[error("Unexpected EOF")]
    UnexpectedEof,
    #[error("Unexpected wire type")]
    UnexpectedWireType(WireType),
    #[error("Incorrect tag")]
    IncorrectTag(u32),
    #[error("Incorrect varint")]
    IncorrectVarint,
    #[error("Invalid UTF-8 sequence")]
    Utf8Error,
    #[error("Invalid enum `{}` value: {}", .0, .1)]
    InvalidEnumValue(&'static str, i32),
    #[error("Over recursion limit")]
    OverRecursionLimit,
    #[error("Truncated message")]
    TruncatedMessage,
    // not really possible
    #[error("Limit overflow")]
    LimitOverflow,
    #[error("New limit must not be greater than current limit")]
    LimitIncrease,
    #[error("Encoded message size {0} is too large")]
    MessageTooLarge(u64),
    #[error("Value too large for u32: {}", .0)]
    U32Overflow(u64),
    #[error("Value too large for i32: {}", .0)]
    I32Overflow(i64),
}

/// Generic protobuf error
#[derive(Debug, thiserror::Error)]
pub(crate) enum ProtobufError {
    /// I/O error when reading or writing
    #[error(transparent)]
    IoError(#[from] io::Error),
    /// Malformed input
    #[error(transparent)]
    WireError(#[from] WireError),
    #[error(transparent)]
    Reflect(#[from] ReflectError),
    /// Protocol contains a string which is not valid UTF-8 string
    #[error("UTF-8 decode error")]
    Utf8(
        #[source]
        #[from]
        str::Utf8Error,
    ),
    /// Not all required fields of message set.
    #[error("Message `{}` is missing required fields", .0)]
    MessageNotInitialized(String),
    /// Message is too large.
    #[error("Provided buffer has not enough capacity to write message `{0}`")]
    BufferHasNotEnoughCapacity(String),
    /// Protobuf type and runtime types mismatch.
    #[error("Protobuf type and runtime types are not compatible")]
    IncompatibleProtobufTypeAndRuntimeType,
    /// Group field type not implemented.
    #[error("Group field is not supported")]
    GroupIsNotImplemented,
}

/// Error type for protobuf operations.
#[derive(Debug, thiserror::Error)]
#[error(transparent)]
pub struct Error(pub(crate) Box<ProtobufError>);

impl From<ProtobufError> for Error {
    #[cold]
    fn from(e: ProtobufError) -> Self {
        Self(Box::new(e))
    }
}

impl From<WireError> for Error {
    #[cold]
    fn from(e: WireError) -> Self {
        Self(Box::new(ProtobufError::WireError(e)))
    }
}

impl From<ReflectError> for Error {
    #[cold]
    fn from(e: ReflectError) -> Self {
        Self(Box::new(ProtobufError::Reflect(e)))
    }
}

impl From<Error> for io::Error {
    #[cold]
    fn from(err: Error) -> Self {
        match *err.0 {
            ProtobufError::IoError(e) => e,
            ProtobufError::WireError(e) => {
                io::Error::new(io::ErrorKind::InvalidData, ProtobufError::WireError(e))
            }
            ProtobufError::MessageNotInitialized(message) => io::Error::new(
                io::ErrorKind::InvalidInput,
                ProtobufError::MessageNotInitialized(message),
            ),
            e => io::Error::new(io::ErrorKind::Other, Box::new(e)),
        }
    }
}

impl From<io::Error> for Error {
    #[cold]
    fn from(err: io::Error) -> Self {
        Error(Box::new(ProtobufError::IoError(err)))
    }
}

#[cfg(test)]
mod test {
    use std::mem;

    #[test]
    fn error_size() {
        assert_eq!(mem::size_of::<usize>(), mem::size_of::<crate::Error>());
    }
}