// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.

use std::convert::{From, Into};
use std::error::Error as StdError;
use std::fmt::{Debug, Display, Formatter};
use std::{error, fmt, io, string};
use try_from::TryFrom;

use ::protocol::{TFieldIdentifier, TInputProtocol, TOutputProtocol, TStructIdentifier, TType};

// FIXME: should all my error structs impl error::Error as well?
// FIXME: should all fields in TransportError, ProtocolError and ApplicationError be optional?

/// Rift error type.
///
/// The error type defined here is used throughout this crate as well as in
/// all Thrift-compiler-generated Rust code. It falls into one of four
/// standard (i.e. defined by convention in Thrift implementations) categories.
/// These are:
///
/// 1. **Transport errors**: errors encountered while writing byes to the I/O
///    channel. These include "connection closed", "bind errors", etc.
/// 2. **Protocol errors**: errors encountered when processing a Thrift message
///    within the rift library. These include "exceeding size limits",
///    "unsupported protocol versions", etc.
/// 3. **Application errors**: errors encountered when Thrift-compiler-generated
///    'application' code encounters conditions that violate the spec. These
///    include "out-of-order messages", "missing required-field values", etc.
///    This category also functions as a catch-all: any error returned by
///    handler functions is automatically encoded as an `ApplicationError` and
///    returned to the caller.
/// 4. **User errors**: exception structs defined within the Thrift IDL.
///
/// With the exception of `Error::User`, each error variant encapsulates a
/// corresponding struct which encodes two required fields:
///
/// 1. kind: an enum indicating what kind of error was encountered
/// 2. message: string with human-readable error information
///
/// These two fields are encoded and sent over the wire to the remote. `kind`
/// is defined by convention while `message` is freeform. If none of the
/// enumerated error kinds seem suitable use the catch-all `Unknown`.
///
/// # Examples
///
/// Creating a `TransportError` explicitly.
///
/// Conversions are defined from `rift::TransportError`, `rift::ProtocolError`
/// and `rift::ApplicationError` to the corresponding `rift::Error` variant
/// (see `err2` below).
///
/// ```
/// use rift;
/// use rift::{TransportError, TransportErrorKind};
///
/// let err0: rift::Result<()> = Err(
///   rift::Error::Transport(
///     TransportError {
///       kind: TransportErrorKind::TimedOut,
///       message: format!("connection to server timed out")
///     }
///   )
/// );
///
/// let err1: rift::Result<()> = Err(
///   rift::Error::Transport(
///     TransportError::new(
///       TransportErrorKind::TimedOut,
///       format!("connection to server timed out")
///     )
///   )
/// );
///
/// let err2: rift::Result<()> = Err(
///   rift::Error::from(
///     TransportError::new(
///       TransportErrorKind::TimedOut,
///       format!("connection to server timed out")
///     )
///   )
/// );
///
/// ```
///
/// Creating an arbitrary error from a string
///
/// ```
/// use rift;
/// use rift::{ApplicationError, ApplicationErrorKind};
///
/// let err0: rift::Result<()> = Err(
///   rift::Error::from("This is an error")
/// );
///
/// // err0 is equivalent to...
///
/// let err1: rift::Result<()> = Err(
///   rift::Error::Application(
///     ApplicationError::new(
///       ApplicationErrorKind::Unknown,
///       format!("This is an error")
///     )
///   )
/// );
/// ```
///
/// Returning a user-defined (using the Thrift IDL) exception struct.
///
/// ```text
/// // Thrift IDL exception definition.
/// exception Xception {
///   1: i32 errorCode,
///   2: string message
/// }
/// ```
///
/// ```
/// use std::convert::From;
/// use std::error::Error;
/// use std::fmt;
/// use std::fmt::{Display, Formatter};
///
/// // auto-generated by the Thrift compiler
/// #[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
/// pub struct Xception {
///   pub error_code: Option<i32>,
///   pub message: Option<String>,
/// }
///
/// // auto-generated by the Thrift compiler
/// impl Error for Xception {
///   fn description(&self) -> &str {
///     "remote service threw Xception"
///   }
/// }
///
/// // auto-generated by the Thrift compiler
/// impl From<Xception> for rift::Error {
///   fn from(e: Xception) -> Self {
///     rift::Error::User(Box::new(e))
///   }
/// }
///
/// // auto-generated by the Thrift compiler
/// impl Display for Xception {
///   fn fmt(&self, f: &mut Formatter) -> fmt::Result {
///     self.description().fmt(f)
///   }
/// }
///
/// // in user code...
/// let err: rift::Result<()> = Err(
///   rift::Error::from(Xception { error_code: Some(1), message: None })
/// );
///```
pub enum Error {
    /// Errors encountered while writing byes to the I/O channel.
    ///
    /// These include "connection closed", "bind errors", etc.
    Transport(TransportError),
    /// Errors encountered when processing a Thrift message within the rift
    /// library.
    ///
    /// These include "exceeding size limits", "unsupported protocol versions",
    /// etc.
    Protocol(ProtocolError),
    /// Errors encountered when Thrift-compiler-generated 'application' code
    /// encounters conditions that violate the spec.
    ///
    /// These include "out-of-order messages", "missing required-field values",
    /// etc. This variant also functions as a catch-all: any error returned by
    /// handler functions is automatically encoded as an `ApplicationError` and
    /// returned to the caller.
    Application(ApplicationError),
    /// Carries exception structs defined within the Thrift IDL.
    User(Box<error::Error + Sync + Send>),
}

impl Error {
    /// Read the wire representation of an application exception thrown by the
    /// remote Thrift endpoint into its corresponding rift `ApplicationError`
    /// representation.
    ///
    /// Application code should never call this method directly.
    pub fn read_application_error_from_in_protocol(i: &mut TInputProtocol) -> ::Result<ApplicationError> {
        let mut message = "general remote error".to_owned();
        let mut kind = ApplicationErrorKind::Unknown;

        try!(i.read_struct_begin());

        loop {
            let field_ident = try!(i.read_field_begin());

            if field_ident.field_type == TType::Stop {
                break;
            }

            let id = field_ident.id.expect("sender should always specify id for non-STOP field");

            match id {
                1 => {
                    let remote_message = try!(i.read_string());
                    try!(i.read_field_end());
                    message = remote_message;
                },
                2 => {
                    let remote_type_as_int = try!(i.read_i32());
                    let remote_kind: ApplicationErrorKind = TryFrom::try_from(remote_type_as_int).unwrap_or(ApplicationErrorKind::Unknown);
                    try!(i.read_field_end());
                    kind = remote_kind;
                },
                _ => {
                    try!(i.skip(field_ident.field_type));
                },
            }
        }

        try!(i.read_struct_end());

        Ok(ApplicationError { kind: kind, message: message })
    }

    /// Write an `ApplicationError` into its cross-platform wire representation.
    ///
    /// Application code should never call this method directly.
    pub fn write_application_error_to_out_protocol(e: &ApplicationError, o: &mut TOutputProtocol) -> ::Result<()> {
        try!(o.write_struct_begin(&TStructIdentifier { name: "TApplicationException".to_owned() }));

        let message_field = TFieldIdentifier::new("message", TType::String, 1);
        let type_field = TFieldIdentifier::new("type", TType::I32, 2);

        try!(o.write_field_begin(&message_field));
        try!(o.write_string(&e.message));
        try!(o.write_field_end());

        try!(o.write_field_begin(&type_field));
        try!(o.write_i32(e.kind as i32));
        try!(o.write_field_end());

        try!(o.write_field_stop());
        try!(o.write_struct_end());

        o.flush()
    }
}

impl error::Error for Error {
    fn description(&self) -> &str {
        match *self {
            Error::Transport(ref e) => TransportError::description(&e),
            Error::Protocol(ref e) => ProtocolError::description(&e),
            Error::Application(ref e) => ApplicationError::description(&e),
            Error::User(ref e) => e.description(),
        }
    }
}

impl Debug for Error {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        match *self {
            Error::Transport(ref e) => Debug::fmt(&e, f),
            Error::Protocol(ref e) => Debug::fmt(&e, f),
            Error::Application(ref e) => Debug::fmt(&e, f),
            Error::User(ref e) => Debug::fmt(&e, f),
        }
    }
}

impl Display for Error {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        match *self {
            Error::Transport(ref e) => Display::fmt(&e, f),
            Error::Protocol(ref e) => Display::fmt(&e, f),
            Error::Application(ref e) => Display::fmt(&e, f),
            Error::User(ref e) => Display::fmt(&e, f),
        }
    }
}

impl From<String> for Error {
    fn from(s: String) -> Self {
       Error::Application(
           ApplicationError {
               kind: ApplicationErrorKind::Unknown,
               message: s,
           }
       )
    }
}

impl<'a> From<&'a str> for Error {
    fn from(s: &'a str) -> Self {
       Error::Application(
           ApplicationError {
               kind: ApplicationErrorKind::Unknown,
               message: String::from(s),
           }
       )
    }
}

impl From<TransportError> for Error {
    fn from(e: TransportError) -> Self {
       Error::Transport(e)
    }
}

impl From<ProtocolError> for Error {
    fn from(e: ProtocolError) -> Self {
       Error::Protocol(e)
    }
}

impl From<ApplicationError> for Error {
    fn from(e: ApplicationError) -> Self {
       Error::Application(e)
    }
}

/// Encodes information about I/O errors encountered within the rift library.
#[derive(Debug)]
pub struct TransportError {
    /// Specific I/O error kind.
    ///
    /// If a specific `TransportErrorKind` does not apply use
    /// `TransportErrorKind::Unknown`.
    pub kind: TransportErrorKind,
    /// Human-readable error message.
    pub message: String,
}

impl TransportError {
    /// Convenience constructor to create a new `TransportError` instance.
    pub fn new<S: Into<String>>(kind: TransportErrorKind, message: S) -> TransportError {
        TransportError { kind: kind, message: message.into() }
    }
}

/// A list specifying general categories of I/O error.
///
/// This list may grow, and it is not recommended to match against it.
#[derive(Clone, Copy, Eq, Debug, PartialEq)]
pub enum TransportErrorKind {
    /// Catch-all I/O error.
    Unknown      = 0,
    /// An I/O operation was attempted when the transport channel was not open.
    NotOpen      = 1,
    /// The transport channel cannot be opened because it was opened previously.
    AlreadyOpen  = 2,
    /// An I/O operation timed out.
    TimedOut     = 3,
    /// A read could not complete because no bytes were available.
    EndOfFile    = 4,
    /// An invalid (buffer/message) size was requested or received.
    NegativeSize = 5 ,
    /// Too large a buffer or message size was requested or received.
    SizeLimit    = 6,
}

impl TransportError {
    fn description(&self) -> &str {
        match self.kind {
            TransportErrorKind::Unknown => "transport error",
            TransportErrorKind::NotOpen => "not open",
            TransportErrorKind::AlreadyOpen => "already open",
            TransportErrorKind::TimedOut => "timed out",
            TransportErrorKind::EndOfFile => "end of file",
            TransportErrorKind::NegativeSize => "negative size message",
            TransportErrorKind::SizeLimit => "message too long",
        }
    }
}

impl Display for TransportError {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        write!(f, "{}", self.description())
    }
}

impl TryFrom<i32> for TransportErrorKind {
    type Err = Error;
    fn try_from(from: i32) -> Result<Self, Self::Err> {
        match from {
            0 => Ok(TransportErrorKind::Unknown),
            1 => Ok(TransportErrorKind::NotOpen),
            2 => Ok(TransportErrorKind::AlreadyOpen),
            3 => Ok(TransportErrorKind::TimedOut),
            4 => Ok(TransportErrorKind::EndOfFile),
            5 => Ok(TransportErrorKind::NegativeSize),
            6 => Ok(TransportErrorKind::SizeLimit),
            _ => Err(
                Error::Protocol(
                    ProtocolError {
                        kind: ProtocolErrorKind::Unknown,
                        message: format!("cannot convert {} to TransportErrorKind", from)
                    }
                )
            )
        }
    }
}

impl From<io::Error> for Error {
    fn from(err: io::Error) -> Self {
        match err.kind() {
            io::ErrorKind::ConnectionReset | io::ErrorKind::ConnectionRefused | io::ErrorKind::NotConnected => Error::Transport(
                TransportError {
                    kind: TransportErrorKind::NotOpen,
                    message: err.description().to_owned(),
                }
            ),
            io::ErrorKind::AlreadyExists => Error::Transport(
                TransportError {
                    kind: TransportErrorKind::AlreadyOpen,
                    message: err.description().to_owned(),
                }
            ),
            io::ErrorKind::TimedOut => Error::Transport(
                TransportError {
                    kind: TransportErrorKind::TimedOut,
                    message: err.description().to_owned(),
                }
            ),
            io::ErrorKind::UnexpectedEof => Error::Transport(
                TransportError {
                    kind: TransportErrorKind::EndOfFile,
                    message: err.description().to_owned(),
                }
            ),
            _ => Error::Transport(
                TransportError {
                    kind: TransportErrorKind::Unknown,
                    message: err.description().to_owned(), // FIXME: use io error's debug string
                }
            ),
        }
    }
}

impl From<string::FromUtf8Error> for Error {
    fn from(err: string::FromUtf8Error) -> Self {
        Error::Protocol(
            ProtocolError {
                kind: ProtocolErrorKind::InvalidData,
                message: err.description().to_owned(), // FIXME: use fmt::Error's debug string
            }
        )
    }
}

/// Encodes information about errors encountered within rift library code.
#[derive(Debug)]
pub struct ProtocolError {
    /// Specific Thrift protocol error kind.
    ///
    /// If a specific `ProtocolErrorKind` does not apply use
    /// `ProtocolErrorKind::Unknown`.
    pub kind: ProtocolErrorKind,
    /// Human-readable error message.
    pub message: String,
}

impl ProtocolError {
    /// Convenience constructor to create a new `ProtocolError` instance.
    pub fn new<S: Into<String>>(kind: ProtocolErrorKind, message: S) -> ProtocolError {
        ProtocolError { kind: kind, message: message.into() }
    }
}

/// A list specifying general categories of rift library error.
///
/// This list may grow, and it is not recommended to match against it.
#[derive(Clone, Copy, Eq, Debug, PartialEq)]
pub enum ProtocolErrorKind {
    /// Catch-all library error.
    Unknown        = 0,
    /// An invalid argument was supplied to a library function, or invalid data
    /// was received from the remote Thrift service endpoint.
    InvalidData    = 1,
    /// An invalid size was received in a protocol-encoding field.
    NegativeSize   = 2,
    /// A Thrift message or field was too long.
    SizeLimit      = 3,
    /// Unsupported or unknown Thrift protocol version.
    BadVersion     = 4,
    /// A thrift protocol type, server type, or field type is unsupported.
    NotImplemented = 5,
    /// Reached the maximum nested depth to which an unknown field or container
    /// value could be skipped.
    DepthLimit     = 6,
}

impl ProtocolError {
    fn description(&self) -> &str {
        match self.kind {
            ProtocolErrorKind::Unknown => "protocol error",
            ProtocolErrorKind::InvalidData => "bad data",
            ProtocolErrorKind::NegativeSize => "negative message size",
            ProtocolErrorKind::SizeLimit => "message too long",
            ProtocolErrorKind::BadVersion => "invalid thrift version",
            ProtocolErrorKind::NotImplemented => "not implemented",
            ProtocolErrorKind::DepthLimit => "maximum skip depth reached",
        }
    }
}

impl Display for ProtocolError {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        write!(f, "{}", self.description())
    }
}

impl TryFrom<i32> for ProtocolErrorKind {
    type Err = Error;
    fn try_from(from: i32) -> Result<Self, Self::Err> {
        match from {
            0 => Ok(ProtocolErrorKind::Unknown),
            1 => Ok(ProtocolErrorKind::InvalidData),
            2 => Ok(ProtocolErrorKind::NegativeSize),
            3 => Ok(ProtocolErrorKind::SizeLimit),
            4 => Ok(ProtocolErrorKind::BadVersion),
            5 => Ok(ProtocolErrorKind::NotImplemented),
            6 => Ok(ProtocolErrorKind::DepthLimit),
            _ => Err(
                Error::Protocol(
                    ProtocolError {
                        kind: ProtocolErrorKind::Unknown,
                        message: format!("cannot convert {} to ProtocolErrorKind", from)
                    }
                )
            )
        }
    }
}

/// Encodes information about errors encountered within auto-generated code
/// or within the user-implemented service handlers.
#[derive(Debug)]
pub struct ApplicationError {
    /// Specific Thrift application error kind.
    ///
    /// If a specific `ApplicationErrorKind` does not apply use
    /// `ApplicationErrorKind::Unknown`.
    pub kind: ApplicationErrorKind,
    /// Human-readable error message.
    pub message: String,
}

impl ApplicationError {
    /// Convenience constructor to create a new `ApplicationError` instance.
    pub fn new<S: Into<String>>(kind: ApplicationErrorKind, message: S) -> ApplicationError {
        ApplicationError { kind: kind, message: message.into() }
    }
}

/// A list specifying general categories of application error.
///
/// This list may grow, and it is not recommended to match against it.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum ApplicationErrorKind {
    /// Catch-all application error.
    Unknown               = 0,
    /// Service call made to/for an unknown service method.
    UnknownMethod         = 1,
    /// Received an unknown Thrift message type. That is, not one of the
    /// variants specified in `rift::protocol::TMessageType`.
    InvalidMessageType    = 2,
    /// Incoming Thrift reply does not specify the correct method name for the
    /// service call it's replying to.
    WrongMethodName       = 3,
    /// Auto-generated code received an out-of-order Thrift message.
    BadSequenceId         = 4,
    MissingResult         = 5,
    /// Auto-generated code failed unexpectedly.
    InternalError         = 6,
    /// Generic Thrift protocol error. When possible use `ProtocolError` with
    /// a specific `ProtocolErrorKind` instead.
    ProtocolError         = 7,
    /// Unknown. Only for compatibility with existing Thrift implementations.
    InvalidTransform      = 8, // ??
    /// Remote Thrift service endpoint requested, or is using, an unsupported
    /// wire encoding.
    InvalidProtocol       = 9, // ??
    /// Remote Thrift service endpoint requested, or is using, an unsupported
    /// auto-generated client type.
    UnsupportedClientType = 10, // ??
}

impl ApplicationError {
    fn description(&self) -> &str {
        match self.kind {
            ApplicationErrorKind::Unknown => "service error",
            ApplicationErrorKind::UnknownMethod => "unknown service method",
            ApplicationErrorKind::InvalidMessageType => "wrong message type received",
            ApplicationErrorKind::WrongMethodName => "unknown method reply received",
            ApplicationErrorKind::BadSequenceId => "out of order sequence id",
            ApplicationErrorKind::MissingResult => "missing method result",
            ApplicationErrorKind::InternalError => "remote service threw exception",
            ApplicationErrorKind::ProtocolError => "protocol error",
            ApplicationErrorKind::InvalidTransform => "invalid transform",
            ApplicationErrorKind::InvalidProtocol => "invalid protocol requested",
            ApplicationErrorKind::UnsupportedClientType => "unsupported protocol client",
        }
    }
}

impl Display for ApplicationError {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        write!(f, "{}", self.description())
    }
}

impl TryFrom<i32> for ApplicationErrorKind {
    type Err = Error;
    fn try_from(from: i32) -> Result<Self, Self::Err> {
        match from {
            0 => Ok(ApplicationErrorKind::Unknown),
            1 => Ok(ApplicationErrorKind::UnknownMethod),
            2 => Ok(ApplicationErrorKind::InvalidMessageType),
            3 => Ok(ApplicationErrorKind::WrongMethodName),
            4 => Ok(ApplicationErrorKind::BadSequenceId),
            5 => Ok(ApplicationErrorKind::MissingResult),
            6 => Ok(ApplicationErrorKind::InternalError),
            7 => Ok(ApplicationErrorKind::ProtocolError),
            8 => Ok(ApplicationErrorKind::InvalidTransform),
            9 => Ok(ApplicationErrorKind::InvalidProtocol),
            10 => Ok(ApplicationErrorKind::UnsupportedClientType),
            _ => Err(
                Error::Application(
                    ApplicationError {
                        kind: ApplicationErrorKind::Unknown,
                        message: format!("cannot convert {} to ApplicationErrorKind", from)
                    }
                )
            )
        }
    }
}