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// Copyright (c) 2015-2017 Georg Brandl.  Licensed under the Apache License,
// Version 2.0 <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0>
// or the MIT license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at
// your option. This file may not be copied, modified, or distributed except
// according to those terms.

//! Error objects and codes

use std::fmt;
use std::io;
use std::error;
use std::result;
use serde::{ser, de};

#[derive(Clone, PartialEq, Debug)]
pub enum ErrorCode {
    /// Unsupported opcode
    Unsupported(char),
    /// EOF while parsing op argument
    EOFWhileParsing,
    /// Stack underflowed
    StackUnderflow,
    /// Length prefix found negative
    NegativeLength,
    /// String decoding as UTF-8 failed
    StringNotUTF8,
    /// Wrong stack top type for opcode
    InvalidStackTop(&'static str, String),
    /// Value not hashable, but used as dict key or set item
    ValueNotHashable,
    /// Recursive structure found, which we don't support
    Recursive,
    /// A "module global" reference wasn't resolved by REDUCE
    UnresolvedGlobal,
    /// A "module global" isn't supported
    UnsupportedGlobal(Vec<u8>, Vec<u8>),
    /// A value was missing from the memo
    MissingMemo(u32),
    /// Invalid literal found
    InvalidLiteral(Vec<u8>),
    /// Found trailing bytes after STOP opcode
    TrailingBytes,
    /// Invalid value in pickle stream
    InvalidValue(String),
    /// Structure deserialization error (e.g., unknown variant)
    Structure(String),
}

impl fmt::Display for ErrorCode {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            ErrorCode::Unsupported(ch) => write!(fmt, "unsupported opcode {:?}", ch),
            ErrorCode::EOFWhileParsing => write!(fmt, "EOF while parsing"),
            ErrorCode::StackUnderflow => write!(fmt, "pickle stack underflow"),
            ErrorCode::NegativeLength => write!(fmt, "negative length prefix"),
            ErrorCode::StringNotUTF8 => write!(fmt, "string is not UTF-8 encoded"),
            ErrorCode::InvalidStackTop(what, ref it) =>
                write!(fmt, "invalid stack top, expected {}, got {}", what, it),
            ErrorCode::ValueNotHashable => write!(fmt, "dict key or set item not hashable"),
            ErrorCode::Recursive => write!(fmt, "recursive structure found"),
            ErrorCode::UnresolvedGlobal => write!(fmt, "unresolved global reference"),
            ErrorCode::UnsupportedGlobal(ref m, ref g) =>
                write!(fmt, "unsupported global: {}.{}",
                       String::from_utf8_lossy(m), String::from_utf8_lossy(g)),
            ErrorCode::MissingMemo(n) => write!(fmt, "missing memo with id {}", n),
            ErrorCode::InvalidLiteral(ref l) =>
                write!(fmt, "literal is invalid: {}", String::from_utf8_lossy(l)),
            ErrorCode::TrailingBytes => write!(fmt, "trailing bytes found"),
            ErrorCode::InvalidValue(ref s) => write!(fmt, "invalid value: {}", s),
            ErrorCode::Structure(ref s) => fmt.write_str(s),
        }
    }
}

/// This type represents all possible errors that can occur when serializing or
/// deserializing a value.
#[derive(Debug)]
pub enum Error {
    /// Some IO error occurred when serializing or deserializing a value.
    Io(io::Error),
    /// The pickle had some error while interpreting.
    Eval(ErrorCode, usize),
    /// Syntax error while transforming into Rust values.
    Syntax(ErrorCode),
}

impl From<io::Error> for Error {
    fn from(error: io::Error) -> Error {
        Error::Io(error)
    }
}

pub type Result<T> = result::Result<T, Error>;

impl fmt::Display for Error {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Error::Io(ref error) => error.fmt(fmt),
            Error::Eval(ref code, offset) => write!(fmt, "eval error at offset {}: {}",
                                                    offset, code),
            Error::Syntax(ref code) => write!(fmt, "decoding error: {}", code)
        }
    }
}

impl error::Error for Error {
    fn description(&self) -> &str {
        match *self {
            Error::Io(ref error) => error::Error::description(error),
            Error::Eval(..) => "pickle eval error",
            Error::Syntax(..) => "serde decoding error",
        }
    }
}

impl de::Error for Error {
    fn custom<T: fmt::Display>(msg: T) -> Error {
        Error::Syntax(ErrorCode::Structure(msg.to_string()))
    }
}

impl ser::Error for Error {
    fn custom<T: fmt::Display>(msg: T) -> Error {
        Error::Syntax(ErrorCode::Structure(msg.to_string()))
    }
}