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// Copyright 2017 Jeremy Wall <jeremy@marzhillstudios.com>
//
//  Licensed 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.

//! Errors for use by the ucg compiler.
use std::error;
use std::fmt;

use ast::*;

use nom;

/// ErrorType defines the various types of errors that can result from compiling UCG into an
/// output format.
pub enum ErrorType {
    // Build Errors
    TypeFail,
    DuplicateBinding,
    IncompleteParsing,
    Unsupported,
    NoSuchSymbol,
    BadArgLen,
    FormatError,
    // Parsing Errors
    UnexpectedToken,
    EmptyExpression,
    ParseError,
}

impl fmt::Display for ErrorType {
    fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
        let name = match self {
            &ErrorType::TypeFail => "TypeFail",
            &ErrorType::DuplicateBinding => "DuplicateBinding",
            &ErrorType::IncompleteParsing => "IncompleteParsing",
            &ErrorType::Unsupported => "Unsupported",
            &ErrorType::NoSuchSymbol => "NoSuchSymbol",
            &ErrorType::BadArgLen => "BadArgLen",
            &ErrorType::FormatError => "FormatError",
            &ErrorType::UnexpectedToken => "UnexpectedToken",
            &ErrorType::EmptyExpression => "EmptyExpression",
            &ErrorType::ParseError => "ParseError",
        };
        w.write_str(name)
    }
}

/// Error defines an Error type for parsing and building UCG code.
pub struct Error {
    pub err_type: ErrorType,
    pub pos: Position,
    pub msg: String,
    pub cause: Option<Box<Error>>,
    _pkgonly: (),
}

impl Error {
    pub fn new<S: Into<String>>(msg: S, t: ErrorType, pos: Position) -> Self {
        Error {
            err_type: t,
            pos: pos,
            msg: msg.into(),
            cause: None,
            _pkgonly: (),
        }
    }

    pub fn new_with_cause<S: Into<String>>(msg: S, t: ErrorType, cause: Error) -> Self {
        let mut e = Self::new(msg, t, cause.pos.clone());
        e.cause = Some(Box::new(cause));
        return e;
    }

    pub fn new_with_errorkind<S: Into<String>>(
        msg: S,
        t: ErrorType,
        pos: Position,
        cause: nom::ErrorKind<Error>,
    ) -> Self {
        match cause {
            nom::ErrorKind::Custom(e) => Self::new_with_cause(msg, t, e),
            _ => Self::new(msg, t, pos),
        }
    }

    fn render(&self, w: &mut fmt::Formatter) -> fmt::Result {
        try!(write!(
            w,
            "{}: \"{}\" at line: {} column: {}",
            self.err_type, self.msg, self.pos.line, self.pos.column
        ));
        if let Some(ref cause) = self.cause {
            try!(write!(w, "\n\tCaused By: {}", cause));
        }
        Ok(())
    }
}

impl fmt::Debug for Error {
    fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
        self.render(w)
    }
}

impl fmt::Display for Error {
    fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
        self.render(w)
    }
}

impl error::Error for Error {
    fn description(&self) -> &str {
        &self.msg
    }
}