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use std;
use std::str;
use std::io;
use std::fmt;
use std::string;
use std::error;

use serde_json;

/// Represents results from this library
pub type Result<T> = std::result::Result<T, Error>;

/// Represents different failure cases
#[derive(Debug)]
pub enum Error {
    /// a std::io error
    Io(io::Error),
    /// a std::str::Utf8Error
    Utf8(str::Utf8Error),
    /// a JSON parsing related failure
    BadJson(usize, usize, String),
    /// a VLQ string was malformed and data was left over
    VlqLeftover,
    /// a VLQ string was empty and no values could be decoded.
    VlqNoValues,
    /// a mapping segment had an unsupported size
    BadSegmentSize(u32),
    /// a reference to a non existing source was encountered
    BadSourceReference(u32),
    /// a reference to a non existing name was encountered
    BadNameReference(u32),
    /// Indicates that an indexed sourcemap was encountered when
    /// a regular sourcemap was expected
    IndexedSourcemap,
    /// Indicates that an regular (non-indexed) sourcemap was when
    /// a sourcemap index was expected
    RegularSourcemap,
    /// Indicates an invalid data URL
    InvalidDataUrl,
    /// Flatten failed
    CannotFlatten(String),
}

impl Error {

    /// If the error originated in a JSON file that can be located, then
    /// this method returns that location.
    pub fn source_location(&self) -> Option<(usize, usize)> {
        match *self {
            Error::BadJson(lineno, col, _) => Some((lineno, col)),
            _ => None,
        }
    }
}


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

impl From<string::FromUtf8Error> for Error {
    fn from(err: string::FromUtf8Error) -> Error {
        From::from(err.utf8_error())
    }
}

impl From<str::Utf8Error> for Error {
    fn from(err: str::Utf8Error) -> Error {
        Error::Utf8(err)
    }
}

impl From<serde_json::Error> for Error {
    fn from(err: serde_json::Error) -> Error {
        use serde_json::Error::*;
        match err {
            Io(err) => From::from(err),
            Syntax(code, line, col) => {
                Error::BadJson(line, col, format!("{:?}", code))
            }
        }
    }
}

impl error::Error for Error {
    fn description(&self) -> &str {
        use Error::*;
        match *self {
            Io(ref err) => err.description(),
            Utf8(ref err) => err.description(),
            BadJson(_, _, _) => "bad json",
            VlqLeftover => "vlq leftover",
            VlqNoValues => "no vlq values",
            BadSegmentSize(_) => "bad segment size",
            BadSourceReference(_) => "bad source reference",
            BadNameReference(_) => "bad name reference",
            IndexedSourcemap => "unexpected indexed sourcemap",
            RegularSourcemap => "unexpected sourcemap",
            InvalidDataUrl => "invalid data URL",
            CannotFlatten(_) => "cannot flatten the given indexed sourcemap",
        }
    }

    fn cause(&self) -> Option<&error::Error> {
        use Error::*;
        match *self {
            Io(ref err) => Some(&*err),
            Utf8(ref err) => Some(&*err),
            _ => None,
        }
    }
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        use Error::*;
        match *self {
            Io(ref msg) => write!(f, "{}", msg),
            Utf8(ref msg) => write!(f, "{}", msg),
            BadJson(line, col, ref msg) => write!(f, "bad json in line {}, column {}: {}", line, col, msg),
            VlqLeftover => write!(f, "leftover cur/shift in vlq decode"),
            VlqNoValues => write!(f, "vlq decode did not produce any values"),
            BadSegmentSize(size) => write!(f, "got {} segments, expected 4 or 5", size),
            BadSourceReference(id) => write!(f, "bad reference to source #{}", id),
            BadNameReference(id) => write!(f, "bad reference to name #{}", id),
            IndexedSourcemap => write!(f, "encountered unexpected indexed sourcemap"),
            RegularSourcemap => write!(f, "encountered unexpected sourcemap where index was expected"),
            InvalidDataUrl => write!(f, "the provided data URL is invalid"),
            CannotFlatten(ref msg) => write!(f, "cannot flatten the indexed sourcemap: {}", msg),
        }
    }
}