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use std::fmt;
use hyper::Error as HyperError;
use hyper::error::ParseError;
use std::error::Error as StdError;
use std::io;
use std::collections::HashMap;
use serde_json;
use serde_json::Error as JsonError;

use self::Error::{Json, Http, Io, Query, Url};

#[derive(Debug)]
pub enum Error {
    Json(serde_json::Error),
    Http(HyperError),
    Url(ParseError),
    Io(io::Error),
    Query { error: String, description: String },
}

impl Error {
    pub fn from_couch(msg: &str) -> Error {
        let convert = match serde_json::from_str::<HashMap<String, String>>(msg) {
            Ok(map) => map,
            Err(e) => return Json(e),
        };

        let err = match convert.get("error") {
            Some(msg) => msg.to_string(),
            None => "Unknown".to_string(),
        };

        let description = match convert.get("reason") {
            Some(msg) => msg.to_string(),
            None => "unknown reason".to_string(),
        };

        Query {
            error: err,
            description: description,
        }
    }
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Json(ref e) => write!(f, "{}", e),
            Http(ref e) => write!(f, "{}", e),
            Io(ref e) => write!(f, "{}", e),
            Url(ref e) => write!(f, "{}", e),
            Query { ref error, ref description } => write!(f, "{}:{}", error, description),
        }
    }
}

impl StdError for Error {
    fn description(&self) -> &str {
        match *self {
            Json(ref e) => e.description(),
            Http(ref e) => e.description(),
            Io(ref e) => e.description(),
            Url(ref e) => e.description(),
            Query { .. } => "CouchDB responded with an error",
        }
    }

    fn cause(&self) -> Option<&StdError> {
        match *self {
            Json(ref e) => Some(e),
            Http(ref e) => Some(e),
            Io(ref e) => Some(e),
            Url(ref e) => Some(e),
            Query { .. } => None,
        }
    }
}


impl From<HyperError> for Error {
    fn from(err: HyperError) -> Error {
        Http(err)
    }
}

impl From<ParseError> for Error {
    fn from(err: ParseError) -> Error {
        Url(err)
    }
}

impl From<JsonError> for Error {
    fn from(err: JsonError) -> Error {
        Json(err)
    }
}

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

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn from_couch_warns_on_json_parse_error() {
        match Error::from_couch("This will not parse") {
            Json(_) => assert!(true),
            _ => panic!("I was expecting a Json error!"),
        }
    }

    #[test]
    fn from_couch_returns_parsed_json_error() {
        let str = "{\"error\":\"not_found\",\"reason\":\"Database does not exist.\"}";
        match Error::from_couch(str) {
            Query { ref error, .. } => assert_eq!(error, "not_found"),
            _ => panic!("I was expecting query error"),

        }
    }

    #[test]
    fn from_couch_works_with_different_hashmap_values() {
        let str = "{\"oops\":\"not_found\",\"what_happened\":\"Database does not exist.\"}";
        match Error::from_couch(str) {
            Query { ref error, ref description } => {
                assert_eq!(error, "Unknown");
                assert_eq!(description, "unknown reason");
            }
            _ => panic!("I was expecting query error"),
        }
    }
}