use std::fmt;
use std::error::Error as StdError;
use reqwest::Error as ReqError;
use serde::{
    Serialize,
    Deserialize
};

pub type BoxError = Box<(dyn StdError + Send + Sync + 'static)>;
pub type UResult<T> = std::result::Result<T, UError>;

#[derive(Serialize, Deserialize, Clone, Debug)]
pub enum UErrType {
    ConnectionError,
    ParseError,
    JobError,
    Unknown,
    Raw(String)
}

#[derive(Serialize, Deserialize, Clone, Debug)]
struct Inner {
    err_type: UErrType,
    source: Option<BoxError>
}

#[derive(Serialize, Deserialize, Clone)]
pub struct UError {
    inner: Box<Inner>
}

impl UError {
    pub fn new<E: Into<BoxError>>(err_type: UErrType, source: Option<E>) -> Self {
        Self {
            inner: Box::new(Inner {
                source: source.map(Into::into),
                err_type
            })
        }
    }
}

impl fmt::Debug for UError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let mut builder = f.debug_struct("errors::UError");

        builder.field("kind", &self.inner.err_type);

        if let Some(ref source) = self.inner.source {
            builder.field("source", source);
        }

        builder.finish()
    }
}

impl fmt::Display for UError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let e_type = match self.inner.err_type {
            UErrType::Raw(ref msg) => msg,
            UErrType::ConnectionError => "Connection error",
            UErrType::ParseError => "Parse error",
            UErrType::JobError => "Job error",
            UErrType::Unknown => "Unknown error",
        };
        f.write_str(e_type)?;

        if let Some(ref e) = self.inner.source {
            write!(f, ": {}", e)
        } else {
            Ok(())
        }
    }
}

impl From<ReqError> for UError {
    fn from(e: ReqError) -> Self {
        let err_type = if e.is_request() {
            UErrType::ConnectionError
        } else if e.is_decode() {
            UErrType::ParseError
        } else {
            UErrType::Unknown
        };
        UError::new(err_type, Some(e))
    }
}