use std::{error::Error, fmt};

#[derive(Debug)]
pub enum ErrorCode {
    // General
    Undefined(String),
    // Cache
    IDNotFound(String),
}

impl fmt::Display for ErrorCode {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            ErrorCode::Undefined(msg) => write!(f, "{}", msg),
            ErrorCode::IDNotFound(id) => write!(f, "ID '{}' not found", id),
        }
    }
}

mod errorcodes {
    use super::*;

    const ITEMS: [&str; 2] = ["one", "two"];

    #[test]
    fn undefined_display() {
        for item in ITEMS {
            let err = ErrorCode::Undefined(item.to_string());
            assert_eq!(err.to_string(), item);
        }
    }

    #[test]
    fn cache_missing() {
        for item in ITEMS {
            let err = ErrorCode::IDNotFound(item.to_string());
            assert_eq!(err.to_string(), format!("ID '{}' not found", item));
        }
    }
}

#[derive(Debug)]
pub struct MTTError {
    pub code: ErrorCode,
}

impl MTTError {
    pub fn new<S>(msg: S) -> Self
    where
        S: Into<String>,
    {
        let text = msg.into();
        Self {
            code: ErrorCode::Undefined(text),
        }
    }

    pub fn from_code(code: ErrorCode) -> Self {
        Self { code: code }
    }
}

impl Error for MTTError {}

impl fmt::Display for MTTError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.code)
    }
}

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

    #[test]
    fn create_with_str() {
        let msgs = ["one", "two"];
        for msg in msgs {
            let err = MTTError::new(msg);
            assert_eq!(err.to_string(), msg);
        }
    }

    #[test]
    fn create_with_string() {
        let msg = "three";
        let err = MTTError::new(msg.to_string());
        assert_eq!(err.to_string(), msg);
    }

    #[test]
    fn create_from_code() {
        let code = ErrorCode::Undefined("oops".to_string());
        let err = MTTError::from_code(code);
        match err.code {
            ErrorCode::Undefined(_) => (),
            _ => assert!(false, "{:?} is not undefined", err.code),
        }
    }

    #[test]
    fn create_missing_id_from_code() {
        let code = ErrorCode::IDNotFound("123".to_string());
        let err = MTTError::from_code(code);
        match err.code {
            ErrorCode::IDNotFound(_) => (),
            _ => assert!(false, "{:?} is not undefined", err.code),
        }
    }
}