use async_std::path::PathBuf;
use std::{error::Error, fmt};

#[derive(Debug)]
pub enum ErrorCode {
    Undefined(String),
    // Read Write Errors
    CorruptFile,
    // Data Type Errors
    DataTypeIncorrect(String),
    // Entry Errors
    EntryExists(PathBuf),
    EntryWriteFailure(PathBuf),
    EntryReadFailure(PathBuf),
    EntryDeleteFailure(PathBuf),
    // Cache
    CacheReadWrite,
}

impl fmt::Display for ErrorCode {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            ErrorCode::Undefined(msg) => write!(f, "{}", msg),
            ErrorCode::DataTypeIncorrect(dtype) => write!(f, "data type '{}' is not valid", dtype),
            ErrorCode::CorruptFile => write!(f, "corrupt file"),
            ErrorCode::EntryExists(path) => write!(
                f,
                "entry '{}' already exists",
                path.file_name().unwrap().to_str().unwrap()
            ),
            ErrorCode::EntryWriteFailure(path) => write!(
                f,
                "entry '{}' write failure",
                path.file_name().unwrap().to_str().unwrap()
            ),
            ErrorCode::EntryReadFailure(path) => write!(
                f,
                "entry '{}' read failure",
                path.file_name().unwrap().to_str().unwrap()
            ),
            ErrorCode::EntryDeleteFailure(path) => write!(
                f,
                "entry '{}' delete failure",
                path.file_name().unwrap().to_str().unwrap()
            ),
            ErrorCode::CacheReadWrite => write!(f, "cache read write"),
        }
    }
}

#[derive(Debug)]
pub struct DBError {
    pub code: ErrorCode,
    src: Option<Box<dyn Error + 'static>>,
}

impl DBError {
    pub fn new<S>(msg: S) -> Self
    where
        S: Into<String>,
    {
        Self {
            code: ErrorCode::Undefined(msg.into()),
            src: None,
        }
    }

    pub fn from_code(code: ErrorCode) -> Self {
        Self {
            code: code,
            src: None,
        }
    }

    pub fn add_source<E>(&mut self, src: E)
    where
        E: Error + 'static,
    {
        self.src = Some(Box::new(src));
    }
}

impl Error for DBError {
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        match &self.src {
            Some(err) => Some(err.as_ref()),
            None => None,
        }
    }
}

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

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

    #[test]
    fn with_str() {
        let msg = "something happened";
        let err = DBError::new(msg);
        assert!(
            err.to_string() == msg,
            "Got: {} -- Want: {}",
            err.to_string(),
            msg
        );
        assert!(
            err.source().is_none(),
            "Error should initialize with no source."
        );
    }

    #[test]
    fn with_string() {
        let msg = "it went boom".to_string();
        let err = DBError::new(msg.clone());
        assert!(
            err.to_string() == msg,
            "Got: {} -- Want: {}",
            err.to_string(),
            msg
        );
        assert!(
            err.source().is_none(),
            "Error should initialize with no source."
        );
    }

    #[test]
    fn using_error_code() {
        let msg = "utter failure";
        let code = ErrorCode::Undefined(msg.to_string());
        let err = DBError::from_code(code);
        assert_eq!(err.to_string(), msg);
        assert!(err.source().is_none(), "Should be no source");
    }

    #[test]
    fn with_source() {
        let msg = "but this caused the problem";
        let mut par = DBError::new("parent error");
        let src = DBError::new(msg);
        par.add_source(src);
        let output = par.source();
        assert!(output.is_some(), "Should return source.");
        let source = output.unwrap();
        assert!(source.to_string() == msg);
    }
}

#[cfg(test)]
mod codes {
    use super::*;
    use async_std::path::PathBuf;

    const ITEMS: [&str; 2] = ["first", "second"];

    fn create_path_buffer() -> Vec<PathBuf> {
        let mut output = Vec::new();
        for item in ITEMS {
            let mut path = PathBuf::new();
            path.push("thepath");
            path.push(item);
            output.push(path);
        }
        output
    }

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

    #[test]
    fn incorrect_data_type() {
        for item in ITEMS {
            let err = ErrorCode::DataTypeIncorrect(item.to_string());
            assert_eq!(
                err.to_string(),
                format!("data type '{}' is not valid", item)
            );
        }
    }

    #[test]
    fn corrupt_file() {
        assert_eq!(ErrorCode::CorruptFile.to_string(), "corrupt file");
    }

    #[test]
    fn entry_exists() {
        for path in create_path_buffer() {
            let err = ErrorCode::EntryExists(path.clone());
            assert_eq!(
                err.to_string(),
                format!(
                    "entry '{}' already exists",
                    path.file_name().unwrap().to_str().unwrap()
                )
            );
        }
    }

    #[test]
    fn entry_write_failure() {
        for path in create_path_buffer() {
            let err = ErrorCode::EntryWriteFailure(path.clone());
            assert_eq!(
                err.to_string(),
                format!(
                    "entry '{}' write failure",
                    path.file_name().unwrap().to_str().unwrap()
                )
            );
        }
    }

    #[test]
    fn entry_read_failure() {
        for path in create_path_buffer() {
            let err = ErrorCode::EntryReadFailure(path.clone());
            assert_eq!(
                err.to_string(),
                format!(
                    "entry '{}' read failure",
                    path.file_name().unwrap().to_str().unwrap()
                )
            );
        }
    }

    #[test]
    fn entry_delete_failure() {
        for path in create_path_buffer() {
            let err = ErrorCode::EntryDeleteFailure(path.clone());
            assert_eq!(
                err.to_string(),
                format!(
                    "entry '{}' delete failure",
                    path.file_name().unwrap().to_str().unwrap()
                )
            );
        }
    }

    #[test]
    fn cache_read_write_failure() {
        let err = ErrorCode::CacheReadWrite;
        assert_eq!(err.to_string(), "cache read write");
    }
}