use axum::{
    Json,
    http::StatusCode,
    response::{IntoResponse, Response},
};
use serde_json::json;
use thiserror::Error;

pub type Result<T> = std::result::Result<T, AppError>;

#[derive(Error, Debug)]
pub enum AppError {
    #[error("Not Found: {0}")]
    NotFound(String),

    #[error("Forbidden: {0}")]
    Forbidden(String),

    #[error("Internal Server Error: {0}")]
    Internal(String),

    #[error("Bad Request: {0}")]
    BadRequest(String),

    #[error("Serialization Error: {0}")]
    JsonError(#[from] serde_json::Error),

    #[error("I/O Error: {0}")]
    IoError(#[from] std::io::Error),
}

impl From<AppError> for String {
    fn from(err: AppError) -> String {
        err.to_string()
    }
}

impl IntoResponse for AppError {
    fn into_response(self) -> Response {
        let (status, error_message) = match &self {
            AppError::NotFound(msg) => (StatusCode::NOT_FOUND, msg.clone()),
            AppError::Forbidden(msg) => (StatusCode::FORBIDDEN, msg.clone()),
            AppError::BadRequest(msg) => (StatusCode::BAD_REQUEST, msg.clone()),
            AppError::Internal(msg) => (StatusCode::INTERNAL_SERVER_ERROR, msg.clone()),
            AppError::JsonError(e) => (StatusCode::INTERNAL_SERVER_ERROR, format!("JSON Error: {}", e)),
            AppError::IoError(e) => (StatusCode::INTERNAL_SERVER_ERROR, format!("I/O Error: {}", e)),
        };

        let body = Json(json!({
            "error": error_message,
        }));

        (status, body).into_response()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use axum::http::StatusCode;
    use axum::response::IntoResponse;

    #[test]
    fn test_app_error_not_found() {
        let err = AppError::NotFound("item not found".into());
        let res = err.into_response();
        assert_eq!(res.status(), StatusCode::NOT_FOUND);
    }

    #[test]
    fn test_app_error_forbidden() {
        let err = AppError::Forbidden("access denied".into());
        let res = err.into_response();
        assert_eq!(res.status(), StatusCode::FORBIDDEN);
    }

    #[test]
    fn test_app_error_internal() {
        let err = AppError::Internal("db error".into());
        let res = err.into_response();
        assert_eq!(res.status(), StatusCode::INTERNAL_SERVER_ERROR);
    }

    #[test]
    fn test_app_error_bad_request() {
        let err = AppError::BadRequest("invalid json".into());
        let res = err.into_response();
        assert_eq!(res.status(), StatusCode::BAD_REQUEST);
    }

    #[test]
    fn test_app_error_display() {
        let err = AppError::NotFound("test".into());
        assert_eq!(err.to_string(), "Not Found: test");

        let err = AppError::Forbidden("test".into());
        assert_eq!(err.to_string(), "Forbidden: test");

        let err = AppError::Internal("test".into());
        assert_eq!(err.to_string(), "Internal Server Error: test");

        let err = AppError::BadRequest("test".into());
        assert_eq!(err.to_string(), "Bad Request: test");
    }
}

impl From<String> for AppError {
    fn from(msg: String) -> Self {
        AppError::Internal(msg)
    }
}

impl From<&str> for AppError {
    fn from(msg: &str) -> Self {
        AppError::Internal(msg.to_string())
    }
}