use axum::http::StatusCode;
use axum::response::{IntoResponse, Response};

/// Errors from individual volume HTTP requests — used for logging, not HTTP responses.
#[derive(Debug)]
pub enum VolumeError {
    Request { url: String, source: reqwest::Error },
    BadStatus { url: String, status: reqwest::StatusCode },
}

impl std::fmt::Display for VolumeError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            VolumeError::Request { url, source } => {
                write!(f, "volume request to {url} failed: {source}")
            }
            VolumeError::BadStatus { url, status } => {
                write!(f, "volume {url} returned status {status}")
            }
        }
    }
}

/// Application-level errors that map to HTTP responses.
#[derive(Debug)]
pub enum AppError {
    NotFound,
    CorruptRecord { key: String },
    Db(rusqlite::Error),
    InsufficientVolumes { need: usize, have: usize },
    PartialWrite,
}

impl From<rusqlite::Error> for AppError {
    fn from(e: rusqlite::Error) -> Self {
        match e {
            rusqlite::Error::QueryReturnedNoRows => AppError::NotFound,
            other => AppError::Db(other),
        }
    }
}

impl std::fmt::Display for AppError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            AppError::NotFound => write!(f, "not found"),
            AppError::CorruptRecord { key } => {
                write!(f, "corrupt record for key {key}: no volumes")
            }
            AppError::Db(e) => write!(f, "database error: {e}"),
            AppError::InsufficientVolumes { need, have } => {
                write!(f, "need {need} volumes but only {have} available")
            }
            AppError::PartialWrite => write!(f, "not all volume writes succeeded"),
        }
    }
}

impl IntoResponse for AppError {
    fn into_response(self) -> Response {
        let status = match &self {
            AppError::NotFound => StatusCode::NOT_FOUND,
            AppError::CorruptRecord { .. } => StatusCode::INTERNAL_SERVER_ERROR,
            AppError::Db(_) => StatusCode::INTERNAL_SERVER_ERROR,
            AppError::InsufficientVolumes { .. } => StatusCode::SERVICE_UNAVAILABLE,
            AppError::PartialWrite => StatusCode::BAD_GATEWAY,
        };
        (status, self.to_string()).into_response()
    }
}