use std::fmt;

use axum::Json;
use axum::http::StatusCode;
use axum::response::{IntoResponse, Response};
use export::rest::{AppResponseData, NoData};
use utoipa::IntoResponses;

#[derive(Debug, thiserror::Error)]
pub enum CiError {
    #[error("invalid argument: {0}")]
    InvalidArgument(String),
    #[error("conflict: {0}")]
    Conflict(String),
    #[error("resource not found")]
    NotFound,
    #[error("unauthorized")]
    Unauthorized,
    #[error("forbidden")]
    Forbidden,
    #[error("git error: {0}")]
    Git(#[from] git::share::errors::GitError),
    #[error("storage error: {0}")]
    Storage(#[from] storage::StorageError),
    #[error("database error: {0}")]
    Db(#[from] sea_orm::DbErr),
    #[error("serialization error: {0}")]
    Serde(#[from] serde_json::Error),
    #[error("internal error: {0}")]
    Internal(String),
}

pub type CiResult<T> = Result<T, CiError>;

#[derive(Debug)]
pub enum CiApiError {
    BadRequest(String),
    Unauthorized,
    Forbidden,
    NotFound,
    Conflict(String),
    Internal(String),
}

impl fmt::Display for CiApiError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::BadRequest(message) => write!(f, "{message}"),
            Self::Unauthorized => write!(f, "unauthorized"),
            Self::Forbidden => write!(f, "forbidden"),
            Self::NotFound => write!(f, "not found"),
            Self::Conflict(message) => write!(f, "{message}"),
            Self::Internal(message) => write!(f, "{message}"),
        }
    }
}

impl std::error::Error for CiApiError {}

impl From<CiError> for CiApiError {
    fn from(error: CiError) -> Self {
        match error {
            CiError::NotFound => Self::NotFound,
            CiError::Unauthorized => Self::Unauthorized,
            CiError::Forbidden => Self::Forbidden,
            CiError::Conflict(msg) => Self::Conflict(msg),
            CiError::InvalidArgument(msg) => Self::BadRequest(msg),
            other => {
                tracing::warn!(error = %other, "ci handler failed");
                Self::Internal("internal server error".to_string())
            }
        }
    }
}

impl From<sea_orm::DbErr> for CiApiError {
    fn from(error: sea_orm::DbErr) -> Self {
        Self::Internal(format!("database error: {error}"))
    }
}

#[derive(Debug, IntoResponses)]
pub enum ApiError {
    #[response(status = 400, description = "request failed validation")]
    BadRequest(#[to_schema] Box<AppResponseData<NoData>>),
    #[response(status = 401, description = "authentication required")]
    Unauthorized(#[to_schema] Box<AppResponseData<NoData>>),
    #[response(status = 403, description = "operation not allowed")]
    Forbidden(#[to_schema] Box<AppResponseData<NoData>>),
    #[response(status = 404, description = "resource not found")]
    NotFound(#[to_schema] Box<AppResponseData<NoData>>),
    #[response(status = 409, description = "resource conflict")]
    Conflict(#[to_schema] Box<AppResponseData<NoData>>),
    #[response(status = 500, description = "internal server error")]
    Internal(#[to_schema] Box<AppResponseData<NoData>>),
}

impl ApiError {
    /// Boxes a plain envelope into the enum's payload. The box keeps
    /// `Result<T, ApiError>` small: an inline envelope is 128 bytes, which every
    /// handler return type would otherwise carry on the happy path too.
    fn envelope(code: i32, message: impl Into<String>) -> Box<AppResponseData<NoData>> {
        Box::new(AppResponseData::err(code, message))
    }

    pub fn bad_request(message: impl Into<String>) -> Self {
        Self::BadRequest(Self::envelope(400, message))
    }

    pub fn unauthorized() -> Self {
        Self::Unauthorized(Self::envelope(401, "unauthorized"))
    }

    pub fn forbidden() -> Self {
        Self::Forbidden(Self::envelope(403, "forbidden"))
    }

    pub fn not_found() -> Self {
        Self::NotFound(Self::envelope(404, "not found"))
    }

    pub fn conflict(message: impl Into<String>) -> Self {
        Self::Conflict(Self::envelope(409, message))
    }

    pub fn internal() -> Self {
        Self::Internal(Self::envelope(500, "internal server error"))
    }

    fn decompose(self) -> (u16, AppResponseData<NoData>) {
        match self {
            Self::BadRequest(envelope) => (400, *envelope),
            Self::Unauthorized(envelope) => (401, *envelope),
            Self::Forbidden(envelope) => (403, *envelope),
            Self::NotFound(envelope) => (404, *envelope),
            Self::Conflict(envelope) => (409, *envelope),
            Self::Internal(envelope) => (500, *envelope),
        }
    }
}

impl From<CiError> for ApiError {
    fn from(error: CiError) -> Self {
        Self::from(CiApiError::from(error))
    }
}

impl From<CiApiError> for ApiError {
    fn from(error: CiApiError) -> Self {
        match error {
            CiApiError::BadRequest(message) => Self::bad_request(message),
            CiApiError::Unauthorized => Self::unauthorized(),
            CiApiError::Forbidden => Self::forbidden(),
            CiApiError::NotFound => Self::not_found(),
            CiApiError::Conflict(message) => Self::conflict(message),
            CiApiError::Internal(message) => {
                tracing::warn!(message, "ci internal error");
                Self::internal()
            }
        }
    }
}

impl IntoResponse for ApiError {
    fn into_response(self) -> Response {
        let (code, envelope) = self.decompose();
        let status = StatusCode::from_u16(code).unwrap_or(StatusCode::INTERNAL_SERVER_ERROR);
        (status, Json(envelope)).into_response()
    }
}