use axum::{
    Json,
    http::StatusCode,
    response::{IntoResponse, Response},
};
use serde::Serialize;
use utoipa::{IntoResponses, ToSchema};

#[derive(Debug, thiserror::Error)]
pub enum ApiError {
    #[error("{0}")]
    BadRequest(String),
    #[error("authentication is required")]
    Unauthorized,
    #[error("resource not found")]
    NotFound,
    #[error("database has not been configured")]
    DatabaseUnavailable,
    #[error("{0}")]
    ServiceUnavailable(String),
    #[error("internal server error")]
    Internal,
}

/// API 错误响应。
#[derive(Serialize, ToSchema)]
#[schema(example = json!({"error": "resource not found"}))]
pub struct ErrorBody {
    /// 面向调用方的错误信息。
    pub error: String,
}

/// 所有需要数据库和临时用户身份的业务接口都可能返回的公共错误。
#[allow(dead_code)]
#[derive(IntoResponses)]
pub enum CommonApiErrors {
    /// 参数格式或业务校验失败。
    #[response(
        status = 400,
        description = "请求参数无效",
        example = json!({"error": "X-User-Id must be a UUID"})
    )]
    BadRequest(ErrorBody),
    /// 缺少 `X-User-Id` 请求头。
    #[response(
        status = 401,
        description = "缺少开发阶段身份请求头",
        example = json!({"error": "authentication is required"})
    )]
    Unauthorized(ErrorBody),
    /// 服务未配置数据库连接。
    #[response(
        status = 503,
        description = "未配置 DATABASE_URL",
        example = json!({"error": "database has not been configured"})
    )]
    DatabaseUnavailable(ErrorBody),
    /// 数据库查询或服务内部处理失败。
    #[response(
        status = 500,
        description = "服务内部错误",
        example = json!({"error": "internal server error"})
    )]
    Internal(ErrorBody),
}

impl IntoResponse for ApiError {
    fn into_response(self) -> Response {
        let (status, message) = match self {
            Self::BadRequest(message) => (StatusCode::BAD_REQUEST, message),
            Self::Unauthorized => (
                StatusCode::UNAUTHORIZED,
                "authentication is required".to_owned(),
            ),
            Self::NotFound => (StatusCode::NOT_FOUND, "resource not found".to_owned()),
            Self::DatabaseUnavailable => (
                StatusCode::SERVICE_UNAVAILABLE,
                "database has not been configured".to_owned(),
            ),
            Self::ServiceUnavailable(message) => (StatusCode::SERVICE_UNAVAILABLE, message),
            Self::Internal => (
                StatusCode::INTERNAL_SERVER_ERROR,
                "internal server error".to_owned(),
            ),
        };

        (status, Json(ErrorBody { error: message })).into_response()
    }
}

impl From<sqlx::Error> for ApiError {
    fn from(error: sqlx::Error) -> Self {
        tracing::error!(?error, "database query failed");
        Self::Internal
    }
}