use std::fmt;

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

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

impl fmt::Display for ChatError {
    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 ChatError {}

impl From<sea_orm::DbErr> for ChatError {
    fn from(error: sea_orm::DbErr) -> Self {
        if is_unique_violation(&error) {
            return Self::Conflict("resource already exists".to_string());
        }
        Self::Internal(format!("database error: {error}"))
    }
}

impl From<sea_orm::TransactionError<sea_orm::DbErr>> for ChatError {
    fn from(error: sea_orm::TransactionError<sea_orm::DbErr>) -> Self {
        match &error {
            sea_orm::TransactionError::Transaction(db_err) if is_unique_violation(db_err) => {
                Self::Conflict("resource already exists".to_string())
            }
            _ => Self::Internal(format!("database transaction error: {error}")),
        }
    }
}

impl From<sea_orm::TransactionError<ChatError>> for ChatError {
    fn from(error: sea_orm::TransactionError<ChatError>) -> Self {
        match error {
            sea_orm::TransactionError::Connection(db_err) => Self::from(db_err),
            sea_orm::TransactionError::Transaction(chat_err) => chat_err,
        }
    }
}

fn is_unique_violation(err: &sea_orm::DbErr) -> bool {
    let msg = err.to_string().to_lowercase();
    msg.contains("unique") || msg.contains("duplicate") || msg.contains("23505")
}

impl From<space::errors::SpaceError> for ChatError {
    fn from(error: space::errors::SpaceError) -> Self {
        match error {
            space::errors::SpaceError::BadRequest(msg) => Self::BadRequest(msg),
            space::errors::SpaceError::Unauthorized => Self::Unauthorized,
            space::errors::SpaceError::Forbidden => Self::Forbidden,
            space::errors::SpaceError::NotFound => Self::NotFound,
            space::errors::SpaceError::Conflict(msg) => Self::Conflict(msg),
            space::errors::SpaceError::Internal(msg) => Self::Internal(msg),
        }
    }
}

impl From<export::ExportError> for ChatError {
    fn from(error: export::ExportError) -> Self {
        Self::Internal(format!("infrastructure error: {error}"))
    }
}

impl From<storage::StorageError> for ChatError {
    fn from(error: storage::StorageError) -> Self {
        Self::Internal(format!("storage error: {error}"))
    }
}

impl From<redis::RedisError> for ChatError {
    fn from(error: redis::RedisError) -> Self {
        Self::Internal(format!("redis error: {error}"))
    }
}

impl From<serde_json::Error> for ChatError {
    fn from(error: serde_json::Error) -> Self {
        Self::BadRequest(format!("invalid payload: {error}"))
    }
}

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

impl ApiError {
    fn payload(code: i32, message: &'static str) -> AppResponseData<NoData> {
        AppResponseData::err(code, message)
    }

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

impl From<ChatError> for ApiError {
    fn from(error: ChatError) -> Self {
        match error {
            ChatError::BadRequest(msg) => Self::BadRequest(AppResponseData::err(400, msg)),
            ChatError::Unauthorized => Self::Unauthorized(Self::payload(401, "unauthorized")),
            ChatError::Forbidden => Self::Forbidden(Self::payload(403, "forbidden")),
            ChatError::NotFound => Self::NotFound(Self::payload(404, "not found")),
            ChatError::Conflict(msg) => Self::Conflict(AppResponseData::err(409, msg)),
            ChatError::Internal(message) => {
                tracing::warn!(error = %message, "chat handler failed");
                Self::Internal(Self::payload(500, "internal server error"))
            }
        }
    }
}

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

impl From<session::SessionError> for ApiError {
    fn from(error: session::SessionError) -> Self {
        match error {
            session::SessionError::Unauthorized => {
                Self::Unauthorized(Self::payload(401, "unauthorized"))
            }
            session::SessionError::Database(message) => {
                tracing::warn!(error = %message, "chat handler failed");
                Self::Internal(Self::payload(500, "internal server error"))
            }
        }
    }
}

impl From<PathRejection> for ApiError {
    fn from(_error: PathRejection) -> Self {
        Self::BadRequest(Self::payload(400, "bad request"))
    }
}

impl From<serde_json::Error> for ApiError {
    fn from(_error: serde_json::Error) -> Self {
        Self::BadRequest(Self::payload(400, "bad request"))
    }
}

impl From<QueryRejection> for ApiError {
    fn from(_error: QueryRejection) -> Self {
        Self::BadRequest(Self::payload(400, "bad request"))
    }
}