use std::fmt;

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

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

impl fmt::Display for PullError {
    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::RateLimited(message) => write!(f, "{message}"),
            Self::Internal(message) => write!(f, "{message}"),
        }
    }
}

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

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<sea_orm::DbErr> for PullError {
    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 PullError {
    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<PullError>> for PullError {
    fn from(error: sea_orm::TransactionError<PullError>) -> Self {
        match error {
            sea_orm::TransactionError::Connection(db_err) => Self::from(db_err),
            sea_orm::TransactionError::Transaction(pull_err) => pull_err,
        }
    }
}

impl From<git::share::errors::GitError> for PullError {
    fn from(error: git::share::errors::GitError) -> Self {
        use git::share::errors::GitError as G;
        match error {
            G::InvalidArgument(msg) => Self::BadRequest(msg),
            G::NotFound => Self::NotFound,
            G::Unauthorized => Self::Unauthorized,
            G::Forbidden => Self::Forbidden,
            G::Conflict(msg) => Self::Conflict(msg),
            G::Cache(_) | G::Git(_) | G::Internal(_) => Self::Internal(error.to_string()),
        }
    }
}

impl From<issues::errors::IssueError> for PullError {
    fn from(error: issues::errors::IssueError) -> Self {
        match error {
            issues::errors::IssueError::BadRequest(msg) => Self::BadRequest(msg),
            issues::errors::IssueError::Unauthorized => Self::Unauthorized,
            issues::errors::IssueError::Forbidden => Self::Forbidden,
            issues::errors::IssueError::NotFound => Self::NotFound,
            issues::errors::IssueError::Conflict(msg) => Self::Conflict(msg),
            issues::errors::IssueError::RateLimited(msg) => Self::RateLimited(msg),
            issues::errors::IssueError::Internal(msg) => Self::Internal(msg),
        }
    }
}

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

impl From<serde_json::Error> for PullError {
    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 = 429, description = "rate limit exceeded")]
    TooManyRequests(#[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::TooManyRequests(envelope) => (429, envelope),
            Self::Internal(envelope) => (500, envelope),
        }
    }
}

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

impl From<PullError> for ApiError {
    fn from(error: PullError) -> Self {
        match error {
            PullError::BadRequest(msg) => {
                Self::BadRequest(AppResponseData::err(400, msg).with_error_code("bad_request"))
            }
            PullError::Unauthorized => Self::Unauthorized(
                Self::payload(401, "unauthorized").with_error_code("unauthorized"),
            ),
            PullError::Forbidden => {
                Self::Forbidden(Self::payload(403, "forbidden").with_error_code("forbidden"))
            }
            PullError::NotFound => Self::NotFound(
                Self::payload(404, "pull request not found").with_error_code("not_found"),
            ),
            PullError::Conflict(msg) => {
                Self::Conflict(AppResponseData::err(409, msg).with_error_code("merge_blocked"))
            }
            PullError::RateLimited(msg) => Self::TooManyRequests(
                AppResponseData::err(429, msg).with_error_code("rate_limited"),
            ),
            PullError::Internal(message) => {
                tracing::warn!(error = %message, "pulls handler failed");
                Self::Internal(Self::payload(500, "internal server error"))
            }
        }
    }
}

impl From<PathRejection> for ApiError {
    fn from(error: PathRejection) -> Self {
        Self::BadRequest(
            AppResponseData::err(400, "invalid request path").with_error(error.body_text()),
        )
    }
}

impl From<JsonRejection> for ApiError {
    fn from(error: JsonRejection) -> Self {
        Self::BadRequest(
            AppResponseData::err(400, "invalid request body")
                .with_error(error.body_text())
                .with_error_code("invalid_request_body"),
        )
    }
}

impl From<QueryRejection> for ApiError {
    fn from(error: QueryRejection) -> Self {
        Self::BadRequest(
            AppResponseData::err(400, "invalid query parameters").with_error(error.body_text()),
        )
    }
}