//! OAuth endpoints — thin HTTP adapters over `service::oauth`.
//!
//! Business logic lives in `service::oauth`. These handlers only:
//! 1. Extract parameters from the HTTP request.
//! 2. Call the service layer.
//! 3. Map service errors to HTTP responses.
use crate::service::oauth as svc;
use crate::slog;
use poem::handler;
use poem::http::StatusCode;
use poem::web::{Data, Query, Redirect};
use serde::Deserialize;
use std::sync::Arc;

// Re-export service types so that existing tests in this file continue to
// compile unchanged (they use `use super::*` and call these by name).
pub(crate) use svc::OAuthState;
// Re-exported for tests only (tests use `use super::*` to call these by name).
#[cfg(test)]
pub(crate) use svc::pkce::{base64url_encode, compute_code_challenge, random_string};

/// `GET /oauth/authorize` — Initiates the OAuth flow.
///
/// Generates PKCE parameters, stores them, and redirects the browser to
/// Anthropic's authorization page.
#[handler]
pub async fn oauth_authorize(state: Data<&Arc<OAuthState>>) -> Redirect {
    let (_, url) = svc::initiate_flow(&state);
    Redirect::temporary(url)
}

/// Query parameters received on the OAuth callback URL.
#[derive(Deserialize)]
pub struct CallbackParams {
    code: Option<String>,
    state: Option<String>,
    error: Option<String>,
    error_description: Option<String>,
}

/// `GET /oauth/callback` — Handles the OAuth redirect from Anthropic.
///
/// Exchanges the authorization code for tokens and writes them to
/// `~/.claude/.credentials.json`.
#[handler]
pub async fn oauth_callback(
    state: Data<&Arc<OAuthState>>,
    Query(params): Query<CallbackParams>,
) -> poem::Response {
    // Handle provider-side errors (e.g. user denied access).
    if let Some(err) = &params.error {
        let desc = params
            .error_description
            .as_deref()
            .unwrap_or("Unknown error");
        slog!("[oauth] Authorization denied: {} - {}", err, desc);
        return html_response(
            StatusCode::BAD_REQUEST,
            "Authentication Failed",
            &format!("Anthropic denied the request: {desc}"),
        );
    }

    let code = match &params.code {
        Some(c) => c.clone(),
        None => {
            return html_response(
                StatusCode::BAD_REQUEST,
                "Missing Code",
                "No authorization code received from Anthropic.",
            );
        }
    };

    let csrf_state = match &params.state {
        Some(s) => s.clone(),
        None => {
            return html_response(
                StatusCode::BAD_REQUEST,
                "Missing State",
                "No state parameter received. Possible CSRF attack.",
            );
        }
    };

    match svc::exchange_code(&state, &code, &csrf_state).await {
        Ok(()) => html_response(
            StatusCode::OK,
            "Authenticated!",
            "Claude OAuth login successful. You can close this tab and return to Huskies.",
        ),
        Err(e) => map_service_error(e),
    }
}

/// `GET /oauth/status` — Check whether valid (non-expired) OAuth credentials exist.
#[handler]
pub async fn oauth_status() -> poem::Response {
    let status = svc::check_status();
    let body = serde_json::json!({
        "authenticated": status.authenticated,
        "expired": status.expired,
        "expires_at": status.expires_at,
        "has_refresh_token": status.has_refresh_token,
    });
    poem::Response::builder()
        .status(StatusCode::OK)
        .header("Content-Type", "application/json")
        .body(body.to_string())
}

// ── Private helpers ───────────────────────────────────────────────────────────

/// Map a service-layer `Error` to an HTML HTTP response.
fn map_service_error(e: svc::Error) -> poem::Response {
    use svc::Error;
    match e {
        Error::MissingCode => html_response(
            StatusCode::BAD_REQUEST,
            "Missing Code",
            "No authorization code received.",
        ),
        Error::MissingState => html_response(
            StatusCode::BAD_REQUEST,
            "Missing State",
            "No state parameter received.",
        ),
        Error::InvalidState(msg) => html_response(StatusCode::BAD_REQUEST, "Invalid State", &msg),
        Error::AuthorizationDenied(msg) => {
            html_response(StatusCode::BAD_REQUEST, "Authentication Failed", &msg)
        }
        Error::InvalidGrant(msg) => {
            html_response(StatusCode::BAD_REQUEST, "Token Exchange Failed", &msg)
        }
        Error::Network(msg) => html_response(
            StatusCode::INTERNAL_SERVER_ERROR,
            "Token Exchange Failed",
            &msg,
        ),
        Error::TokenExpired(msg) => html_response(StatusCode::UNAUTHORIZED, "Token Expired", &msg),
        Error::TokenStorage(msg) => html_response(
            StatusCode::INTERNAL_SERVER_ERROR,
            "Credential Write Failed",
            &msg,
        ),
        Error::Parse(msg) => html_response(
            StatusCode::INTERNAL_SERVER_ERROR,
            "Token Parse Failed",
            &msg,
        ),
    }
}

fn html_response(status: StatusCode, title: &str, message: &str) -> poem::Response {
    let html = format!(
        r#"<!DOCTYPE html>
<html>
<head><title>{title}</title>
<style>
body {{ font-family: system-ui, sans-serif; display: flex; justify-content: center; align-items: center; min-height: 100vh; margin: 0; background: #1a1a2e; color: #e0e0e0; }}
.card {{ background: #16213e; padding: 2rem; border-radius: 12px; text-align: center; max-width: 400px; box-shadow: 0 4px 24px rgba(0,0,0,0.3); }}
h1 {{ margin-top: 0; }}
</style>
</head>
<body><div class="card"><h1>{title}</h1><p>{message}</p></div></body>
</html>"#
    );
    poem::Response::builder()
        .status(status)
        .header("Content-Type", "text/html; charset=utf-8")
        .body(html)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn base64url_encode_basic() {
        // Test vector: "Hello" → base64 "SGVsbG8=" → base64url "SGVsbG8"
        let encoded = base64url_encode(b"Hello");
        assert_eq!(encoded, "SGVsbG8");
    }

    #[test]
    fn base64url_encode_no_padding() {
        // Ensure no '=' padding characters
        let encoded = base64url_encode(b"a");
        assert!(!encoded.contains('='));
    }

    #[test]
    fn base64url_encode_no_plus_or_slash() {
        // Encode bytes that would produce + and / in standard base64
        let data: Vec<u8> = (0..=255).collect();
        let encoded = base64url_encode(&data);
        assert!(!encoded.contains('+'));
        assert!(!encoded.contains('/'));
    }

    #[test]
    fn compute_code_challenge_returns_nonempty() {
        let challenge = compute_code_challenge("test_verifier_string");
        assert!(!challenge.is_empty());
    }

    #[test]
    fn compute_code_challenge_is_deterministic() {
        let a = compute_code_challenge("same_input");
        let b = compute_code_challenge("same_input");
        assert_eq!(a, b);
    }

    #[test]
    fn random_string_length() {
        let s = random_string(64);
        assert_eq!(s.len(), 64);
    }

    #[test]
    fn random_string_is_alphanumeric() {
        let s = random_string(100);
        assert!(s.chars().all(|c| c.is_ascii_alphanumeric()));
    }

    #[test]
    fn oauth_state_callback_url() {
        let state = OAuthState::new(3001);
        assert_eq!(state.callback_url(), "http://localhost:3001/callback");
    }

    #[test]
    fn oauth_state_callback_url_uses_given_port() {
        // Ensure OAuthState::new uses the port passed to it, not a hardcoded value.
        let state = OAuthState::new(9876);
        assert_eq!(state.callback_url(), "http://localhost:9876/callback");
    }

    #[tokio::test]
    async fn html_response_contains_title_and_message() {
        let resp = html_response(StatusCode::OK, "Test Title", "Test message");
        let body = resp.into_body().into_string().await.unwrap();
        assert!(body.contains("Test Title"));
        assert!(body.contains("Test message"));
    }
}