use std::net::SocketAddr;

use askama::Template;
use axum::{
    extract::{ConnectInfo, Path, Query, State},
    http::{HeaderMap, StatusCode},
    response::{IntoResponse, Redirect, Response},
};
use serde::Deserialize;
use tower_sessions::Session;

use secrets_core::audit::log_login;
use secrets_core::service::user::{
    OAuthProfile, bind_oauth_account, find_or_create_user, unbind_oauth_account,
};

use crate::AppState;
use crate::oauth::{OAuthConfig, OAuthUserInfo, google_auth_url, random_state};

use super::{
    SESSION_KEY_VERSION, SESSION_LOGIN_PROVIDER, SESSION_OAUTH_BIND_MODE, SESSION_OAUTH_STATE,
    SESSION_USER_ID, current_user_id, google_cfg, render_template, request_user_agent,
};

#[derive(Template)]
#[template(path = "login.html")]
struct LoginTemplate {
    has_google: bool,
    base_url: String,
    version: &'static str,
}

#[derive(Template)]
#[template(path = "home.html")]
struct HomeTemplate {
    is_logged_in: bool,
    base_url: String,
    version: &'static str,
}

// ── Home page (public) ───────────────────────────────────────────────────────

pub(super) async fn home_page(
    State(state): State<AppState>,
    session: Session,
) -> Result<Response, StatusCode> {
    let is_logged_in = current_user_id(&session).await.is_some();
    let tmpl = HomeTemplate {
        is_logged_in,
        base_url: state.base_url.clone(),
        version: env!("CARGO_PKG_VERSION"),
    };
    render_template(tmpl)
}

// ── Login page ────────────────────────────────────────────────────────────────

pub(super) async fn login_page(
    State(state): State<AppState>,
    session: Session,
) -> Result<Response, StatusCode> {
    if let Some(_uid) = current_user_id(&session).await {
        return Ok(Redirect::to("/dashboard").into_response());
    }

    let tmpl = LoginTemplate {
        has_google: state.google_config.is_some(),
        base_url: state.base_url.clone(),
        version: env!("CARGO_PKG_VERSION"),
    };
    render_template(tmpl)
}

// ── Google OAuth ──────────────────────────────────────────────────────────────

pub(super) async fn auth_google(
    State(state): State<AppState>,
    session: Session,
) -> Result<Response, StatusCode> {
    let config = google_cfg(&state).ok_or(StatusCode::SERVICE_UNAVAILABLE)?;

    let oauth_state = random_state();
    session
        .insert(SESSION_OAUTH_STATE, &oauth_state)
        .await
        .map_err(|e| {
            tracing::error!(error = %e, "failed to insert oauth_state into session");
            StatusCode::INTERNAL_SERVER_ERROR
        })?;

    let url = google_auth_url(config, &oauth_state);
    Ok(Redirect::to(&url).into_response())
}

#[derive(Deserialize)]
pub(super) struct OAuthCallbackQuery {
    code: Option<String>,
    state: Option<String>,
    error: Option<String>,
}

pub(super) async fn auth_google_callback(
    State(state): State<AppState>,
    connect_info: ConnectInfo<SocketAddr>,
    headers: HeaderMap,
    session: Session,
    Query(params): Query<OAuthCallbackQuery>,
) -> Result<Response, StatusCode> {
    let client_ip = Some(crate::client_ip::extract_client_ip_parts(
        &headers,
        connect_info.0,
    ));
    let user_agent = request_user_agent(&headers);
    handle_oauth_callback(
        &state,
        &session,
        params,
        "google",
        client_ip.as_deref(),
        user_agent.as_deref(),
        |s, cfg, code| {
            Box::pin(crate::oauth::google::exchange_code(
                &s.http_client,
                cfg,
                code,
            ))
        },
    )
    .await
}

// ── Shared OAuth callback handler ─────────────────────────────────────────────

async fn handle_oauth_callback<F>(
    state: &AppState,
    session: &Session,
    params: OAuthCallbackQuery,
    provider: &str,
    client_ip: Option<&str>,
    user_agent: Option<&str>,
    exchange_fn: F,
) -> Result<Response, StatusCode>
where
    F: for<'a> Fn(
        &'a AppState,
        &'a OAuthConfig,
        &'a str,
    ) -> std::pin::Pin<
        Box<dyn std::future::Future<Output = anyhow::Result<OAuthUserInfo>> + Send + 'a>,
    >,
{
    if let Some(err) = params.error {
        tracing::warn!(provider, error = %err, "OAuth error");
        return Ok(Redirect::to("/login?error=oauth_error").into_response());
    }

    let Some(code) = params.code else {
        tracing::warn!(provider, "OAuth callback missing code");
        return Ok(Redirect::to("/login?error=oauth_missing_code").into_response());
    };
    let Some(returned_state) = params.state.as_deref() else {
        tracing::warn!(provider, "OAuth callback missing state");
        return Ok(Redirect::to("/login?error=oauth_missing_state").into_response());
    };

    let expected_state: Option<String> = session.get(SESSION_OAUTH_STATE).await.map_err(|e| {
        tracing::error!(provider, error = %e, "failed to read oauth_state from session");
        StatusCode::INTERNAL_SERVER_ERROR
    })?;
    if expected_state.as_deref() != Some(returned_state) {
        tracing::warn!(
            provider,
            expected_present = expected_state.is_some(),
            "OAuth state mismatch (empty session often means SameSite=Strict or server restart)"
        );
        return Ok(Redirect::to("/login?error=oauth_state").into_response());
    }
    if let Err(e) = session.remove::<String>(SESSION_OAUTH_STATE).await {
        tracing::warn!(provider, error = %e, "failed to remove oauth_state from session");
    }

    let config = match provider {
        "google" => state
            .google_config
            .as_ref()
            .ok_or(StatusCode::SERVICE_UNAVAILABLE)?,
        _ => return Err(StatusCode::BAD_REQUEST),
    };

    let user_info = exchange_fn(state, config, code.as_str())
        .await
        .map_err(|e| {
            tracing::error!(provider, error = %e, "failed to exchange OAuth code");
            StatusCode::INTERNAL_SERVER_ERROR
        })?;

    let bind_mode: bool = match session.get::<bool>(SESSION_OAUTH_BIND_MODE).await {
        Ok(v) => v.unwrap_or(false),
        Err(e) => {
            tracing::error!(
                provider,
                error = %e,
                "failed to read oauth_bind_mode from session"
            );
            return Err(StatusCode::INTERNAL_SERVER_ERROR);
        }
    };

    if bind_mode {
        let user_id = current_user_id(session)
            .await
            .ok_or(StatusCode::UNAUTHORIZED)?;
        if let Err(e) = session.remove::<bool>(SESSION_OAUTH_BIND_MODE).await {
            tracing::warn!(provider, error = %e, "failed to remove oauth_bind_mode from session after bind");
        }

        let profile = OAuthProfile {
            provider: user_info.provider,
            provider_id: user_info.provider_id,
            email: user_info.email,
            name: user_info.name,
            avatar_url: user_info.avatar_url,
        };

        bind_oauth_account(&state.pool, user_id, profile)
            .await
            .map_err(|e| {
                tracing::error!(error = %e, "failed to bind OAuth account");
                StatusCode::INTERNAL_SERVER_ERROR
            })?;

        return Ok(Redirect::to("/dashboard?bound=1").into_response());
    }

    let profile = OAuthProfile {
        provider: user_info.provider,
        provider_id: user_info.provider_id,
        email: user_info.email,
        name: user_info.name,
        avatar_url: user_info.avatar_url,
    };

    let (user, _is_new) = find_or_create_user(&state.pool, profile)
        .await
        .map_err(|e| {
            tracing::error!(error = %e, "failed to find or create user");
            StatusCode::INTERNAL_SERVER_ERROR
        })?;

    session
        .insert(SESSION_USER_ID, user.id.to_string())
        .await
        .map_err(|e| {
            tracing::error!(
                error = %e,
                user_id = %user.id,
                "failed to insert user_id into session after OAuth"
            );
            StatusCode::INTERNAL_SERVER_ERROR
        })?;
    session
        .insert(SESSION_LOGIN_PROVIDER, &provider)
        .await
        .map_err(|e| {
            tracing::error!(
                provider,
                error = %e,
                "failed to insert login_provider into session after OAuth"
            );
            StatusCode::INTERNAL_SERVER_ERROR
        })?;
    if let Err(e) = session.insert(SESSION_KEY_VERSION, user.key_version).await {
        tracing::warn!(error = %e, user_id = %user.id, "failed to insert key_version into session after OAuth");
    }

    log_login(
        &state.pool,
        "oauth",
        provider,
        user.id,
        client_ip,
        user_agent,
    )
    .await;

    Ok(Redirect::to("/dashboard").into_response())
}

// ── Logout ────────────────────────────────────────────────────────────────────

pub(super) async fn auth_logout(session: Session) -> impl IntoResponse {
    if let Err(e) = session.flush().await {
        tracing::warn!(error = %e, "failed to flush session on logout");
    }
    Redirect::to("/")
}

// ── Account bind/unbind ───────────────────────────────────────────────────────

pub(super) async fn account_bind_google(
    State(state): State<AppState>,
    session: Session,
) -> Result<Response, StatusCode> {
    let _ = current_user_id(&session)
        .await
        .ok_or(StatusCode::UNAUTHORIZED)?;

    session
        .insert(SESSION_OAUTH_BIND_MODE, true)
        .await
        .map_err(|e| {
            tracing::error!(error = %e, "failed to insert oauth_bind_mode into session");
            StatusCode::INTERNAL_SERVER_ERROR
        })?;

    let config = google_cfg(&state).ok_or(StatusCode::SERVICE_UNAVAILABLE)?;
    let oauth_state = random_state();
    if let Err(e) = session.insert(SESSION_OAUTH_STATE, &oauth_state).await {
        tracing::error!(error = %e, "failed to insert oauth_state for account bind flow");
        if let Err(rm) = session.remove::<bool>(SESSION_OAUTH_BIND_MODE).await {
            tracing::warn!(error = %rm, "failed to roll back oauth_bind_mode after oauth_state insert failure");
        }
        return Err(StatusCode::INTERNAL_SERVER_ERROR);
    }

    let url = google_auth_url(config, &oauth_state);
    Ok(Redirect::to(&url).into_response())
}

pub(super) async fn account_unbind(
    State(state): State<AppState>,
    Path(provider): Path<String>,
    session: Session,
) -> Result<Response, StatusCode> {
    let user_id = current_user_id(&session)
        .await
        .ok_or(StatusCode::UNAUTHORIZED)?;

    let current_login_provider = session
        .get::<String>(SESSION_LOGIN_PROVIDER)
        .await
        .map_err(|e| {
            tracing::error!(error = %e, "failed to read login_provider from session");
            StatusCode::INTERNAL_SERVER_ERROR
        })?;

    unbind_oauth_account(
        &state.pool,
        user_id,
        &provider,
        current_login_provider.as_deref(),
    )
    .await
    .map_err(|e| {
        tracing::warn!(error = %e, "failed to unbind oauth account");
        StatusCode::BAD_REQUEST
    })?;

    Ok(Redirect::to("/dashboard?unbound=1").into_response())
}