use axum::{
    extract::{Query, State},
    http::StatusCode,
    response::{Html, IntoResponse, Redirect, Response},
    Json,
};
use axum_login::AuthSession;
use sea_orm::{DatabaseConnection, EntityTrait};
use serde::{Deserialize, Serialize};
use sha2::{Digest, Sha256};
use tower_sessions::Session;
use tracing::{info, warn};
use utoipa::ToSchema;

use crate::auth::AuthBackend;
use crate::models::User;
use crate::services::OAuthService;

const CSRF_TOKEN_KEY: &str = "oauth_csrf_token";
const FRONTEND_URL_KEY: &str = "oauth_frontend_url";

fn mobile_secret() -> String {
    std::env::var("MOBILE_SECRET").unwrap_or_else(|_| "family-budget-mobile-secret".to_string())
}

fn sign(data: &str) -> String {
    let secret = mobile_secret();
    let mut hasher = Sha256::new();
    hasher.update(format!("{}:{}", secret, data).as_bytes());
    hex::encode(hasher.finalize())
}

fn make_mobile_csrf_state(nonce: &str) -> String {
    let sig = sign(&format!("csrf.mobile.{}", nonce));
    format!("mobile.{}.{}", nonce, sig)
}

fn verify_mobile_csrf_state(state: &str) -> bool {
    let mut parts = state.splitn(3, '.');
    match (parts.next(), parts.next(), parts.next()) {
        (Some("mobile"), Some(nonce), Some(sig)) => {
            sign(&format!("csrf.mobile.{}", nonce)) == sig
        }
        _ => false,
    }
}

fn make_auth_token(user_id: i32) -> String {
    let timestamp = std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .unwrap()
        .as_secs();
    let payload = format!("{}.{}", user_id, timestamp);
    let sig = sign(&format!("auth.{}", payload));
    format!("{}.{}", payload, sig)
}

fn verify_auth_token(token: &str) -> Option<i32> {
    let mut parts = token.splitn(3, '.');
    let user_id_str = parts.next()?;
    let timestamp_str = parts.next()?;
    let sig = parts.next()?;

    let payload = format!("{}.{}", user_id_str, timestamp_str);
    if sign(&format!("auth.{}", payload)) != sig {
        return None;
    }

    let timestamp: u64 = timestamp_str.parse().ok()?;
    let now = std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .unwrap()
        .as_secs();
    if now.saturating_sub(timestamp) > 300 {
        return None;
    }

    user_id_str.parse().ok()
}

#[derive(Debug, Deserialize, ToSchema)]
pub struct GoogleAuthQuery {
    pub redirect_url: Option<String>,
    pub mobile: Option<bool>,
}

#[derive(Debug, Deserialize)]
pub struct GoogleCallbackQuery {
    pub code: String,
    pub state: String,
}

#[derive(Debug, Serialize, ToSchema)]
pub struct OAuthUrlResponse {
    pub url: String,
}

#[utoipa::path(
    get,
    path = "/auth/google",
    tag = "auth",
    params(
        ("redirect_url" = Option<String>, Query, description = "Frontend URL to redirect after auth"),
        ("mobile" = Option<bool>, Query, description = "Mobile OAuth flow")
    ),
    responses(
        (status = 200, description = "Returns Google OAuth URL", body = OAuthUrlResponse)
    )
)]
pub async fn google_auth(
    session: Session,
    Query(query): Query<GoogleAuthQuery>,
) -> Result<Json<OAuthUrlResponse>, StatusCode> {
    let oauth_service = OAuthService::new();

    if query.mobile.unwrap_or(false) {
        let nonce = uuid::Uuid::new_v4().to_string();
        let mobile_state = make_mobile_csrf_state(&nonce);
        let auth_url = oauth_service.get_auth_url_with_state(mobile_state);
        info!("mobile google_auth: generated signed state for nonce={}", nonce);
        return Ok(Json(OAuthUrlResponse { url: auth_url }));
    }

    let (auth_url, csrf_token) = oauth_service.get_auth_url();

    session
        .insert(CSRF_TOKEN_KEY, csrf_token.secret().clone())
        .await
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;

    if let Some(redirect_url) = query.redirect_url {
        session
            .insert(FRONTEND_URL_KEY, redirect_url)
            .await
            .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
    }

    Ok(Json(OAuthUrlResponse { url: auth_url }))
}

#[utoipa::path(
    get,
    path = "/auth/google/callback",
    tag = "auth",
    responses(
        (status = 302, description = "Redirects to frontend after successful auth"),
        (status = 401, description = "Authentication failed")
    )
)]
pub async fn google_callback(
    mut auth_session: AuthSession<AuthBackend>,
    session: Session,
    State(db): State<DatabaseConnection>,
    Query(query): Query<GoogleCallbackQuery>,
) -> Result<Response, StatusCode> {
    let is_mobile = verify_mobile_csrf_state(&query.state);
    info!("google_callback: state={} is_mobile={}", &query.state[..query.state.len().min(20)], is_mobile);

    if !is_mobile {
        let session_csrf: Option<String> = session
            .get(CSRF_TOKEN_KEY)
            .await
            .unwrap_or(None);
        session.remove::<String>(CSRF_TOKEN_KEY).await.ok();

        match session_csrf {
            Some(csrf) if csrf == query.state => {}
            _ => {
                warn!("google_callback: CSRF mismatch, session_csrf={:?}", session_csrf.as_deref().map(|s| &s[..s.len().min(10)]));
                return Err(StatusCode::UNAUTHORIZED);
            }
        }
    }

    let frontend_url: Option<String> = session
        .get(FRONTEND_URL_KEY)
        .await
        .unwrap_or(None);
    session.remove::<String>(FRONTEND_URL_KEY).await.ok();

    let oauth_service = OAuthService::new();

    let access_token = oauth_service
        .exchange_code(query.code)
        .await
        .map_err(|_| StatusCode::UNAUTHORIZED)?;

    let google_user = oauth_service
        .get_user_info(&access_token)
        .await
        .map_err(|_| StatusCode::UNAUTHORIZED)?;

    let user = oauth_service
        .find_or_create_user(&db, google_user)
        .await
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;

    if is_mobile {
        let token = make_auth_token(user.id);
        info!("google_callback: mobile auth for user_id={}, token_prefix={}", user.id, &token[..token.len().min(20)]);
        let deep_link = format!("com.arrelin.family-budget-android://auth?token={}", token);
        let html = format!(
            r#"<!DOCTYPE html><html><head><meta http-equiv="refresh" content="0;url={0}"></head><body><script>window.location="{0}"</script></body></html>"#,
            deep_link
        );
        return Ok(Html(html).into_response());
    }

    auth_session
        .login(&user)
        .await
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;

    if let Some(family_id) = user.family_id {
        let mut authorized_families: Vec<i32> = session
            .get("authorized_families")
            .await
            .unwrap_or(None)
            .unwrap_or_default();
        if !authorized_families.contains(&family_id) {
            authorized_families.push(family_id);
            session.insert("authorized_families", authorized_families).await.ok();
        }
    }

    let redirect_url = frontend_url.unwrap_or_else(|| "http://localhost:3000".to_string());
    Ok(Redirect::temporary(&redirect_url).into_response())
}

#[derive(Debug, Deserialize)]
pub struct MobileCallbackQuery {
    pub token: String,
}

pub async fn mobile_callback(
    mut auth_session: AuthSession<AuthBackend>,
    session: Session,
    State(db): State<DatabaseConnection>,
    Query(query): Query<MobileCallbackQuery>,
) -> Result<Json<serde_json::Value>, StatusCode> {
    info!("mobile_callback: received token_prefix={}", &query.token[..query.token.len().min(20)]);
    let user_id = match verify_auth_token(&query.token) {
        Some(id) => id,
        None => {
            warn!("mobile_callback: token verification failed for token={}", &query.token[..query.token.len().min(40)]);
            return Err(StatusCode::UNAUTHORIZED);
        }
    };
    info!("mobile_callback: token valid for user_id={}", user_id);

    let user = User::find_by_id(user_id)
        .one(&db)
        .await
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?
        .ok_or(StatusCode::UNAUTHORIZED)?;

    auth_session
        .login(&user)
        .await
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;

    if let Some(family_id) = user.family_id {
        let mut authorized_families: Vec<i32> = session
            .get("authorized_families")
            .await
            .unwrap_or(None)
            .unwrap_or_default();
        if !authorized_families.contains(&family_id) {
            authorized_families.push(family_id);
            session.insert("authorized_families", authorized_families).await.ok();
        }
    }

    Ok(Json(serde_json::json!({"success": true})))
}