use anyhow::{Context, Result as AnyResult};
use axum::{
    Json, Router,
    extract::{Path, Query, State},
    http::{HeaderMap, StatusCode, header},
    response::{Html, IntoResponse, Redirect},
    routing::{get, post},
};
use base64::{Engine as _, engine::general_purpose::URL_SAFE_NO_PAD};
use chrono::{DateTime, Duration, Utc};
use reqwest::Client;
use secrets_application::sync::{fetch_object, sync_pull, sync_push};
use secrets_device_auth::{hash_device_login_token, new_device_fingerprint, new_device_login_token};
use secrets_domain::{
    SyncPullRequest, SyncPullResponse, SyncPushRequest, SyncPushResponse, VaultObjectEnvelope,
};
use serde::{Deserialize, Serialize};
use serde_json::json;
use sha2::{Digest, Sha256};
use sqlx::{PgPool, Postgres, Transaction};
use tracing_subscriber::EnvFilter;
use url::Url;
use uuid::Uuid;

#[derive(Clone)]
struct AppState {
    pool: PgPool,
    http: Client,
}

#[derive(Serialize)]
struct DemoLoginResponse {
    device_token: String,
}

#[derive(Debug, Deserialize)]
struct DesktopLoginStartRequest {
    device_name: String,
    platform: String,
    client_version: String,
    device_fingerprint: String,
}

#[derive(Debug, Deserialize)]
struct DesktopLoginPollQuery {
    session_id: String,
}

#[derive(Debug, Deserialize)]
struct GoogleStartQuery {
    session_id: String,
}

#[derive(Debug, Deserialize)]
struct GoogleCallbackQuery {
    state: Option<String>,
    code: Option<String>,
    error: Option<String>,
}

#[derive(Debug, Deserialize)]
struct GoogleUserInfo {
    sub: String,
    email: String,
    name: Option<String>,
}

#[derive(Clone)]
struct GoogleOAuthConfig {
    client_id: String,
    client_secret: String,
    auth_uri: String,
    token_uri: String,
    redirect_uri: String,
}

#[derive(Serialize)]
struct DesktopLoginStartResponse {
    session_id: String,
    auth_url: String,
    expires_at: String,
}

#[derive(Serialize)]
struct DesktopLoginPollResponse {
    status: String,
    device_token: Option<String>,
    error: Option<String>,
}

#[derive(Debug, Deserialize)]
struct GoogleTokenResponse {
    access_token: String,
}

#[derive(Debug, sqlx::FromRow)]
struct DesktopLoginSessionRow {
    session_id: String,
    oauth_state: String,
    pkce_verifier: String,
    device_name: String,
    platform: String,
    client_version: String,
    device_fingerprint: String,
    status: String,
    error_message: Option<String>,
    expires_at: DateTime<Utc>,
}

#[derive(Serialize)]
struct DeviceView {
    name: String,
    platform: String,
    client_version: String,
    last_seen: String,
    ip: Option<String>,
}

#[derive(Serialize)]
struct UserProfileView {
    id: Uuid,
    name: String,
    email: String,
}

#[derive(Serialize, sqlx::FromRow)]
struct UserRow {
    id: Uuid,
    email: Option<String>,
    name: String,
}

#[derive(Serialize, sqlx::FromRow)]
struct DeviceRow {
    id: Uuid,
    display_name: String,
    platform: String,
    client_version: String,
    last_seen_at: DateTime<Utc>,
    last_ip: Option<String>,
}

#[derive(Debug, Serialize)]
struct ObjectResponse {
    object: VaultObjectEnvelope,
}

const LOGIN_STATUS_PENDING: &str = "pending";
const LOGIN_STATUS_SUCCEEDED: &str = "succeeded";
const LOGIN_STATUS_FAILED: &str = "failed";
const LOGIN_STATUS_EXPIRED: &str = "expired";
const LOGIN_STATUS_CONSUMED: &str = "consumed";
const DESKTOP_LOGIN_SESSION_TTL_MINUTES: i64 = 10;

#[tokio::main]
async fn main() -> AnyResult<()> {
    let _ = dotenvy::dotenv();

    tracing_subscriber::fmt()
        .with_env_filter(
            EnvFilter::try_from_default_env().unwrap_or_else(|_| "secrets_api=info".into()),
        )
        .init();

    let database_url = secrets_infrastructure_db::load_database_url()?;
    let pool = secrets_infrastructure_db::create_pool(&database_url).await?;
    secrets_infrastructure_db::migrate_current_schema(&pool)
        .await
        .context("failed to initialize current database schema")?;

    let bind = std::env::var("SECRETS_API_BIND").unwrap_or_else(|_| "127.0.0.1:9415".to_string());
    let app = Router::new()
        .route("/healthz", get(|| async { "ok" }))
        .route("/auth/demo-login", post(api_demo_login))
        .route("/auth/desktop/start", post(api_desktop_login_start))
        .route("/auth/desktop/poll", get(api_desktop_login_poll))
        .route("/auth/google/start", get(api_google_login_start))
        .route("/auth/google/callback", get(api_google_login_callback))
        .route("/me", get(api_me))
        .route("/sync/pull", post(api_sync_pull))
        .route("/sync/push", post(api_sync_push))
        .route("/sync/objects/{id}", get(api_sync_object))
        .route("/devices", get(api_devices))
        .with_state(AppState {
            pool,
            http: Client::new(),
        });
    let listener = tokio::net::TcpListener::bind(&bind)
        .await
        .with_context(|| format!("failed to bind {}", bind))?;

    tracing::info!(bind = %bind, "secrets-api listening");
    axum::serve(listener, app)
        .await
        .context("api server error")?;
    Ok(())
}

async fn api_demo_login(
    State(state): State<AppState>,
) -> std::result::Result<Json<DemoLoginResponse>, (StatusCode, Json<serde_json::Value>)> {
    let (user_id, device_id) = ensure_demo_user(&state.pool)
        .await
        .map_err(internal_error)?;
    let device_token = new_device_login_token();
    let token_hash = hash_device_login_token(&device_token);

    sqlx::query("DELETE FROM device_login_tokens WHERE device_id = $1")
        .bind(device_id)
        .execute(&state.pool)
        .await
        .map_err(internal_error)?;

    sqlx::query(
        r#"
        INSERT INTO device_login_tokens (device_id, token_hash)
        VALUES ($1, $2)
        "#,
    )
    .bind(device_id)
    .bind(token_hash)
    .execute(&state.pool)
    .await
    .map_err(internal_error)?;

    sqlx::query(
        r#"
        INSERT INTO auth_events (
            user_id, device_id, device_name, platform, client_version, ip_addr, forwarded_ip, login_method, login_result
        )
        VALUES ($1, $2, $3, $4, $5, $6, $7, 'device_token', 'success')
        "#,
    )
    .bind(user_id)
    .bind(device_id)
    .bind("Voson 的 Mac mini")
    .bind("macOS")
    .bind(env!("CARGO_PKG_VERSION"))
    .bind::<Option<String>>(None)
    .bind::<Option<String>>(None)
    .execute(&state.pool)
    .await
    .map_err(internal_error)?;

    Ok(Json(DemoLoginResponse { device_token }))
}

async fn api_desktop_login_start(
    State(state): State<AppState>,
    Json(payload): Json<DesktopLoginStartRequest>,
) -> std::result::Result<Json<DesktopLoginStartResponse>, (StatusCode, Json<serde_json::Value>)> {
    let session_id = new_session_secret();
    let oauth_state = new_session_secret();
    let pkce_verifier = new_session_secret();
    let expires_at = Utc::now() + Duration::minutes(DESKTOP_LOGIN_SESSION_TTL_MINUTES);
    let auth_url = format!(
        "{}/auth/google/start?session_id={}",
        public_base_url().map_err(internal_error)?,
        session_id
    );

    sqlx::query(
        r#"
        INSERT INTO desktop_login_sessions (
            session_id, oauth_state, pkce_verifier, device_name, platform, client_version,
            device_fingerprint, status, expires_at
        )
        VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)
        "#,
    )
    .bind(&session_id)
    .bind(&oauth_state)
    .bind(&pkce_verifier)
    .bind(&payload.device_name)
    .bind(&payload.platform)
    .bind(&payload.client_version)
    .bind(&payload.device_fingerprint)
    .bind(LOGIN_STATUS_PENDING)
    .bind(expires_at)
    .execute(&state.pool)
    .await
    .map_err(internal_error)?;

    Ok(Json(DesktopLoginStartResponse {
        session_id,
        auth_url,
        expires_at: expires_at.to_rfc3339(),
    }))
}

async fn api_google_login_start(
    State(state): State<AppState>,
    Query(query): Query<GoogleStartQuery>,
) -> std::result::Result<Redirect, (StatusCode, Json<serde_json::Value>)> {
    let session = fetch_desktop_login_session(&state.pool, &query.session_id)
        .await
        .map_err(internal_error)?
        .ok_or_else(|| unauthorized("desktop login session not found"))?;
    ensure_login_session_pending(&session).map_err(unauthorized)?;
    let google = google_oauth_config().map_err(internal_error)?;
    let challenge = pkce_challenge(&session.pkce_verifier);

    let mut auth_url = Url::parse(&google.auth_uri).map_err(internal_error)?;
    auth_url
        .query_pairs_mut()
        .append_pair("client_id", &google.client_id)
        .append_pair("redirect_uri", &google.redirect_uri)
        .append_pair("response_type", "code")
        .append_pair("scope", "openid email profile")
        .append_pair("state", &session.oauth_state)
        .append_pair("code_challenge", &challenge)
        .append_pair("code_challenge_method", "S256")
        .append_pair("access_type", "offline")
        .append_pair("prompt", "consent");

    Ok(Redirect::temporary(auth_url.as_str()))
}

async fn api_google_login_callback(
    State(state): State<AppState>,
    Query(query): Query<GoogleCallbackQuery>,
) -> std::result::Result<impl IntoResponse, (StatusCode, Json<serde_json::Value>)> {
    let oauth_state = query
        .state
        .as_deref()
        .filter(|value| !value.is_empty())
        .ok_or_else(|| unauthorized("missing oauth state"))?;
    let mut tx = state.pool.begin().await.map_err(internal_error)?;
    let session = fetch_desktop_login_session_by_state(&mut tx, oauth_state)
        .await
        .map_err(internal_error)?
        .ok_or_else(|| unauthorized("desktop login session not found"))?;

    if let Some(error) = query.error.as_deref().filter(|value| !value.is_empty()) {
        mark_login_session_failed(&mut tx, &session.session_id, &format!("google oauth error: {error}"))
            .await
            .map_err(internal_error)?;
        tx.commit().await.map_err(internal_error)?;
        return Ok(Html(login_result_html(
            "登录未完成",
            "你已取消 Google 授权或授权未成功，可以返回 Secrets 重试。",
        )));
    }

    ensure_login_session_pending(&session).map_err(unauthorized)?;
    let code = query
        .code
        .as_deref()
        .filter(|value| !value.is_empty())
        .ok_or_else(|| unauthorized("missing google auth code"))?;
    let google = google_oauth_config().map_err(internal_error)?;
    let google_token = exchange_google_auth_code(&state.http, &google, code, &session.pkce_verifier)
        .await
        .map_err(internal_error)?;
    let google_user = fetch_google_userinfo(&state.http, &google_token.access_token)
        .await
        .map_err(internal_error)?;

    let user_id = upsert_user_from_google(&state.pool, &google_user)
        .await
        .map_err(internal_error)?;
    upsert_google_oauth_account(&state.pool, user_id, &google_user)
        .await
        .map_err(internal_error)?;
    let device_id = upsert_device_for_login(
        &state.pool,
        user_id,
        &session.device_name,
        &session.platform,
        &session.client_version,
        &session.device_fingerprint,
    )
    .await
    .map_err(internal_error)?;

    let device_token = issue_device_login_token(
        &state.pool,
        user_id,
        device_id,
        &session.device_name,
        &session.platform,
        &session.client_version,
    )
    .await
    .map_err(internal_error)?;

    mark_login_session_succeeded(
        &mut tx,
        &session.session_id,
        user_id,
        device_id,
        device_token.clone(),
        hash_device_login_token(&device_token),
    )
    .await
    .map_err(internal_error)?;
    tx.commit().await.map_err(internal_error)?;

    Ok(Html(login_result_html(
        "登录成功",
        "Google 授权已完成，可以返回 Secrets 桌面端继续。",
    )))
}

async fn api_desktop_login_poll(
    State(state): State<AppState>,
    Query(query): Query<DesktopLoginPollQuery>,
) -> std::result::Result<Json<DesktopLoginPollResponse>, (StatusCode, Json<serde_json::Value>)> {
    let mut tx = state.pool.begin().await.map_err(internal_error)?;
    let session = fetch_desktop_login_session_for_update(&mut tx, &query.session_id)
        .await
        .map_err(internal_error)?
        .ok_or_else(|| unauthorized("desktop login session not found"))?;
    let now = Utc::now();

    if session.expires_at < now && session.status == LOGIN_STATUS_PENDING {
        mark_login_session_expired(&mut tx, &session.session_id)
            .await
            .map_err(internal_error)?;
        tx.commit().await.map_err(internal_error)?;
        return Ok(Json(DesktopLoginPollResponse {
            status: LOGIN_STATUS_EXPIRED.to_string(),
            device_token: None,
            error: Some("login session expired".to_string()),
        }));
    }

    match session.status.as_str() {
        LOGIN_STATUS_PENDING => {
            tx.commit().await.map_err(internal_error)?;
            Ok(Json(DesktopLoginPollResponse {
                status: LOGIN_STATUS_PENDING.to_string(),
                device_token: None,
                error: None,
            }))
        }
        LOGIN_STATUS_FAILED => {
            tx.commit().await.map_err(internal_error)?;
            Ok(Json(DesktopLoginPollResponse {
                status: LOGIN_STATUS_FAILED.to_string(),
                device_token: None,
                error: session.error_message,
            }))
        }
        LOGIN_STATUS_EXPIRED => {
            tx.commit().await.map_err(internal_error)?;
            Ok(Json(DesktopLoginPollResponse {
                status: LOGIN_STATUS_EXPIRED.to_string(),
                device_token: None,
                error: session.error_message.or(Some("login session expired".to_string())),
            }))
        }
        LOGIN_STATUS_CONSUMED => {
            tx.commit().await.map_err(internal_error)?;
            Ok(Json(DesktopLoginPollResponse {
                status: LOGIN_STATUS_CONSUMED.to_string(),
                device_token: None,
                error: Some("login session already consumed".to_string()),
            }))
        }
        LOGIN_STATUS_SUCCEEDED => {
            let device_token = consume_device_token_for_poll(&mut tx, &session.session_id)
                .await
                .map_err(internal_error)?;
            sqlx::query(
                "UPDATE desktop_login_sessions SET status = $2, consumed_at = NOW(), updated_at = NOW() WHERE session_id = $1",
            )
            .bind(&session.session_id)
            .bind(LOGIN_STATUS_CONSUMED)
            .execute(&mut *tx)
            .await
            .map_err(internal_error)?;
            tx.commit().await.map_err(internal_error)?;
            Ok(Json(DesktopLoginPollResponse {
                status: LOGIN_STATUS_SUCCEEDED.to_string(),
                device_token: Some(device_token),
                error: None,
            }))
        }
        _ => {
            tx.commit().await.map_err(internal_error)?;
            Ok(Json(DesktopLoginPollResponse {
                status: LOGIN_STATUS_FAILED.to_string(),
                device_token: None,
                error: Some("invalid login session status".to_string()),
            }))
        }
    }
}

async fn api_sync_pull(
    State(state): State<AppState>,
    headers: HeaderMap,
    Json(payload): Json<SyncPullRequest>,
) -> std::result::Result<Json<SyncPullResponse>, (StatusCode, Json<serde_json::Value>)> {
    let (user, _) = require_auth(&state.pool, &headers).await?;
    let response = sync_pull(&state.pool, user.id, payload)
        .await
        .map_err(internal_error)?;
    Ok(Json(response))
}

async fn api_sync_push(
    State(state): State<AppState>,
    headers: HeaderMap,
    Json(payload): Json<SyncPushRequest>,
) -> std::result::Result<Json<SyncPushResponse>, (StatusCode, Json<serde_json::Value>)> {
    let (user, _) = require_auth(&state.pool, &headers).await?;
    let response = sync_push(&state.pool, user.id, payload)
        .await
        .map_err(internal_error)?;
    Ok(Json(response))
}

async fn api_sync_object(
    State(state): State<AppState>,
    headers: HeaderMap,
    Path(object_id): Path<Uuid>,
) -> std::result::Result<Json<ObjectResponse>, (StatusCode, Json<serde_json::Value>)> {
    let (user, _) = require_auth(&state.pool, &headers).await?;
    let object = fetch_object(&state.pool, user.id, object_id)
        .await
        .map_err(internal_error)?
        .ok_or_else(|| unauthorized("object not found"))?;
    Ok(Json(ObjectResponse { object }))
}

async fn api_devices(
    State(state): State<AppState>,
    headers: HeaderMap,
) -> std::result::Result<Json<Vec<DeviceView>>, (StatusCode, Json<serde_json::Value>)> {
    let (user, _) = require_auth(&state.pool, &headers).await?;
    let rows = sqlx::query_as::<_, DeviceRow>(
        r#"
        SELECT
            d.id,
            d.display_name,
            d.platform,
            d.client_version,
            d.last_seen_at,
            COALESCE(NULLIF(a.forwarded_ip, ''), NULLIF(a.ip_addr, '')) AS last_ip
        FROM devices d
        LEFT JOIN LATERAL (
            SELECT ip_addr, forwarded_ip
            FROM auth_events
            WHERE device_id = d.id
            ORDER BY created_at DESC
            LIMIT 1
        ) a ON TRUE
        WHERE d.user_id = $1
        ORDER BY last_seen_at DESC
        "#,
    )
    .bind(user.id)
    .fetch_all(&state.pool)
    .await
    .map_err(internal_error)?;

    let devices = rows
        .into_iter()
        .map(|row| DeviceView {
            name: row.display_name,
            platform: row.platform,
            client_version: row.client_version,
            last_seen: row.last_seen_at.format("%Y-%m-%d %H:%M").to_string(),
            ip: row.last_ip,
        })
        .collect();

    Ok(Json(devices))
}

async fn api_me(
    State(state): State<AppState>,
    headers: HeaderMap,
) -> std::result::Result<Json<UserProfileView>, (StatusCode, Json<serde_json::Value>)> {
    let (user, _) = require_auth(&state.pool, &headers).await?;
    Ok(Json(UserProfileView {
        id: user.id,
        name: user.name,
        email: user.email.unwrap_or_default(),
    }))
}

fn public_base_url() -> AnyResult<String> {
    std::env::var("SECRETS_PUBLIC_BASE_URL")
        .or_else(|_| std::env::var("SECRETS_API_BASE"))
        .context("SECRETS_PUBLIC_BASE_URL or SECRETS_API_BASE must be set")
}

fn google_oauth_config() -> AnyResult<GoogleOAuthConfig> {
    Ok(GoogleOAuthConfig {
        client_id: std::env::var("GOOGLE_OAUTH_CLIENT_ID")
            .context("GOOGLE_OAUTH_CLIENT_ID is not set")?,
        client_secret: std::env::var("GOOGLE_OAUTH_CLIENT_SECRET")
            .context("GOOGLE_OAUTH_CLIENT_SECRET is not set")?,
        auth_uri: std::env::var("GOOGLE_OAUTH_AUTH_URI")
            .unwrap_or_else(|_| "https://accounts.google.com/o/oauth2/v2/auth".to_string()),
        token_uri: std::env::var("GOOGLE_OAUTH_TOKEN_URI")
            .unwrap_or_else(|_| "https://oauth2.googleapis.com/token".to_string()),
        redirect_uri: std::env::var("GOOGLE_OAUTH_REDIRECT_URI")
            .context("GOOGLE_OAUTH_REDIRECT_URI is not set")?,
    })
}

fn new_session_secret() -> String {
    new_device_login_token()
}

fn pkce_challenge(verifier: &str) -> String {
    let digest = Sha256::digest(verifier.as_bytes());
    URL_SAFE_NO_PAD.encode(digest)
}

fn login_result_html(title: &str, message: &str) -> String {
    format!(
        "<html><body><h3>{}</h3><p>{}</p><p>现在可以返回 Secrets 桌面端。</p></body></html>",
        title, message
    )
}

fn ensure_login_session_pending(session: &DesktopLoginSessionRow) -> Result<(), &'static str> {
    if session.expires_at < Utc::now() {
        return Err("desktop login session expired");
    }
    if session.status != LOGIN_STATUS_PENDING {
        return Err("desktop login session is no longer pending");
    }
    Ok(())
}

async fn fetch_desktop_login_session(
    pool: &PgPool,
    session_id: &str,
) -> AnyResult<Option<DesktopLoginSessionRow>> {
    sqlx::query_as::<_, DesktopLoginSessionRow>(
        r#"
        SELECT
            session_id, oauth_state, pkce_verifier, device_name, platform, client_version,
            device_fingerprint, status, error_message, user_id, device_id, device_token,
            device_token_hash, expires_at
        FROM desktop_login_sessions
        WHERE session_id = $1
        "#,
    )
    .bind(session_id)
    .fetch_optional(pool)
    .await
    .context("failed to load desktop login session")
}

async fn fetch_desktop_login_session_for_update(
    tx: &mut Transaction<'_, Postgres>,
    session_id: &str,
) -> AnyResult<Option<DesktopLoginSessionRow>> {
    sqlx::query_as::<_, DesktopLoginSessionRow>(
        r#"
        SELECT
            session_id, oauth_state, pkce_verifier, device_name, platform, client_version,
            device_fingerprint, status, error_message, user_id, device_id, device_token,
            device_token_hash, expires_at
        FROM desktop_login_sessions
        WHERE session_id = $1
        FOR UPDATE
        "#,
    )
    .bind(session_id)
    .fetch_optional(&mut **tx)
    .await
    .context("failed to lock desktop login session")
}

async fn fetch_desktop_login_session_by_state(
    tx: &mut Transaction<'_, Postgres>,
    oauth_state: &str,
) -> AnyResult<Option<DesktopLoginSessionRow>> {
    sqlx::query_as::<_, DesktopLoginSessionRow>(
        r#"
        SELECT
            session_id, oauth_state, pkce_verifier, device_name, platform, client_version,
            device_fingerprint, status, error_message, user_id, device_id, device_token,
            device_token_hash, expires_at
        FROM desktop_login_sessions
        WHERE oauth_state = $1
        FOR UPDATE
        "#,
    )
    .bind(oauth_state)
    .fetch_optional(&mut **tx)
    .await
    .context("failed to load desktop login session by oauth state")
}

async fn mark_login_session_failed(
    tx: &mut Transaction<'_, Postgres>,
    session_id: &str,
    message: &str,
) -> AnyResult<()> {
    sqlx::query(
        "UPDATE desktop_login_sessions SET status = $2, error_message = $3, updated_at = NOW() WHERE session_id = $1",
    )
    .bind(session_id)
    .bind(LOGIN_STATUS_FAILED)
    .bind(message)
    .execute(&mut **tx)
    .await?;
    Ok(())
}

async fn mark_login_session_expired(
    tx: &mut Transaction<'_, Postgres>,
    session_id: &str,
) -> AnyResult<()> {
    sqlx::query(
        "UPDATE desktop_login_sessions SET status = $2, error_message = $3, updated_at = NOW() WHERE session_id = $1",
    )
    .bind(session_id)
    .bind(LOGIN_STATUS_EXPIRED)
    .bind("login session expired")
    .execute(&mut **tx)
    .await?;
    Ok(())
}

async fn mark_login_session_succeeded(
    tx: &mut Transaction<'_, Postgres>,
    session_id: &str,
    user_id: Uuid,
    device_id: Uuid,
    device_token: String,
    device_token_hash: String,
) -> AnyResult<()> {
    sqlx::query(
        r#"
        UPDATE desktop_login_sessions
        SET status = $2,
            user_id = $3,
            device_id = $4,
            device_token = $5,
            device_token_hash = $6,
            updated_at = NOW()
        WHERE session_id = $1
        "#,
    )
    .bind(session_id)
    .bind(LOGIN_STATUS_SUCCEEDED)
    .bind(user_id)
    .bind(device_id)
    .bind(device_token)
    .bind(device_token_hash)
    .execute(&mut **tx)
    .await?;
    Ok(())
}

async fn exchange_google_auth_code(
    http: &Client,
    google: &GoogleOAuthConfig,
    code: &str,
    code_verifier: &str,
) -> AnyResult<GoogleTokenResponse> {
    http.post(&google.token_uri)
        .form(&[
            ("client_id", google.client_id.clone()),
            ("client_secret", google.client_secret.clone()),
            ("code", code.to_string()),
            ("code_verifier", code_verifier.to_string()),
            ("grant_type", "authorization_code".to_string()),
            ("redirect_uri", google.redirect_uri.clone()),
        ])
        .send()
        .await
        .context("failed to exchange google auth code")?
        .error_for_status()
        .context("google token exchange failed")?
        .json::<GoogleTokenResponse>()
        .await
        .context("failed to decode google token response")
}

async fn fetch_google_userinfo(http: &Client, access_token: &str) -> AnyResult<GoogleUserInfo> {
    http.get("https://openidconnect.googleapis.com/v1/userinfo")
        .bearer_auth(access_token)
        .send()
        .await
        .context("failed to request google userinfo")?
        .error_for_status()
        .context("google userinfo request failed")?
        .json::<GoogleUserInfo>()
        .await
        .context("failed to decode google userinfo")
}

async fn require_auth(
    pool: &PgPool,
    headers: &HeaderMap,
) -> std::result::Result<(UserRow, DeviceRow), (StatusCode, Json<serde_json::Value>)> {
    let auth = headers
        .get(header::AUTHORIZATION)
        .and_then(|v| v.to_str().ok())
        .and_then(|raw| raw.strip_prefix("Bearer "))
        .map(str::trim)
        .filter(|value| !value.is_empty())
        .ok_or_else(|| unauthorized("missing bearer token"))?;
    let token_hash = hash_device_login_token(auth);

    let row = sqlx::query_as::<_, DeviceRow>(
        r#"
        SELECT
            d.id,
            d.display_name,
            d.platform,
            d.client_version,
            d.last_seen_at,
            NULL::text AS last_ip
        FROM device_login_tokens t
        JOIN devices d ON d.id = t.device_id
        WHERE t.token_hash = $1
        "#,
    )
    .bind(&token_hash)
    .fetch_optional(pool)
    .await
    .map_err(internal_error)?
    .ok_or_else(|| unauthorized("invalid device token"))?;

    sqlx::query("UPDATE device_login_tokens SET last_seen_at = NOW() WHERE token_hash = $1")
        .bind(&token_hash)
        .execute(pool)
        .await
        .map_err(internal_error)?;
    sqlx::query("UPDATE devices SET last_seen_at = NOW() WHERE id = $1")
        .bind(row.id)
        .execute(pool)
        .await
        .map_err(internal_error)?;

    let user = sqlx::query_as::<_, UserRow>(
        r#"
        SELECT u.id, u.email, u.name
        FROM users u
        JOIN devices d ON d.user_id = u.id
        WHERE d.id = $1
        "#,
    )
    .bind(row.id)
    .fetch_one(pool)
    .await
    .map_err(internal_error)?;

    Ok((user, row))
}

async fn ensure_demo_user(pool: &PgPool) -> AnyResult<(Uuid, Uuid)> {
    let existing =
        sqlx::query_as::<_, UserRow>("SELECT id, email, name FROM users WHERE email = $1 LIMIT 1")
            .bind("voson.wang.s@gmail.com")
            .fetch_optional(pool)
            .await?;

    let user_id = if let Some(user) = existing {
        user.id
    } else {
        sqlx::query_scalar::<_, Uuid>(
            r#"
            INSERT INTO users (email, name)
            VALUES ($1, $2)
            RETURNING id
            "#,
        )
        .bind("voson.wang.s@gmail.com")
        .bind("Voson")
        .fetch_one(pool)
        .await?
    };

    let existing_device = sqlx::query_scalar::<_, Uuid>(
        "SELECT id FROM devices WHERE user_id = $1 AND display_name = $2 LIMIT 1",
    )
    .bind(user_id)
    .bind("Voson 的 Mac mini")
    .fetch_optional(pool)
    .await?;

    let device_id = if let Some(id) = existing_device {
        id
    } else {
        sqlx::query_scalar::<_, Uuid>(
            r#"
            INSERT INTO devices (user_id, display_name, platform, client_version, device_fingerprint)
            VALUES ($1, $2, $3, $4, $5)
            RETURNING id
            "#,
        )
        .bind(user_id)
        .bind("Voson 的 Mac mini")
        .bind("macOS")
        .bind(env!("CARGO_PKG_VERSION"))
        .bind(new_device_fingerprint())
        .fetch_one(pool)
        .await?
    };

    Ok((user_id, device_id))
}

async fn upsert_user_from_google(pool: &PgPool, google_user: &GoogleUserInfo) -> AnyResult<Uuid> {
    let existing = sqlx::query_scalar::<_, Uuid>("SELECT id FROM users WHERE email = $1 LIMIT 1")
        .bind(&google_user.email)
        .fetch_optional(pool)
        .await?;

    if let Some(user_id) = existing {
        sqlx::query("UPDATE users SET name = $1, updated_at = NOW() WHERE id = $2")
            .bind(
                google_user
                    .name
                    .clone()
                    .unwrap_or_else(|| google_user.email.clone()),
            )
            .bind(user_id)
            .execute(pool)
            .await?;
        return Ok(user_id);
    }

    sqlx::query_scalar::<_, Uuid>(
        r#"
        INSERT INTO users (email, name)
        VALUES ($1, $2)
        RETURNING id
        "#,
    )
    .bind(&google_user.email)
    .bind(
        google_user
            .name
            .clone()
            .unwrap_or_else(|| google_user.email.clone()),
    )
    .fetch_one(pool)
    .await
    .context("failed to create user from google login")
}

async fn upsert_google_oauth_account(
    pool: &PgPool,
    user_id: Uuid,
    google_user: &GoogleUserInfo,
) -> AnyResult<()> {
    sqlx::query(
        r#"
        INSERT INTO oauth_accounts (user_id, provider, provider_id, email, name)
        VALUES ($1, 'google', $2, $3, $4)
        ON CONFLICT (provider, provider_id)
        DO UPDATE SET
            user_id = EXCLUDED.user_id,
            email = EXCLUDED.email,
            name = EXCLUDED.name
        "#,
    )
    .bind(user_id)
    .bind(&google_user.sub)
    .bind(&google_user.email)
    .bind(
        google_user
            .name
            .clone()
            .unwrap_or_else(|| google_user.email.clone()),
    )
    .execute(pool)
    .await
    .context("failed to upsert google oauth account")?;
    Ok(())
}

async fn upsert_device_for_login(
    pool: &PgPool,
    user_id: Uuid,
    device_name: &str,
    platform: &str,
    client_version: &str,
    device_fingerprint: &str,
) -> AnyResult<Uuid> {
    let existing = sqlx::query_scalar::<_, Uuid>(
        "SELECT id FROM devices WHERE user_id = $1 AND device_fingerprint = $2 LIMIT 1",
    )
    .bind(user_id)
    .bind(device_fingerprint)
    .fetch_optional(pool)
    .await?;

    if let Some(device_id) = existing {
        sqlx::query(
            r#"
            UPDATE devices
            SET display_name = $1, platform = $2, client_version = $3, last_seen_at = NOW()
            WHERE id = $4
            "#,
        )
        .bind(device_name)
        .bind(platform)
        .bind(client_version)
        .bind(device_id)
        .execute(pool)
        .await?;
        return Ok(device_id);
    }

    sqlx::query_scalar::<_, Uuid>(
        r#"
        INSERT INTO devices (user_id, display_name, platform, client_version, device_fingerprint)
        VALUES ($1, $2, $3, $4, $5)
        RETURNING id
        "#,
    )
    .bind(user_id)
    .bind(device_name)
    .bind(platform)
    .bind(client_version)
    .bind(device_fingerprint)
    .fetch_one(pool)
    .await
    .context("failed to create device")
}

async fn issue_device_login_token(
    pool: &PgPool,
    user_id: Uuid,
    device_id: Uuid,
    device_name: &str,
    platform: &str,
    client_version: &str,
) -> AnyResult<String> {
    let device_token = new_device_login_token();
    let token_hash = hash_device_login_token(&device_token);

    sqlx::query("DELETE FROM device_login_tokens WHERE device_id = $1")
        .bind(device_id)
        .execute(pool)
        .await?;
    sqlx::query("INSERT INTO device_login_tokens (device_id, token_hash) VALUES ($1, $2)")
        .bind(device_id)
        .bind(token_hash)
        .execute(pool)
        .await?;
    sqlx::query(
        r#"
        INSERT INTO auth_events (
            user_id, device_id, device_name, platform, client_version, ip_addr, forwarded_ip, login_method, login_result
        )
        VALUES ($1, $2, $3, $4, $5, $6, $7, 'google_desktop', 'success')
        "#,
    )
    .bind(user_id)
    .bind(device_id)
    .bind(device_name)
    .bind(platform)
    .bind(client_version)
    .bind::<Option<String>>(None)
    .bind::<Option<String>>(None)
    .execute(pool)
    .await?;

    Ok(device_token)
}

async fn consume_device_token_for_poll(
    tx: &mut Transaction<'_, Postgres>,
    session_id: &str,
) -> AnyResult<String> {
    let token = sqlx::query_scalar::<_, Option<String>>(
        "SELECT device_token FROM desktop_login_sessions WHERE session_id = $1 FOR UPDATE",
    )
    .bind(session_id)
    .fetch_one(&mut **tx)
    .await?
    .context("device token already consumed")?;

    sqlx::query(
        "UPDATE desktop_login_sessions SET device_token = NULL, updated_at = NOW() WHERE session_id = $1",
    )
    .bind(session_id)
    .execute(&mut **tx)
    .await?;

    Ok(token)
}

fn internal_error<E: std::fmt::Display>(error: E) -> (StatusCode, Json<serde_json::Value>) {
    (
        StatusCode::INTERNAL_SERVER_ERROR,
        Json(json!({ "error": error.to_string() })),
    )
}

fn unauthorized(message: &str) -> (StatusCode, Json<serde_json::Value>) {
    (StatusCode::UNAUTHORIZED, Json(json!({ "error": message })))
}