//! `/api/v1/admin/auth/*` — login, logout, who-am-I.
//!
//! Login mints an opaque session token, stores its SHA-256, sets the
//! `picloud_session` HttpOnly cookie, and also returns the raw token in
//! the JSON body for non-browser clients. The same token works as
//! `Authorization: Bearer …` afterward; there is no separate "API
//! token" concept yet.
//!
//! Logout deletes the session row regardless of whether the supplied
//! token matched anything (idempotent). `me` returns the row that the
//! middleware already attached to the request extensions.

use axum::body::Body;
use axum::extract::{Extension, Request, State};
use axum::http::{header, HeaderMap, HeaderValue, StatusCode};
use axum::middleware::from_fn_with_state;
use axum::response::{IntoResponse, Json, Response};
use axum::routing::{get, post};
use axum::Router;
use chrono::{DateTime, Duration as ChronoDuration, Utc};
use picloud_shared::{AdminUserId, InstanceRole};
use serde::{Deserialize, Serialize};
use serde_json::json;

use picloud_shared::Principal;

use crate::auth::{generate_session_token, hash_token, verify_password};
use crate::auth_middleware::{require_authenticated, AuthState, SESSION_COOKIE};

pub fn auth_router(state: AuthState) -> Router {
    // /login + /logout are unguarded (login is how you get in; logout
    // is idempotent). /me is guarded — by definition it needs to know
    // who you are, so the middleware must run first.
    let guarded = Router::new()
        .route("/auth/me", get(me))
        .route_layer(from_fn_with_state(state.clone(), require_authenticated));

    Router::new()
        .route("/auth/login", post(login))
        .route("/auth/logout", post(logout))
        .merge(guarded)
        .with_state(state)
}

// ----------------------------------------------------------------------------
// DTOs
// ----------------------------------------------------------------------------

#[derive(Debug, Deserialize)]
pub struct LoginRequest {
    pub username: String,
    pub password: String,
}

#[derive(Debug, Serialize)]
pub struct LoginResponse {
    pub user: AdminUserDto,
    pub token: String,
    pub expires_at: DateTime<Utc>,
}

#[derive(Debug, Serialize)]
pub struct AdminUserDto {
    pub id: AdminUserId,
    pub username: String,
    pub instance_role: InstanceRole,
    pub email: Option<String>,
}

// ----------------------------------------------------------------------------
// Handlers
// ----------------------------------------------------------------------------

async fn login(State(state): State<AuthState>, Json(input): Json<LoginRequest>) -> Response {
    // Always perform a verify, even on missing/inactive users, to flatten
    // timing and prevent username enumeration. The dummy hash is a real
    // Argon2id PHC string for "x" — the verify will simply fail.
    const DUMMY_HASH: &str = "$argon2id$v=19$m=19456,t=2,p=1$dGltaW5nLWZsYXR0ZW4$Ux6dgPqgX1Mhg5fRgIeKZF3MWdYqJplKEz/cKLcSdks";

    let creds = match state
        .users
        .get_credentials_by_username(&input.username)
        .await
    {
        Ok(c) => c,
        Err(err) => {
            tracing::error!(?err, "admin_users credentials lookup failed");
            return internal_error();
        }
    };

    // username from creds is discarded — the re-fetch below carries the
    // canonical row used in the response DTO.
    let (stored_hash, user_id, is_active) = match creds {
        Some(c) => (c.password_hash, Some(c.id), c.is_active),
        None => (DUMMY_HASH.to_string(), None, false),
    };

    let password_ok = verify_password(&stored_hash, &input.password);
    if !password_ok || user_id.is_none() || !is_active {
        return invalid_credentials();
    }
    let user_id = user_id.unwrap();

    // Re-fetch the full row so the login response carries the same
    // shape /me does (instance_role, email). The credentials struct
    // intentionally omits email; one extra query per login is fine.
    let user_row = match state.users.get(user_id).await {
        Ok(Some(row)) => row,
        Ok(None) => return invalid_credentials(),
        Err(err) => {
            tracing::error!(?err, "admin_users lookup after login failed");
            return internal_error();
        }
    };

    let token = generate_session_token();
    let expires_at = Utc::now()
        + ChronoDuration::from_std(state.ttl).unwrap_or_else(|_| ChronoDuration::hours(24));

    if let Err(err) = state
        .sessions
        .create(user_id, &token.hash, expires_at)
        .await
    {
        tracing::error!(?err, "admin_sessions insert failed");
        return internal_error();
    }
    if let Err(err) = state.users.touch_last_login(user_id).await {
        // Non-fatal — log and continue. Login itself succeeded.
        tracing::warn!(?err, "failed to touch admin last_login_at");
    }

    let mut headers = HeaderMap::new();
    headers.insert(
        header::SET_COOKIE,
        HeaderValue::from_str(&build_cookie(&token.raw, state.ttl)).unwrap_or_else(|_| {
            // Cookie text is ASCII-clean by construction; this branch is
            // unreachable in practice but the type signature requires it.
            HeaderValue::from_static("")
        }),
    );

    (
        StatusCode::OK,
        headers,
        Json(LoginResponse {
            user: AdminUserDto {
                id: user_row.id,
                username: user_row.username,
                instance_role: user_row.instance_role,
                email: user_row.email,
            },
            token: token.raw,
            expires_at,
        }),
    )
        .into_response()
}

async fn logout(State(state): State<AuthState>, req: Request<Body>) -> Response {
    // Pull token without requiring a valid session (logout is idempotent
    // and we still want to clear the cookie on the client side).
    let token = extract_token_for_logout(&req);
    if let Some(raw) = token {
        let hash = hash_token(&raw);
        if let Err(err) = state.sessions.delete(&hash).await {
            tracing::error!(?err, "admin_sessions delete failed");
            // Still clear the cookie below.
        }
    }

    let mut headers = HeaderMap::new();
    headers.insert(
        header::SET_COOKIE,
        HeaderValue::from_static("picloud_session=; HttpOnly; Path=/; SameSite=Lax; Max-Age=0"),
    );
    (StatusCode::NO_CONTENT, headers).into_response()
}

async fn me(
    State(state): State<AuthState>,
    Extension(principal): Extension<Principal>,
) -> Response {
    // /me consumes the resolved Principal directly; we re-fetch the
    // user row only to surface a fresh username (it can change via
    // PATCH while a session/key is still valid).
    match state.users.get(principal.user_id).await {
        Ok(Some(row)) => Json(AdminUserDto {
            id: row.id,
            username: row.username,
            instance_role: row.instance_role,
            email: row.email,
        })
        .into_response(),
        Ok(None) => invalid_credentials(),
        Err(err) => {
            tracing::error!(?err, "admin_users lookup for /me failed");
            internal_error()
        }
    }
}

// ----------------------------------------------------------------------------
// Helpers
// ----------------------------------------------------------------------------

fn build_cookie(raw_token: &str, ttl: std::time::Duration) -> String {
    // Secure is on by default; flip to off for HTTP-only dev with
    // PICLOUD_COOKIE_SECURE=0. The header-injected bearer token works
    // either way, so this is purely for browsers that prefer the cookie
    // path (e.g., direct API hits without the dashboard's auth.ts).
    let secure = std::env::var("PICLOUD_COOKIE_SECURE").ok().is_none_or(|v| {
        !matches!(
            v.to_ascii_lowercase().as_str(),
            "0" | "false" | "no" | "off"
        )
    });
    let secure_attr = if secure { "; Secure" } else { "" };
    format!(
        "{SESSION_COOKIE}={raw_token}; HttpOnly{secure_attr}; SameSite=Lax; Path=/; Max-Age={}",
        ttl.as_secs()
    )
}

fn extract_token_for_logout(req: &Request<Body>) -> Option<String> {
    // Same precedence as the middleware — Authorization first, cookie
    // fallback. Duplicated here because logout has to read the request
    // before any middleware would run.
    if let Some(value) = req.headers().get(header::AUTHORIZATION) {
        if let Ok(s) = value.to_str() {
            if let Some(token) = s.strip_prefix("Bearer ") {
                let trimmed = token.trim();
                if !trimmed.is_empty() {
                    return Some(trimmed.to_string());
                }
            }
        }
    }
    if let Some(value) = req.headers().get(header::COOKIE) {
        if let Ok(s) = value.to_str() {
            for chunk in s.split(';') {
                let chunk = chunk.trim();
                if let Some(rest) = chunk.strip_prefix(&format!("{SESSION_COOKIE}=")) {
                    if !rest.is_empty() {
                        return Some(rest.to_string());
                    }
                }
            }
        }
    }
    None
}

fn invalid_credentials() -> Response {
    (
        StatusCode::UNAUTHORIZED,
        Json(json!({ "error": "invalid credentials" })),
    )
        .into_response()
}

fn internal_error() -> Response {
    (
        StatusCode::INTERNAL_SERVER_ERROR,
        Json(json!({ "error": "internal error" })),
    )
        .into_response()
}