package weixin_ilink

// This file exposes the non-blocking scan-login surface the admin panel drives
// (design/08 §4): StartLogin mints (or returns the in-progress) QR code without
// blocking, and LoginStatus reports where the bind stands so the panel can poll
// idle → waiting → confirmed. Connect (login.go) reuses StartLogin internally and
// then waits, so a panel-initiated login and the bridge's Connect never start two
// concurrent QR binds.

import (
	"context"
	"errors"
	"fmt"
	"sync"
	"time"
)

// Login status values reported by Adapter.LoginStatus.
const (
	// LoginStatusIdle means no bot token and no scan-login in progress.
	LoginStatusIdle = "idle"
	// LoginStatusWaiting means a QR code is displayed and the user has not yet
	// confirmed the bind.
	LoginStatusWaiting = "waiting"
	// LoginStatusConfirmed means a bot token is present (either a fresh scan or a
	// pre-configured one).
	LoginStatusConfirmed = "confirmed"
	// LoginStatusFailed means the last scan/login attempt errored or timed out.
	LoginStatusFailed = "failed"
	// LoginStatusNeedVerifyCode means the WeChat server asks for a pairing code
	// shown on the phone WeChat; the panel should prompt the user to enter it.
	LoginStatusNeedVerifyCode = "need_verifycode"
)

// loginNeedVerifyCodeHint is the detail LoginStatus reports for need_verifycode so
// the panel can prompt the user; loginBindedRedirectDetail is what a binded_redirect
// outcome reports.
const (
	loginNeedVerifyCodeHint   = "请输入微信显示的数字"
	loginBindedRedirectDetail = "已连接过此 OpenClaw，无需重复连接"
	// loginScannedDetail is the detail reported while the QR has been scanned and is
	// awaiting confirmation on the phone. It reuses LoginStatusWaiting so the panel
	// stays backward-compatible; the raw wire "scaned" state is tracked separately on
	// the session (loginSession.phase) so StartLogin can protect the bind from being
	// re-minted mid-confirmation.
	loginScannedDetail = "已被扫描，请在微信确认"
)

// ErrAlreadyLoggedIn is returned by StartLogin when a bot token is already
// configured, so the scan flow is moot.
var ErrAlreadyLoggedIn = errors.New("weixin_ilink: already logged in")

// LoginQR is the artifact StartLogin returns for the panel to render: Qrcode is
// the raw scan identifier the adapter echoes to get_qrcode_status, and Image is
// the QR image content (currently the image URL returned by get_bot_qrcode).
type LoginQR struct {
	Qrcode string
	Image  string
}

// loginSession tracks one scan-login run. It is guarded by Adapter.loginMu.
type loginSession struct {
	qrcode    string
	image     string
	startedAt time.Time
	// cancel stops the poll goroutine early (e.g. Connect's deadline elapsed).
	cancel context.CancelFunc
	// done carries the login outcome; the poll goroutine writes exactly once.
	done chan error

	// phase is the latest get_qrcode_status value the poll goroutine observed. It is
	// guarded by phaseMu and is distinct from loginStatus, which is the panel-observable
	// state and stays backward-compatible ("waiting") during a "scaned" confirmation.
	phaseMu sync.Mutex
	phase   string
}

// setPhase records the latest observed wire status.
func (s *loginSession) setPhase(p string) {
	s.phaseMu.Lock()
	s.phase = p
	s.phaseMu.Unlock()
}

// currentPhase returns the latest observed wire status.
func (s *loginSession) currentPhase() string {
	s.phaseMu.Lock()
	defer s.phaseMu.Unlock()
	return s.phase
}

// confirmingPhase reports whether the QR bind is mid-flow in a way that re-minting a
// fresh code would discard: the code has been scanned and awaits confirmation, the
// server redirected the polling host after a scan, or the server asked for a pairing
// code. Such sessions are reused, never re-minted.
func (s *loginSession) confirmingPhase() bool {
	switch s.currentPhase() {
	case "scaned", "scaned_but_redirect", "need_verifycode":
		return true
	default:
		return false
	}
}

// qrReuseWindow is how long a just-minted QR is reused on an immediate re-click
// before StartLogin re-mints a fresh one. WeChat bot QRs are short-lived, so a
// "扫码登录/刷新二维码" click must yield a brand-new code — reusing an old QR is
// exactly what makes WeChat report "二维码过期". A QR that is already scanned
// (confirmingPhase) is always reused regardless of this window so the bind is not
// dropped mid-confirmation.
const qrReuseWindow = 5 * time.Second

// StartLogin begins a scan-login and returns the QR code to display. It is
// idempotent: when a login is already in progress it returns the current QR
// without issuing a new get_bot_qrcode, and when a bot token is already present it
// returns ErrAlreadyLoggedIn. It never blocks on the user's scan — the status poll
// runs in a background goroutine that LoginStatus reports on.
func (a *Adapter) StartLogin(ctx context.Context) (LoginQR, error) {
	a.loginMu.Lock()
	defer a.loginMu.Unlock()

	// Already bound → scanning is moot.
	if a.hasToken() {
		return LoginQR{}, ErrAlreadyLoggedIn
	}
	if sess := a.loginSession; sess != nil {
		// A bind is in progress. Re-minting would cancel the poll and, if the user has
		// already scanned or the server is mid-flow, discard the pending confirmation —
		// WeChat's confirm would then never land. Protect those sessions by reusing the
		// current QR unconditionally. Only a QR still waiting to be scanned and past the
		// tiny reuse window is re-minted, so an explicit "刷新二维码" yields a fresh code.
		if sess.confirmingPhase() {
			a.log.Info("weixin_ilink: login in progress, reusing qrcode", "phase", sess.currentPhase())
			return LoginQR{Qrcode: sess.qrcode, Image: sess.image}, nil
		}
		// A literal double-click within the reuse window: serve the same code.
		if time.Since(sess.startedAt) < qrReuseWindow {
			return LoginQR{Qrcode: sess.qrcode, Image: sess.image}, nil
		}
		// Not scanned yet and past the reuse window: mint a fresh code, cancelling the
		// old (unscanned) poll. failLogin guards a cancelled goroutine from clobbering
		// the new session's state.
		a.log.Info("weixin_ilink: previous qrcode not scanned, minting a fresh one")
		if sess.cancel != nil {
			sess.cancel()
		}
		a.loginSession = nil
	}

	raw, err := a.fetchQRCode(ctx)
	if err != nil {
		a.setLoginState(LoginStatusFailed, err.Error())
		return LoginQR{}, fmt.Errorf("weixin_ilink: fetch qrcode: %w", err)
	}

	sessCtx, cancel := context.WithCancel(context.Background())
	sess := &loginSession{
		qrcode:    raw.Qrcode,
		image:     raw.QrcodeImgContent,
		startedAt: time.Now(),
		cancel:    cancel,
		done:      make(chan error, 1),
	}
	a.loginSession = sess
	a.setLoginState(LoginStatusWaiting, "")
	// Reset any IDC redirect host recorded by a previous (re-)scan so a new login
	// starts polling the configured base URL.
	a.setPollBaseURL("")

	go a.runLogin(sess, sessCtx)
	return LoginQR{Qrcode: sess.qrcode, Image: sess.image}, nil
}

// LoginStatus reports the current scan-login state. A non-empty bot token
// overrides to "confirmed" even if a stale session is still recorded, so the panel
// always sees the true binding. detail provides the bot id on confirmation and the
// failure reason on failure.
func (a *Adapter) LoginStatus(ctx context.Context) (status, detail string) {
	a.mu.RLock()
	defer a.mu.RUnlock()
	if a.cfg.BotToken != "" {
		return LoginStatusConfirmed, a.cfg.BotID
	}
	return a.loginStatus, a.loginDetail
}

// hasToken reports whether a bot token is configured. It reads cfg, so callers
// must not rely on it while holding a.mu.
func (a *Adapter) hasToken() bool {
	a.mu.RLock()
	defer a.mu.RUnlock()
	return a.cfg.BotToken != ""
}

// setLoginState writes the observable login status under a.mu. It may be called
// with loginMu held (StartLogin) or from the poll goroutine; a.mu outlives both.
func (a *Adapter) setLoginState(status, detail string) {
	a.mu.Lock()
	a.loginStatus = status
	a.loginDetail = detail
	a.mu.Unlock()
}