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 (
	"time"
	"context"
	"errors"
	"fmt"
)

// 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"
)

// 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
}

// qrRefreshTTL bounds how long a WeChat bot QR is usable before StartLogin re-mints
// a fresh one. iLink bot QRs are short-lived; an idempotent StartLogin must not keep
// serving a long-expired QR (the user would scan it and get "二维码过期").
const qrRefreshTTL = 90 * 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 {
		// Idempotent for a fresh QR, but re-mint once the current QR has aged past
		// qrRefreshTTL so the panel's 刷新二维码 always yields a scannable code.
		if time.Since(sess.startedAt) < qrRefreshTTL {
			return LoginQR{Qrcode: sess.qrcode, Image: sess.image}, nil
		}
		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, "")
	// Log only the renderable URL, never the raw qrcode (it is a secret).
	a.log.Info("scan the qr code to bind the bot", "url", raw.QrcodeImgContent)

	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()
}