package weixin_ilink

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"strconv"
	"time"
)

// loginPollInterval is the default how often Connect polls the QR confirmation
// status. It is the documented ~1s cadence; the Config.LoginInterval field
// overrides it (used by tests to keep the flow short).
const loginPollInterval = 1 * time.Second

// qrcodeResp is the get_bot_qrcode response.
type qrcodeResp struct {
	Qrcode           string `json:"qrcode"`
	QrcodeImgContent string `json:"qrcode_img_content"`
}

// qrcodeStatusResp is the get_qrcode_status response. The token and ids are
// only populated once status is "confirmed".
type qrcodeStatusResp struct {
	Status   string `json:"status"`
	BotToken string `json:"bot_token"`
	BotID    string `json:"ilink_bot_id"`
	UserID   string `json:"ilink_user_id"`
	BaseURL  string `json:"baseurl"`
	// RedirectHost carries the IDC host to poll next when status is
	// "scaned_but_redirect" (official currentApiBaseUrl redirect).
	RedirectHost string `json:"redirect_host"`
}

// login is the Connect-side scan-code binding (design/08 §4). It joins (or
// starts) a scan-login via StartLogin and blocks until the user confirms or the
// window elapses. Because it shares the session machinery with the panel's
// StartLogin, a panel-initiated login and Connect never run two QR binds at once.
func (a *Adapter) login(ctx context.Context) error {
	_, err := a.StartLogin(ctx)
	if errors.Is(err, ErrAlreadyLoggedIn) {
		return nil
	}
	if err != nil {
		return err
	}

	a.loginMu.Lock()
	sess := a.loginSession
	a.loginMu.Unlock()
	if sess == nil {
		return fmt.Errorf("weixin_ilink: login session missing")
	}

	select {
	case lerr := <-sess.done:
		return lerr
	case <-ctx.Done():
		sess.cancel()
		return fmt.Errorf("%w: %w", ErrLoginTimeout, ctx.Err())
	}
}

// runLogin polls get_qrcode_status until the QR is confirmed or the login window
// elapses, then records the outcome under the session. It runs in a goroutine so
// StartLogin returns immediately while the panel polls LoginStatus.
func (a *Adapter) runLogin(sess *loginSession, sessCtx context.Context) {
	timeoutCtx, cancel := context.WithTimeout(sessCtx, a.cfg.LoginTimeout)
	defer cancel()
	ticker := time.NewTicker(a.cfg.LoginInterval)
	defer ticker.Stop()

	prevStatus := ""
	for {
		status, err := a.pollQRStatus(timeoutCtx, sess.qrcode)
		if err != nil {
			// A deadline/cancel during the poll means the whole window elapsed;
			// surface ErrLoginTimeout rather than the raw transport error.
			if timeoutCtx.Err() != nil {
				a.failLogin(sess, fmt.Errorf("%w: %w", ErrLoginTimeout, timeoutCtx.Err()))
			} else {
				a.failLogin(sess, fmt.Errorf("weixin_ilink: poll qr status: %w", err))
			}
			return
		}
		// Track the raw wire phase so StartLogin can protect a scanned/confirming bind
		// from being re-minted. Log only on a status change to avoid noise, and never
		// the qrcode identifier or tokens.
		sess.setPhase(status.Status)
		if status.Status != prevStatus {
			prevStatus = status.Status
			a.log.Info("weixin_ilink: get_qrcode_status", "status", status.Status)
		}

		switch status.Status {
		case "confirmed":
			if status.BotToken == "" {
				a.failLogin(sess, fmt.Errorf("weixin_ilink: login confirmed but no bot_token returned"))
				return
			}
			a.completeLogin(sess, status)
			return
		case "binded_redirect":
			// The scanned bot is already bound to this instance; no new credentials
			// are issued. Treat it as an already-bound (successful) outcome.
			a.completeBindedRedirect(sess)
			return
		case "verify_code_blocked":
			a.failLogin(sess, fmt.Errorf("weixin_ilink: verify code blocked, too many failed attempts"))
			return
		case "scaned":
			// The code has been scanned and awaits confirmation on the phone. Keep the
			// session and keep polling — re-minting here would discard the pending
			// confirmation. Expose the state through the backward-compatible waiting
			// status plus a detail so the panel can prompt the user to confirm.
			a.setLoginState(LoginStatusWaiting, loginScannedDetail)
		case "scaned_but_redirect":
			if status.RedirectHost != "" {
				a.setPollBaseURL(status.RedirectHost)
				a.log.Info("weixin_ilink: idc redirect, switching polling host", "host", status.RedirectHost)
			} else {
				a.log.Warn("weixin_ilink: scaned_but_redirect without redirect_host, continuing on current host")
			}
		case "need_verifycode":
			// The server asks for a pairing code shown in the phone WeChat. Expose
			// the state and a hint so the panel can prompt the user; the code itself
			// is not yet plumbed back to the poll (see TODO).
			a.setLoginState(LoginStatusNeedVerifyCode, loginNeedVerifyCodeHint)
		}
		// wait / scaned / expired / need_verifycode / scaned_but_redirect keep
		// polling until confirmed or the window elapses.
		select {
		case <-timeoutCtx.Done():
			a.failLogin(sess, fmt.Errorf("%w: %w", ErrLoginTimeout, timeoutCtx.Err()))
			return
		case <-ticker.C:
		}
	}
}

// completeLogin persists the confirmed credentials and marks the session live.
// It writes cfg under a.mu, then clears the session under loginMu (never nesting
// the two locks), and finally signals the waiting Connect path.
func (a *Adapter) completeLogin(sess *loginSession, status qrcodeStatusResp) {
	a.mu.Lock()
	a.cfg.BotToken = status.BotToken
	a.cfg.BotID = status.BotID
	a.cfg.OwnerID = status.UserID
	if status.BaseURL != "" {
		a.cfg.BaseURL = status.BaseURL
	}
	a.connected = true
	a.loginStatus = LoginStatusConfirmed
	a.loginDetail = ""
	a.mu.Unlock()

	a.log.Info("weixin_ilink: login confirmed", "bot_id", status.BotID)

	a.loginMu.Lock()
	if a.loginSession == sess {
		a.loginSession = nil
	}
	a.loginMu.Unlock()

	sess.done <- nil
}

// completeBindedRedirect treats binded_redirect as an already-bound outcome: the
// scanned bot is already linked to this instance, so the server issues no new
// credentials and any existing token remains valid.
func (a *Adapter) completeBindedRedirect(sess *loginSession) {
	a.log.Info("weixin_ilink: login already bound (binded_redirect)")
	a.mu.Lock()
	a.connected = a.cfg.BotToken != ""
	a.loginStatus = LoginStatusConfirmed
	a.loginDetail = loginBindedRedirectDetail
	a.mu.Unlock()

	a.loginMu.Lock()
	if a.loginSession == sess {
		a.loginSession = nil
	}
	a.loginMu.Unlock()

	sess.done <- nil
}

// failLogin records a failed scan-login and signals the waiting Connect path. A
// superseded session (one cancelled so StartLogin could mint a fresh QR for an
// unscanned code) never clobbers the newer session's state, but its Connect wait
// must still be released.
func (a *Adapter) failLogin(sess *loginSession, err error) {
	a.loginMu.Lock()
	isCurrent := a.loginSession == sess
	if isCurrent {
		a.loginSession = nil
	}
	a.loginMu.Unlock()

	if isCurrent {
		a.log.Warn("weixin_ilink: login failed", "err", err)
		a.setLoginState(LoginStatusFailed, err.Error())
	}
	sess.done <- err
}

// localTokenList returns the locally-held bot tokens to advertise on
// get_bot_qrcode, so an already-bound bot can be detected (binded_redirect). On a
// fresh bind it returns an empty (non-nil) slice so the wire carries `[]` rather
// than `null`, matching the official client.
func (a *Adapter) localTokenList() []string {
	a.mu.RLock()
	defer a.mu.RUnlock()
	if a.cfg.BotToken == "" {
		return []string{}
	}
	return []string{a.cfg.BotToken}
}

// fetchQRCode requests a new bot login QR code. The official client issues this as
// a POST carrying local_token_list so the server can detect an existing bind and
// answer binded_redirect instead of a fresh code.
func (a *Adapter) fetchQRCode(ctx context.Context) (qrcodeResp, error) {
	path := a.apiURL("/ilink/bot/get_bot_qrcode?bot_type=" + strconv.Itoa(botType))
	body, err := json.Marshal(map[string]any{"local_token_list": a.localTokenList()})
	if err != nil {
		return qrcodeResp{}, fmt.Errorf("weixin_ilink: marshal get_bot_qrcode body: %w", err)
	}
	var out qrcodeResp
	if err := a.doJSON(ctx, http.MethodPost, path, bytes.NewReader(body), &out); err != nil {
		return qrcodeResp{}, err
	}
	if out.Qrcode == "" {
		return qrcodeResp{}, fmt.Errorf("weixin_ilink: get_bot_qrcode returned empty qrcode")
	}
	// Log only the renderable QR URL, never the raw qrcode identifier (it is a secret
	// echoed to get_qrcode_status). The timestamp is attached by the logger.
	a.log.Info("weixin_ilink: get_bot_qrcode ok", "url", out.QrcodeImgContent)
	return out, nil
}

// pollQRStatus checks whether a QR code has been confirmed. It polls the IDC
// redirect host if one was recorded (scaned_but_redirect), else the base URL.
func (a *Adapter) pollQRStatus(ctx context.Context, qrcode string) (qrcodeStatusResp, error) {
	path := "/ilink/bot/get_qrcode_status?qrcode=" + url.QueryEscape(qrcode)
	var out qrcodeStatusResp
	if err := a.doJSON(ctx, http.MethodGet, joinURL(a.pollBase(), path), nil, &out); err != nil {
		return qrcodeStatusResp{}, err
	}
	return out, nil
}