package app

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"strconv"
	"strings"
	"sync"
	"time"
)

// Until now the app collected push tokens and never sent anything: with the App
// in the background there is no socket, so a message simply arrived silently.
// This is the other half — deciding who should be told, and telling them.
//
// The decision is deliberately conservative. A push goes out only to a
// recipient who is not connected right now, has not muted the conversation, and
// has not switched the notification off. Everyone else already sees the message
// where they are looking.

const (
	pushTokenSafetyWindow = 5 * time.Minute
	pushRequestTimeout    = 8 * time.Second
	pushPreviewRunes      = 30
)

type pushTarget struct {
	UserID   int64
	Token    string
	Platform string
}

type pushCredentials struct {
	AppID        string
	AppKey       string
	MasterSecret string
	BaseURL      string
}

func (c pushCredentials) complete() bool {
	return c.AppID != "" && c.AppKey != "" && c.MasterSecret != ""
}

type pushAuth struct {
	mu      sync.Mutex
	token   string
	expires time.Time
	forKey  string
}

func (a *App) pushSettings(ctx context.Context) (pushCredentials, bool) {
	if !a.configBool(ctx, "push.enabled", false) {
		return pushCredentials{}, false
	}
	credentials := pushCredentials{
		AppID:        strings.TrimSpace(a.configPlain(ctx, "push.app_id", "")),
		AppKey:       strings.TrimSpace(a.configPlain(ctx, "push.app_key", "")),
		MasterSecret: strings.TrimSpace(a.configPlain(ctx, "push.master_secret", "")),
		BaseURL:      strings.TrimRight(strings.TrimSpace(a.configPlain(ctx, "push.base_url", "https://restapi.getui.com")), "/"),
	}
	if credentials.BaseURL == "" {
		credentials.BaseURL = "https://restapi.getui.com"
	}
	return credentials, credentials.complete()
}

// token returns a cached auth token, refreshing it when it is close to expiry.
// Getui allows 100 auth calls a minute, so caching is not optional.
func (a *App) pushToken(ctx context.Context, credentials pushCredentials) (string, error) {
	a.push.mu.Lock()
	defer a.push.mu.Unlock()
	key := credentials.AppID + ":" + credentials.AppKey
	if a.push.forKey == key && a.push.token != "" && time.Now().Add(pushTokenSafetyWindow).Before(a.push.expires) {
		return a.push.token, nil
	}
	timestamp := strconv.FormatInt(time.Now().UnixMilli(), 10)
	digest := sha256.Sum256([]byte(credentials.AppKey + timestamp + credentials.MasterSecret))
	body, err := a.pushPost(ctx, credentials, "/auth", "", map[string]string{
		"sign":      hex.EncodeToString(digest[:]),
		"timestamp": timestamp,
		"appkey":    credentials.AppKey,
	})
	if err != nil {
		return "", err
	}
	var payload struct {
		Code int    `json:"code"`
		Msg  string `json:"msg"`
		Data struct {
			Token      string `json:"token"`
			ExpireTime string `json:"expire_time"`
		} `json:"data"`
	}
	if err = json.Unmarshal(body, &payload); err != nil {
		return "", fmt.Errorf("推送鉴权响应无法解析")
	}
	if payload.Code != 0 || payload.Data.Token == "" {
		return "", fmt.Errorf("推送鉴权失败：%s", payload.Msg)
	}
	expires := time.Now().Add(12 * time.Hour)
	if milliseconds, convErr := strconv.ParseInt(payload.Data.ExpireTime, 10, 64); convErr == nil && milliseconds > 0 {
		expires = time.UnixMilli(milliseconds)
	}
	a.push.token, a.push.expires, a.push.forKey = payload.Data.Token, expires, key
	return a.push.token, nil
}

func (a *App) pushPost(ctx context.Context, credentials pushCredentials, path, token string, payload any) ([]byte, error) {
	encoded, err := json.Marshal(payload)
	if err != nil {
		return nil, err
	}
	endpoint := credentials.BaseURL + "/v2/" + credentials.AppID + path
	request, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, bytes.NewReader(encoded))
	if err != nil {
		return nil, err
	}
	request.Header.Set("Content-Type", "application/json;charset=utf-8")
	if token != "" {
		request.Header.Set("token", token)
	}
	response, err := (&http.Client{Timeout: pushRequestTimeout}).Do(request)
	if err != nil {
		return nil, fmt.Errorf("推送服务不可达")
	}
	defer response.Body.Close()
	body, err := io.ReadAll(io.LimitReader(response.Body, 1<<20))
	if err != nil {
		return nil, err
	}
	if response.StatusCode < 200 || response.StatusCode >= 300 {
		return nil, fmt.Errorf("推送服务返回 HTTP %d", response.StatusCode)
	}
	return body, nil
}

// pushRecipients is the whole policy in one query: who, of these members, is
// away from the app and still wants to hear about it.
func (a *App) pushRecipients(ctx context.Context, conversationID, senderID int64, members []int64) []pushTarget {
	targets := []pushTarget{}
	for _, member := range members {
		if member == senderID || a.hub.online(member) {
			continue
		}
		var muted, allowed int
		if err := a.db.QueryRowContext(ctx, `SELECT m.muted,COALESCE(ns.im_enabled,1)
			FROM im_conversation_members m LEFT JOIN user_notification_settings ns ON ns.user_id=m.user_id
			WHERE m.conversation_id=? AND m.user_id=? AND m.status=1`, conversationID, member).Scan(&muted, &allowed); err != nil {
			continue
		}
		if muted == 1 || allowed != 1 {
			continue
		}
		rows, err := a.db.QueryContext(ctx, `SELECT push_token,platform FROM user_push_tokens WHERE user_id=? AND status=1 AND push_token<>''`, member)
		if err != nil {
			continue
		}
		for rows.Next() {
			target := pushTarget{UserID: member}
			if rows.Scan(&target.Token, &target.Platform) == nil {
				targets = append(targets, target)
			}
		}
		_ = rows.Close()
	}
	return targets
}

func pushPreview(messageType int, content any, showPreview bool) string {
	switch messageType {
	case messageTypeImage:
		return "[图片]"
	case messageTypeVoice:
		return "[语音]"
	}
	if !showPreview {
		return "给你发来一条消息"
	}
	data, _ := content.(map[string]any)
	text, _ := data["text"].(string)
	text = strings.TrimSpace(text)
	if text == "" {
		return "给你发来一条消息"
	}
	if runes := []rune(text); len(runes) > pushPreviewRunes {
		text = string(runes[:pushPreviewRunes]) + "…"
	}
	return text
}

// notifyOfflineMessage runs after the send has already succeeded, on its own
// context: a slow or broken push service must never delay or fail a message
// that is already delivered to everyone who is online.
func (a *App) notifyOfflineMessage(conversationID, senderID int64, members []int64, item messageView) {
	credentials, ready := a.pushSettings(context.Background())
	if !ready {
		return
	}
	go func() {
		ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
		defer cancel()
		targets := a.pushRecipients(ctx, conversationID, senderID, members)
		if len(targets) == 0 {
			return
		}
		var sender string
		_ = a.db.QueryRowContext(ctx, `SELECT nickname FROM user_profiles WHERE user_id=?`, senderID).Scan(&sender)
		if strings.TrimSpace(sender) == "" {
			sender = "新消息"
		}
		body := pushPreview(item.Type, item.Content, a.configBool(ctx, "push.show_preview", true))
		token, err := a.pushToken(ctx, credentials)
		if err != nil {
			log.Printf("push: 鉴权失败 conversation=%d: %v", conversationID, err)
			return
		}
		for _, target := range targets {
			if err := a.sendPush(ctx, credentials, token, target, sender, body, conversationID); err != nil {
				log.Printf("push: 下发失败 user=%d: %v", target.UserID, err)
			}
		}
	}()
}

func (a *App) sendPush(ctx context.Context, credentials pushCredentials, token string, target pushTarget, title, body string, conversationID int64) error {
	payload := map[string]any{
		"request_id": randomToken()[:24],
		"settings":   map[string]any{"ttl": 3600000},
		"audience":   map[string]any{"cid": []string{target.Token}},
		"push_message": map[string]any{
			"notification": map[string]any{
				"title":      title,
				"body":       body,
				"click_type": "payload",
				// The client opens the conversation from this payload.
				"payload": fmt.Sprintf(`{"type":"conversation","conversationId":%d}`, conversationID),
			},
		},
	}
	raw, err := a.pushPost(ctx, credentials, "/push/single/cid", token, payload)
	if err != nil {
		return err
	}
	var result struct {
		Code int    `json:"code"`
		Msg  string `json:"msg"`
	}
	if err = json.Unmarshal(raw, &result); err != nil {
		return fmt.Errorf("推送响应无法解析")
	}
	// 10001/10002 mean the client id is unknown or retired; stop pushing to it.
	if result.Code == 10001 || result.Code == 10002 {
		_, _ = a.db.ExecContext(ctx, `UPDATE user_push_tokens SET status=0 WHERE user_id=? AND push_token=?`, target.UserID, target.Token)
		return nil
	}
	if result.Code != 0 {
		return fmt.Errorf("推送服务返回 %d：%s", result.Code, result.Msg)
	}
	return nil
}