package services

// 多通知通道(飞书/Lark 群机器人)CRUD 与按通道发送。
// 取代旧的单 webhook 全局配置:每个告警群一个通道,告警规则各自关联。
import (
	"bytes"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"net/http"
	"time"

	"lokistack/models"
	"lokistack/pkg/crypto"
	"lokistack/repository"
)

const channelHTTPTimeout = 10 * time.Second

func ListNotifyChannels() []map[string]interface{} {
	db := repository.GetDB()
	db.RLock()
	out := make([]map[string]interface{}, 0, len(db.NotifyChannels))
	for i := range db.NotifyChannels {
		out = append(out, db.NotifyChannels[i].Sanitized())
	}
	db.RUnlock()
	return out
}

func GetNotifyChannel(id uint) *models.NotifyChannel {
	db := repository.GetDB()
	db.RLock()
	defer db.RUnlock()
	for i := range db.NotifyChannels {
		if db.NotifyChannels[i].ID == id {
			c := db.NotifyChannels[i]
			return &c
		}
	}
	return nil
}

// GetNotifyChannelDecrypted 取通道并解密凭证(发送用)
func GetNotifyChannelDecrypted(id uint) *models.NotifyChannel {
	c := GetNotifyChannel(id)
	if c == nil {
		return nil
	}
	if w, err := DecryptCred(c.Webhook); err == nil {
		c.Webhook = w
	}
	if s, err := DecryptCred(c.SigningSecret); err == nil {
		c.SigningSecret = s
	}
	return c
}

// SaveNotifyChannel 新建(id=0)或更新;webhook/secret 非空才更新(留空=保留旧值)
func SaveNotifyChannel(id uint, name, webhook, secret string, enabled bool) (*models.NotifyChannel, error) {
	db := repository.GetDB()
	// 更新:留空字段回填旧值(旧值已是密文)
	if id > 0 {
		db.RLock()
		var old models.NotifyChannel
		found := false
		for i := range db.NotifyChannels {
			if db.NotifyChannels[i].ID == id {
				old = db.NotifyChannels[i]
				found = true
				break
			}
		}
		db.RUnlock()
		if !found {
			return nil, fmt.Errorf("通道不存在")
		}
		if webhook == "" {
			webhook = old.Webhook
		} else if enc, err := crypto.EncryptField(webhook); err == nil {
			webhook = enc
		}
		if secret == "" {
			secret = old.SigningSecret
		} else if enc, err := crypto.EncryptField(secret); err == nil {
			secret = enc
		}
		db.Lock()
		defer db.Unlock()
		for i := range db.NotifyChannels {
			if db.NotifyChannels[i].ID == id {
				db.NotifyChannels[i].Name = name
				db.NotifyChannels[i].Webhook = webhook
				db.NotifyChannels[i].SigningSecret = secret
				db.NotifyChannels[i].Enabled = enabled
				db.NotifyChannels[i].UpdatedAt = time.Now()
				db.RequestSave()
				c := db.NotifyChannels[i]
				return &c, nil
			}
		}
		return nil, fmt.Errorf("通道不存在")
	}

	// 新建
	if name == "" {
		return nil, fmt.Errorf("通道名称不能为空")
	}
	if webhook == "" {
		return nil, fmt.Errorf("webhook 不能为空")
	}
	if enc, err := crypto.EncryptField(webhook); err == nil {
		webhook = enc
	}
	if secret != "" {
		if enc, err := crypto.EncryptField(secret); err == nil {
			secret = enc
		}
	}
	newID := db.NextID("notifyChannels")
	ch := &models.NotifyChannel{
		ID: newID, Name: name, Webhook: webhook, SigningSecret: secret, Enabled: enabled,
	}
	db.Lock()
	defer db.Unlock()
	db.NotifyChannels = append(db.NotifyChannels, *ch)
	db.RequestSave()
	return ch, nil
}

func DeleteNotifyChannel(id uint) error {
	// 有关联规则时拒绝删除
	db := repository.GetDB()
	db.RLock()
	for i := range db.AlertRules {
		for _, chID := range db.AlertRules[i].ChannelIDs {
			if chID == id {
				db.RUnlock()
				return fmt.Errorf("仍有告警规则关联此通道,请先解除关联")
			}
		}
	}
	db.RUnlock()
	db.Lock()
	defer db.Unlock()
	for i := range db.NotifyChannels {
		if db.NotifyChannels[i].ID == id {
			db.NotifyChannels = append(db.NotifyChannels[:i], db.NotifyChannels[i+1:]...)
			db.RequestSave()
			return nil
		}
	}
	return fmt.Errorf("通道不存在")
}

// larkSignChannel 飞书签名
func larkSignChannel(secret string, ts int64) string {
	stringToSign := fmt.Sprintf("%d\n%s", ts, secret)
	h := hmac.New(sha256.New, []byte(stringToSign))
	return base64.StdEncoding.EncodeToString(h.Sum(nil))
}

// SendLarkCardToChannel 向指定通道发送卡片
func SendLarkCardToChannel(channelID uint, title, color string, lines []string) error {
	ch := GetNotifyChannelDecrypted(channelID)
	if ch == nil {
		return fmt.Errorf("通知通道不存在")
	}
	if !ch.Enabled {
		return fmt.Errorf("通道「%s」已禁用", ch.Name)
	}
	content := joinNonEmpty(lines, "\n")
	payload := map[string]interface{}{
		"msg_type": "interactive",
		"card": map[string]interface{}{
			"config": map[string]interface{}{"wide_screen_mode": true},
			"header": map[string]interface{}{
				"title":    map[string]string{"tag": "plain_text", "content": title},
				"template": color,
			},
			"elements": []interface{}{
				map[string]interface{}{"tag": "div", "text": map[string]string{"tag": "lark_md", "content": content}},
				map[string]interface{}{"tag": "note", "elements": []interface{}{map[string]string{"tag": "plain_text", "content": "LokiStack 日志告警"}}},
			},
		},
	}
	if ch.SigningSecret != "" {
		ts := time.Now().Unix()
		payload["timestamp"] = fmt.Sprintf("%d", ts)
		payload["sign"] = larkSignChannel(ch.SigningSecret, ts)
	}
	body, _ := json.Marshal(payload)
	resp, err := (&http.Client{Timeout: channelHTTPTimeout}).Post(ch.Webhook, "application/json", bytes.NewReader(body))
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode != 200 {
		return fmt.Errorf("飞书返回 HTTP %d", resp.StatusCode)
	}
	var out struct {
		Code int    `json:"code"`
		Msg  string `json:"msg"`
	}
	_ = json.NewDecoder(resp.Body).Decode(&out)
	if out.Code != 0 {
		return fmt.Errorf("飞书拒绝: %s", out.Msg)
	}
	return nil
}

func joinNonEmpty(items []string, sep string) string {
	result := ""
	for _, item := range items {
		if item == "" {
			continue
		}
		if result != "" {
			result += sep
		}
		result += item
	}
	return result
}