package controllers

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"time"

	"git.apinb.com/bsm-sdk/core/infra"
	"git.apinb.com/ops/logs/internal/config"
	"git.apinb.com/ops/logs/internal/impl"
	"git.apinb.com/ops/logs/internal/models"
	"github.com/gin-gonic/gin"
	"gorm.io/gorm"
)

const (
	resourceEventUpsert = "resource.upsert"
	resourceEventDelete = "resource.delete"
)

type resourceEventRequest struct {
	EventID      string            `json:"event_id"`
	EventTime    string            `json:"event_time"`
	EventType    string            `json:"event_type"`
	ResourceType string            `json:"resource_type"`
	ResourceID   string            `json:"resource_id"`
	ResourceName string            `json:"resource_name"`
	IPs          []string          `json:"ips"`
	Hostnames    []string          `json:"hostnames"`
	Labels       map[string]string `json:"labels"`
	Version      int64             `json:"version"`
}

// ReceiveResourceEvent 接收 dc-control 推送的资源变更事件并落库。
func ReceiveResourceEvent(ctx *gin.Context) {
	raw, err := ctx.GetRawData()
	if err != nil {
		infra.Response.Error(ctx, err)
		return
	}
	if err := verifyResourceEventSignature(ctx.GetHeader("X-Event-Signature"), raw); err != nil {
		infra.Response.Error(ctx, err)
		return
	}

	var req resourceEventRequest
	if err := json.Unmarshal(raw, &req); err != nil {
		infra.Response.Error(ctx, err)
		return
	}
	eventTime, err := validateResourceEventRequest(&req)
	if err != nil {
		infra.Response.Error(ctx, err)
		return
	}
	if err := validateEventTimeSkew(eventTime); err != nil {
		infra.Response.Error(ctx, err)
		return
	}
	if ok, err := tryInsertResourceEventDedup(req.EventID, eventTime, req.ResourceType, req.ResourceID); err != nil {
		infra.Response.Error(ctx, err)
		return
	} else if !ok {
		infra.Response.Success(ctx, gin.H{
			"ignored": true,
			"reason":  "duplicate_event_id",
			"event_id": req.EventID,
		})
		return
	}

	var row models.ResourceMapping
	err = impl.DBService.Where("resource_type = ? AND resource_id = ?", req.ResourceType, req.ResourceID).First(&row).Error
	if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
		infra.Response.Error(ctx, err)
		return
	}

	// 已存在记录且版本回退时忽略该事件，避免乱序覆盖。
	if err == nil && row.Version > req.Version {
		infra.Response.Success(ctx, gin.H{
			"ignored": true,
			"reason":  "stale_version",
			"current": row.Version,
			"incoming": req.Version,
		})
		return
	}

	ipsJSON, _ := json.Marshal(nonEmptyUnique(req.IPs))
	hostnamesJSON, _ := json.Marshal(nonEmptyUnique(req.Hostnames))
	labelsJSON, _ := json.Marshal(req.Labels)

	row.ResourceType = req.ResourceType
	row.ResourceID = req.ResourceID
	row.ResourceName = req.ResourceName
	row.IPsJSON = string(ipsJSON)
	row.HostnamesJSON = string(hostnamesJSON)
	row.LabelsJSON = string(labelsJSON)
	row.Version = req.Version
	row.LastEventID = req.EventID
	row.EventTime = eventTime
	row.IsDeleted = req.EventType == resourceEventDelete

	if err := impl.DBService.Save(&row).Error; err != nil {
		infra.Response.Error(ctx, err)
		return
	}
	infra.Response.Success(ctx, gin.H{
		"resource_type": row.ResourceType,
		"resource_id":   row.ResourceID,
		"version":       row.Version,
		"is_deleted":    row.IsDeleted,
	})
}

func validateResourceEventRequest(req *resourceEventRequest) (time.Time, error) {
	req.EventID = strings.TrimSpace(req.EventID)
	req.EventType = strings.TrimSpace(req.EventType)
	req.ResourceType = strings.TrimSpace(req.ResourceType)
	req.ResourceID = strings.TrimSpace(req.ResourceID)
	req.ResourceName = strings.TrimSpace(req.ResourceName)
	req.EventTime = strings.TrimSpace(req.EventTime)

	if req.EventID == "" {
		return time.Time{}, errors.New("event_id is required")
	}
	if req.EventType != resourceEventUpsert && req.EventType != resourceEventDelete {
		return time.Time{}, errors.New("event_type must be resource.upsert or resource.delete")
	}
	if req.ResourceType == "" {
		return time.Time{}, errors.New("resource_type is required")
	}
	if req.ResourceID == "" {
		return time.Time{}, errors.New("resource_id is required")
	}
	if req.Version <= 0 {
		return time.Time{}, errors.New("version must be positive")
	}
	if req.EventTime == "" {
		return time.Time{}, errors.New("event_time is required")
	}
	tm, err := time.Parse(time.RFC3339, req.EventTime)
	if err != nil {
		return time.Time{}, errors.New("event_time must be RFC3339")
	}
	return tm, nil
}

func nonEmptyUnique(items []string) []string {
	if len(items) == 0 {
		return nil
	}
	seen := make(map[string]struct{}, len(items))
	out := make([]string, 0, len(items))
	for _, item := range items {
		v := strings.TrimSpace(item)
		if v == "" {
			continue
		}
		if _, ok := seen[v]; ok {
			continue
		}
		seen[v] = struct{}{}
		out = append(out, v)
	}
	return out
}

func verifyResourceEventSignature(signature string, body []byte) error {
	signature = strings.TrimSpace(signature)
	signature = strings.TrimPrefix(strings.ToLower(signature), "sha256=")
	secret := strings.TrimSpace(config.Spec.ResourceEvent.HMACSecret)
	if secret == "" {
		return errors.New("resource_event hmac_secret is not configured")
	}
	if signature == "" {
		return errors.New("missing X-Event-Signature")
	}
	mac := hmac.New(sha256.New, []byte(secret))
	mac.Write(body)
	expected := fmt.Sprintf("%x", mac.Sum(nil))
	if !hmac.Equal([]byte(strings.ToLower(signature)), []byte(expected)) {
		return errors.New("invalid X-Event-Signature")
	}
	return nil
}

func validateEventTimeSkew(eventTime time.Time) error {
	maxSkew := config.Spec.ResourceEvent.MaxSkewSecs
	if maxSkew <= 0 {
		maxSkew = 300
	}
	diff := time.Since(eventTime)
	if diff < 0 {
		diff = -diff
	}
	if diff > time.Duration(maxSkew)*time.Second {
		return errors.New("event_time out of allowed skew window")
	}
	return nil
}

func tryInsertResourceEventDedup(eventID string, eventTime time.Time, resourceType, resourceID string) (bool, error) {
	// 先查询再插入，避免依赖数据库唯一索引存在与否。
	var existed models.ResourceEventDedup
	if err := impl.DBService.Where("event_id = ?", eventID).First(&existed).Error; err == nil {
		return false, nil
	}
	row := models.ResourceEventDedup{
		EventID:      eventID,
		EventTime:    eventTime,
		ResourceType: resourceType,
		ResourceID:   resourceID,
	}
	if err := impl.DBService.Create(&row).Error; err != nil {
		if strings.Contains(strings.ToLower(err.Error()), "duplicate") || strings.Contains(strings.ToLower(err.Error()), "unique") {
			return false, nil
		}
		return false, err
	}
	return true, nil
}