package ingest

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"git.apinb.com/ops/logs/internal/config"
)

const alertResponseBodyLimit = 1 << 20

// AlertReceiveBody 与 alert ReceiveRequest 对齐（含必填 raw_data）
type AlertReceiveBody struct {
	AlertName    string            `json:"alert_name"`
	Summary      string            `json:"summary"`
	Description  string            `json:"description"`
	SeverityCode string            `json:"severity_code"`
	Value        string            `json:"value"`
	Threshold    string            `json:"threshold"`
	Labels       map[string]string `json:"labels"`
	Agent        string            `json:"agent"`
	PolicyID     uint              `json:"policy_id"`
	RawData      json.RawMessage   `json:"raw_data"`
}

type RawEventIngestBody struct {
	SourceType  string            `json:"source_type"`
	ResourceUID string            `json:"resource_uid,omitempty"`
	EventTime   time.Time         `json:"event_time"`
	Severity    string            `json:"severity"`
	Title       string            `json:"title"`
	Message     string            `json:"message"`
	Labels      map[string]string `json:"labels,omitempty"`
	Annotations map[string]string `json:"annotations,omitempty"`
	ParseStatus string            `json:"parse_status"`
	RawPayload  json.RawMessage   `json:"raw_payload"`
	TraceID     string            `json:"trace_id,omitempty"`
}

func forwardAlert(body AlertReceiveBody) error {
	cfg := config.Spec.AlertForward
	if cfg == nil || !cfg.Enabled || cfg.BaseURL == "" {
		return nil
	}
	if len(body.RawData) == 0 {
		return fmt.Errorf("raw_data 不能为空")
	}
	if body.AlertName == "" {
		body.AlertName = "日志告警"
	}
	if body.PolicyID == 0 && cfg.DefaultPolicyID > 0 {
		body.PolicyID = cfg.DefaultPolicyID
	}
	raw, err := json.Marshal(body)
	if err != nil {
		return err
	}
	return postAlertPayload(cfg, "/Alert/v1/alerts/receive", raw)
}

func postAlertPayload(cfg *config.AlertForwardConf, path string, payload []byte) error {
	req, err := http.NewRequest(http.MethodPost, cfg.BaseURL+path, bytes.NewReader(payload))
	if err != nil {
		return fmt.Errorf("创建 Alert 转发请求失败：%w", err)
	}
	req.Header.Set("Content-Type", "application/json")
	if cfg.InternalKey != "" {
		req.Header.Set("X-Internal-Key", cfg.InternalKey)
	}
	client := &http.Client{
		Timeout: 10 * time.Second,
		CheckRedirect: func(_ *http.Request, _ []*http.Request) error {
			return http.ErrUseLastResponse
		},
	}
	resp, err := client.Do(req)
	if err != nil {
		return fmt.Errorf("发送 Alert 转发请求失败：%w", err)
	}
	defer resp.Body.Close()

	responseBody, err := io.ReadAll(io.LimitReader(resp.Body, alertResponseBodyLimit+1))
	if err != nil {
		return fmt.Errorf("读取 Alert 响应失败：%w", err)
	}
	if len(responseBody) > alertResponseBodyLimit {
		return fmt.Errorf("Alert 响应体超过 %d 字节限制，请稍后重试", alertResponseBodyLimit)
	}
	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("Alert 返回 HTTP %d，请稍后重试", resp.StatusCode)
	}

	var result struct {
		Code *int32 `json:"code"`
	}
	if err := json.Unmarshal(responseBody, &result); err != nil {
		return fmt.Errorf("Alert 响应不是有效 JSON：%v；请稍后重试", err)
	}
	if result.Code == nil {
		return fmt.Errorf("Alert 响应缺少 code，无法确认转发成功；请稍后重试")
	}
	if *result.Code != 0 {
		return fmt.Errorf("Alert 拒绝转发，业务 code=%d；请稍后重试", *result.Code)
	}
	return nil
}

func buildRawEventIngestBody(body AlertReceiveBody, parseStatus string) RawEventIngestBody {
	sourceType := rawEventSourceType(body)
	if parseStatus == "" {
		parseStatus = "parsed"
	}
	annotations := map[string]string{
		"description": body.Description,
		"value":       body.Value,
		"threshold":   body.Threshold,
		"agent":       body.Agent,
	}
	return RawEventIngestBody{
		SourceType:  sourceType,
		ResourceUID: rawEventResourceUID(body.Labels),
		EventTime:   time.Now().UTC(),
		Severity:    body.SeverityCode,
		Title:       firstNonEmpty(body.AlertName, "日志事件"),
		Message:     firstNonEmpty(body.Summary, body.Description),
		Labels:      body.Labels,
		Annotations: annotations,
		ParseStatus: parseStatus,
		RawPayload:  body.RawData,
	}
}

func rawEventSourceType(body AlertReceiveBody) string {
	if body.Labels != nil {
		switch strings.TrimSpace(body.Labels["source_subtype"]) {
		case "syslog":
			return "syslog"
		case "snmp_trap":
			return "trap"
		}
	}
	switch body.Agent {
	case "logs-syslog":
		return "syslog"
	case "logs-trap":
		return "trap"
	default:
		return "syslog"
	}
}

func rawEventResourceUID(labels map[string]string) string {
	if labels == nil {
		return ""
	}
	if uid := strings.TrimSpace(labels["resource_uid"]); uid != "" {
		return uid
	}
	category := strings.TrimSpace(labels["resource_category"])
	identity := strings.TrimSpace(labels["service_identity"])
	if category != "" && identity != "" {
		return category + ":" + identity
	}
	return ""
}