package ingest

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

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

const alertResponseBodyLimit = 1 << 20

var errAlertForwardDisabled = errors.New("Alert 转发未启用或 base_url 为空")

type alertForwardResponse struct {
	Code    *int32          `json:"code"`
	Details json.RawMessage `json:"details"`
}

// 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"`
	State          string            `json:"state,omitempty"`
	SourceEventKey string            `json:"source_event_key"`
	OccurredAt     time.Time         `json:"occurred_at"`
	RawData        json.RawMessage   `json:"raw_data"`
}

type RawEventIngestBody struct {
	SourceType     string            `json:"source_type"`
	SourceEventKey string            `json:"source_event_key"`
	State          string            `json:"state,omitempty"`
	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 errAlertForwardDisabled
	}
	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
	}
	result, err := postAlertPayload(cfg, "/Alert/v1/alerts/receive", raw)
	if err != nil {
		return err
	}
	var details struct {
		ID            uint   `json:"id"`
		RawEventID    uint   `json:"raw_event_id"`
		AlertRecordID uint   `json:"alert_record_id"`
		IncidentID    uint   `json:"incident_id"`
		Status        string `json:"status"`
		Fingerprint   string `json:"fingerprint"`
	}
	if err := json.Unmarshal(result.Details, &details); err != nil {
		return fmt.Errorf("Alert 响应 details 无效：%v；请稍后重试", err)
	}
	alertRecordID := details.AlertRecordID
	if alertRecordID == 0 {
		alertRecordID = details.ID
	}
	if details.RawEventID == 0 || alertRecordID == 0 || details.IncidentID == 0 ||
		(details.ID != 0 && details.AlertRecordID != 0 && details.ID != details.AlertRecordID) ||
		(details.Status != "firing" && details.Status != "resolved") || !validFingerprint(details.Fingerprint) {
		return fmt.Errorf("Alert 响应缺少完整写入结果，无法确认转发成功；请稍后重试")
	}
	return nil
}

func postAlertPayload(cfg *config.AlertForwardConf, path string, payload []byte) (*alertForwardResponse, error) {
	req, err := http.NewRequest(http.MethodPost, cfg.BaseURL+path, bytes.NewReader(payload))
	if err != nil {
		return nil, 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 nil, 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 nil, fmt.Errorf("读取 Alert 响应失败：%w", err)
	}
	if len(responseBody) > alertResponseBodyLimit {
		return nil, 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 nil, fmt.Errorf("Alert 返回 HTTP %d，请稍后重试", resp.StatusCode)
	}

	var result alertForwardResponse
	if err := json.Unmarshal(responseBody, &result); err != nil {
		return nil, fmt.Errorf("Alert 响应不是有效 JSON：%v；请稍后重试", err)
	}
	if result.Code == nil {
		return nil, 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 nil, fmt.Errorf("Alert 拒绝转发，业务 code=%d；请稍后重试", *result.Code)
	}
	if len(result.Details) == 0 || string(result.Details) == "null" || string(result.Details) == `""` {
		return nil, fmt.Errorf("Alert 响应缺少 details，无法确认转发成功；请稍后重试")
	}
	return &result, 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,
		SourceEventKey: body.SourceEventKey,
		State:          body.State,
		ResourceUID:    rawEventResourceUID(body.Labels),
		EventTime:      body.OccurredAt,
		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 validFingerprint(value string) bool {
	if len(value) != 64 {
		return false
	}
	decoded, err := hex.DecodeString(value)
	return err == nil && len(decoded) == 32
}

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 ""
}