package metrics

import (
	"sort"

	dto "github.com/prometheus/client_model/go"
)

// PathCount 单个路由模板的累计请求数
type PathCount struct {
	Path  string  `json:"path"`
	Count float64 `json:"count"`
}

// Summary 面板自监控快照:从 registry 聚合出的精简结构(/api/v1/system/metrics-summary)
type Summary struct {
	HTTP struct {
		Total    float64            `json:"total"`
		ByStatus map[string]float64 `json:"byStatus"`
		InFlight float64            `json:"inFlight"`
		TopPaths []PathCount        `json:"topPaths"`
	} `json:"http"`
	DB struct {
		SizeBytes    float64            `json:"sizeBytes"`
		Saves        float64            `json:"saves"`
		SaveFailures float64            `json:"saveFailures"`
		Records      map[string]float64 `json:"records"`
	} `json:"db"`
	Alerts struct {
		Evaluations map[string]float64 `json:"evaluations"`
	} `json:"alerts"`
	Loki struct {
		Queries map[string]float64 `json:"queries"`
	} `json:"loki"`
	Runtime struct {
		Goroutines float64 `json:"goroutines"`
		GoVersion  string  `json:"goVersion"`
		Version    string  `json:"version"`
	} `json:"runtime"`
}

// Snapshot 聚合当前指标为面板结构(聚合失败返回零值,监控页降级展示)
func Snapshot() Summary {
	s := Summary{}
	s.HTTP.ByStatus = map[string]float64{}
	s.DB.Records = map[string]float64{}
	s.Alerts.Evaluations = map[string]float64{}
	s.Loki.Queries = map[string]float64{}

	families, err := registry.Gather()
	if err != nil {
		return s
	}
	byPath := map[string]float64{}
	for _, mf := range families {
		for _, m := range mf.GetMetric() {
			labels := labelMap(m)
			switch mf.GetName() {
			case "lokistack_http_requests_total":
				v := m.GetCounter().GetValue()
				s.HTTP.Total += v
				s.HTTP.ByStatus[labels["status"]] += v
				byPath[labels["path"]] += v
			case "lokistack_http_in_flight_requests":
				s.HTTP.InFlight = m.GetGauge().GetValue()
			case "lokistack_db_size_bytes":
				s.DB.SizeBytes = m.GetGauge().GetValue()
			case "lokistack_db_save_total":
				v := m.GetCounter().GetValue()
				s.DB.Saves += v
				if labels["result"] != "success" {
					s.DB.SaveFailures += v
				}
			case "lokistack_db_records":
				s.DB.Records[labels["collection"]] = m.GetGauge().GetValue()
			case "lokistack_alert_evaluations_total":
				s.Alerts.Evaluations[labels["result"]] += m.GetCounter().GetValue()
			case "lokistack_loki_queries_total":
				s.Loki.Queries[labels["result"]] += m.GetCounter().GetValue()
			case "go_goroutines":
				s.Runtime.Goroutines = m.GetGauge().GetValue()
			case "lokistack_build_info":
				s.Runtime.GoVersion = labels["go_version"]
				s.Runtime.Version = labels["version"]
			}
		}
	}
	paths := make([]PathCount, 0, len(byPath))
	for p, c := range byPath {
		paths = append(paths, PathCount{Path: p, Count: c})
	}
	sort.Slice(paths, func(i, j int) bool { return paths[i].Count > paths[j].Count })
	if len(paths) > 8 {
		paths = paths[:8]
	}
	s.HTTP.TopPaths = paths
	return s
}

func labelMap(m *dto.Metric) map[string]string {
	out := map[string]string{}
	for _, lp := range m.GetLabel() {
		out[lp.GetName()] = lp.GetValue()
	}
	return out
}