package main

import (
	"context"
	"encoding/json"
	"flag"
	"log"
	"os"
	"path/filepath"
	"time"

	"github.com/bergabruh/stats-gateway/internal/storage"
)

type sample struct {
	TS     string  `json:"ts"`
	HTTPMs float64 `json:"http_ms"`
	TLSMs  float64 `json:"tls_ms"`
	TCPMs  float64 `json:"tcp_ms"`
}

type nodeData struct {
	Recent []sample `json:"recent"`
}

type snapshot struct {
	GeneratedAt string              `json:"generated_at"`
	Nodes       map[string]nodeData `json:"nodes"`
}

func main() {
	dbPath := flag.String("db", "/var/lib/stats-gateway/stats.db", "")
	out := flag.String("out", "/var/www/stats-site/data/snapshot.json", "")
	limitPerNode := flag.Int("limit", 288, "max samples per node (288 = ~24h at 5min interval)")
	flag.Parse()

	st, err := storage.Open(*dbPath)
	if err != nil {
		log.Fatalf("open db: %v", err)
	}
	defer st.Close()

	s := snapshot{
		GeneratedAt: time.Now().UTC().Format(time.RFC3339),
		Nodes:       map[string]nodeData{},
	}
	ctx := context.Background()
	for _, node := range []string{"fl", "pl1"} {
		samples, err := st.QueryRecent(ctx, node, *limitPerNode, time.Time{})
		if err != nil {
			log.Printf("query %s: %v", node, err)
			continue
		}
		nd := nodeData{Recent: make([]sample, 0, len(samples))}
		for _, sm := range samples {
			nd.Recent = append(nd.Recent, sample{
				TS:     sm.Timestamp.Format(time.RFC3339Nano),
				HTTPMs: sm.HTTPLatencyMs,
				TLSMs:  sm.TLSHandshakeMs,
				TCPMs:  sm.TCPRttMs,
			})
		}
		s.Nodes[node] = nd
	}

	if err := os.MkdirAll(filepath.Dir(*out), 0755); err != nil {
		log.Fatalf("mkdir %s: %v", filepath.Dir(*out), err)
	}

	// Atomic write: write to .tmp then rename.
	tmp := *out + ".tmp"
	f, err := os.Create(tmp)
	if err != nil {
		log.Fatalf("create %s: %v", tmp, err)
	}
	enc := json.NewEncoder(f)
	enc.SetIndent("", "  ")
	if err := enc.Encode(s); err != nil {
		f.Close()
		os.Remove(tmp)
		log.Fatalf("encode: %v", err)
	}
	f.Close()
	if err := os.Rename(tmp, *out); err != nil {
		log.Fatalf("rename: %v", err)
	}

	log.Printf("snapshot: nodes=%d → %s", len(s.Nodes), *out)
}