initial scaffold

- module layout: cmd/mithril-go, internal/{aggregator,artifact,verify,networks}
- aggregator REST client, list command working against mainnet
- download/extract/verify stubbed
- no deps yet, pure stdlib

cmd/mithril-go/main.go

@@ -0,0 +1,147 @@
+// Command mithril-go is a pure-Go client for the Cardano Mithril protocol.
+//
+// It downloads, verifies, and extracts Mithril-certified snapshots of the
+// Cardano database without requiring the upstream Rust mithril-client.
+//
+// Subcommands:
+//   list     — list available cardano-database snapshots on an aggregator
+//   download — fetch a snapshot (verify + extract optional)
+//   verify   — verify an already-downloaded snapshot
+//   info     — show aggregator + network details
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"os"
+	"text/tabwriter"
+
+	"git.sulkta.coop/Sulkta-Coop/mithril-go/internal/aggregator"
+	"git.sulkta.coop/Sulkta-Coop/mithril-go/internal/networks"
+)
+
+const version = "0.0.1-dev"
+
+func main() {
+	if len(os.Args) < 2 {
+		usage()
+		os.Exit(2)
+	}
+	cmd := os.Args[1]
+	args := os.Args[2:]
+	switch cmd {
+	case "list":
+		os.Exit(cmdList(args))
+	case "download":
+		os.Exit(cmdDownload(args))
+	case "verify":
+		os.Exit(cmdVerify(args))
+	case "info":
+		os.Exit(cmdInfo(args))
+	case "version", "--version", "-v":
+		fmt.Println("mithril-go", version)
+	case "help", "--help", "-h":
+		usage()
+	default:
+		fmt.Fprintf(os.Stderr, "unknown command: %s\n\n", cmd)
+		usage()
+		os.Exit(2)
+	}
+}
+
+func usage() {
+	fmt.Fprintln(os.Stderr, `mithril-go — pure Go Mithril snapshot client
+
+Usage:
+  mithril-go <command> [flags]
+
+Commands:
+  list       List available cardano-database snapshots
+  download   Download + verify + extract a snapshot
+  verify     Verify an already-downloaded snapshot
+  info       Show network + aggregator info
+  version    Print version
+  help       Show this help
+
+Common flags:
+  -network   mainnet | preprod | preview (default: preprod)`)
+}
+
+func resolveNetwork(fs *flag.FlagSet, args []string) (networks.Network, []string, error) {
+	networkName := fs.String("network", "preprod", "Cardano network: mainnet | preprod | preview")
+	if err := fs.Parse(args); err != nil {
+		return networks.Network{}, nil, err
+	}
+	n, ok := networks.ByName(*networkName)
+	if !ok {
+		return networks.Network{}, nil, fmt.Errorf("unknown network: %s", *networkName)
+	}
+	return n, fs.Args(), nil
+}
+
+func cmdList(args []string) int {
+	fs := flag.NewFlagSet("list", flag.ExitOnError)
+	n, _, err := resolveNetwork(fs, args)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		return 2
+	}
+	client := aggregator.New(n.AggregatorURL)
+	snaps, err := client.ListCardanoDBSnapshots(context.Background())
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "list:", err)
+		return 1
+	}
+	tw := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
+	fmt.Fprintln(tw, "HASH\tEPOCH\tIMMUTABLE\tSIZE\tCREATED")
+	for _, s := range snaps {
+		fmt.Fprintf(tw, "%.16s\t%d\t%d\t%s\t%s\n",
+			s.Hash, s.Beacon.Epoch, s.Beacon.ImmutableFileNumber,
+			humanSize(s.TotalDBSizeUncompressed),
+			s.CreatedAt.UTC().Format("2006-01-02 15:04 MST"))
+	}
+	if err := tw.Flush(); err != nil {
+		fmt.Fprintln(os.Stderr, "flush:", err)
+		return 1
+	}
+	return 0
+}
+
+func cmdDownload(args []string) int {
+	fmt.Fprintln(os.Stderr, "download: not yet implemented")
+	return 1
+}
+
+func cmdVerify(args []string) int {
+	fmt.Fprintln(os.Stderr, "verify: not yet implemented")
+	return 1
+}
+
+func cmdInfo(args []string) int {
+	fs := flag.NewFlagSet("info", flag.ExitOnError)
+	n, _, err := resolveNetwork(fs, args)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		return 2
+	}
+	fmt.Printf("network:           %s\n", n.Name)
+	fmt.Printf("aggregator:        %s\n", n.AggregatorURL)
+	fmt.Printf("genesis verify key: %s…\n", n.GenesisVerifyKey[:16])
+	return 0
+}
+
+func humanSize(b uint64) string {
+	const k = 1024
+	if b < k {
+		return fmt.Sprintf("%dB", b)
+	}
+	units := []string{"K", "M", "G", "T"}
+	v := float64(b)
+	u := 0
+	for v >= k && u < len(units)-1 {
+		v /= k
+		u++
+	}
+	return fmt.Sprintf("%.1f%s", v, units[u])
+}