// Decision verification uses the unchanged Access Engine producer implementation.
package main

import (
	"crypto/ed25519"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"github.com/netkingdom/access-engine/internal/sign"
	"io"
	"os"
)

type input struct {
	Envelope json.RawMessage   `json:"envelope"`
	Keys     map[string]string `json:"keys"`
}

func run() error {
	var in input
	if err := json.NewDecoder(io.LimitReader(os.Stdin, 1048577)).Decode(&in); err != nil {
		return err
	}
	envelope, err := sign.DecodeEnvelope(in.Envelope)
	if err != nil {
		return err
	}
	keys := map[string]ed25519.PublicKey{}
	for kid, encoded := range in.Keys {
		raw, err := base64.RawURLEncoding.Strict().DecodeString(encoded)
		if err != nil || len(raw) != ed25519.PublicKeySize || kid == "" {
			return fmt.Errorf("invalid admitted key")
		}
		keys[kid] = ed25519.PublicKey(raw)
	}
	if err := sign.Verify(envelope, keys); err != nil {
		return err
	}
	// Return the exact typed interpretation authenticated by the producer; Python
	// must never act on a second interpretation of unverified response fields.
	return json.NewEncoder(os.Stdout).Encode(envelope)
}
func main() {
	if run() != nil {
		fmt.Fprintln(os.Stderr, "decision signature verification refused")
		os.Exit(1)
	}
}