package erasure

import (
	"context"
	"bytes"
	"testing"

	"forge-mesh/internal/db"
)

func TestEncodeReconstruct4Plus2(t *testing.T) {
	conn, err := db.Open(t.TempDir() + "/test.db")
	if err != nil {
		t.Fatal(err)
	}
	defer conn.Close()

	svc := NewService(conn)
	ctx := context.Background()
	payload := []byte("forge-mesh erasure shard payload for T12 reassembly")

	bundle, err := svc.Encode(ctx, "test-bundle", payload)
	if err != nil {
		t.Fatal(err)
	}
	if bundle.DataShards != 4 || bundle.ParityShards != 2 {
		t.Fatalf("expected 4+2, got %d+%d", bundle.DataShards, bundle.ParityShards)
	}

	// Reconstruct with any 4 of 6 shards
	rebuilt, err := svc.Reconstruct(ctx, bundle.ID, []int{0, 1, 2, 5})
	if err != nil {
		t.Fatal(err)
	}
	if !bytes.Equal(payload, rebuilt) {
		t.Fatalf("reconstruct mismatch: got %q want %q", rebuilt, payload)
	}
}

func TestReconstructNeedsMinShards(t *testing.T) {
	conn, err := db.Open(t.TempDir() + "/test.db")
	if err != nil {
		t.Fatal(err)
	}
	defer conn.Close()

	svc := NewService(conn)
	ctx := context.Background()
	bundle, err := svc.Encode(ctx, "small", []byte("x"))
	if err != nil {
		t.Fatal(err)
	}

	_, err = svc.Reconstruct(ctx, bundle.ID, []int{0, 1, 2})
	if err == nil {
		t.Fatal("expected error when fewer than 4 shards provided")
	}
}