package agate

import (
	"context"
	"crypto/sha256"
	"io"
	"log"
	"os"
	"path/filepath"
	"testing"
	"time"

	"gitea.unprism.ru/KRBL/Agate/remote"
)

// TestGRPCServerClient tests the interaction between a gRPC server and client.
// It creates multiple snapshots with different content on the server,
// connects a client to the server, downloads the latest snapshot,
// and verifies the contents of the files.
func TestGRPCServerClient(t *testing.T) {
	// Skip this test in short mode
	if testing.Short() {
		t.Skip("Skipping gRPC server-client test in short mode")
	}

	// --- Setup Server ---
	serverDir, err := os.MkdirTemp("", "agate-server-*")
	if err != nil {
		t.Fatalf("Failed to create server temp directory: %v", err)
	}
	defer os.RemoveAll(serverDir)

	serverAgate, err := New(AgateOptions{WorkDir: serverDir})
	if err != nil {
		t.Fatalf("Failed to create server Agate instance: %v", err)
	}
	defer serverAgate.Close()

	dataDir := serverAgate.options.BlobStore.GetActiveDir()
	if err := os.MkdirAll(dataDir, 0755); err != nil {
		t.Fatalf("Failed to create data directory: %v", err)
	}

	// Create initial test files for the first snapshot
	if err := os.WriteFile(filepath.Join(dataDir, "file1.txt"), []byte("content1"), 0644); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(dataDir, "file2.txt"), []byte("content2"), 0644); err != nil {
		t.Fatal(err)
	}

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	snapshot1ID, err := serverAgate.SaveSnapshot(ctx, "Snapshot 1", "")
	if err != nil {
		t.Fatalf("Failed to create first snapshot: %v", err)
	}
	t.Logf("Created first snapshot with ID: %s", snapshot1ID)

	// Modify content for the second snapshot
	if err := os.WriteFile(filepath.Join(dataDir, "file1.txt"), []byte("modified content1"), 0644); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(dataDir, "file3.txt"), []byte("new file3"), 0644); err != nil {
		t.Fatal(err)
	}

	snapshot2ID, err := serverAgate.SaveSnapshot(ctx, "Snapshot 2", snapshot1ID)
	if err != nil {
		t.Fatalf("Failed to create second snapshot: %v", err)
	}
	t.Logf("Created second snapshot with ID: %s", snapshot2ID)

	// Start the gRPC server
	serverAddress := "localhost:50051"
	server := remote.NewServer(serverAgate.manager)
	go func() {
		if err := server.Start(ctx, serverAddress); err != nil {
			log.Printf("Server start error: %v", err)
		}
	}()
	defer server.Stop()
	time.Sleep(100 * time.Millisecond)

	// --- Setup Client ---
	clientDir, err := os.MkdirTemp("", "agate-client-*")
	if err != nil {
		t.Fatalf("Failed to create client temp directory: %v", err)
	}
	defer os.RemoveAll(clientDir)

	clientAgate, err := New(AgateOptions{WorkDir: clientDir, CleanOnRestore: true})
	if err != nil {
		t.Fatalf("Failed to create client Agate instance: %v", err)
	}
	defer clientAgate.Close()

	// --- Test Scenario ---
	// 1. Client downloads the first snapshot completely
	t.Log("Client downloading Snapshot 1...")
	if err := clientAgate.GetRemoteSnapshot(ctx, serverAddress, snapshot1ID, ""); err != nil {
		t.Fatalf("Client failed to get snapshot 1: %v", err)
	}

	// Verify content of snapshot 1
	if err := clientAgate.RestoreSnapshot(ctx, snapshot1ID); err != nil {
		t.Fatalf("Failed to restore snapshot 1: %v", err)
	}
	verifyFileContent(t, clientAgate.GetActiveDir(), "file1.txt", "content1")
	verifyFileContent(t, clientAgate.GetActiveDir(), "file2.txt", "content2")

	// 2. Client downloads the second snapshot incrementally
	t.Log("Client downloading Snapshot 2 (incrementally)...")
	if err := clientAgate.GetRemoteSnapshot(ctx, serverAddress, snapshot2ID, snapshot1ID); err != nil {
		t.Fatalf("Client failed to get snapshot 2: %v", err)
	}

	// Verify content of snapshot 2
	if err := clientAgate.RestoreSnapshot(ctx, snapshot2ID); err != nil {
		t.Fatalf("Failed to restore snapshot 2: %v", err)
	}
	verifyFileContent(t, clientAgate.GetActiveDir(), "file1.txt", "modified content1")
	verifyFileContent(t, clientAgate.GetActiveDir(), "file3.txt", "new file3")
	// file2.txt should no longer exist if CleanOnRestore is true and snapshot2 is based on snapshot1 where file2 was not changed.
	// But our diff logic is additive. Let's re-check the logic. The logic is: parent + diff = new. So file2 should exist.
	verifyFileContent(t, clientAgate.GetActiveDir(), "file2.txt", "content2")
}

func verifyFileContent(t *testing.T, dir, filename, expectedContent string) {
	t.Helper()
	content, err := os.ReadFile(filepath.Join(dir, filename))
	if err != nil {
		t.Fatalf("Failed to read file %s: %v", filename, err)
	}
	if string(content) != expectedContent {
		t.Errorf("File %s has wrong content: got '%s', want '%s'", filename, string(content), expectedContent)
	}
}

// TestGRPC_GetRemoteSnapshot_FullDownload tests a full download when no parent is specified.
func TestGRPC_GetRemoteSnapshot_FullDownload(t *testing.T) {
	// --- Setup Server ---
	serverDir, _ := os.MkdirTemp("", "agate-server-*")
	defer os.RemoveAll(serverDir)
	serverAgate, _ := New(AgateOptions{WorkDir: serverDir})
	defer serverAgate.Close()
	dataDir := serverAgate.options.BlobStore.GetActiveDir()
	os.MkdirAll(dataDir, 0755)
	os.WriteFile(filepath.Join(dataDir, "file1.txt"), []byte("full download"), 0644)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	snapshotID, err := serverAgate.SaveSnapshot(ctx, "FullSnapshot", "")
	if err != nil {
		t.Fatalf("Failed to create snapshot: %v", err)
	}

	// Start Server
	serverAddress := "localhost:50052"
	server := remote.NewServer(serverAgate.manager)
	go func() { server.Start(ctx, serverAddress) }()
	defer server.Stop()
	time.Sleep(100 * time.Millisecond)

	// --- Setup Client ---
	clientDir, _ := os.MkdirTemp("", "agate-client-*")
	defer os.RemoveAll(clientDir)
	clientAgate, _ := New(AgateOptions{WorkDir: clientDir, CleanOnRestore: true})
	defer clientAgate.Close()

	// --- Test Scenario ---
	t.Log("Client performing full download...")
	if err := clientAgate.GetRemoteSnapshot(ctx, serverAddress, snapshotID, ""); err != nil {
		t.Fatalf("Client failed to get snapshot: %v", err)
	}

	// Verify content
	if err := clientAgate.RestoreSnapshot(ctx, snapshotID); err != nil {
		t.Fatalf("Failed to restore snapshot: %v", err)
	}
	verifyFileContent(t, clientAgate.GetActiveDir(), "file1.txt", "full download")
}

// TestGRPC_DownloadSnapshotDiff_Resumption tests the download resumption logic.
func TestGRPC_DownloadSnapshotDiff_Resumption(t *testing.T) {
	// --- Setup Server ---
	serverDir, _ := os.MkdirTemp("", "agate-server-*")
	defer os.RemoveAll(serverDir)
	serverAgate, _ := New(AgateOptions{WorkDir: serverDir})
	defer serverAgate.Close()
	dataDir := serverAgate.options.BlobStore.GetActiveDir()
	os.MkdirAll(dataDir, 0755)
	os.WriteFile(filepath.Join(dataDir, "file1.txt"), []byte("content1"), 0644)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	// Snap 1
	snapshot1ID, _ := serverAgate.SaveSnapshot(ctx, "Snap1", "")
	// Snap 2 (with changes)
	os.WriteFile(filepath.Join(dataDir, "file2.txt"), make([]byte, 1024*128), 0644) // 128KB file to make diff non-trivial
	snapshot2ID, _ := serverAgate.SaveSnapshot(ctx, "Snap2", snapshot1ID)

	// Start Server
	serverAddress := "localhost:50053"
	server := remote.NewServer(serverAgate.manager)
	go func() { server.Start(ctx, serverAddress) }()
	defer server.Stop()
	time.Sleep(100 * time.Millisecond)

	// --- Setup Client ---
	clientDir, _ := os.MkdirTemp("", "agate-client-*")
	defer os.RemoveAll(clientDir)
	rClient, err := remote.NewClient(serverAddress)
	if err != nil {
		t.Fatalf("Failed to create remote client: %v", err)
	}
	defer rClient.Close()

	// --- Test Scenario ---
	// 1. Manually download first part of the diff archive
	diffPath := filepath.Join(clientDir, "diff.zip.part")
	diffReader, err := serverAgate.manager.StreamSnapshotDiff(ctx, snapshot2ID, snapshot1ID, 0)
	if err != nil {
		t.Fatalf("Failed to get diff stream from manager: %v", err)
	}
	defer diffReader.Close()

	// Read first 64KB
	firstChunk := make([]byte, 64*1024)
	n, err := io.ReadFull(diffReader, firstChunk)
	if err != nil && err != io.ErrUnexpectedEOF {
		t.Fatalf("Failed to read first chunk: %v, read %d bytes", err, n)
	}
	if err := os.WriteFile(diffPath, firstChunk[:n], 0644); err != nil {
		t.Fatalf("Failed to write partial file: %v", err)
	}
	diffReader.Close() // Simulate connection drop

	// 2. Resume download using the client
	t.Log("Resuming download...")
	if err := rClient.DownloadSnapshotDiff(ctx, snapshot2ID, snapshot1ID, diffPath); err != nil {
		t.Fatalf("Failed to resume download: %v", err)
	}

	// 3. Verify final file
	// Get the full diff from server for comparison
	fullDiffReader, _ := serverAgate.manager.StreamSnapshotDiff(ctx, snapshot2ID, snapshot1ID, 0)
	defer fullDiffReader.Close()
	fullDiffData, _ := io.ReadAll(fullDiffReader)

	resumedData, _ := os.ReadFile(diffPath)

	if len(resumedData) != len(fullDiffData) {
		t.Errorf("Resumed file size is incorrect. Got %d, want %d", len(resumedData), len(fullDiffData))
	}

	if sha256.Sum256(resumedData) != sha256.Sum256(fullDiffData) {
		t.Error("File content mismatch after resumption")
	}
}