package remote_cache

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/exec"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/credentials"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/s3"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// Test configuration
// Uses two SeaweedFS instances:
// - Primary: The one being tested (has remote caching)
// - Remote: Acts as the "remote" S3 storage
const (
	// Primary SeaweedFS
	primaryEndpoint   = "http://localhost:8333"
	primaryMasterPort = "9333"

	// Remote SeaweedFS (acts as remote storage)
	remoteEndpoint = "http://localhost:8334"

	// Credentials (anonymous access for testing)
	accessKey = "some_access_key1"
	secretKey = "some_secret_key1"

	// Bucket name - mounted on primary as remote storage
	testBucket = "remotemounted"

	// Bucket name on the remote that testBucket is mounted on
	remoteBucket = "remotesourcebucket"

	// Path to weed binary
	weedBinary = "../../../weed/weed_binary"
)

var (
	primaryClient     *s3.S3
	primaryClientOnce sync.Once
)

func getPrimaryClient() *s3.S3 {
	primaryClientOnce.Do(func() {
		primaryClient = createS3Client(primaryEndpoint)
	})
	return primaryClient
}

func createS3Client(endpoint string) *s3.S3 {
	sess, err := session.NewSession(&aws.Config{
		Region:           aws.String("us-east-1"),
		Endpoint:         aws.String(endpoint),
		Credentials:      credentials.NewStaticCredentials(accessKey, secretKey, ""),
		DisableSSL:       aws.Bool(!strings.HasPrefix(endpoint, "https")),
		S3ForcePathStyle: aws.Bool(true),
	})
	if err != nil {
		panic(fmt.Sprintf("failed to create session: %v", err))
	}
	return s3.New(sess)
}

// checkServersRunning ensures the servers are running and fails if they aren't
func checkServersRunning(t *testing.T) {
	resp, err := http.Get(primaryEndpoint)
	require.NoErrorf(t, err, "Primary SeaweedFS not running at %s", primaryEndpoint)
	resp.Body.Close()

	resp, err = http.Get(remoteEndpoint)
	require.NoErrorf(t, err, "Remote SeaweedFS not running at %s", remoteEndpoint)
	resp.Body.Close()
}

// stripLogs removes SeaweedFS log lines from the output
func stripLogs(output string) string {
	lines := strings.Split(output, "\n")
	var filtered []string
	for _, line := range lines {
		trimmed := strings.TrimSpace(line)
		if len(trimmed) > 0 && (trimmed[0] == 'I' || trimmed[0] == 'W' || trimmed[0] == 'E' || trimmed[0] == 'F') && len(trimmed) > 5 && isDigit(trimmed[1]) {
			continue
		}
		filtered = append(filtered, line)
	}
	return strings.Join(filtered, "\n")
}

func isDigit(b byte) bool {
	return b >= '0' && b <= '9'
}

// runWeedShell executes a weed shell command
func runWeedShell(t *testing.T, command string) (string, error) {
	cmd := exec.Command(weedBinary, "shell", "-master=localhost:"+primaryMasterPort)
	cmd.Stdin = strings.NewReader(command + "\nexit\n")
	output, err := cmd.CombinedOutput()
	result := stripLogs(string(output))
	if err != nil {
		t.Logf("weed shell command '%s' failed: %v, output: %s", command, err, result)
		return result, err
	}
	return result, nil
}

// runWeedShellWithOutput executes a weed shell command and returns output even on error
func runWeedShellWithOutput(t *testing.T, command string) (output string, err error) {
	cmd := exec.Command(weedBinary, "shell", "-master=localhost:"+primaryMasterPort)
	cmd.Stdin = strings.NewReader(command + "\nexit\n")
	outputBytes, err := cmd.CombinedOutput()
	output = stripLogs(string(outputBytes))
	if err != nil {
		t.Logf("weed shell command '%s' output: %s", command, output)
	}
	return output, err
}

// createTestFile creates a test file with specific content via S3
func createTestFile(t *testing.T, key string, size int) []byte {
	data := make([]byte, size)
	for i := range data {
		data[i] = byte(i % 256)
	}
	uploadToPrimary(t, key, data)
	return data
}

// verifyFileContent verifies file content matches expected data
func verifyFileContent(t *testing.T, key string, expected []byte) {
	actual := getFromPrimary(t, key)
	assert.Equal(t, expected, actual, "file content mismatch for %s", key)
}

// waitForCondition waits for a condition to be true with timeout
func waitForCondition(t *testing.T, condition func() bool, timeout time.Duration, message string) bool {
	deadline := time.Now().Add(timeout)
	for time.Now().Before(deadline) {
		if condition() {
			return true
		}
		time.Sleep(100 * time.Millisecond)
	}
	t.Logf("Timeout waiting for: %s", message)
	return false
}

// fileExists checks if a file exists via S3
func fileExists(t *testing.T, key string) bool {
	_, err := getPrimaryClient().HeadObject(&s3.HeadObjectInput{
		Bucket: aws.String(testBucket),
		Key:    aws.String(key),
	})
	return err == nil
}

// uploadToPrimary uploads an object to the primary SeaweedFS (local write)
func uploadToPrimary(t *testing.T, key string, data []byte) {
	_, err := getPrimaryClient().PutObject(&s3.PutObjectInput{
		Bucket: aws.String(testBucket),
		Key:    aws.String(key),
		Body:   bytes.NewReader(data),
	})
	require.NoError(t, err, "failed to upload to primary SeaweedFS")
}

// getFromPrimary gets an object from primary SeaweedFS
func getFromPrimary(t *testing.T, key string) []byte {
	resp, err := getPrimaryClient().GetObject(&s3.GetObjectInput{
		Bucket: aws.String(testBucket),
		Key:    aws.String(key),
	})
	require.NoError(t, err, "failed to get from primary SeaweedFS")
	defer resp.Body.Close()

	data, err := io.ReadAll(resp.Body)
	require.NoError(t, err, "failed to read response body")
	return data
}

// uncacheLocal purges the local cache, forcing data to be fetched from remote
func uncacheLocal(t *testing.T, pattern string) {
	t.Logf("Purging local cache for pattern: %s", pattern)
	output, err := runWeedShell(t, fmt.Sprintf("remote.uncache -dir=/buckets/%s -include=%s", testBucket, pattern))
	if err != nil {
		t.Logf("uncacheLocal warning: %v", err)
	}
	t.Log(output)
	time.Sleep(500 * time.Millisecond)
}

// TestRemoteCacheBasic tests the basic caching workflow:
// 1. Write to local
// 2. Uncache (push to remote, remove local chunks)
// 3. Read (triggers caching from remote)
func TestRemoteCacheBasic(t *testing.T) {
	checkServersRunning(t)

	testKey := fmt.Sprintf("test-basic-%d.txt", time.Now().UnixNano())
	testData := []byte("Hello, this is test data for remote caching!")

	// Step 1: Write to local
	t.Log("Step 1: Writing object to primary SeaweedFS (local)...")
	uploadToPrimary(t, testKey, testData)

	// Verify it's readable
	result := getFromPrimary(t, testKey)
	assert.Equal(t, testData, result, "initial read mismatch")

	// Step 2: Uncache - push to remote and remove local chunks
	t.Log("Step 2: Uncaching (pushing to remote, removing local chunks)...")
	uncacheLocal(t, testKey)

	// Step 3: Read - this should trigger caching from remote
	t.Log("Step 3: Reading object (should trigger caching from remote)...")
	start := time.Now()
	result = getFromPrimary(t, testKey)
	firstReadDuration := time.Since(start)

	assert.Equal(t, testData, result, "data mismatch after cache")
	t.Logf("First read (from remote) took %v", firstReadDuration)

	// Step 4: Read again - should be from local cache
	t.Log("Step 4: Reading again (should be from local cache)...")
	start = time.Now()
	result = getFromPrimary(t, testKey)
	secondReadDuration := time.Since(start)

	assert.Equal(t, testData, result, "data mismatch on cached read")
	t.Logf("Second read (from cache) took %v", secondReadDuration)

	t.Log("Basic caching test passed")
}

// TestRemoteCacheConcurrent tests that concurrent reads of the same
// remote object only trigger ONE caching operation (singleflight deduplication)
func TestRemoteCacheConcurrent(t *testing.T) {
	checkServersRunning(t)

	testKey := fmt.Sprintf("test-concurrent-%d.txt", time.Now().UnixNano())
	// Use larger data to make caching take measurable time
	testData := make([]byte, 1024*1024) // 1MB
	for i := range testData {
		testData[i] = byte(i % 256)
	}

	// Step 1: Write to local
	t.Log("Step 1: Writing 1MB object to primary SeaweedFS...")
	uploadToPrimary(t, testKey, testData)

	// Verify it's readable
	result := getFromPrimary(t, testKey)
	assert.Equal(t, len(testData), len(result), "initial size mismatch")

	// Step 2: Uncache
	t.Log("Step 2: Uncaching (pushing to remote)...")
	uncacheLocal(t, testKey)

	// Step 3: Launch many concurrent reads - singleflight should deduplicate
	numRequests := 10
	var wg sync.WaitGroup
	var successCount atomic.Int32
	var errorCount atomic.Int32
	results := make(chan []byte, numRequests)

	t.Logf("Step 3: Launching %d concurrent requests...", numRequests)
	startTime := time.Now()

	for i := 0; i < numRequests; i++ {
		wg.Add(1)
		go func(idx int) {
			defer wg.Done()
			resp, err := getPrimaryClient().GetObject(&s3.GetObjectInput{
				Bucket: aws.String(testBucket),
				Key:    aws.String(testKey),
			})
			if err != nil {
				t.Logf("Request %d failed: %v", idx, err)
				errorCount.Add(1)
				return
			}
			defer resp.Body.Close()

			data, err := io.ReadAll(resp.Body)
			if err != nil {
				t.Logf("Request %d read failed: %v", idx, err)
				errorCount.Add(1)
				return
			}

			results <- data
			successCount.Add(1)
		}(i)
	}

	wg.Wait()
	close(results)
	totalDuration := time.Since(startTime)

	t.Logf("All %d requests completed in %v", numRequests, totalDuration)
	t.Logf("Successful: %d, Failed: %d", successCount.Load(), errorCount.Load())

	// Verify all successful requests returned correct data
	for data := range results {
		assert.Equal(t, len(testData), len(data), "data length mismatch")
	}

	// All requests should succeed
	assert.Equal(t, int32(numRequests), successCount.Load(), "some requests failed")
	assert.Equal(t, int32(0), errorCount.Load(), "no requests should fail")

	t.Log("Concurrent caching test passed")
}

// TestRemoteCacheLargeObject tests caching of larger objects
func TestRemoteCacheLargeObject(t *testing.T) {
	checkServersRunning(t)

	testKey := fmt.Sprintf("test-large-%d.bin", time.Now().UnixNano())
	// 5MB object
	testData := make([]byte, 5*1024*1024)
	for i := range testData {
		testData[i] = byte(i % 256)
	}

	// Step 1: Write to local
	t.Log("Step 1: Writing 5MB object to primary SeaweedFS...")
	uploadToPrimary(t, testKey, testData)

	// Verify it's readable
	result := getFromPrimary(t, testKey)
	assert.Equal(t, len(testData), len(result), "initial size mismatch")

	// Step 2: Uncache
	t.Log("Step 2: Uncaching...")
	uncacheLocal(t, testKey)

	// Step 3: Read from remote
	t.Log("Step 3: Reading 5MB object (should cache from remote)...")
	start := time.Now()
	result = getFromPrimary(t, testKey)
	duration := time.Since(start)

	assert.Equal(t, len(testData), len(result), "size mismatch")
	assert.Equal(t, testData, result, "data mismatch")
	t.Logf("Large object cached in %v", duration)

	t.Log("Large object caching test passed")
}

// TestRemoteCacheRangeRequest tests that range requests work after caching
func TestRemoteCacheRangeRequest(t *testing.T) {
	checkServersRunning(t)

	testKey := fmt.Sprintf("test-range-%d.txt", time.Now().UnixNano())
	testData := []byte("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ")

	// Write, uncache, then test range request
	t.Log("Writing and uncaching object...")
	uploadToPrimary(t, testKey, testData)
	uncacheLocal(t, testKey)

	// Range request should work and trigger caching
	t.Log("Testing range request (bytes 10-19)...")
	resp, err := getPrimaryClient().GetObject(&s3.GetObjectInput{
		Bucket: aws.String(testBucket),
		Key:    aws.String(testKey),
		Range:  aws.String("bytes=10-19"),
	})
	require.NoError(t, err)
	defer resp.Body.Close()

	rangeData, err := io.ReadAll(resp.Body)
	require.NoError(t, err)

	expected := testData[10:20] // "ABCDEFGHIJ"
	assert.Equal(t, expected, rangeData, "range data mismatch")
	t.Logf("Range request returned: %s", string(rangeData))

	t.Log("Range request test passed")
}

// mountRemote remounts the test bucket, keeping the metadata already pulled,
// with the given extra remote.mount flags.
func mountRemote(t *testing.T, extraFlags string) {
	cmd := fmt.Sprintf("remote.mount -dir=/buckets/%s -remote=seaweedremote/%s -nonempty -metadataStrategy=lazy %s", testBucket, remoteBucket, extraFlags)
	output, err := runWeedShell(t, cmd)
	require.NoErrorf(t, err, "remount failed: %s", output)
	time.Sleep(time.Second)
}

// copyLocalToRemote pushes matching local objects to the remote, which is what
// lets remote.uncache drop their local chunks afterwards.
func copyLocalToRemote(t *testing.T, pattern string) {
	output, err := runWeedShell(t, fmt.Sprintf("remote.copy.local -dir=/buckets/%s -include=%s", testBucket, pattern))
	require.NoErrorf(t, err, "remote.copy.local failed: %s", output)
}

// localChunkCount reports how many local chunks an entry has, so a test can
// tell a cached read from one served straight out of the remote.
func localChunkCount(t *testing.T, key string) string {
	meta, err := runWeedShell(t, fmt.Sprintf("fs.meta.cat /buckets/%s/%s", testBucket, key))
	require.NoError(t, err)
	// fs.meta.cat closes with "chunks N meta size: ..."
	summary := strings.LastIndex(meta, "chunks ")
	require.GreaterOrEqualf(t, summary, 0, "no chunk count in %s", meta)
	return strings.Fields(meta[summary+len("chunks "):])[0]
}

// TestRemoteCacheWaitZero tests that a mount with -cacheWait=0 serves a read of
// an uncached object from the remote without caching it locally.
func TestRemoteCacheWaitZero(t *testing.T) {
	checkServersRunning(t)

	testKey := fmt.Sprintf("test-cachewait-%d.bin", time.Now().UnixNano())
	testData := make([]byte, 1024*1024)
	for i := range testData {
		testData[i] = byte(i % 256)
	}

	t.Log("Step 1: Writing 1MB object, pushing it to the remote and dropping the local chunks...")
	uploadToPrimary(t, testKey, testData)
	copyLocalToRemote(t, testKey)
	uncacheLocal(t, testKey)
	require.Equal(t, "0", localChunkCount(t, testKey), "the object must start out remote-only")

	t.Log("Step 2: Remounting with -cacheWait=0...")
	mountRemote(t, "-cacheWait=0")
	defer mountRemote(t, "")

	t.Log("Step 3: Reading the object (should stream from remote)...")
	assert.Equal(t, testData, getFromPrimary(t, testKey), "data mismatch reading from remote")
	assert.Equal(t, "0", localChunkCount(t, testKey), "the read must not cache chunks locally")

	t.Log("Step 4: Reading with the size based wait (should cache locally)...")
	mountRemote(t, "")
	assert.Equal(t, testData, getFromPrimary(t, testKey), "data mismatch reading through the cache")
	assert.NotEqual(t, "0", localChunkCount(t, testKey), "the read must cache chunks locally")

	t.Log("Zero cache wait test passed")
}

// TestRemoteCacheNotFound tests that non-existent objects return proper errors
func TestRemoteCacheNotFound(t *testing.T) {
	checkServersRunning(t)

	testKey := fmt.Sprintf("non-existent-object-%d", time.Now().UnixNano())

	_, err := getPrimaryClient().GetObject(&s3.GetObjectInput{
		Bucket: aws.String(testBucket),
		Key:    aws.String(testKey),
	})

	assert.Error(t, err, "should get error for non-existent object")
	t.Logf("Got expected error: %v", err)

	t.Log("Not found test passed")
}

// TestMain sets up and tears down the test environment
func TestMain(m *testing.M) {
	if !isServerRunning(primaryEndpoint) {
		fmt.Println("WARNING: Primary SeaweedFS not running at", primaryEndpoint)
		fmt.Println("   Run 'make test-with-server' to start servers automatically")
	}
	if !isServerRunning(remoteEndpoint) {
		fmt.Println("WARNING: Remote SeaweedFS not running at", remoteEndpoint)
		fmt.Println("   Run 'make test-with-server' to start servers automatically")
	}

	os.Exit(m.Run())
}

func isServerRunning(url string) bool {
	resp, err := http.Get(url)
	if err != nil {
		return false
	}
	resp.Body.Close()
	return true
}