// Package client provides ZFS snapshot backup client functionality.
// This file contains snapshot management functions for creating and sending snapshots.
package client

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/exec"
	"strings"
	"time"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/config"
	"github.com/aws/aws-sdk-go-v2/credentials"
	"github.com/aws/aws-sdk-go-v2/service/s3"
	"github.com/mistifyio/go-zfs"
	"github.com/pierrec/lz4/v4"
)

// CreateBookmark creates a ZFS bookmark from a snapshot.
// Bookmarks allow incremental sends even after the source snapshot is deleted.
func (c *Client) CreateBookmark(snapshot *zfs.Dataset) error {
	// Extract snapshot name from full path (dataset@snapshot -> snapshot)
	parts := strings.Split(snapshot.Name, "@")
	if len(parts) != 2 {
		return fmt.Errorf("invalid snapshot name format: %s", snapshot.Name)
	}
	snapshotName := parts[1]
	bookmarkName := fmt.Sprintf("%s#%s", c.config.LocalDataset, snapshotName)

	// Create bookmark using zfs command
	cmd := exec.Command("zfs", "bookmark", snapshot.Name, bookmarkName)
	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("failed to create bookmark: %v: %s", err, string(output))
	}

	fmt.Printf("✓ Created bookmark: %s\n", bookmarkName)
	return nil
}

// GetLastBookmark returns the most recent bookmark for the dataset.
// Bookmarks are used as the base for incremental sends.
func (c *Client) GetLastBookmark() (string, error) {
	// List all bookmarks for the dataset
	cmd := exec.Command("zfs", "list", "-t", "bookmark", "-o", "name", "-H", "-r", c.config.LocalDataset)
	output, err := cmd.Output()
	if err != nil {
		return "", nil // No bookmarks yet
	}

	bookmarks := strings.Split(strings.TrimSpace(string(output)), "\n")
	if len(bookmarks) == 0 || bookmarks[0] == "" {
		return "", nil
	}

	// Return the last bookmark (most recent)
	return bookmarks[len(bookmarks)-1], nil
}

// GetLastSnapshot returns the most recent snapshot for the dataset.
func (c *Client) GetLastSnapshot() (*zfs.Dataset, error) {
	ds, err := zfs.GetDataset(c.config.LocalDataset)
	if err != nil {
		return nil, fmt.Errorf("failed to get dataset: %v", err)
	}

	snapshots, err := ds.Snapshots()
	if err != nil {
		return nil, fmt.Errorf("failed to list snapshots: %v", err)
	}

	if len(snapshots) == 0 {
		return nil, nil
	}

	// Return the last snapshot (most recent)
	return snapshots[len(snapshots)-1], nil
}

// SendIncremental sends an incremental stream from a bookmark or snapshot.
// If base is empty, sends a full stream.
func (c *Client) SendIncremental(snapshot *zfs.Dataset, base string) error {
	estimatedSize := c.GetSnapshotSize(snapshot)

	// Determine if this is incremental or full
	isIncremental := base != ""
	var uploadMethod string
	if isIncremental {
		uploadMethod = "incremental"
	} else {
		uploadMethod = "full"
	}

	// Request upload authorization from server
	uploadReq := map[string]interface{}{
		"client_id":      c.config.ClientID,
		"api_key":        c.config.APIKey,
		"dataset_name":   c.config.LocalDataset,
		"timestamp":      time.Now().Format(time.RFC3339),
		"compressed":     c.config.Compress,
		"estimated_size": estimatedSize,
		"incremental":    isIncremental,
		"base_snapshot":  base,
	}

	reqBody, _ := json.Marshal(uploadReq)
	resp, err := http.Post(c.config.ServerURL+"/upload", "application/json", bytes.NewBuffer(reqBody))
	if err != nil {
		return fmt.Errorf("failed to request upload: %v", err)
	}
	defer resp.Body.Close()

	var uploadResp struct {
		Success      bool   `json:"success"`
		Message      string `json:"message"`
		UploadURL    string `json:"upload_url"`
		UploadMethod string `json:"upload_method"`
		StorageKey   string `json:"storage_key"`
	}

	if err := json.NewDecoder(resp.Body).Decode(&uploadResp); err != nil {
		return fmt.Errorf("failed to decode response: %v", err)
	}

	if !uploadResp.Success {
		return fmt.Errorf("upload not authorized: %s", uploadResp.Message)
	}

	fmt.Printf("→ Upload authorized\n")
	fmt.Printf("  Method: %s\n", uploadResp.UploadMethod)
	fmt.Printf("  Type: %s\n", uploadMethod)
	fmt.Printf("  Storage key: %s\n", uploadResp.StorageKey)

	// Choose upload method based on server response
	if uploadResp.UploadMethod == "s3" {
		return c.streamIncrementalToS3(snapshot, base, uploadResp.UploadURL, uploadResp.StorageKey)
	}
	return c.sendIncrementalViaZFS(snapshot, base, uploadResp.StorageKey)
}

// streamIncrementalToS3 streams an incremental ZFS snapshot to S3 using AWS SDK.
func (c *Client) streamIncrementalToS3(snapshot *zfs.Dataset, base, uploadURL, storageKey string) error {
	fmt.Printf("→ Uploading snapshot to S3...\n")

	// Ensure endpoint has valid URI scheme
	endpoint := c.config.S3Endpoint
	if endpoint != "" && !strings.HasPrefix(endpoint, "http://") && !strings.HasPrefix(endpoint, "https://") {
		endpoint = "http://" + endpoint
	}

	// Create AWS config
	awsCfg, err := config.LoadDefaultConfig(context.TODO(),
		config.WithRegion(c.config.S3Region),
		config.WithCredentialsProvider(credentials.NewStaticCredentialsProvider(
			c.config.S3AccessKey,
			c.config.S3SecretKey,
			"",
		)),
	)
	if err != nil {
		return fmt.Errorf("failed to load AWS config: %v", err)
	}

	// Determine if using custom endpoint (non-AWS)
	customEndpoint := endpoint != "" && endpoint != "http://s3.amazonaws.com" && endpoint != "https://s3.amazonaws.com"

	// Create S3 client
	s3Client := s3.NewFromConfig(awsCfg, func(o *s3.Options) {
		if customEndpoint {
			o.BaseEndpoint = aws.String(endpoint)
			o.UsePathStyle = true // Required for MinIO compatible storage
		}
	})

	// Create ZFS send command
	var cmd *exec.Cmd
	if base != "" {
		// Incremental send from bookmark or snapshot
		fmt.Printf("  Base: %s\n", base)
		cmd = exec.Command("zfs", "send", "-i", base, snapshot.Name)
	} else {
		// Full send
		cmd = exec.Command("zfs", "send", snapshot.Name)
	}

	zfsOut, err := cmd.StdoutPipe()
	if err != nil {
		return fmt.Errorf("failed to create pipe: %v", err)
	}

	if err := cmd.Start(); err != nil {
		return fmt.Errorf("failed to start zfs send: %v", err)
	}

	var reader io.Reader = zfsOut

	// Apply LZ4 compression if enabled
	if c.config.Compress {
		fmt.Printf("  Compressing with LZ4...\n")
		pr, pw := io.Pipe()
		lz4Writer := lz4.NewWriter(pw)
		lz4Writer.Apply(lz4.BlockSizeOption(lz4.BlockSize(4 * 1024 * 1024))) // 4MB blocks for better performance

		go func() {
			// Copy zfs output to LZ4 writer
			io.Copy(lz4Writer, zfsOut)
			// Close LZ4 writer first to flush, then close pipe
			lz4Writer.Close()
			pw.Close()
		}()

		reader = pr
	}

	// Upload to S3 using PutObject
	_, err = s3Client.PutObject(context.TODO(), &s3.PutObjectInput{
		Bucket:      aws.String(c.config.S3Bucket),
		Key:         aws.String(storageKey),
		Body:        reader,
		ContentType: aws.String("application/octet-stream"),
	})

	// Wait for zfs send to complete
	if err := cmd.Wait(); err != nil {
		return fmt.Errorf("zfs send failed: %v", err)
	}

	if err != nil {
		return fmt.Errorf("failed to upload to S3: %v", err)
	}

	fmt.Printf("✓ Snapshot uploaded to S3 successfully!\n")

	return nil
}

// sendIncrementalViaZFS sends an incremental snapshot via ZFS send/receive over SSH.
// This method is used when the server uses local ZFS storage.
func (c *Client) sendIncrementalViaZFS(snapshot *zfs.Dataset, base, receivePath string) error {
	fmt.Printf("→ Sending via ZFS send/receive...\n")

	// Extract server host from URL
	serverHost := c.config.ServerURL
	if len(serverHost) > 7 && strings.HasPrefix(serverHost, "http://") {
		serverHost = serverHost[7:]
	} else if len(serverHost) > 8 && strings.HasPrefix(serverHost, "https://") {
		serverHost = serverHost[8:]
	}

	// Remove port if present
	if idx := strings.LastIndex(serverHost, ":"); idx > 0 {
		serverHost = serverHost[:idx]
	}

	// Build zfs send command
	var zfsSendCmd string
	if base != "" {
		// Incremental send
		fmt.Printf("  Base: %s\n", base)
		zfsSendCmd = fmt.Sprintf("zfs send -i %s %s", base, snapshot.Name)
	} else {
		// Full send
		zfsSendCmd = fmt.Sprintf("zfs send %s", snapshot.Name)
	}

	// Execute ZFS send over SSH
	cmd := exec.Command("sh", "-c",
		fmt.Sprintf("%s | ssh %s 'zfs recv -F %s'", zfsSendCmd, serverHost, receivePath))

	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr

	if err := cmd.Run(); err != nil {
		return fmt.Errorf("failed to send snapshot: %v", err)
	}

	fmt.Printf("✓ Snapshot sent successfully!\n")
	return nil
}