fetch.go

package main

import (
	"context"
	"encoding/hex"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"

	"github.com/hedzr/progressbar"
	"github.com/zeebo/blake3"
)

func fetchBinaryFromURLToDest(ctx context.Context, bar progressbar.PB, url, checksum, destination string) (string, error) {
	// Create a new HTTP request with cache-control headers
	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
	if err != nil {
		return "", fmt.Errorf("failed to create request for %s: %v", url, err)
	}

	// Add headers to disable caching
	req.Header.Set("Cache-Control", "no-cache, no-store, must-revalidate")
	req.Header.Set("Pragma", "no-cache")
	req.Header.Set("Expires", "0")
	req.Header.Set("User-Agent", fmt.Sprintf("dbin/%s", Version))

	// Perform the request
	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	bar.UpdateRange(0, resp.ContentLength)

	// Ensure the parent directory exists
	if err := os.MkdirAll(filepath.Dir(destination), 0755); err != nil {
		return "", fmt.Errorf("failed to create parent directories for %s: %v", destination, err)
	}

	// Create temp file
	tempFile := destination + ".tmp"
	out, err := os.Create(tempFile)
	if err != nil {
		return "", err
	}
	defer out.Close()

	buf := make([]byte, 4096)

	hash := blake3.New()

downloadLoop:
	for {
		select {
		case <-ctx.Done():
			_ = os.Remove(tempFile)
			return "", ctx.Err()
		default:
			n, err := resp.Body.Read(buf)
			if n > 0 {
				if _, err = io.MultiWriter(out, hash, bar).Write(buf[:n]); err != nil {
					_ = os.Remove(tempFile)
					return "", err
				}
			}
			if err == io.EOF {
				break downloadLoop
			}
			if err != nil {
				_ = os.Remove(tempFile)
				return "", err
			}
		}
	}

	// Final checksum verification
	if checksum != "" {
		calculatedChecksum := hex.EncodeToString(hash.Sum(nil))
		if calculatedChecksum != checksum && checksum != "null" {
			fmt.Fprintf(os.Stderr, "checksum verification failed: expected %s, got %s\n", checksum, calculatedChecksum)
		}
	} else {
		fmt.Println("Warning: No checksum exists for this binary in the metadata files, skipping verification.")
	}

	// Make a few corrections in case the downloaded binary is a nix object
	if err := removeNixGarbageFoundInTheRepos(tempFile); err != nil {
		_ = os.Remove(tempFile)
		return "", err
	}

	if err := os.Rename(tempFile, destination); err != nil {
		_ = os.Remove(tempFile)
		return "", err
	}

	if err := os.Chmod(destination, 0755); err != nil {
		_ = os.Remove(destination)
		return "", fmt.Errorf("failed to set executable bit for %s: %v", destination, err)
	}

	// Mark the binary as ours
	//if err := xattr.Set(destination, "user.ManagedBy", []byte("dbin")); err != nil {
	//	return "", fmt.Errorf("failed to set xattr for %s: %v", destination, err)
	//}

	return destination, nil
}