Add support for defaulting to latest version and improve code structure

pkg/registry/client.go

@@ -0,0 +1,110 @@
+package registry
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+
+	"github.com/safedep/pmg/pkg/models"
+)
+
+// RegistryClient defines the interface for making requests to a registry
+type RegistryClient interface {
+	// FetchPackageInfo fetches metadata for a specific package version
+	FetchPackageInfo(ctx context.Context, pkg models.Package) (*models.PackageInfo, error)
+	// GetLatestVersion fetches the latest version for a package
+	GetLatestVersion(ctx context.Context, packageName string) (string, error)
+}
+
+// HttpRegistryClient is a basic HTTP client for registry APIs
+type HttpRegistryClient struct {
+	httpClient *http.Client
+	urlFormat  string
+	parser     func([]byte) (*models.PackageInfo, error)
+}
+
+// NewHttpRegistryClient creates a new HTTP registry client
+func NewHttpRegistryClient(
+	timeout time.Duration,
+	urlFormat string,
+	parser func([]byte) (*models.PackageInfo, error),
+) *HttpRegistryClient {
+	return &HttpRegistryClient{
+		httpClient: &http.Client{Timeout: timeout},
+		urlFormat:  urlFormat,
+		parser:     parser,
+	}
+}
+
+// FetchPackageInfo fetches package metadata from the registry
+func (c *HttpRegistryClient) FetchPackageInfo(ctx context.Context, pkg models.Package) (*models.PackageInfo, error) {
+	url := fmt.Sprintf(c.urlFormat, pkg.Name, pkg.Version)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, fmt.Errorf("creating request: %w", err)
+	}
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("making request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("registry returned status: %s", resp.Status)
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("reading response body: %w", err)
+	}
+
+	return c.parser(body)
+}
+
+// GetLatestVersion fetches the latest version for an NPM package
+func (c *HttpRegistryClient) GetLatestVersion(ctx context.Context, packageName string) (string, error) {
+	// For NPM, we can get latest version by querying the base package URL
+	url := fmt.Sprintf("https://registry.npmjs.org/%s", packageName)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return "", fmt.Errorf("creating request: %w", err)
+	}
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("making request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("registry returned status: %s", resp.Status)
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", fmt.Errorf("reading response body: %w", err)
+	}
+
+	// Parse the response to get the latest version
+	var pkgData struct {
+		DistTags struct {
+			Latest string `json:"latest"`
+		} `json:"dist-tags"`
+	}
+
+	if err := json.Unmarshal(body, &pkgData); err != nil {
+		return "", fmt.Errorf("parsing package info: %w", err)
+	}
+
+	if pkgData.DistTags.Latest == "" {
+		return "", fmt.Errorf("no latest version found for package %s", packageName)
+	}
+
+	return pkgData.DistTags.Latest, nil
+}