Initial push

internal/dkr/client.go

@@ -0,0 +1,55 @@
+// Package dkr wraps the Docker Engine API with the operations the migration
+// tool needs: reading a full container inventory, streaming data out of a
+// container's mounts, and streaming image layers.
+package dkr
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/docker/docker/api/types/system"
+	"github.com/docker/docker/client"
+)
+
+// Client is a connection to one Docker daemon.
+type Client struct {
+	api *client.Client
+	// Endpoint is the daemon address, shown in the UI.
+	Endpoint string
+}
+
+// New connects to the daemon described by the standard DOCKER_* environment
+// variables, or to host when it is non-empty (e.g. unix:///var/run/docker.sock
+// or tcp://10.0.0.5:2375).
+func New(host string) (*Client, error) {
+	opts := []client.Opt{client.FromEnv, client.WithAPIVersionNegotiation()}
+	if host != "" {
+		opts = append(opts, client.WithHost(host))
+	}
+	api, err := client.NewClientWithOpts(opts...)
+	if err != nil {
+		return nil, fmt.Errorf("create docker client: %w", err)
+	}
+	return &Client{api: api, Endpoint: api.DaemonHost()}, nil
+}
+
+// API exposes the underlying SDK client for callers that need an operation
+// this package does not wrap.
+func (c *Client) API() *client.Client { return c.api }
+
+// Close releases the daemon connection.
+func (c *Client) Close() error { return c.api.Close() }
+
+// Info returns daemon information, and doubles as a connectivity check.
+func (c *Client) Info(ctx context.Context) (system.Info, error) {
+	return c.api.Info(ctx)
+}
+
+// Ping verifies the daemon is reachable and returns its version string.
+func (c *Client) Ping(ctx context.Context) (string, error) {
+	v, err := c.api.ServerVersion(ctx)
+	if err != nil {
+		return "", err
+	}
+	return v.Version, nil
+}