// 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
}