package docker // import "docker.io/go-docker"

import (
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"os"
	"path"
	"path/filepath"
	"strings"

	"docker.io/go-docker/api"
	"docker.io/go-docker/api/types"
	"docker.io/go-docker/api/types/versions"
	"github.com/docker/go-connections/sockets"
	"github.com/docker/go-connections/tlsconfig"
	"golang.org/x/net/context"
)

// ErrRedirect is the error returned by checkRedirect when the request is non-GET.
var ErrRedirect = errors.New("unexpected redirect in response")

// Client is the API client that performs all operations
// against a docker server.
type Client struct {
	// scheme sets the scheme for the client
	scheme string
	// host holds the server address to connect to
	host string
	// proto holds the client protocol i.e. unix.
	proto string
	// addr holds the client address.
	addr string
	// basePath holds the path to prepend to the requests.
	basePath string
	// client used to send and receive http requests.
	client *http.Client
	// version of the server to talk to.
	version string
	// custom http headers configured by users.
	customHTTPHeaders map[string]string
	// manualOverride is set to true when the version was set by users.
	manualOverride bool
}

// CheckRedirect specifies the policy for dealing with redirect responses:
// If the request is non-GET return `ErrRedirect`. Otherwise use the last response.
//
// Go 1.8 changes behavior for HTTP redirects (specifically 301, 307, and 308) in the client .
// The Docker client (and by extension docker API client) can be made to to send a request
// like POST /containers//start where what would normally be in the name section of the URL is empty.
// This triggers an HTTP 301 from the daemon.
// In go 1.8 this 301 will be converted to a GET request, and ends up getting a 404 from the daemon.
// This behavior change manifests in the client in that before the 301 was not followed and
// the client did not generate an error, but now results in a message like Error response from daemon: page not found.
func CheckRedirect(req *http.Request, via []*http.Request) error {
	if via[0].Method == http.MethodGet {
		return http.ErrUseLastResponse
	}
	return ErrRedirect
}

// NewEnvClient initializes a new API client based on environment variables.
// Use DOCKER_HOST to set the url to the docker server.
// Use DOCKER_API_VERSION to set the version of the API to reach, leave empty for latest.
// Use DOCKER_CERT_PATH to load the TLS certificates from.
// Use DOCKER_TLS_VERIFY to enable or disable TLS verification, off by default.
func NewEnvClient() (*Client, error) {
	var client *http.Client
	if dockerCertPath := os.Getenv("DOCKER_CERT_PATH"); dockerCertPath != "" {
		options := tlsconfig.Options{
			CAFile:             filepath.Join(dockerCertPath, "ca.pem"),
			CertFile:           filepath.Join(dockerCertPath, "cert.pem"),
			KeyFile:            filepath.Join(dockerCertPath, "key.pem"),
			InsecureSkipVerify: os.Getenv("DOCKER_TLS_VERIFY") == "",
		}
		tlsc, err := tlsconfig.Client(options)
		if err != nil {
			return nil, err
		}

		client = &http.Client{
			Transport: &http.Transport{
				TLSClientConfig: tlsc,
			},
			CheckRedirect: CheckRedirect,
		}
	}

	host := os.Getenv("DOCKER_HOST")
	if host == "" {
		host = DefaultDockerHost
	}
	version := os.Getenv("DOCKER_API_VERSION")
	if version == "" {
		version = api.DefaultVersion
	}

	cli, err := NewClient(host, version, client, nil)
	if err != nil {
		return cli, err
	}
	if os.Getenv("DOCKER_API_VERSION") != "" {
		cli.manualOverride = true
	}
	return cli, nil
}

// NewClient initializes a new API client for the given host and API version.
// It uses the given http client as transport.
// It also initializes the custom http headers to add to each request.
//
// It won't send any version information if the version number is empty. It is
// highly recommended that you set a version or your client may break if the
// server is upgraded.
func NewClient(host string, version string, client *http.Client, httpHeaders map[string]string) (*Client, error) {
	hostURL, err := ParseHostURL(host)
	if err != nil {
		return nil, err
	}

	if client != nil {
		if _, ok := client.Transport.(http.RoundTripper); !ok {
			return nil, fmt.Errorf("unable to verify TLS configuration, invalid transport %v", client.Transport)
		}
	} else {
		transport := new(http.Transport)
		sockets.ConfigureTransport(transport, hostURL.Scheme, hostURL.Host)
		client = &http.Client{
			Transport:     transport,
			CheckRedirect: CheckRedirect,
		}
	}

	scheme := "http"
	tlsConfig := resolveTLSConfig(client.Transport)
	if tlsConfig != nil {
		// TODO(stevvooe): This isn't really the right way to write clients in Go.
		// `NewClient` should probably only take an `*http.Client` and work from there.
		// Unfortunately, the model of having a host-ish/url-thingy as the connection
		// string has us confusing protocol and transport layers. We continue doing
		// this to avoid breaking existing clients but this should be addressed.
		scheme = "https"
	}

	// TODO: store URL instead of proto/addr/basePath
	return &Client{
		scheme:            scheme,
		host:              host,
		proto:             hostURL.Scheme,
		addr:              hostURL.Host,
		basePath:          hostURL.Path,
		client:            client,
		version:           version,
		customHTTPHeaders: httpHeaders,
	}, nil
}

// Close the transport used by the client
func (cli *Client) Close() error {
	if t, ok := cli.client.Transport.(*http.Transport); ok {
		t.CloseIdleConnections()
	}
	return nil
}

// getAPIPath returns the versioned request path to call the api.
// It appends the query parameters to the path if they are not empty.
func (cli *Client) getAPIPath(p string, query url.Values) string {
	var apiPath string
	if cli.version != "" {
		v := strings.TrimPrefix(cli.version, "v")
		apiPath = path.Join(cli.basePath, "/v"+v, p)
	} else {
		apiPath = path.Join(cli.basePath, p)
	}
	return (&url.URL{Path: apiPath, RawQuery: query.Encode()}).String()
}

// ClientVersion returns the API version used by this client.
func (cli *Client) ClientVersion() string {
	return cli.version
}

// NegotiateAPIVersion queries the API and updates the version to match the
// API version. Any errors are silently ignored.
func (cli *Client) NegotiateAPIVersion(ctx context.Context) {
	ping, _ := cli.Ping(ctx)
	cli.NegotiateAPIVersionPing(ping)
}

// NegotiateAPIVersionPing updates the client version to match the Ping.APIVersion
// if the ping version is less than the default version.
func (cli *Client) NegotiateAPIVersionPing(p types.Ping) {
	if cli.manualOverride {
		return
	}

	// try the latest version before versioning headers existed
	if p.APIVersion == "" {
		p.APIVersion = "1.24"
	}

	// if the client is not initialized with a version, start with the latest supported version
	if cli.version == "" {
		cli.version = api.DefaultVersion
	}

	// if server version is lower than the maximum version supported by the Client, downgrade
	if versions.LessThan(p.APIVersion, api.DefaultVersion) {
		cli.version = p.APIVersion
	}
}

// DaemonHost returns the host address used by the client
func (cli *Client) DaemonHost() string {
	return cli.host
}

// ParseHost parses a url string, validates the strings is a host url, and returns
// the parsed host as: protocol, address, and base path
// Deprecated: use ParseHostURL
func ParseHost(host string) (string, string, string, error) {
	hostURL, err := ParseHostURL(host)
	if err != nil {
		return "", "", "", err
	}
	return hostURL.Scheme, hostURL.Host, hostURL.Path, nil
}

// ParseHostURL parses a url string, validates the string is a host url, and
// returns the parsed URL
func ParseHostURL(host string) (*url.URL, error) {
	protoAddrParts := strings.SplitN(host, "://", 2)
	if len(protoAddrParts) == 1 {
		return nil, fmt.Errorf("unable to parse docker host `%s`", host)
	}

	var basePath string
	proto, addr := protoAddrParts[0], protoAddrParts[1]
	if proto == "tcp" {
		parsed, err := url.Parse("tcp://" + addr)
		if err != nil {
			return nil, err
		}
		addr = parsed.Host
		basePath = parsed.Path
	}
	return &url.URL{
		Scheme: proto,
		Host:   addr,
		Path:   basePath,
	}, nil
}

// CustomHTTPHeaders returns the custom http headers stored by the client.
func (cli *Client) CustomHTTPHeaders() map[string]string {
	m := make(map[string]string)
	for k, v := range cli.customHTTPHeaders {
		m[k] = v
	}
	return m
}

// SetCustomHTTPHeaders that will be set on every HTTP request made by the client.
func (cli *Client) SetCustomHTTPHeaders(headers map[string]string) {
	cli.customHTTPHeaders = headers
}