// Copyright (c) 2020 TypeFox GmbH. All rights reserved.
// Licensed under the GNU Affero General Public License (AGPL).
// See License-AGPL.txt in the project root for license information.

package proxy

import (
	"context"
	"io"
	"net/url"
	"strconv"
	"sync"
	"time"

	"github.com/gitpod-io/gitpod/common-go/log"
	"github.com/gitpod-io/gitpod/common-go/util"
	wsapi "github.com/gitpod-io/gitpod/ws-manager/api"

	validation "github.com/go-ozzo/ozzo-validation"
	"golang.org/x/xerrors"
	"google.golang.org/grpc"
)

// WorkspaceCoords represents the coordinates of a workspace (port)
type WorkspaceCoords struct {
	// The workspace ID
	ID string
	// The workspace port. "" in case of Theia
	Port string
}

// WorkspaceInfoProvider is an entity that is able to provide workspaces related information
type WorkspaceInfoProvider interface {
	// WorkspaceInfo returns the workspace information of a workspace using it's workspace ID
	WorkspaceInfo(workspaceID string) *WorkspaceInfo

	// WorkspaceCoords provides workspace coordinates for a workspace using the public port
	// exposed by this service.
	WorkspaceCoords(publicPort string) *WorkspaceCoords
}

// WorkspaceInfoProviderConfig configures a WorkspaceInfoProvider
type WorkspaceInfoProviderConfig struct {
	WsManagerAddr     string        `json:"wsManagerAddr"`
	ReconnectInterval util.Duration `json:"reconnectInterval"`
}

// Validate validates the configuration to catch issues during startup and not at runtime
func (c *WorkspaceInfoProviderConfig) Validate() error {
	if c == nil {
		return xerrors.Errorf("WorkspaceInfoProviderConfig not configured")
	}

	err := validation.ValidateStruct(c,
		validation.Field(&c.WsManagerAddr, validation.Required),
	)
	return err
}

// WorkspaceInfo is all the infos ws-proxy needs to know about a workspace
type WorkspaceInfo struct {
	WorkspaceID string
	InstanceID  string
	URL         string

	IDEImage string

	// (parsed from URL)
	IDEPublicPort string

	Ports []PortInfo
	Auth  *wsapi.WorkspaceAuthentication
}

// PortInfo contains all information ws-proxy needs to know about a workspace port
type PortInfo struct {
	wsapi.PortSpec

	// The publicly visible proxy port it is exposed on
	PublicPort string
}

// RemoteWorkspaceInfoProvider provides (cached) infos about running workspaces that it queries from ws-manager
type RemoteWorkspaceInfoProvider struct {
	Config WorkspaceInfoProviderConfig

	ready bool
	mu    sync.Mutex
	cache *workspaceInfoCache
}

// NewRemoteWorkspaceInfoProvider creates a fresh WorkspaceInfoProvider
func NewRemoteWorkspaceInfoProvider(config WorkspaceInfoProviderConfig) *RemoteWorkspaceInfoProvider {
	return &RemoteWorkspaceInfoProvider{
		Config: config,
		cache:  newWorkspaceInfoCache(),
	}
}

// Run is meant to be called as a go-routine and streams the current state of all workspace statuus from ws-manager,
// transforms the relevent pieces into WorkspaceInfos and stores them in the cache
func (p *RemoteWorkspaceInfoProvider) Run() (err error) {
	connect := func(target string) (*grpc.ClientConn, wsapi.WorkspaceManagerClient, error) {
		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()

		conn, err := grpc.DialContext(ctx, target, grpc.WithInsecure(), grpc.WithBlock())
		if err != nil {
			return nil, nil, err
		}

		client := wsapi.NewWorkspaceManagerClient(conn)
		return conn, client, err
	}

	// create initial connection
	target := p.Config.WsManagerAddr
	conn, client, err := connect(target)
	if err != nil {
		return xerrors.Errorf("error while connecting to ws-manager: %w", err)
	}

	// do the initial fetching synchronously
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	infos, err := p.fetchInitialWorkspaceInfo(ctx, client)
	if err != nil {
		return err
	}
	p.cache.reinit(infos)

	// maintain connection and stream workspace statuus
	go func(conn *grpc.ClientConn, client wsapi.WorkspaceManagerClient) {
		for {
			p.mu.Lock()
			p.ready = true
			p.mu.Unlock()

			err := p.listen(client)
			if xerrors.Is(err, io.EOF) {
				log.Warn("ws-manager closed the connection, reconnecting after timeout...")
			} else if err != nil {
				log.WithError(err).Warnf("error while listening for workspace status updates, reconnecting after timeout")
			}

			conn.Close()
			p.mu.Lock()
			p.ready = false
			p.mu.Unlock()

			for {
				time.Sleep(time.Duration(p.Config.ReconnectInterval))

				conn, client, err = connect(target)
				if err != nil {
					log.WithError(err).Warnf("error while connecting to ws-manager, reconnecting after timeout...")
					continue
				}
				break
			}
		}
	}(conn, client)

	return nil
}

// Ready returns true if the info provider is up and running
func (p *RemoteWorkspaceInfoProvider) Ready() bool {
	p.mu.Lock()
	defer p.mu.Unlock()

	return p.ready
}

// listen starts listening to WorkspaceStatus updates from ws-manager
func (p *RemoteWorkspaceInfoProvider) listen(client wsapi.WorkspaceManagerClient) (err error) {
	defer func() {
		if err != nil {
			err = xerrors.Errorf("error while starting streaming status updates from ws-manager: %w", err)
		}
	}()

	// rebuild entire cache on (re-)connect
	ctx := context.Background()
	infos, err := p.fetchInitialWorkspaceInfo(ctx, client)
	if err != nil {
		return err
	}
	p.cache.reinit(infos)

	// start streaming status updates
	stream, err := client.Subscribe(ctx, &wsapi.SubscribeRequest{})
	if err != nil {
		return err
	}
	for {
		resp, err := stream.Recv()
		if err != nil {
			return err
		}

		status := resp.GetStatus()
		if status.Phase == wsapi.WorkspacePhase_STOPPED {
			p.cache.delete(status.Metadata.MetaId)
		} else {
			info := mapWorkspaceStatusToInfo(status)
			p.cache.insert(info)
		}
	}
}

// fetchInitialWorkspaceInfo retrieves initial WorkspaceStatus' from ws-manager and maps them into WorkspaceInfos
func (p *RemoteWorkspaceInfoProvider) fetchInitialWorkspaceInfo(ctx context.Context, client wsapi.WorkspaceManagerClient) ([]*WorkspaceInfo, error) {
	initialResp, err := client.GetWorkspaces(ctx, &wsapi.GetWorkspacesRequest{})
	if err != nil {
		return nil, xerrors.Errorf("error while retrieving initial state from ws-manager: %w", err)
	}

	var infos []*WorkspaceInfo
	for _, status := range initialResp.GetStatus() {
		infos = append(infos, mapWorkspaceStatusToInfo(status))
	}
	return infos, nil
}

func mapWorkspaceStatusToInfo(status *wsapi.WorkspaceStatus) *WorkspaceInfo {
	var portInfos []PortInfo
	for _, spec := range status.Spec.ExposedPorts {
		proxyPort := getPortStr(spec.Url)
		if proxyPort == "" {
			continue
		}

		portInfos = append(portInfos, PortInfo{
			PortSpec:   *spec,
			PublicPort: proxyPort,
		})
	}

	return &WorkspaceInfo{
		WorkspaceID:   status.Metadata.MetaId,
		InstanceID:    status.Id,
		URL:           status.Spec.Url,
		IDEImage:      status.Spec.IdeImage,
		IDEPublicPort: getPortStr(status.Spec.Url),
		Ports:         portInfos,
		Auth:          status.Auth,
	}
}

// WorkspaceInfo return the WorkspaceInfo avaiable for the given workspaceID
func (p *RemoteWorkspaceInfoProvider) WorkspaceInfo(workspaceID string) *WorkspaceInfo {
	info, present := p.cache.getByID(workspaceID)
	if !present {
		return nil
	}
	return info
}

// WorkspaceCoords returns the WorkspaceCoords the given publicPort is associated with
func (p *RemoteWorkspaceInfoProvider) WorkspaceCoords(publicPort string) *WorkspaceCoords {
	coords, present := p.cache.getCoordsByPublicPort(publicPort)
	if !present {
		return nil
	}
	return coords
}

// getPortStr extracts the port part from a given URL string. Returns "" if parsing fails or port is not specified
func getPortStr(urlStr string) string {
	portURL, err := url.Parse(urlStr)
	if err != nil {
		return ""
	}
	return portURL.Port()
}

// workspaceInfoCache stores WorkspaceInfo in a manner which is easy to query for WorkspaceInfoProvider
type workspaceInfoCache struct {
	// WorkspaceInfos indexed by workspaceID
	infos map[string]*WorkspaceInfo
	// WorkspaceCoords indexed by public (proxy) port (string)
	coordsByPublicPort map[string]*WorkspaceCoords

	mu sync.RWMutex
}

func newWorkspaceInfoCache() *workspaceInfoCache {
	return &workspaceInfoCache{
		infos:              make(map[string]*WorkspaceInfo),
		coordsByPublicPort: make(map[string]*WorkspaceCoords),
	}
}

func (c *workspaceInfoCache) reinit(infos []*WorkspaceInfo) {
	c.mu.Lock()
	defer c.mu.Unlock()

	c.infos = make(map[string]*WorkspaceInfo, len(infos))
	c.coordsByPublicPort = make(map[string]*WorkspaceCoords, len(c.coordsByPublicPort))

	for _, info := range infos {
		c.doInsert(info)
	}
}

func (c *workspaceInfoCache) insert(info *WorkspaceInfo) {
	c.mu.Lock()
	defer c.mu.Unlock()

	c.doInsert(info)
}

func (c *workspaceInfoCache) doInsert(info *WorkspaceInfo) {
	c.infos[info.WorkspaceID] = info
	c.coordsByPublicPort[info.IDEPublicPort] = &WorkspaceCoords{
		ID: info.WorkspaceID,
	}

	for _, p := range info.Ports {
		c.coordsByPublicPort[p.PublicPort] = &WorkspaceCoords{
			ID:   info.WorkspaceID,
			Port: strconv.Itoa(int(p.Port)),
		}
	}
}

func (c *workspaceInfoCache) delete(workspaceID string) {
	c.mu.Lock()
	defer c.mu.Unlock()

	info, present := c.infos[workspaceID]
	if !present || info == nil {
		return
	}
	delete(c.coordsByPublicPort, info.IDEPublicPort)
	delete(c.infos, workspaceID)
}

func (c *workspaceInfoCache) getByID(workspaceID string) (*WorkspaceInfo, bool) {
	c.mu.RLock()
	defer c.mu.RUnlock()

	info, ok := c.infos[workspaceID]
	return info, ok
}

func (c *workspaceInfoCache) getCoordsByPublicPort(wsProxyPort string) (*WorkspaceCoords, bool) {
	c.mu.RLock()
	defer c.mu.RUnlock()

	coords, ok := c.coordsByPublicPort[wsProxyPort]
	return coords, ok
}

type fixedInfoProvider struct {
	Infos  map[string]*WorkspaceInfo
	Coords map[string]*WorkspaceCoords
}

// WorkspaceInfo returns the workspace information of a workspace using it's workspace ID
func (fp *fixedInfoProvider) WorkspaceInfo(workspaceID string) *WorkspaceInfo {
	if fp.Infos == nil {
		return nil
	}
	return fp.Infos[workspaceID]
}

// WorkspaceCoords provides workspace coordinates for a workspace using the public port exposed by this service.
func (fp *fixedInfoProvider) WorkspaceCoords(publicPort string) *WorkspaceCoords {
	if fp.Coords == nil {
		return nil
	}
	return fp.Coords[publicPort]
}