// Copyright (C) The Arvados Authors. All rights reserved.
//
// SPDX-License-Identifier: AGPL-3.0

package federation

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"regexp"
	"strings"
	"time"

	"git.arvados.org/arvados.git/lib/config"
	"git.arvados.org/arvados.git/lib/controller/localdb"
	"git.arvados.org/arvados.git/lib/controller/rpc"
	"git.arvados.org/arvados.git/sdk/go/arvados"
	"git.arvados.org/arvados.git/sdk/go/auth"
	"git.arvados.org/arvados.git/sdk/go/ctxlog"
)

type Conn struct {
	cluster *arvados.Cluster
	local   backend
	remotes map[string]backend
}

func New(cluster *arvados.Cluster) *Conn {
	local := localdb.NewConn(cluster)
	remotes := map[string]backend{}
	for id, remote := range cluster.RemoteClusters {
		if !remote.Proxy || id == cluster.ClusterID {
			continue
		}
		conn := rpc.NewConn(id, &url.URL{Scheme: remote.Scheme, Host: remote.Host}, remote.Insecure, saltedTokenProvider(local, id))
		// Older versions of controller rely on the Via header
		// to detect loops.
		conn.SendHeader = http.Header{"Via": {"HTTP/1.1 arvados-controller"}}
		remotes[id] = conn
	}

	return &Conn{
		cluster: cluster,
		local:   local,
		remotes: remotes,
	}
}

// Return a new rpc.TokenProvider that takes the client-provided
// tokens from an incoming request context, determines whether they
// should (and can) be salted for the given remoteID, and returns the
// resulting tokens.
func saltedTokenProvider(local backend, remoteID string) rpc.TokenProvider {
	return func(ctx context.Context) ([]string, error) {
		var tokens []string
		incoming, ok := auth.FromContext(ctx)
		if !ok {
			return nil, errors.New("no token provided")
		}
		for _, token := range incoming.Tokens {
			salted, err := auth.SaltToken(token, remoteID)
			switch err {
			case nil:
				tokens = append(tokens, salted)
			case auth.ErrSalted:
				tokens = append(tokens, token)
			case auth.ErrObsoleteToken:
				ctx := auth.NewContext(ctx, &auth.Credentials{Tokens: []string{token}})
				aca, err := local.APIClientAuthorizationCurrent(ctx, arvados.GetOptions{})
				if errStatus(err) == http.StatusUnauthorized {
					// pass through unmodified
					tokens = append(tokens, token)
					continue
				} else if err != nil {
					return nil, err
				}
				salted, err := auth.SaltToken(aca.TokenV2(), remoteID)
				if err != nil {
					return nil, err
				}
				tokens = append(tokens, salted)
			default:
				return nil, err
			}
		}
		return tokens, nil
	}
}

// Return suitable backend for a query about the given cluster ID
// ("aaaaa") or object UUID ("aaaaa-dz642-abcdefghijklmno").
func (conn *Conn) chooseBackend(id string) backend {
	if len(id) == 27 {
		id = id[:5]
	} else if len(id) != 5 {
		// PDH or bogus ID
		return conn.local
	}
	if id == conn.cluster.ClusterID {
		return conn.local
	} else if be, ok := conn.remotes[id]; ok {
		return be
	} else {
		// TODO: return an "always error" backend?
		return conn.local
	}
}

// Call fn with the local backend; then, if fn returned 404, call fn
// on the available remote backends (possibly concurrently) until one
// succeeds.
//
// The second argument to fn is the cluster ID of the remote backend,
// or "" for the local backend.
//
// A non-nil error means all backends failed.
func (conn *Conn) tryLocalThenRemotes(ctx context.Context, forwardedFor string, fn func(context.Context, string, backend) error) error {
	if err := fn(ctx, "", conn.local); err == nil || errStatus(err) != http.StatusNotFound || forwardedFor != "" {
		// Note: forwardedFor != "" means this request came
		// from a remote cluster, so we don't take a second
		// hop. This avoids cycles, redundant calls to a
		// mutually reachable remote, and use of double-salted
		// tokens.
		return err
	}

	ctx, cancel := context.WithCancel(ctx)
	defer cancel()
	errchan := make(chan error, len(conn.remotes))
	for remoteID, be := range conn.remotes {
		remoteID, be := remoteID, be
		go func() {
			errchan <- fn(ctx, remoteID, be)
		}()
	}
	all404 := true
	var errs []error
	for i := 0; i < cap(errchan); i++ {
		err := <-errchan
		if err == nil {
			return nil
		}
		all404 = all404 && errStatus(err) == http.StatusNotFound
		errs = append(errs, err)
	}
	if all404 {
		return notFoundError{}
	}
	return httpErrorf(http.StatusBadGateway, "errors: %v", errs)
}

func (conn *Conn) CollectionCreate(ctx context.Context, options arvados.CreateOptions) (arvados.Collection, error) {
	return conn.chooseBackend(options.ClusterID).CollectionCreate(ctx, options)
}

func (conn *Conn) CollectionUpdate(ctx context.Context, options arvados.UpdateOptions) (arvados.Collection, error) {
	return conn.chooseBackend(options.UUID).CollectionUpdate(ctx, options)
}

func rewriteManifest(mt, remoteID string) string {
	return regexp.MustCompile(` [0-9a-f]{32}\+[^ ]*`).ReplaceAllStringFunc(mt, func(tok string) string {
		return strings.Replace(tok, "+A", "+R"+remoteID+"-", -1)
	})
}

func (conn *Conn) ConfigGet(ctx context.Context) (json.RawMessage, error) {
	var buf bytes.Buffer
	err := config.ExportJSON(&buf, conn.cluster)
	return json.RawMessage(buf.Bytes()), err
}

func (conn *Conn) Login(ctx context.Context, options arvados.LoginOptions) (arvados.LoginResponse, error) {
	if id := conn.cluster.Login.LoginCluster; id != "" && id != conn.cluster.ClusterID {
		// defer entire login procedure to designated cluster
		remote, ok := conn.remotes[id]
		if !ok {
			return arvados.LoginResponse{}, fmt.Errorf("configuration problem: designated login cluster %q is not defined", id)
		}
		baseURL := remote.BaseURL()
		target, err := baseURL.Parse(arvados.EndpointLogin.Path)
		if err != nil {
			return arvados.LoginResponse{}, fmt.Errorf("internal error getting redirect target: %s", err)
		}
		params := url.Values{
			"return_to": []string{options.ReturnTo},
		}
		if options.Remote != "" {
			params.Set("remote", options.Remote)
		}
		target.RawQuery = params.Encode()
		return arvados.LoginResponse{
			RedirectLocation: target.String(),
		}, nil
	} else {
		return conn.local.Login(ctx, options)
	}
}

func (conn *Conn) Logout(ctx context.Context, options arvados.LogoutOptions) (arvados.LogoutResponse, error) {
	// If the logout request comes with an API token from a known
	// remote cluster, redirect to that cluster's logout handler
	// so it has an opportunity to clear sessions, expire tokens,
	// etc. Otherwise use the local endpoint.
	reqauth, ok := auth.FromContext(ctx)
	if !ok || len(reqauth.Tokens) == 0 || len(reqauth.Tokens[0]) < 8 || !strings.HasPrefix(reqauth.Tokens[0], "v2/") {
		return conn.local.Logout(ctx, options)
	}
	id := reqauth.Tokens[0][3:8]
	if id == conn.cluster.ClusterID {
		return conn.local.Logout(ctx, options)
	}
	remote, ok := conn.remotes[id]
	if !ok {
		return conn.local.Logout(ctx, options)
	}
	baseURL := remote.BaseURL()
	target, err := baseURL.Parse(arvados.EndpointLogout.Path)
	if err != nil {
		return arvados.LogoutResponse{}, fmt.Errorf("internal error getting redirect target: %s", err)
	}
	target.RawQuery = url.Values{"return_to": {options.ReturnTo}}.Encode()
	return arvados.LogoutResponse{RedirectLocation: target.String()}, nil
}

func (conn *Conn) CollectionGet(ctx context.Context, options arvados.GetOptions) (arvados.Collection, error) {
	if len(options.UUID) == 27 {
		// UUID is really a UUID
		c, err := conn.chooseBackend(options.UUID).CollectionGet(ctx, options)
		if err == nil && options.UUID[:5] != conn.cluster.ClusterID {
			c.ManifestText = rewriteManifest(c.ManifestText, options.UUID[:5])
		}
		return c, err
	} else {
		// UUID is a PDH
		first := make(chan arvados.Collection, 1)
		err := conn.tryLocalThenRemotes(ctx, options.ForwardedFor, func(ctx context.Context, remoteID string, be backend) error {
			remoteOpts := options
			remoteOpts.ForwardedFor = conn.cluster.ClusterID + "-" + options.ForwardedFor
			c, err := be.CollectionGet(ctx, remoteOpts)
			if err != nil {
				return err
			}
			// options.UUID is either hash+size or
			// hash+size+hints; only hash+size need to
			// match the computed PDH.
			if pdh := arvados.PortableDataHash(c.ManifestText); pdh != options.UUID && !strings.HasPrefix(options.UUID, pdh+"+") {
				err = httpErrorf(http.StatusBadGateway, "bad portable data hash %q received from remote %q (expected %q)", pdh, remoteID, options.UUID)
				ctxlog.FromContext(ctx).Warn(err)
				return err
			}
			if remoteID != "" {
				c.ManifestText = rewriteManifest(c.ManifestText, remoteID)
			}
			select {
			case first <- c:
				return nil
			default:
				// lost race, return value doesn't matter
				return nil
			}
		})
		if err != nil {
			return arvados.Collection{}, err
		}
		return <-first, nil
	}
}

func (conn *Conn) CollectionList(ctx context.Context, options arvados.ListOptions) (arvados.CollectionList, error) {
	return conn.generated_CollectionList(ctx, options)
}

func (conn *Conn) CollectionProvenance(ctx context.Context, options arvados.GetOptions) (map[string]interface{}, error) {
	return conn.chooseBackend(options.UUID).CollectionProvenance(ctx, options)
}

func (conn *Conn) CollectionUsedBy(ctx context.Context, options arvados.GetOptions) (map[string]interface{}, error) {
	return conn.chooseBackend(options.UUID).CollectionUsedBy(ctx, options)
}

func (conn *Conn) CollectionDelete(ctx context.Context, options arvados.DeleteOptions) (arvados.Collection, error) {
	return conn.chooseBackend(options.UUID).CollectionDelete(ctx, options)
}

func (conn *Conn) CollectionTrash(ctx context.Context, options arvados.DeleteOptions) (arvados.Collection, error) {
	return conn.chooseBackend(options.UUID).CollectionTrash(ctx, options)
}

func (conn *Conn) CollectionUntrash(ctx context.Context, options arvados.UntrashOptions) (arvados.Collection, error) {
	return conn.chooseBackend(options.UUID).CollectionUntrash(ctx, options)
}

func (conn *Conn) ContainerList(ctx context.Context, options arvados.ListOptions) (arvados.ContainerList, error) {
	return conn.generated_ContainerList(ctx, options)
}

func (conn *Conn) ContainerCreate(ctx context.Context, options arvados.CreateOptions) (arvados.Container, error) {
	return conn.chooseBackend(options.ClusterID).ContainerCreate(ctx, options)
}

func (conn *Conn) ContainerUpdate(ctx context.Context, options arvados.UpdateOptions) (arvados.Container, error) {
	return conn.chooseBackend(options.UUID).ContainerUpdate(ctx, options)
}

func (conn *Conn) ContainerGet(ctx context.Context, options arvados.GetOptions) (arvados.Container, error) {
	return conn.chooseBackend(options.UUID).ContainerGet(ctx, options)
}

func (conn *Conn) ContainerDelete(ctx context.Context, options arvados.DeleteOptions) (arvados.Container, error) {
	return conn.chooseBackend(options.UUID).ContainerDelete(ctx, options)
}

func (conn *Conn) ContainerLock(ctx context.Context, options arvados.GetOptions) (arvados.Container, error) {
	return conn.chooseBackend(options.UUID).ContainerLock(ctx, options)
}

func (conn *Conn) ContainerUnlock(ctx context.Context, options arvados.GetOptions) (arvados.Container, error) {
	return conn.chooseBackend(options.UUID).ContainerUnlock(ctx, options)
}

func (conn *Conn) SpecimenList(ctx context.Context, options arvados.ListOptions) (arvados.SpecimenList, error) {
	return conn.generated_SpecimenList(ctx, options)
}

func (conn *Conn) SpecimenCreate(ctx context.Context, options arvados.CreateOptions) (arvados.Specimen, error) {
	return conn.chooseBackend(options.ClusterID).SpecimenCreate(ctx, options)
}

func (conn *Conn) SpecimenUpdate(ctx context.Context, options arvados.UpdateOptions) (arvados.Specimen, error) {
	return conn.chooseBackend(options.UUID).SpecimenUpdate(ctx, options)
}

func (conn *Conn) SpecimenGet(ctx context.Context, options arvados.GetOptions) (arvados.Specimen, error) {
	return conn.chooseBackend(options.UUID).SpecimenGet(ctx, options)
}

func (conn *Conn) SpecimenDelete(ctx context.Context, options arvados.DeleteOptions) (arvados.Specimen, error) {
	return conn.chooseBackend(options.UUID).SpecimenDelete(ctx, options)
}

var userAttrsCachedFromLoginCluster = map[string]bool{
	"created_at":  true,
	"email":       true,
	"first_name":  true,
	"is_active":   true,
	"is_admin":    true,
	"last_name":   true,
	"modified_at": true,
	"prefs":       true,
	"username":    true,

	"etag":                    false,
	"full_name":               false,
	"identity_url":            false,
	"is_invited":              false,
	"modified_by_client_uuid": false,
	"modified_by_user_uuid":   false,
	"owner_uuid":              false,
	"uuid":                    false,
	"writable_by":             false,
}

func (conn *Conn) UserList(ctx context.Context, options arvados.ListOptions) (arvados.UserList, error) {
	logger := ctxlog.FromContext(ctx)
	if id := conn.cluster.Login.LoginCluster; id != "" && id != conn.cluster.ClusterID {
		resp, err := conn.chooseBackend(id).UserList(ctx, options)
		if err != nil {
			return resp, err
		}
		batchOpts := arvados.UserBatchUpdateOptions{Updates: map[string]map[string]interface{}{}}
		for _, user := range resp.Items {
			if !strings.HasPrefix(user.UUID, id) {
				continue
			}
			logger.Debugf("cache user info for uuid %q", user.UUID)

			// If the remote cluster has null timestamps
			// (e.g., test server with incomplete
			// fixtures) use dummy timestamps (instead of
			// the zero time, which causes a Rails API
			// error "year too big to marshal: 1 UTC").
			if user.ModifiedAt.IsZero() {
				user.ModifiedAt = time.Now()
			}
			if user.CreatedAt.IsZero() {
				user.CreatedAt = time.Now()
			}

			var allFields map[string]interface{}
			buf, err := json.Marshal(user)
			if err != nil {
				return arvados.UserList{}, fmt.Errorf("error encoding user record from remote response: %s", err)
			}
			err = json.Unmarshal(buf, &allFields)
			if err != nil {
				return arvados.UserList{}, fmt.Errorf("error transcoding user record from remote response: %s", err)
			}
			updates := allFields
			if len(options.Select) > 0 {
				updates = map[string]interface{}{}
				for _, k := range options.Select {
					if v, ok := allFields[k]; ok && userAttrsCachedFromLoginCluster[k] {
						updates[k] = v
					}
				}
			} else {
				for k := range updates {
					if !userAttrsCachedFromLoginCluster[k] {
						delete(updates, k)
					}
				}
			}
			batchOpts.Updates[user.UUID] = updates
		}
		if len(batchOpts.Updates) > 0 {
			ctxRoot := auth.NewContext(ctx, &auth.Credentials{Tokens: []string{conn.cluster.SystemRootToken}})
			_, err = conn.local.UserBatchUpdate(ctxRoot, batchOpts)
			if err != nil {
				return arvados.UserList{}, fmt.Errorf("error updating local user records: %s", err)
			}
		}
		return resp, nil
	} else {
		return conn.generated_UserList(ctx, options)
	}
}

func (conn *Conn) UserCreate(ctx context.Context, options arvados.CreateOptions) (arvados.User, error) {
	return conn.chooseBackend(options.ClusterID).UserCreate(ctx, options)
}

func (conn *Conn) UserUpdate(ctx context.Context, options arvados.UpdateOptions) (arvados.User, error) {
	return conn.chooseBackend(options.UUID).UserUpdate(ctx, options)
}

func (conn *Conn) UserUpdateUUID(ctx context.Context, options arvados.UpdateUUIDOptions) (arvados.User, error) {
	return conn.chooseBackend(options.UUID).UserUpdateUUID(ctx, options)
}

func (conn *Conn) UserMerge(ctx context.Context, options arvados.UserMergeOptions) (arvados.User, error) {
	return conn.chooseBackend(options.OldUserUUID).UserMerge(ctx, options)
}

func (conn *Conn) UserActivate(ctx context.Context, options arvados.UserActivateOptions) (arvados.User, error) {
	return conn.chooseBackend(options.UUID).UserActivate(ctx, options)
}

func (conn *Conn) UserSetup(ctx context.Context, options arvados.UserSetupOptions) (map[string]interface{}, error) {
	return conn.chooseBackend(options.UUID).UserSetup(ctx, options)
}

func (conn *Conn) UserUnsetup(ctx context.Context, options arvados.GetOptions) (arvados.User, error) {
	return conn.chooseBackend(options.UUID).UserUnsetup(ctx, options)
}

func (conn *Conn) UserGet(ctx context.Context, options arvados.GetOptions) (arvados.User, error) {
	return conn.chooseBackend(options.UUID).UserGet(ctx, options)
}

func (conn *Conn) UserGetCurrent(ctx context.Context, options arvados.GetOptions) (arvados.User, error) {
	return conn.chooseBackend(options.UUID).UserGetCurrent(ctx, options)
}

func (conn *Conn) UserGetSystem(ctx context.Context, options arvados.GetOptions) (arvados.User, error) {
	return conn.chooseBackend(options.UUID).UserGetSystem(ctx, options)
}

func (conn *Conn) UserDelete(ctx context.Context, options arvados.DeleteOptions) (arvados.User, error) {
	return conn.chooseBackend(options.UUID).UserDelete(ctx, options)
}

func (conn *Conn) UserBatchUpdate(ctx context.Context, options arvados.UserBatchUpdateOptions) (arvados.UserList, error) {
	return conn.local.UserBatchUpdate(ctx, options)
}

func (conn *Conn) APIClientAuthorizationCurrent(ctx context.Context, options arvados.GetOptions) (arvados.APIClientAuthorization, error) {
	return conn.chooseBackend(options.UUID).APIClientAuthorizationCurrent(ctx, options)
}

type backend interface {
	arvados.API
	BaseURL() url.URL
}

type notFoundError struct{}

func (notFoundError) HTTPStatus() int { return http.StatusNotFound }
func (notFoundError) Error() string   { return "not found" }

func errStatus(err error) int {
	if httpErr, ok := err.(interface{ HTTPStatus() int }); ok {
		return httpErr.HTTPStatus()
	} else {
		return http.StatusInternalServerError
	}
}