// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
// See LICENSE.txt for license information.

package app

import (
	"net/http"
	"os"
	"os/signal"
	"runtime"
	"strings"
	"sync"
	"sync/atomic"
	"syscall"
	"time"

	"github.com/pkg/errors"

	"github.com/mattermost/mattermost/server/public/model"
	"github.com/mattermost/mattermost/server/public/plugin"
	"github.com/mattermost/mattermost/server/public/shared/mlog"
	"github.com/mattermost/mattermost/server/public/shared/request"
	"github.com/mattermost/mattermost/server/v8/channels/app/imaging"
	"github.com/mattermost/mattermost/server/v8/config"
	"github.com/mattermost/mattermost/server/v8/einterfaces"
	"github.com/mattermost/mattermost/server/v8/platform/services/imageproxy"
	"github.com/mattermost/mattermost/server/v8/platform/shared/filestore"
)

type configService interface {
	Config() *model.Config
	AddConfigListener(listener func(*model.Config, *model.Config)) string
	RemoveConfigListener(id string)
	UpdateConfig(f func(*model.Config))
	SaveConfig(newCfg *model.Config, sendConfigChangeClusterMessage bool) (*model.Config, *model.Config, *model.AppError)
}

// Channels contains all channels related state.
type Channels struct {
	srv             *Server
	cfgSvc          configService
	filestore       filestore.FileBackend
	exportFilestore filestore.FileBackend

	postActionCookieSecret []byte

	pluginCommandsLock            sync.RWMutex
	pluginCommands                []*PluginCommand
	pluginsLock                   sync.RWMutex
	pluginsEnvironment            *plugin.Environment
	pluginConfigListenerID        string
	pluginClusterLeaderListenerID string

	// guardCache caches ChannelGuards rows by ChannelId -> []*store.ChannelGuard.
	guardCache atomic.Pointer[sync.Map]

	// guardCacheRetryInFlight collapses concurrent reload-failure retries to a single goroutine.
	// See scheduleGuardCacheReloadRetry.
	guardCacheRetryInFlight atomic.Bool

	imageProxy *imageproxy.ImageProxy

	agentsBridge AgentsBridge

	// cached counts that are used during notice condition validation
	cachedPostCount   int64
	cachedUserCount   int64
	cachedDBMSVersion string
	// previously fetched notices
	cachedNotices model.ProductNotices

	managedCategoryGroupID string
	managedCategoryFieldID string

	AccountMigration einterfaces.AccountMigrationInterface
	Compliance       einterfaces.ComplianceInterface
	DataRetention    einterfaces.DataRetentionInterface
	MessageExport    einterfaces.MessageExportInterface
	Saml             einterfaces.SamlInterface
	Notification     einterfaces.NotificationInterface
	Ldap             einterfaces.LdapInterface
	AccessControl    einterfaces.AccessControlServiceInterface
	Intune           einterfaces.IntuneInterface

	attributeViewRefreshMut  sync.Mutex
	attributeViewRefreshLast time.Time

	// These are used to prevent concurrent upload requests
	// for a given upload session which could cause inconsistencies
	// and data corruption.
	uploadLockMapMut sync.Mutex
	uploadLockMap    map[string]bool

	imgDecoder *imaging.Decoder
	imgEncoder *imaging.Encoder

	dndTaskMut sync.Mutex
	dndTask    *model.ScheduledTask

	postReminderMut  sync.Mutex
	postReminderTask *model.ScheduledTask

	interruptQuitChan chan struct{}
	scheduledPostMut  sync.Mutex
	scheduledPostTask *model.ScheduledTask
}

func NewChannels(s *Server) (*Channels, error) {
	ch := &Channels{
		srv:               s,
		imageProxy:        imageproxy.MakeImageProxy(s.platform, s.httpService, s.Log()),
		uploadLockMap:     map[string]bool{},
		filestore:         s.FileBackend(),
		exportFilestore:   s.ExportFileBackend(),
		cfgSvc:            s.Platform(),
		interruptQuitChan: make(chan struct{}),
	}
	ch.guardCache.Store(&sync.Map{})

	if s.agentsBridgeOverride != nil {
		ch.agentsBridge = s.agentsBridgeOverride
	} else {
		ch.agentsBridge = newLiveAgentsBridge(ch)
	}

	// We are passing a partially filled Channels struct so that the enterprise
	// methods can have access to app methods.
	// Otherwise, passing server would mean it has to call s.Channels(),
	// which would be nil at this point.
	if complianceInterface != nil {
		ch.Compliance = complianceInterface(New(ServerConnector(ch)))
	}
	if messageExportInterface != nil {
		ch.MessageExport = messageExportInterface(New(ServerConnector(ch)))
	}
	if dataRetentionInterface != nil {
		ch.DataRetention = dataRetentionInterface(New(ServerConnector(ch)))
	}
	if accountMigrationInterface != nil {
		ch.AccountMigration = accountMigrationInterface(New(ServerConnector(ch)))
	}
	if ldapInterface != nil {
		ch.Ldap = ldapInterface(New(ServerConnector(ch)))
	}
	if notificationInterface != nil {
		ch.Notification = notificationInterface(New(ServerConnector(ch)))
	}
	if samlInterface != nil {
		ch.Saml = samlInterface(New(ServerConnector(ch)))
		if err := ch.Saml.ConfigureSP(request.EmptyContext(s.Log())); err != nil {
			s.Log().Error("An error occurred while configuring SAML Service Provider", mlog.Err(err))
		}

		ch.AddConfigListener(func(_, _ *model.Config) {
			if err := ch.Saml.ConfigureSP(request.EmptyContext(s.Log())); err != nil {
				s.Log().Error("An error occurred while configuring SAML Service Provider", mlog.Err(err))
			}
		})
	}

	if intuneInterface != nil {
		ch.Intune = intuneInterface(New(ServerConnector(ch)))
	}

	if pushProxyInterface != nil {
		app := New(ServerConnector(ch))
		s.PushProxy = pushProxyInterface(app)

		// Add config listener to regenerate token when push proxy URL changes
		app.AddConfigListener(func(oldCfg, newCfg *model.Config) {
			// Only cluster leader should regenerate to avoid duplicate requests
			if !app.IsLeader() {
				return
			}

			oldURL := model.SafeDereference(oldCfg.EmailSettings.PushNotificationServer)
			newURL := model.SafeDereference(newCfg.EmailSettings.PushNotificationServer)

			// If push proxy URL changed
			if oldURL != newURL {
				if newURL != "" {
					// URL changed to a new value, regenerate token
					s.Log().Info("Push notification server URL changed, regenerating auth token",
						mlog.String("old_url", oldURL),
						mlog.String("new_url", newURL))

					if err := s.PushProxy.GenerateAuthToken(); err != nil {
						s.Log().Error("Failed to regenerate auth token after config change", mlog.Err(err))
					}
				} else if oldURL != "" {
					// URL was cleared, delete the old token
					s.Log().Info("Push notification server URL cleared, removing auth token")
					if err := s.PushProxy.DeleteAuthToken(); err != nil {
						s.Log().Error("Failed to delete auth token after URL cleared", mlog.Err(err))
					}
				}
			}
		})
	}

	if accessControlServiceInterface != nil {
		app := New(ServerConnector(ch))
		ch.AccessControl = accessControlServiceInterface(app)

		appErr := ch.AccessControl.Init(request.EmptyContext(s.Log()))
		if appErr != nil && appErr.StatusCode != http.StatusNotImplemented {
			s.Log().Error("An error occurred while initializing Access Control", mlog.Err(appErr))
		}

		app.AddLicenseListener(func(newCfg, old *model.License) {
			if ch.AccessControl != nil {
				if appErr := ch.AccessControl.Init(request.EmptyContext(s.Log())); appErr != nil && appErr.StatusCode != http.StatusNotImplemented {
					s.Log().Error("An error occurred while initializing Access Control", mlog.Err(appErr))
				}
			}
		})
	}

	var imgErr error
	decoderConcurrency := int(*ch.cfgSvc.Config().FileSettings.MaxImageDecoderConcurrency)
	if decoderConcurrency == -1 {
		decoderConcurrency = runtime.NumCPU()
	}
	ch.imgDecoder, imgErr = imaging.NewDecoder(imaging.DecoderOptions{
		ConcurrencyLevel: decoderConcurrency,
	})
	if imgErr != nil {
		return nil, errors.Wrap(imgErr, "failed to create image decoder")
	}
	ch.imgEncoder, imgErr = imaging.NewEncoder(imaging.EncoderOptions{
		ConcurrencyLevel: runtime.NumCPU(),
	})
	if imgErr != nil {
		return nil, errors.Wrap(imgErr, "failed to create image encoder")
	}

	// Setup routes.
	pluginsRoute := ch.srv.Router.PathPrefix("/plugins/{plugin_id:[A-Za-z0-9\\_\\-\\.]+}").Subrouter()
	pluginsRoute.HandleFunc("", ch.ServePluginRequest)
	pluginsRoute.HandleFunc("/public/{public_file:.*}", ch.ServePluginPublicRequest)
	pluginsRoute.HandleFunc("/{anything:.*}", ch.ServePluginRequest)

	if err := ch.reloadGuardCache(request.EmptyContext(s.Log()), s.Store()); err != nil {
		s.Log().Warn(
			"Failed to load channel guard cache at startup; retry scheduled",
			mlog.Bool("clustered", s.platform.Cluster() != nil),
			mlog.Err(err),
		)
		ch.scheduleGuardCacheReloadRetry()
	}

	return ch, nil
}

func (ch *Channels) SetAgentsBridge(bridge AgentsBridge) {
	ch.agentsBridge = bridge
}

func (ch *Channels) Start() error {
	// Start plugins
	ctx := request.EmptyContext(ch.srv.Log())
	ch.initPlugins(ctx, *ch.cfgSvc.Config().PluginSettings.Directory, *ch.cfgSvc.Config().PluginSettings.ClientDirectory)

	interruptChan := make(chan os.Signal, 1)
	signal.Notify(interruptChan, syscall.SIGINT, syscall.SIGTERM)
	go func() {
		select {
		case <-interruptChan:
			if err := ch.Stop(); err != nil {
				ch.srv.Log().Warn("Error stopping channels", mlog.Err(err))
			}
			os.Exit(1)
		case <-ch.interruptQuitChan:
			return
		}
	}()

	ch.AddConfigListener(func(prevCfg, cfg *model.Config) {
		// We compute the difference between configs
		// to ensure we don't re-init plugins unnecessarily.
		diffs, err := config.Diff(prevCfg, cfg)
		if err != nil {
			ch.srv.Log().Warn("Error in comparing configs", mlog.Err(err))
			return
		}

		hasDiff := false
		// TODO: This could be a method on ConfigDiffs itself
		for _, diff := range diffs {
			if strings.HasPrefix(diff.Path, "PluginSettings.") {
				hasDiff = true
				break
			}
		}

		// Do only if some plugin related settings has changed.
		if hasDiff {
			if *cfg.PluginSettings.Enable {
				ch.initPlugins(ctx, *cfg.PluginSettings.Directory, *ch.cfgSvc.Config().PluginSettings.ClientDirectory)
			} else {
				ch.ShutDownPlugins()
			}
		}
	})

	// TODO: This should be moved to the platform service.
	if err := ch.srv.platform.EnsureAsymmetricSigningKey(); err != nil {
		return errors.Wrapf(err, "unable to ensure asymmetric signing key")
	}

	if err := ch.ensurePostActionCookieSecret(); err != nil {
		return errors.Wrapf(err, "unable to ensure PostAction cookie secret")
	}

	return nil
}

func (ch *Channels) Stop() error {
	ch.ShutDownPlugins()

	ch.dndTaskMut.Lock()
	if ch.dndTask != nil {
		ch.dndTask.Cancel()
	}
	ch.dndTaskMut.Unlock()

	close(ch.interruptQuitChan)

	return nil
}

func (ch *Channels) AddConfigListener(listener func(*model.Config, *model.Config)) string {
	return ch.cfgSvc.AddConfigListener(listener)
}

func (ch *Channels) RemoveConfigListener(id string) {
	ch.cfgSvc.RemoveConfigListener(id)
}

func (ch *Channels) RunMultiHook(hookRunnerFunc func(hooks plugin.Hooks, manifest *model.Manifest) bool, hookId int) {
	if env := ch.GetPluginsEnvironment(); env != nil {
		env.RunMultiPluginHook(hookRunnerFunc, hookId)
	}
}

// RunMultiHookExcluding is like RunMultiHook but skips plugins whose IDs appear in excludePluginIDs.
// Fail-open semantics are preserved.
func (ch *Channels) RunMultiHookExcluding(excludePluginIDs []string, hookRunnerFunc func(plugin.Hooks, *model.Manifest) bool, hookId int) {
	if env := ch.GetPluginsEnvironment(); env != nil {
		env.RunMultiPluginHookExcluding(excludePluginIDs, hookRunnerFunc, hookId)
	}
}

// RunMultiHookWithRPCErr dispatches a hook closure across active plugins, surfacing RPC transport
// errors. Returns nil in two cases that callers must distinguish themselves: (a) the plugin
// environment is unavailable (plugins disabled, or not yet initialized), so the closure was never
// invoked; (b) iteration completed and every closure invocation returned nil. Callers that need
// fail-closed semantics on case (a) must check `ch.GetPluginsEnvironment() != nil` at the call site
// before invoking — the right policy when plugins are disabled by config is caller-specific.
func (ch *Channels) RunMultiHookWithRPCErr(hookRunnerFunc func(hooks plugin.HooksWithRPCErr, manifest *model.Manifest) (bool, error), hookId int) error {
	if env := ch.GetPluginsEnvironment(); env != nil {
		return env.RunMultiPluginHookWithRPCErr(hookRunnerFunc, hookId)
	}
	return nil
}

func (ch *Channels) HooksForPlugin(id string) (plugin.Hooks, error) {
	env := ch.GetPluginsEnvironment()
	if env == nil {
		return nil, errors.New("plugins are not initialized")
	}

	hooks, err := env.HooksForPlugin(id)
	if err != nil {
		return nil, err
	}

	return hooks, nil
}

// HooksForPluginWithRPCErr returns the full *WithRPCErr hook surface for the named plugin.
// Returns an error if the plugin environment is unavailable, the plugin is not found, or not active.
func (ch *Channels) HooksForPluginWithRPCErr(id string) (plugin.HooksWithRPCErr, error) {
	env := ch.GetPluginsEnvironment()
	if env == nil {
		return nil, errors.New("plugin environment not available")
	}
	return env.HooksForPluginWithRPCErr(id)
}