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

package app

import (
	"encoding/json"
	"io"
	"net/http"

	"github.com/pkg/errors"

	"github.com/mattermost/mattermost/server/public/model"
	"github.com/mattermost/mattermost/server/public/shared/request"
)

const permissionsExportBatchSize = 100
const systemSchemeName = "00000000-0000-0000-0000-000000000000" // Prevents collisions with user-created schemes.

func (a *App) ResetPermissionsSystem() *model.AppError {
	// Reset all Teams to not have a scheme.
	if err := a.Srv().Store().Team().ResetAllTeamSchemes(); err != nil {
		return model.NewAppError("ResetPermissionsSystem", "app.team.reset_all_team_schemes.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
	}

	// Reset all Channels to not have a scheme.
	if err := a.Srv().Store().Channel().ResetAllChannelSchemes(); err != nil {
		return model.NewAppError("ResetPermissionsSystem", "app.channel.reset_all_channel_schemes.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
	}

	// Reset all Custom Role assignments to Users.
	if err := a.Srv().Store().User().ClearAllCustomRoleAssignments(); err != nil {
		return model.NewAppError("ResetPermissionsSystem", "app.user.clear_all_custom_role_assignments.select.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
	}

	// Reset all Custom Role assignments to TeamMembers.
	if err := a.Srv().Store().Team().ClearAllCustomRoleAssignments(); err != nil {
		return model.NewAppError("ResetPermissionsSystem", "app.team.clear_all_custom_role_assignments.select.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
	}

	// Reset all Custom Role assignments to ChannelMembers.
	if err := a.Srv().Store().Channel().ClearAllCustomRoleAssignments(); err != nil {
		return model.NewAppError("ResetPermissionsSystem", "app.channel.clear_all_custom_role_assignments.select.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
	}

	// Purge all schemes from the database.
	if err := a.Srv().Store().Scheme().PermanentDeleteAll(); err != nil {
		return model.NewAppError("ResetPermissionsSystem", "app.scheme.permanent_delete_all.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
	}

	// Purge all roles from the database.
	if err := a.Srv().Store().Role().PermanentDeleteAll(); err != nil {
		return model.NewAppError("ResetPermissionsSystem", "app.role.permanent_delete_all.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
	}

	// Remove the "System" table entry that marks the advanced permissions migration as done.
	if _, err := a.Srv().Store().System().PermanentDeleteByName(model.AdvancedPermissionsMigrationKey); err != nil {
		return model.NewAppError("ResetPermissionSystem", "app.system.permanent_delete_by_name.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
	}

	// Remove the "System" table entry that marks the emoji permissions migration as done.
	if _, err := a.Srv().Store().System().PermanentDeleteByName(EmojisPermissionsMigrationKey); err != nil {
		return model.NewAppError("ResetPermissionSystem", "app.system.permanent_delete_by_name.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
	}

	// Remove the "System" table entry that marks the guest roles permissions migration as done.
	if _, err := a.Srv().Store().System().PermanentDeleteByName(GuestRolesCreationMigrationKey); err != nil {
		return model.NewAppError("ResetPermissionSystem", "app.system.permanent_delete_by_name.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
	}

	// Now that the permissions system has been reset, re-run the migration to reinitialise it.
	a.DoAppMigrations()

	return nil
}

func (a *App) ExportPermissions(rctx request.CTX, w io.Writer) error {
	next := a.SchemesIterator("", permissionsExportBatchSize)
	var schemeBatch []*model.Scheme

	for schemeBatch = next(); len(schemeBatch) > 0; schemeBatch = next() {
		for _, scheme := range schemeBatch {
			roleNames := []string{
				scheme.DefaultTeamAdminRole,
				scheme.DefaultTeamUserRole,
				scheme.DefaultTeamGuestRole,
				scheme.DefaultChannelAdminRole,
				scheme.DefaultChannelUserRole,
				scheme.DefaultChannelGuestRole,
			}

			roles := []*model.Role{}
			for _, roleName := range roleNames {
				if roleName == "" {
					continue
				}
				role, err := a.GetRoleByName(rctx, roleName)
				if err != nil {
					return err
				}
				roles = append(roles, role)
			}

			schemeExport, err := json.Marshal(&model.SchemeConveyor{
				Name:         scheme.Name,
				DisplayName:  scheme.DisplayName,
				Description:  scheme.Description,
				Scope:        scheme.Scope,
				TeamAdmin:    scheme.DefaultTeamAdminRole,
				TeamUser:     scheme.DefaultTeamUserRole,
				TeamGuest:    scheme.DefaultTeamGuestRole,
				ChannelAdmin: scheme.DefaultChannelAdminRole,
				ChannelUser:  scheme.DefaultChannelUserRole,
				ChannelGuest: scheme.DefaultChannelGuestRole,
				Roles:        roles,
			})
			if err != nil {
				return err
			}

			schemeExport = append(schemeExport, []byte("\n")...)

			_, err = w.Write(schemeExport)
			if err != nil {
				return err
			}
		}
	}

	defaultRoleNames := []string{}
	for _, dr := range model.MakeDefaultRoles() {
		defaultRoleNames = append(defaultRoleNames, dr.Name)
	}

	roles, appErr := a.GetRolesByNames(defaultRoleNames)
	if appErr != nil {
		return errors.New(appErr.Message)
	}

	schemeExport, err := json.Marshal(&model.SchemeConveyor{
		Name:  systemSchemeName,
		Roles: roles,
	})
	if err != nil {
		return err
	}

	schemeExport = append(schemeExport, []byte("\n")...)

	_, err = w.Write(schemeExport)
	return err
}