// Mgmt
// Copyright (C) James Shubin and the project contributors
// Written by James Shubin <james@shubin.ca> and the project contributors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
// Additional permission under GNU GPL version 3 section 7
//
// If you modify this program, or any covered work, by linking or combining it
// with embedded mcl code and modules (and that the embedded mcl code and
// modules which link with this program, contain a copy of their source code in
// the authoritative form) containing parts covered by the terms of any other
// license, the licensors of this program grant you additional permission to
// convey the resulting work. Furthermore, the licensors of this program grant
// the original author, James Shubin, additional permission to update this
// additional permission if he deems it necessary to achieve the goals of this
// additional permission.

package engine

import (
	"context"

	"github.com/purpleidea/mgmt/etcd/interfaces"
	"github.com/purpleidea/mgmt/etcd/scheduler"
)

// World is an interface to the rest of the different graph state. It allows the
// GAPI to store state and exchange information throughout the cluster. It is
// the interface each machine uses to communicate with the rest of the world.
type World interface { // TODO: is there a better name for this interface?
	StrWorld

	ResWorld

	// URI returns the current FS URI.
	// TODO: Can we improve this API or deprecate it entirely?
	URI() string

	// Fs takes a URI and returns the filesystem that corresponds to that.
	// This is a way to turn a unique string handle into an appropriate
	// filesystem object that we can interact with.
	Fs(uri string) (Fs, error)
}

// StrWorld is a world interface which is useful for reading, writing, and
// watching strings in a shared, distributed database. It is likely that much of
// the functionality is built upon these primitives.
// XXX: We should consider improving this API if possible.
type StrWorld interface {
	StrWatch(ctx context.Context, namespace string) (chan error, error)
	StrIsNotExist(error) bool
	StrGet(ctx context.Context, namespace string) (string, error)
	StrSet(ctx context.Context, namespace, value string) error
	StrDel(ctx context.Context, namespace string) error

	// XXX: add the exchange primitives in here directly?
	StrMapWatch(ctx context.Context, namespace string) (chan error, error)
	StrMapGet(ctx context.Context, namespace string) (map[string]string, error)
	StrMapSet(ctx context.Context, namespace, value string) error
	StrMapDel(ctx context.Context, namespace string) error
}

// ResWorld is a world interface that lets us store, pull and watch resources in
// a distributed database.
// XXX: These API's are likely to change.
type ResWorld interface {
	ResWatch(context.Context) (chan error, error)
	ResExport(context.Context, []Res) error
	// FIXME: should this method take a "filter" data struct instead of many args?
	ResCollect(ctx context.Context, hostnameFilter, kindFilter []string) ([]Res, error)
}

// SchedulerWorld is an interface that has to do with distributed scheduling.
// XXX: This should be abstracted to remove the etcd specific types if possible.
type SchedulerWorld interface {
	// Scheduler runs a distributed scheduler.
	Scheduler(namespace string, opts ...scheduler.Option) (*scheduler.Result, error)
}

// EtcdWorld is a world interface that should be implemented if the world
// backend is implementing etcd, and if it supports dynamically resizing things.
// TODO: In theory we could generalize this to support other backends, but lets
// assume it's specific to etcd only for now.
type EtcdWorld interface {
	IdealClusterSizeWatch(context.Context) (chan error, error)
	IdealClusterSizeGet(context.Context) (uint16, error)
	IdealClusterSizeSet(context.Context, uint16) (bool, error)

	// WatchMembers returns a channel of changing members in the cluster.
	WatchMembers(context.Context) (<-chan *interfaces.MembersResult, error)
}