// Mgmt
// Copyright (C) 2013-2019+ 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 <http://www.gnu.org/licenses/>.

package str

import (
	"context"
	"fmt"

	"github.com/purpleidea/mgmt/etcd/interfaces"
	"github.com/purpleidea/mgmt/util/errwrap"

	etcd "github.com/coreos/etcd/clientv3"
	etcdutil "github.com/coreos/etcd/clientv3/clientv3util"
)

const (
	ns = "" // in case we want to add one back in
)

// WatchStr returns a channel which spits out events on key activity.
// FIXME: It should close the channel when it's done, and spit out errors when
// something goes wrong.
// XXX: since the caller of this (via the World API) has no way to tell it it's
// done, does that mean we leak go-routines since it might still be running, but
// perhaps even blocked??? Could this cause a dead-lock? Should we instead return
// some sort of struct which has a close method with it to ask for a shutdown?
func WatchStr(ctx context.Context, client interfaces.Client, key string) (chan error, error) {
	// new key structure is $NS/strings/$key = $data
	path := fmt.Sprintf("%s/strings/%s", ns, key)
	return client.Watcher(ctx, path)
}

// GetStr collects the string which matches a global namespace in etcd.
func GetStr(ctx context.Context, client interfaces.Client, key string) (string, error) {
	// new key structure is $NS/strings/$key = $data
	path := fmt.Sprintf("%s/strings/%s", ns, key)
	keyMap, err := client.Get(ctx, path, etcd.WithPrefix())
	if err != nil {
		return "", errwrap.Wrapf(err, "could not get strings in: %s", key)
	}

	if len(keyMap) == 0 {
		return "", interfaces.ErrNotExist
	}

	if count := len(keyMap); count != 1 {
		return "", fmt.Errorf("returned %d entries", count)
	}

	val, exists := keyMap[path]
	if !exists {
		return "", fmt.Errorf("path `%s` is missing", path)
	}

	return val, nil
}

// SetStr sets a key and hostname pair to a certain value. If the value is
// nil, then it deletes the key. Otherwise the value should point to a string.
// TODO: TTL or delete disconnect?
func SetStr(ctx context.Context, client interfaces.Client, key string, data *string) error {
	// key structure is $NS/strings/$key = $data
	path := fmt.Sprintf("%s/strings/%s", ns, key)
	ifs := []etcd.Cmp{} // list matching the desired state
	ops := []etcd.Op{}  // list of ops in this transaction (then)
	els := []etcd.Op{}  // list of ops in this transaction (else)
	if data == nil {    // perform a delete
		ifs = append(ifs, etcdutil.KeyExists(path))
		//ifs = append(ifs, etcd.Compare(etcd.Version(path), ">", 0))
		ops = append(ops, etcd.OpDelete(path))
	} else {
		data := *data                                                // get the real value
		ifs = append(ifs, etcd.Compare(etcd.Value(path), "=", data)) // desired state
		els = append(els, etcd.OpPut(path, data))
	}

	// it's important to do this in one transaction, and atomically, because
	// this way, we only generate one watch event, and only when it's needed
	_, err := client.Txn(ctx, ifs, ops, els) // TODO: do we need to look at response?
	return errwrap.Wrapf(err, "could not set strings in: %s", key)
}
