package etcdb

import (
	"context"
	"fmt"
	"strings"

	etcdclient "go.etcd.io/etcd/client/v3"
	"go.etcd.io/etcd/client/v3/mirror"
	"go.etcd.io/etcd/client/v3/namespace"
)

type EtcdSpec struct {
	client *ClientSpec
	prefix string
}

func (spec EtcdSpec) Sub(prefix string) EtcdSpec {
	p := spec.prefix + prefix
	if !strings.HasSuffix(p, "/") {
		p += "/"
	}

	return EtcdSpec{
		client: spec.client,
		prefix: p,
	}
}

func (spec EtcdSpec) In(ctx context.Context) DB {
	client := spec.client.Client()

	client.KV = namespace.NewKV(client.KV, spec.prefix)
	client.Watcher = namespace.NewWatcher(client.Watcher, spec.prefix)
	client.Lease = namespace.NewLease(client.Lease, spec.prefix)

	return EtcdDB{
		client: client,
		ctx:    ctx,
	}
}

type EtcdDB struct {
	client *etcdclient.Client
	ctx    context.Context
}

func (db EtcdDB) Get(key string) (value []byte, ok bool, err error) {
	get, err := db.client.KV.Get(db.ctx, key)
	if err != nil {
		return
	}

	if len(get.Kvs) == 0 {
		return
	}

	value = get.Kvs[0].Value
	ok = true
	return
}

func (db EtcdDB) Put(key string, val []byte) (err error) {
	_, err = db.client.KV.Put(db.ctx, key, string(val))
	return
}

func (db EtcdDB) Del(key string) (err error) {
	_, err = db.client.KV.Delete(db.ctx, key)
	return
}

func (db EtcdDB) ForEach(callback func(key string, value []byte) (cont bool)) (err error) {
	withSort := etcdclient.WithSort(etcdclient.SortByKey, etcdclient.SortAscend)

	opts := []etcdclient.OpOption{withSort, etcdclient.WithFromKey()}
	key := "\x00"

	for {
		get, err := db.client.KV.Get(db.ctx, key, opts...)
		if err != nil {
			return err
		}

		for _, kv := range get.Kvs {
			cont := callback(string(kv.Key), kv.Value)
			if !cont {
				return nil
			}
		}

		if !get.More {
			return nil
		}

		// wait, there's more!
		key = string(append(get.Kvs[len(get.Kvs)-1].Key, 0))
	}
}

func (db EtcdDB) Watch(rev int64) <-chan WatchEvent {
	ch := make(chan WatchEvent, 1)

	go func() {
		defer close(ch)

		sync := mirror.NewSyncer(db.client, "", rev)

		gets, errs := sync.SyncBase(db.ctx)

		var maxRev int64
		for get := range gets {
			for _, kv := range get.Kvs {
				ch <- WatchEvent{
					Key:   string(kv.Key),
					Value: kv.Value,
				}
			}

			if get.Header.Revision > maxRev {
				maxRev = get.Header.Revision
			}
		}

		err, _ := <-errs
		if err != nil {
			ch <- WatchEvent{Err: err}
			return
		}

		if maxRev != 0 {
			ch <- WatchEvent{NewRev: maxRev}
		}

		watchChan := sync.SyncUpdates(db.ctx)
		for watchEvent := range watchChan {
			for _, evt := range watchEvent.Events {
				switch evt.Type {
				case etcdclient.EventTypePut:
					ch <- WatchEvent{
						Key:   string(evt.Kv.Key),
						Value: evt.Kv.Value,
					}
				case etcdclient.EventTypeDelete:
					ch <- WatchEvent{
						Key:    string(evt.Kv.Key),
						Delete: true,
						Value:  evt.Kv.Value,
					}
				default:
					ch <- WatchEvent{
						Err: fmt.Errorf("unknown event type: %d", evt.Type),
					}
				}
			}

			err := watchEvent.Err()
			if err == nil {
				ch <- WatchEvent{
					NewRev: watchEvent.Header.Revision,
				}
			} else {
				ch <- WatchEvent{
					Err: err,
				}
			}
		}
	}()

	return ch
}