From c23e98a5e6983ea50daa2f3ecf5a2992e90a514c Mon Sep 17 00:00:00 2001
From: Daniel Nephin <dnephin@hashicorp.com>
Date: Mon, 19 Oct 2020 19:32:39 -0400
Subject: [PATCH] submatview: setup the interface for the store

---
 agent/submatview/store.go | 98 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 agent/submatview/store.go

diff --git a/agent/submatview/store.go b/agent/submatview/store.go
new file mode 100644
index 000000000..e5603102f
--- /dev/null
+++ b/agent/submatview/store.go
@@ -0,0 +1,98 @@
+package submatview
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/hashicorp/consul/agent/cache"
+	"github.com/hashicorp/consul/lib/ttlcache"
+)
+
+type Store struct {
+	lock       sync.RWMutex
+	byKey      map[string]*Materializer
+	expiryHeap *ttlcache.ExpiryHeap
+}
+
+func NewStore() *Store {
+	return &Store{
+		byKey:      make(map[string]*Materializer),
+		expiryHeap: ttlcache.NewExpiryHeap(),
+	}
+}
+
+// Get a value from the store, blocking if the store has not yet seen the
+// req.Index value.
+// See agent/cache.Cache.Get for complete documentation.
+func (s *Store) Get(
+	ctx context.Context,
+	typ string,
+	req cache.Request,
+) (result interface{}, meta cache.ResultMeta, err error) {
+	return nil, cache.ResultMeta{}, nil
+}
+
+// Notify the updateCh when there are updates to the entry identified by req.
+// See agent/cache.Cache.Notify for complete documentation.
+func (s *Store) Notify(
+	ctx context.Context,
+	typ string,
+	req cache.Request,
+	correlationID string,
+	updateCh chan<- cache.UpdateEvent,
+) error {
+	return nil
+}
+
+func (s *Store) getMaterializer(opts GetOptions) *Materializer {
+	// TODO: use makeEntryKey
+	var key string
+
+	s.lock.RLock()
+	mat, ok := s.byKey[key]
+	s.lock.RUnlock()
+
+	if ok {
+		return mat
+	}
+
+	s.lock.Lock()
+	mat, ok = s.byKey[key]
+	if !ok {
+		mat = opts.NewMaterializer()
+		s.byKey[opts.Key] = mat
+	}
+	s.lock.Unlock()
+	return mat
+}
+
+// makeEntryKey matches agent/cache.makeEntryKey, but may change in the future.
+func makeEntryKey(t, dc, token, key string) string {
+	return fmt.Sprintf("%s/%s/%s/%s", t, dc, token, key)
+}
+
+type GetOptions struct {
+	// TODO: needs to use makeEntryKey
+	Key string
+
+	// MinIndex is the index previously seen by the caller. If MinIndex>0 Fetch
+	// will not return until the index is >MinIndex, or Timeout is hit.
+	MinIndex uint64
+
+	// TODO: maybe remove and use a context deadline.
+	Timeout time.Duration
+
+	// NewMaterializer returns a new Materializer to be used if the store does
+	// not have one already running for the given key.
+	NewMaterializer func() *Materializer
+}
+
+type FetchResult struct {
+	// Value is the result of the fetch.
+	Value interface{}
+
+	// Index is the corresponding index value for this data.
+	Index uint64
+}