From 3de3e2b68862e405a8e2c779cc6420ac362b8fae Mon Sep 17 00:00:00 2001
From: Christian Schwarz <me@cschwarz.com>
Date: Thu, 10 Oct 2019 13:34:33 +0200
Subject: [PATCH] WIP: draft incomplete keep rule for keeping most recent
 common ancestor

---
 config/samples/local.yml                      |  1 +
 pruning/keep_most_recent_common_ancestor.go   | 29 +++++++++++++++++
 .../keep_most_recent_common_ancestor_test.go  | 31 +++++++++++++++++++
 pruning/pruning.go                            |  1 +
 pruning/pruning_test.go                       |  1 +
 5 files changed, 63 insertions(+)
 create mode 100644 pruning/keep_most_recent_common_ancestor.go
 create mode 100644 pruning/keep_most_recent_common_ancestor_test.go

diff --git a/config/samples/local.yml b/config/samples/local.yml
index fbf7861..05baf9e 100644
--- a/config/samples/local.yml
+++ b/config/samples/local.yml
@@ -26,6 +26,7 @@ jobs:
       - type: last_n
         count: 10
       keep_receiver:
+      - type: most_recent_common_snapshot
       - type: grid
         grid: 1x1h(keep=all) | 24x1h | 35x1d | 6x30d
         regex: "zrepl_.*"
\ No newline at end of file
diff --git a/pruning/keep_most_recent_common_ancestor.go b/pruning/keep_most_recent_common_ancestor.go
new file mode 100644
index 0000000..da73e54
--- /dev/null
+++ b/pruning/keep_most_recent_common_ancestor.go
@@ -0,0 +1,29 @@
+package pruning
+
+import "sort"
+
+type KeepMostRecentCommonAncestor struct {
+	_opaque struct{}
+}
+
+func NewKeepMostRecentCommonAncestor() *KeepMostRecentCommonAncestor {
+	return &KeepMostRecentCommonAncestor{}
+}
+
+func (k *KeepMostRecentCommonAncestor) KeepRule(snaps []Snapshot) (destroyList []Snapshot) {
+	var bothSides []Snapshot
+	for _, s := range snaps {
+		if s.PresentOnBothSides() {
+			bothSides = append(bothSides, s)
+		}
+	}
+	if len(bothSides) == 0 {
+		return []Snapshot{}
+	}
+
+	sort.Slice(bothSides, func(i, j int) bool {
+		return bothSides[i].Date().After(bothSides[j].Date())
+	})
+
+	return []Snapshot{bothSides[0]}
+}
diff --git a/pruning/keep_most_recent_common_ancestor_test.go b/pruning/keep_most_recent_common_ancestor_test.go
new file mode 100644
index 0000000..daeb546
--- /dev/null
+++ b/pruning/keep_most_recent_common_ancestor_test.go
@@ -0,0 +1,31 @@
+package pruning
+
+import "testing"
+
+func TestKeppMostRecentCommonAncestor(t *testing.T) {
+
+	o := func(minutes int) time.Time {
+		return time.Unix(123, 0).Add(time.Duration(minutes) * time.Minute)
+	}
+
+	tcs := map[string]testCase{
+		"empty": {
+			inputs:     []Snapshot{},
+			rules:      []KeepRule{NewKeepMostRecentCommonAncestor()},
+			expDestroy: map[string]bool{},
+		},
+		"nil": {
+			inputs:     nil,
+			rules:      []KeepRule{NewKeepMostRecentCommonAncestor()},
+			expDestroy: map[string]bool{},
+		},
+		"": {
+			inputs: []Snapshot{
+				stubSnap{name: "s1", date: o(5), bothSides: }
+			},
+		}
+	}
+
+	testTable(tcs, t)
+
+}
diff --git a/pruning/pruning.go b/pruning/pruning.go
index 9f36581..f7db2c2 100644
--- a/pruning/pruning.go
+++ b/pruning/pruning.go
@@ -17,6 +17,7 @@ type Snapshot interface {
 	Name() string
 	Replicated() bool
 	Date() time.Time
+	PresentOnBothSides() bool
 }
 
 // The returned snapshot list is guaranteed to only contains elements of input parameter snaps
diff --git a/pruning/pruning_test.go b/pruning/pruning_test.go
index 2755dde..efd6f54 100644
--- a/pruning/pruning_test.go
+++ b/pruning/pruning_test.go
@@ -9,6 +9,7 @@ type stubSnap struct {
 	name       string
 	replicated bool
 	date       time.Time
+	bothSides bool
 }
 
 func (s stubSnap) Name() string { return s.name }