From 7df51ce8b18b10ccdef60575174470f19486dc24 Mon Sep 17 00:00:00 2001
From: Adin Schmahmann <adin.schmahmann@gmail.com>
Date: Mon, 16 Jan 2023 00:26:48 -0500
Subject: [PATCH 1/2] feat(cmd): add index create subcommand to create an
 external carv2 index

---
 cmd/car/car.go   |  5 +++++
 cmd/car/index.go | 42 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/cmd/car/car.go b/cmd/car/car.go
index c66232f7..70c9eb32 100644
--- a/cmd/car/car.go
+++ b/cmd/car/car.go
@@ -153,6 +153,11 @@ func main1() int {
 						Usage: "Write output as a v1 or v2 format car",
 					},
 				},
+				Subcommands: []*cli.Command{{
+					Name:   "create",
+					Usage:  "Write out a detached index",
+					Action: CreateIndex,
+				}},
 			},
 			{
 				Name:   "inspect",
diff --git a/cmd/car/index.go b/cmd/car/index.go
index 031df2ad..fc6bd5d6 100644
--- a/cmd/car/index.go
+++ b/cmd/car/index.go
@@ -166,3 +166,45 @@ func IndexCar(c *cli.Context) error {
 	_, err = index.WriteTo(idx, outStream)
 	return err
 }
+
+// CreateIndex is a command to write out an index of the CAR file
+func CreateIndex(c *cli.Context) error {
+	r, err := carv2.OpenReader(c.Args().Get(0))
+	if err != nil {
+		return err
+	}
+	defer r.Close()
+
+	outStream := os.Stdout
+	if c.Args().Len() >= 2 {
+		outStream, err = os.Create(c.Args().Get(1))
+		if err != nil {
+			return err
+		}
+	}
+	defer outStream.Close()
+
+	var mc multicodec.Code
+	if err := mc.Set(c.String("codec")); err != nil {
+		return err
+	}
+	idx, err := index.New(mc)
+	if err != nil {
+		return err
+	}
+
+	dr, err := r.DataReader()
+	if err != nil {
+		return err
+	}
+
+	if err := carv2.LoadIndex(idx, dr); err != nil {
+		return err
+	}
+
+	if _, err := index.WriteTo(idx, outStream); err != nil {
+		return err
+	}
+
+	return nil
+}

From 4038bee446e9a87507783aea936493f0a5f9234b Mon Sep 17 00:00:00 2001
From: Adin Schmahmann <adin.schmahmann@gmail.com>
Date: Mon, 30 Jan 2023 11:03:31 -0500
Subject: [PATCH 2/2] test(cmd): add index creation test

---
 cmd/car/testdata/script/index-create.txt | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 cmd/car/testdata/script/index-create.txt

diff --git a/cmd/car/testdata/script/index-create.txt b/cmd/car/testdata/script/index-create.txt
new file mode 100644
index 00000000..bfdfe65c
--- /dev/null
+++ b/cmd/car/testdata/script/index-create.txt
@@ -0,0 +1,3 @@
+car index create ${INPUTS}/sample-v1.car sample-v1.car.idx
+car detach-index ${INPUTS}/sample-wrapped-v2.car sample-wrapped-v2.car.idx
+cmp sample-v1.car.idx sample-wrapped-v2.car.idx