From d0e0822854f14b5066c3d694878bb00b32479379 Mon Sep 17 00:00:00 2001
From: Lars Gierth <larsg@systemli.org>
Date: Thu, 17 Nov 2016 14:40:43 +0100
Subject: [PATCH] Add Parse func accepting various types

---
 cid.go      | 19 +++++++++++++++++++
 cid_test.go | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)

diff --git a/cid.go b/cid.go
index 88243d3..68f1c01 100644
--- a/cid.go
+++ b/cid.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/binary"
 	"fmt"
+	"strings"
 
 	mbase "github.com/multiformats/go-multibase"
 	mh "github.com/multiformats/go-multihash"
@@ -47,6 +48,24 @@ type Cid struct {
 	hash    mh.Multihash
 }
 
+func Parse(v interface{}) (*Cid, error) {
+	switch v2 := v.(type) {
+	case string:
+		if strings.Contains(v2, "/ipfs/") {
+			return Decode(strings.Split(v2, "/ipfs/")[1])
+		}
+		return Decode(v2)
+	case []byte:
+		return Cast(v2)
+	case mh.Multihash:
+		return NewCidV0(v2), nil
+	case *Cid:
+		return v2, nil
+	default:
+		return nil, fmt.Errorf("can't parse %+v as Cid", v2)
+	}
+}
+
 func Decode(v string) (*Cid, error) {
 	if len(v) < 2 {
 		return nil, fmt.Errorf("cid too short")
diff --git a/cid_test.go b/cid_test.go
index 48bb1e4..0c51bdb 100644
--- a/cid_test.go
+++ b/cid_test.go
@@ -2,7 +2,9 @@ package cid
 
 import (
 	"bytes"
+	"fmt"
 	"math/rand"
+	"strings"
 	"testing"
 
 	mh "github.com/multiformats/go-multihash"
@@ -125,3 +127,55 @@ func TestFuzzCid(t *testing.T) {
 		_, _ = Cast(buf[:s])
 	}
 }
+
+func TestParse(t *testing.T) {
+	cid, err := Parse(123)
+	if err == nil {
+		t.Fatalf("expected error from Parse()")
+	}
+	if !strings.Contains(err.Error(), "can't parse 123 as Cid") {
+		t.Fatalf("expected int error, got %s", err.Error())
+	}
+
+	theHash := "QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n"
+	h, err := mh.FromB58String(theHash)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assertions := [][]interface{}{
+		[]interface{}{NewCidV0(h), theHash},
+		[]interface{}{NewCidV0(h).Bytes(), theHash},
+		[]interface{}{h, theHash},
+		[]interface{}{theHash, theHash},
+		[]interface{}{"/ipfs/" + theHash, theHash},
+		[]interface{}{"https://ipfs.io/ipfs/" + theHash, theHash},
+		[]interface{}{"http://localhost:8080/ipfs/" + theHash, theHash},
+	}
+
+	assert := func(arg interface{}, expected string) error {
+		cid, err = Parse(arg)
+		if err != nil {
+			return err
+		}
+		if cid.version != 0 {
+			return fmt.Errorf("expected version 0, got %s", string(cid.version))
+		}
+		actual := cid.Hash().B58String()
+		if actual != expected {
+			return fmt.Errorf("expected hash %s, got %s", expected, actual)
+		}
+		actual = cid.String()
+		if actual != expected {
+			return fmt.Errorf("expected string %s, got %s", expected, actual)
+		}
+		return nil
+	}
+
+	for _, args := range assertions {
+		err := assert(args[0], args[1].(string))
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+}