From 8ad554e7301b90c72ed91a0e72f33f4218b31090 Mon Sep 17 00:00:00 2001
From: Dylan Cant <dylan@dylancant.ca>
Date: Mon, 13 Jan 2025 09:14:47 +0100
Subject: [PATCH] ConditionalMatch with multiple etags

---
 fs_local.go    | 25 +++++++++++++------------
 webdav.go      | 37 ++++++++++++++++++++++++++++++++-----
 webdav_test.go | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 91 insertions(+), 17 deletions(-)
 create mode 100644 webdav_test.go

diff --git a/fs_local.go b/fs_local.go
index c2cfd46..ce3c363 100644
--- a/fs_local.go
+++ b/fs_local.go
@@ -126,19 +126,20 @@ func (fs LocalFileSystem) Create(ctx context.Context, name string, body io.ReadC
 		etag = fi.ETag
 	}
 
-	if opts.IfMatch.IsSet() {
-		if ok, err := opts.IfMatch.MatchETag(etag); err != nil {
-			return nil, false, NewHTTPError(http.StatusBadRequest, err)
-		} else if !ok {
-			return nil, false, NewHTTPError(http.StatusPreconditionFailed, fmt.Errorf("If-Match condition failed"))
-		}
+	if isSet, ok, err := opts.IfMatch.MatchETag(etag); !isSet {
+		// not set so continue
+	} else if err != nil {
+		return nil, false, NewHTTPError(http.StatusBadRequest, err)
+	} else if isSet && !ok {
+		return nil, false, NewHTTPError(http.StatusPreconditionFailed, fmt.Errorf("If-Match condition failed"))
 	}
-	if opts.IfNoneMatch.IsSet() {
-		if ok, err := opts.IfNoneMatch.MatchETag(etag); err != nil {
-			return nil, false, NewHTTPError(http.StatusBadRequest, err)
-		} else if ok {
-			return nil, false, NewHTTPError(http.StatusPreconditionFailed, fmt.Errorf("If-None-Match condition failed"))
-		}
+
+	if isSet, ok, err := opts.IfNoneMatch.MatchETag(etag); !isSet {
+		// not set so continue
+	} else if err != nil {
+		return nil, false, NewHTTPError(http.StatusBadRequest, err)
+	} else if isSet && ok {
+		return nil, false, NewHTTPError(http.StatusPreconditionFailed, fmt.Errorf("If-None-Match condition failed"))
 	}
 
 	wc, err := os.Create(p)
diff --git a/webdav.go b/webdav.go
index eb5c742..243c82c 100644
--- a/webdav.go
+++ b/webdav.go
@@ -4,6 +4,7 @@
 package webdav
 
 import (
+	"strings"
 	"time"
 
 	"github.com/emersion/go-webdav/internal"
@@ -54,10 +55,36 @@ func (val ConditionalMatch) ETag() (string, error) {
 	return string(e), nil
 }
 
-func (val ConditionalMatch) MatchETag(etag string) (bool, error) {
-	if val.IsWildcard() {
-		return true, nil
+// MatchETag checks if the ETag provided matches any of the ETags in the ConditionalMatch header value.
+//
+// Parameters:
+//   - etag: The ETag to match against.
+//
+// Returns:
+//   - isSet: Indicates if the ConditionalMatch has any ETags set, or is wildcard.
+//   - match: True if the etag matches any of the ETags in ConditionalMatch, false otherwise.
+//   - err: An error if there was a problem parsing one of the ETags.
+//     If an error occurs during parsing, match will be set to false, but isSet will be true.
+//     Callers should check for a non-nil error to ensure the match result is valid.
+//
+// The function returns early if no ETags are set (isSet is false) or if a wildcard (*) is used,
+// in which case all ETags match. For multiple ETags, it checks each one until a match is found or all are checked.
+func (val ConditionalMatch) MatchETag(etag string) (isSet bool, match bool, err error) {
+	if !val.IsSet() {
+		return false, false, nil
+	} else if val.IsWildcard() {
+		return true, true, nil
+	}
+	quoted_etags := strings.Split(string(val), ", ")
+	for _, quoted_etag := range quoted_etags {
+		var e internal.ETag
+		if err := e.UnmarshalText([]byte(quoted_etag)); err != nil {
+			// opinionated returning `false` on match so caller
+			// should definitely check for non-nil `err`
+			return true, false, err
+		} else if string(e) == etag {
+			return true, true, nil
+		}
 	}
-	t, err := val.ETag()
-	return t == etag, err
+	return true, false, nil
 }
diff --git a/webdav_test.go b/webdav_test.go
new file mode 100644
index 0000000..4773aab
--- /dev/null
+++ b/webdav_test.go
@@ -0,0 +1,46 @@
+package webdav
+
+import (
+	"testing"
+)
+
+func TestConditionalMatch(t *testing.T) {
+	// testing match and no match
+	val := ConditionalMatch("\"AAA\", \"BBB\", \"CCC\"")
+	if isSet, ok, err := val.MatchETag("AAA"); err != nil {
+		t.Fatal(err)
+	} else if !isSet {
+		t.Fatalf("Expected isSet true")
+	} else if !ok {
+		t.Fatalf("Expected ok true")
+	}
+	if isSet, ok, err := val.MatchETag("DDD"); err != nil {
+		t.Fatal(err)
+	} else if !isSet {
+		t.Fatalf("Expected isSet true")
+	} else if ok {
+		t.Fatalf("Expected ok false")
+	}
+
+	// testing parse error
+	val = ConditionalMatch("\"AAA\", BBB, CCC")
+	if _, _, err := val.MatchETag("BBB"); err == nil {
+		t.Fatalf("Expected non-nil error")
+	}
+
+	// testing WildCard
+	val = ConditionalMatch("*")
+	if isSet, ok, err := val.MatchETag("BBB"); err != nil {
+		t.Fatal(err)
+	} else if !isSet {
+		t.Fatalf("Expected isSet true")
+	} else if !ok {
+		t.Fatalf("Expected ok true")
+	}
+
+	// testing isSet
+	val = ConditionalMatch("")
+	if isSet, _, _ := val.MatchETag("BBB"); isSet {
+		t.Fatalf("Expected isSet false")
+	}
+}