From 894b27f32e129d996a64e3ffe1c3c4b3bfafef80 Mon Sep 17 00:00:00 2001
From: Michael Martin <michael.martin@konghq.com>
Date: Wed, 5 Jun 2024 11:15:42 -0700
Subject: [PATCH] fix(*): support mime type structured syntax suffix

---
 Cargo.lock    |  7 +++++++
 Cargo.toml    |  1 +
 src/filter.rs | 35 +++++++++++++++++++++++++++++++++--
 3 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 50ae54d..0343edc 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -40,6 +40,12 @@ version = "0.4.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b5e6163cb8c49088c2c36f57875e58ccd8c87c7427f7fbd50ea6710b2f3f2e8f"
 
+[[package]]
+name = "mime"
+version = "0.3.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6877bb514081ee2a7ff5ef9de3281f14a4dd4bceac4c09388074a6b5df8a139a"
+
 [[package]]
 name = "once_cell"
 version = "1.18.0"
@@ -70,6 +76,7 @@ name = "proxy-wasm-rust-response-transformer"
 version = "0.1.0"
 dependencies = [
  "log",
+ "mime",
  "proxy-wasm",
  "serde",
  "serde_json",
diff --git a/Cargo.toml b/Cargo.toml
index 74cdb15..c36dab4 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,3 +14,4 @@ proxy-wasm = "0.2"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 log = "0.4"
+mime = "0.3.17"
diff --git a/src/filter.rs b/src/filter.rs
index 5ac48fe..681dc65 100644
--- a/src/filter.rs
+++ b/src/filter.rs
@@ -19,7 +19,17 @@ proxy_wasm::main! {{
 
 const CONTENT_LENGTH: &str = "content-length";
 const CONTENT_TYPE: &str = "content-type";
-const JSON_CONTENT_TYPE: &str = "application/json";
+
+fn is_json_mime_type<T: AsRef<str>>(ct: T) -> bool {
+    let Ok(mt) = ct.as_ref().parse::<mime::Mime>() else {
+        return false;
+    };
+
+    matches!(
+        (mt.type_(), mt.subtype(), mt.suffix()),
+        (mime::APPLICATION, mime::JSON, _) | (mime::APPLICATION, _, Some(mime::JSON))
+    )
+}
 
 struct ResponseTransformerRoot {
     config: Option<Rc<Config>>,
@@ -132,7 +142,7 @@ impl HttpContext for ResponseTransformerHttp {
 impl ResponseTransformerHttp {
     fn is_json_response(&self) -> bool {
         self.get_http_response_header(CONTENT_TYPE)
-            .map_or(false, |ct| ct.eq_ignore_ascii_case(JSON_CONTENT_TYPE))
+            .map_or(false, is_json_mime_type)
     }
 
     fn transform_headers(&self, tx: &Headers) {
@@ -267,3 +277,24 @@ impl ResponseTransformerHttp {
         self.set_http_response_body(0, body.len(), body.as_slice());
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_json_mime_type_detection() {
+        assert!(is_json_mime_type("application/json"));
+        assert!(is_json_mime_type("APPLICATION/json"));
+        assert!(is_json_mime_type("APPLICATION/JSON"));
+        assert!(is_json_mime_type("application/JSON"));
+        assert!(is_json_mime_type("application/json; charset=utf-8"));
+        assert!(is_json_mime_type("application/problem+json"));
+        assert!(is_json_mime_type("application/problem+JSON"));
+        assert!(is_json_mime_type("application/problem+json; charset=utf-8"));
+
+        assert!(!is_json_mime_type("text/plain"));
+        assert!(!is_json_mime_type("application/not-json"));
+        assert!(!is_json_mime_type("nope/json"));
+    }
+}