add credential_type method to constraint field

Signed-off-by: Ryan Tate <[email protected]>

src/core/input_descriptor.rs

@@ -1,3 +1,5 @@
+use std::collections::HashSet;
+
 use super::{credential_format::*, presentation_submission::*};
 use crate::utils::NonEmptyVec;
 
@@ -135,6 +137,23 @@ impl InputDescriptor {
         self
     }
 
+    /// Return the format of the input descriptor.
+    ///
+    /// The Input Descriptor Object MAY contain a format property. If present,
+    /// its value MUST be an object with one or more properties matching the registered
+    /// Claim Format Designations (e.g., jwt, jwt_vc, jwt_vp, etc.).
+    ///
+    /// This format property is identical in value signature to the top-level format object,
+    /// but can be used to specifically constrain submission of a single input to a subset of formats or algorithms.
+    pub fn format(&self) -> &ClaimFormatMap {
+        &self.format
+    }
+
+    /// Return the format designations of the input descriptor as a hash set.
+    pub fn format_designations(&self) -> HashSet<&ClaimFormatDesignation> {
+        self.format.keys().collect()
+    }
+
     /// Set the group of the constraints field.
     pub fn set_group(mut self, group: Vec<GroupId>) -> Self {
         self.group = group;
@@ -253,18 +272,6 @@ impl InputDescriptor {
 
         Ok(())
     }
-
-    /// Return the format of the input descriptor.
-    ///
-    /// The Input Descriptor Object MAY contain a format property. If present,
-    /// its value MUST be an object with one or more properties matching the registered
-    /// Claim Format Designations (e.g., jwt, jwt_vc, jwt_vp, etc.).
-    ///
-    /// This format property is identical in value signature to the top-level format object,
-    /// but can be used to specifically constrain submission of a single input to a subset of formats or algorithms.
-    pub fn format(&self) -> &ClaimFormatMap {
-        &self.format
-    }
 }
 
 /// Constraints are objects used to describe the constraints that a [Holder](https://identity.foundation/presentation-exchange/spec/v2.0.0/#term:holder) must satisfy to fulfill an Input Descriptor.
@@ -588,6 +595,53 @@ impl ConstraintsField {
             })
             .collect()
     }
+
+    /// Return the Credential Type of the constraints field
+    pub fn credential_type(&self) -> Option<CredentialType> {
+        // NOTE: There may be other ways to search for a valid the credential type
+        // that meets the input descriptor constraints.
+        //
+        // A more exhaustive search may require parsing each credential to
+        // check if it contains a certain field, e.g. `firstName`, `familyName`, etc.,
+        // and see if it will satisfy the constraints.
+        //
+        // For now, we explicity check the type of the credential if it is present
+        // in the credential `type` field.
+
+        if self
+            .path
+            .as_ref()
+            .iter()
+            // Check if any of the paths contain a reference to type.
+            // NOTE: I am not sure if this is normative to add a `type` field to the path
+            // for a verifiable credential.
+            .any(|path| path.contains(&"type".to_string()))
+        {
+            // Check the filter field to determine the `const`
+            // value for the credential type, e.g. `iso.org.18013.5.1.mDL`, etc.
+            if let Some(credential) = self.filter.as_ref().and_then(|filter| {
+                filter
+                    .get("const")
+                    .and_then(serde_json::Value::as_str)
+                    .map(CredentialType::from)
+            }) {
+                return Some(credential);
+            }
+
+            // The `type` field may be an array with a nested const value.
+            if let Some(credential) = self.filter.as_ref().and_then(|filter| {
+                filter
+                    .get("contains")
+                    .and_then(|value| value.get("const"))
+                    .and_then(serde_json::Value::as_str)
+                    .map(CredentialType::from)
+            }) {
+                return Some(credential);
+            }
+        }
+
+        None
+    }
 }
 
 #[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq)]