feat(validation): add manifest validation

This commit adds validation functions along with utility accessors to
`Manifest` to enable checking WADM manifests for common errors.

As the validation functions are exposed they can be used by downstream
crates (ex. `wash`) to validate WADM manifests or try to catch
errors *before* a manifest is used.

Signed-off-by: Victor Adossi <vadossi@cosmonic.com>

src/model/mod.rs

@@ -3,6 +3,7 @@ use std::collections::{BTreeMap, HashMap};
 use serde::{Deserialize, Serialize};
 
 pub(crate) mod internal;
+pub mod validation;
 
 /// The default weight for a spread
 pub const DEFAULT_SPREAD_WEIGHT: usize = 100;
@@ -59,6 +60,38 @@ impl Manifest {
             .get(DESCRIPTION_ANNOTATION_KEY)
             .map(|v| v.as_str())
     }
+
+    /// Returns the components in the manifest
+    pub fn components(&self) -> impl Iterator<Item = &Component> {
+        self.spec.components.iter()
+    }
+
+    /// Returns only the WebAssembly components in the manifest
+    pub fn wasm_components(&self) -> impl Iterator<Item = &Component> {
+        self.components()
+            .filter(|c| matches!(c.properties, Properties::Component { .. }))
+    }
+
+    /// Returns only the provider components in the manifest
+    pub fn capability_providers(&self) -> impl Iterator<Item = &Component> {
+        self.components()
+            .filter(|c| matches!(c.properties, Properties::Capability { .. }))
+    }
+
+    /// Returns a map of component names to components in the manifest
+    pub fn component_lookup(&self) -> HashMap<&String, &Component> {
+        self.components()
+            .map(|c| (&c.name, c))
+            .collect::<HashMap<&String, &Component>>()
+    }
+
+    /// Returns only links in the manifest
+    pub fn links(&self) -> impl Iterator<Item = &Trait> {
+        self.components()
+            .flat_map(|c| c.traits.as_ref())
+            .flatten()
+            .filter(|t| t.is_link())
+    }
 }
 
 /// The metadata describing the manifest
@@ -153,6 +186,11 @@ impl Trait {
         }
     }
 
+    /// Check if a trait is a link
+    pub fn is_link(&self) -> bool {
+        self.trait_type == LINK_TRAIT
+    }
+
     /// Helper that creates a new spreadscaler type trait with the given properties
     pub fn new_spreadscaler(props: SpreadScalerProperty) -> Trait {
         Trait {