feat: implement single hasher selection for digest plugin

Co-authored-by: aider (openai/andrew/openrouter/deepseek/deepseek-chat-v3.1) <aider@aider.chat>

src/meta_plugin/digest.rs

@@ -2,11 +2,51 @@ use sha2::{Digest, Sha256, Sha512};
 use md5::Md5;
 use crate::meta_plugin::MetaPlugin;
 
+#[derive(Debug, Clone)]
+enum Hasher {
+    Md5(Md5),
+    Sha256(Sha256),
+    Sha512(Sha512),
+}
+
+impl Hasher {
+    fn update(&mut self, data: &[u8]) {
+        match self {
+            Hasher::Md5(hasher) => hasher.update(data),
+            Hasher::Sha256(hasher) => hasher.update(data),
+            Hasher::Sha512(hasher) => hasher.update(data),
+        }
+    }
+    
+    fn finalize(&mut self) -> String {
+        match self {
+            Hasher::Md5(hasher) => {
+                let result = std::mem::replace(hasher, Md5::new()).finalize();
+                format!("{:x}", result)
+            }
+            Hasher::Sha256(hasher) => {
+                let result = std::mem::replace(hasher, Sha256::new()).finalize_reset();
+                format!("{:x}", result)
+            }
+            Hasher::Sha512(hasher) => {
+                let result = std::mem::replace(hasher, Sha512::new()).finalize_reset();
+                format!("{:x}", result)
+            }
+        }
+    }
+    
+    fn output_name(&self) -> &'static str {
+        match self {
+            Hasher::Md5(_) => "digest_md5",
+            Hasher::Sha256(_) => "digest_sha256",
+            Hasher::Sha512(_) => "digest_sha512",
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct DigestMetaPlugin {
-    md5_hasher: Md5,
-    sha256_hasher: Sha256,
-    sha512_hasher: Sha512,
+    hasher: Option<Hasher>,
     is_finalized: bool,
     meta_name: String,
     outputs: std::collections::HashMap<String, serde_yaml::Value>,
@@ -16,9 +56,7 @@ pub struct DigestMetaPlugin {
 impl Default for DigestMetaPlugin {
     fn default() -> Self {
         Self {
-            md5_hasher: Md5::new(),
-            sha256_hasher: Sha256::new(),
-            sha512_hasher: Sha512::new(),
+            hasher: None,
             is_finalized: false,
             meta_name: "digest".to_string(),
             outputs: std::collections::HashMap::new(),
@@ -58,6 +96,23 @@ impl DigestMetaPlugin {
             }
         }
         
+        // Initialize the hasher based on the method option
+        if let Some(method_value) = plugin.options.get("method") {
+            if let Some(method_str) = method_value.as_str() {
+                plugin.hasher = match method_str {
+                    "md5" => Some(Hasher::Md5(Md5::new())),
+                    "sha256" => Some(Hasher::Sha256(Sha256::new())),
+                    "sha512" => Some(Hasher::Sha512(Sha512::new())),
+                    _ => None,
+                };
+            }
+        }
+        
+        // Default to sha256 if no valid method is specified
+        if plugin.hasher.is_none() {
+            plugin.hasher = Some(Hasher::Sha256(Sha256::new()));
+        }
+        
         plugin
     }
     
@@ -92,35 +147,18 @@ impl MetaPlugin for DigestMetaPlugin {
         
         let mut metadata = Vec::new();
 
-        // Always compute all three hashes
-        let md5_result = self.md5_hasher.clone().finalize();
-        let md5_hex = format!("{:x}", md5_result);
-        if let Some(meta_data) = crate::meta_plugin::process_metadata_outputs(
-            "digest_md5", 
-            md5_hex, 
-            &self.outputs
-        ) {
-            metadata.push(meta_data);
-        }
-
-        let sha256_result = self.sha256_hasher.clone().finalize_reset();
-        let sha256_hex = format!("{:x}", sha256_result);
-        if let Some(meta_data) = crate::meta_plugin::process_metadata_outputs(
-            "digest_sha256", 
-            sha256_hex, 
-            &self.outputs
-        ) {
-            metadata.push(meta_data);
-        }
-
-        let sha512_result = self.sha512_hasher.clone().finalize_reset();
-        let sha512_hex = format!("{:x}", sha512_result);
-        if let Some(meta_data) = crate::meta_plugin::process_metadata_outputs(
-            "digest_sha512", 
-            sha512_hex, 
-            &self.outputs
-        ) {
-            metadata.push(meta_data);
+        // Compute the selected hash
+        if let Some(hasher) = &mut self.hasher {
+            let hash_value = hasher.finalize();
+            let output_name = hasher.output_name();
+            
+            if let Some(meta_data) = crate::meta_plugin::process_metadata_outputs(
+                output_name, 
+                hash_value, 
+                &self.outputs
+            ) {
+                metadata.push(meta_data);
+            }
         }
         
         self.is_finalized = true;
@@ -138,10 +176,10 @@ impl MetaPlugin for DigestMetaPlugin {
             };
         }
         
-        // Update all hashers
-        self.md5_hasher.update(data);
-        self.sha256_hasher.update(data);
-        self.sha512_hasher.update(data);
+        // Update the active hasher
+        if let Some(hasher) = &mut self.hasher {
+            hasher.update(data);
+        }
         
         crate::meta_plugin::MetaPluginResponse {
             metadata: Vec::new(),