feat: add env meta plugin for environment variables

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

src/meta_plugin/env.rs

@@ -0,0 +1,139 @@
+use crate::meta_plugin::{MetaPlugin, MetaPluginType, process_metadata_outputs};
+use log::debug;
+use std::collections::HashMap;
+
+#[derive(Debug, Clone)]
+pub struct EnvMetaPlugin {
+    is_finalized: bool,
+    outputs: std::collections::HashMap<String, serde_yaml::Value>,
+    env_vars: Vec<(String, String)>,
+}
+
+impl EnvMetaPlugin {
+    pub fn new(
+        _options: Option<std::collections::HashMap<String, serde_yaml::Value>>,
+        outputs: Option<std::collections::HashMap<String, serde_yaml::Value>>,
+    ) -> Self {
+        // Collect environment variables starting with KEEP_META_
+        let mut env_vars = Vec::new();
+        let mut outputs_map = std::collections::HashMap::new();
+        
+        for (key, value) in std::env::vars() {
+            if let Some(stripped_key) = key.strip_prefix("KEEP_META_") {
+                // Add to env_vars to process later
+                env_vars.push((stripped_key.to_string(), value));
+                // Add to outputs with default mapping to the stripped name
+                outputs_map.insert(
+                    stripped_key.to_string(), 
+                    serde_yaml::Value::String(stripped_key.to_string())
+                );
+            }
+        }
+        
+        // Override with provided outputs
+        if let Some(provided_outputs) = outputs {
+            for (key, value) in provided_outputs {
+                outputs_map.insert(key, value);
+            }
+        }
+        
+        EnvMetaPlugin {
+            is_finalized: false,
+            outputs: outputs_map,
+            env_vars,
+        }
+    }
+}
+
+impl MetaPlugin for EnvMetaPlugin {
+    fn meta_type(&self) -> MetaPluginType {
+        MetaPluginType::Env
+    }
+    
+    fn is_finalized(&self) -> bool {
+        self.is_finalized
+    }
+    
+    fn set_finalized(&mut self, finalized: bool) {
+        self.is_finalized = finalized;
+    }
+    
+    fn initialize(&mut self) -> crate::meta_plugin::MetaPluginResponse {
+        // If already finalized, don't process again
+        if self.is_finalized {
+            return crate::meta_plugin::MetaPluginResponse {
+                metadata: Vec::new(),
+                is_finalized: true,
+            };
+        }
+        
+        // Process all collected environment variables
+        let mut metadata = Vec::new();
+        for (name, value) in &self.env_vars {
+            if let Some(meta_data) = process_metadata_outputs(
+                name,
+                serde_yaml::Value::String(value.clone()),
+                &self.outputs
+            ) {
+                metadata.push(meta_data);
+            }
+        }
+        
+        // Mark as finalized since this plugin only needs to run once
+        self.is_finalized = true;
+        
+        crate::meta_plugin::MetaPluginResponse {
+            metadata,
+            is_finalized: true,
+        }
+    }
+    
+    fn update(&mut self, _data: &[u8]) -> crate::meta_plugin::MetaPluginResponse {
+        // If already finalized, don't process more data
+        if self.is_finalized {
+            return crate::meta_plugin::MetaPluginResponse {
+                metadata: Vec::new(),
+                is_finalized: true,
+            };
+        }
+        
+        crate::meta_plugin::MetaPluginResponse {
+            metadata: Vec::new(),
+            is_finalized: false,
+        }
+    }
+
+    fn finalize(&mut self) -> crate::meta_plugin::MetaPluginResponse {
+        // If not already finalized, we can call initialize
+        if !self.is_finalized {
+            return self.initialize();
+        }
+        
+        crate::meta_plugin::MetaPluginResponse {
+            metadata: Vec::new(),
+            is_finalized: true,
+        }
+    }
+    
+    fn outputs(&self) -> &std::collections::HashMap<String, serde_yaml::Value> {
+        &self.outputs
+    }
+    
+    fn outputs_mut(&mut self) -> &mut std::collections::HashMap<String, serde_yaml::Value> {
+        &mut self.outputs
+    }
+    
+    fn default_outputs(&self) -> Vec<String> {
+        self.env_vars.iter()
+            .map(|(name, _)| name.clone())
+            .collect()
+    }
+    
+    fn options(&self) -> &std::collections::HashMap<String, serde_yaml::Value> {
+        &std::collections::HashMap::new()
+    }
+    
+    fn options_mut(&mut self) -> &mut std::collections::HashMap<String, serde_yaml::Value> {
+        panic!("options_mut() not implemented for EnvMetaPlugin")
+    }
+}