[Router] Consolidate duplicate ConnectionMode enums

[YouNeedCryDear]

Problem Statement

The codebase currently has two separate ConnectionMode enums with the same name but in different modules:

1. config::types::ConnectionMode (in src/config/types.rs)
2. core::worker::ConnectionMode (in src/core/worker.rs)

This duplication creates confusion, maintenance burden, and potential for bugs when the wrong type is imported.

Current State

config/types.rs ConnectionMode

#[derive(Debug, Clone, Serialize, Deserialize, Default, PartialEq)]
#[serde(tag = "type")]
pub enum ConnectionMode {
    #[default]
    #[serde(rename = "http")]
    Http,
    #[serde(rename = "grpc")]
    Grpc,  // ← Simple unit variant
}

core/worker.rs ConnectionMode

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum ConnectionMode {
    Http,
    Grpc {
        port: Option<u16>,  // ← Struct variant with port field
    },
}

Key Differences

Aspect	config::ConnectionMode	core::ConnectionMode
Grpc variant	Unit variant (no fields)	Struct variant with port: Option<u16>
Derives	Serialize, Deserialize, Default	Eq, Hash
Purpose	User-facing configuration	Runtime worker connection
Serde	Has JSON parsing annotations	No serde support

Problems

1. Name collision confusion: Same name in same crate causes import ambiguity
2. No conversion exists: No impl From to convert between the two types
3. Duplication of concept: Both represent "how to connect to workers"
4. Maintenance burden: Changes must be kept in sync across two definitions
5. Easy to import wrong type: Developers may accidentally use the wrong one

Proposed Solution

Consolidate into a single unified ConnectionMode enum that serves both configuration and runtime purposes:

// Location: src/core/worker.rs or src/types.rs
#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
#[serde(tag = "type", rename_all = "lowercase")]
pub enum ConnectionMode {
    Http,
    Grpc {
        #[serde(skip_serializing_if = "Option::is_none")]
        #[serde(default)]
        port: Option<u16>,
    },
}

How This Works

For Configuration (JSON/YAML):

• Users can omit port: { "type": "grpc" } → Grpc { port: None } (auto-detect)
• Users can specify port: { "type": "grpc", "port": 50051 } → Grpc { port: Some(50051) }
• The #[serde(skip_serializing_if = "Option::is_none")] keeps serialized output clean

For Runtime:

• Port information is available when needed
• Can derive Eq and Hash for use in collections (WorkerRegistry)
• Maintains all runtime capabilities

Benefits

One source of truth - Single definition eliminates confusion
Config flexibility - Optional port field works for both simple and advanced configs
Runtime capability - Port information available when needed
All traits supported - Can derive Serialize, Deserialize, Eq, Hash simultaneously
Cleaner imports - Only one ConnectionMode to import
Better maintainability - Changes only need to be made in one place

Migration Steps

1. Add serde derives to core::worker::ConnectionMode:

   #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
   #[serde(tag = "type", rename_all = "lowercase")]
   pub enum ConnectionMode {
       Http,
       Grpc {
           #[serde(skip_serializing_if = "Option::is_none")]
           #[serde(default)]
           port: Option<u16>,
       },
   }

2. Remove config::ConnectionMode from src/config/types.rs

3. Update all imports throughout the codebase:

   • Find: use crate::config::ConnectionMode or use crate::config::types::ConnectionMode
   • Replace with: use crate::core::ConnectionMode

4. Test configuration parsing to ensure JSON/YAML deserialization works correctly

5. Update tests if any specifically test config parsing

Impact

• Breaking change: No, the unified type is backward compatible for configs
• Migration effort: Low - mostly import statement updates
• Risk: Low - types are structurally compatible
• Files affected: Approximately 5-10 files with import changes

Additional Context

This issue was discovered while implementing IGW mode multi-router support, where the distinction between the two types caused confusion and led to type mismatch errors. Having a single well-designed type will prevent similar issues in the future.

---

Related: This consolidation should be done before or in conjunction with the router selection fixes for proper gRPC worker support in IGW mode.