refactor!: Simplify request/response system with enum-based approach

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+This is a streaming, sans-IO Electrum client library for Rust that provides low-level primitives and high-level clients for communicating with Electrum servers over JSON-RPC. The library supports both async (`futures`/`tokio`) and blocking transport models.
+
+## Common Development Commands
+
+### Build and Check
+- `cargo build` - Build the project
+- `cargo check` - Check if the project compiles without building
+- `cargo clippy` - Run the Rust linter for code quality
+- `cargo clippy --fix` - Auto-fix clippy warnings
+
+### Testing
+- `cargo test` - Run all tests
+- `cargo test [TESTNAME]` - Run tests containing specific string in their names
+- `cargo test --no-fail-fast` - Run all tests regardless of failures
+
+### Documentation
+- `cargo doc --open` - Build and open the documentation
+
+## Architecture
+
+### Core Components
+
+1. **State Management (`src/state.rs`)**
+   - Central `State<T>` struct that tracks pending requests and processes server messages
+   - Maps request IDs to pending requests
+   - Processes incoming notifications and responses into `Event`s
+
+2. **Client Implementations (`src/client.rs`)**
+   - `AsyncClient`: Async client for `futures`/`tokio` based transports
+   - `BlockingClient`: Blocking client for synchronous operations
+   - Both use channels to communicate between request sending and response handling
+
+3. **Request/Response System**
+   - `src/request.rs`: Strongly typed Electrum method wrappers
+   - `src/response.rs`: Response type definitions
+   - `src/batch_request.rs`: Support for batched requests
+   - `src/pending_request.rs`: Tracks in-flight requests
+
+4. **I/O Layer (`src/io.rs`)**
+   - Transport-agnostic read/write utilities
+   - `ReadStreamer`: Parses incoming JSON-RPC messages from a stream
+   - Handles both single and batched messages
+
+5. **Type System**
+   - `MaybeBatch<T>`: Handles both single items and batches
+   - `Event`: High-level events (responses, errors, notifications)
+   - Custom serde implementations in `src/custom_serde.rs`
+
+### Key Design Patterns
+
+- **Sans-IO Core**: The `State` struct is transport-agnostic, handling protocol logic without I/O
+- **Channel-based Architecture**: Clients use channels to separate request sending from response handling
+- **Future-based Async**: Async requests return futures that resolve when responses arrive
+- **Type Safety**: Each Electrum method has its own strongly-typed request and response structs
+
+## Dependencies
+
+- `bitcoin 0.32`: Bitcoin primitives and types
+- `serde`/`serde_json`: JSON serialization
+- `futures 0.3`: Async runtime abstractions
+- `tokio` (optional): Tokio-specific async support via feature flag
+
+## Testing Infrastructure
+
+The project uses `bdk_testenv` for integration testing against real Electrum servers. Tests are located in `tests/synopsis.rs`.

examples/blocking_example.rs

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+use electrum_streaming_client::BlockingClient;
+use std::net::TcpStream;
+use std::time::Duration;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // Connect to a public Electrum server (blockstream.info)
+    let stream = TcpStream::connect("blockstream.info:110")?;
+    stream.set_nonblocking(false)?;
+    stream.set_read_timeout(Some(Duration::from_secs(10)))?;
+    stream.set_write_timeout(Some(Duration::from_secs(10)))?;
+
+    let (reader, writer) = (stream.try_clone()?, stream);
+    let (client, _event_rx, _handle) = BlockingClient::new(reader, writer);
+
+    // Test ping
+    println!("Sending ping...");
+    client.ping()?;
+    println!("Ping successful!");
+
+    // Test getting relay fee
+    println!("Getting relay fee...");
+    let relay_fee = client.relay_fee()?;
+    println!("Relay fee: {:?}", relay_fee.fee);
+
+    // Test getting a banner
+    println!("Getting server banner...");
+    let banner = client.banner()?;
+    println!("Server banner: {}", banner);
+
+    // Test getting a header
+    println!("Getting header at height 100000...");
+    let header = client.header(100000)?;
+    println!(
+        "Block hash at height 100000: {}",
+        header.header.block_hash()
+    );
+
+    Ok(())
+}