granc 0.2.2

# Granc 🦀

[![granc on crates.io](https://img.shields.io/crates/v/granc)](https://crates.io/crates/granc)

> ⚠️ **Status: Experimental**
>
> This project is currently in a **highly experimental phase**. It is a working prototype intended for testing and development purposes. APIs, command-line arguments, and internal logic are subject to breaking changes. Please use with caution.

**Granc** (gRPC + Cranc, Crab in Catalan) is a lightweight, dynamic gRPC CLI tool written in Rust.

It allows you to make gRPC calls to any server using simple JSON payloads, without needing to compile the specific Protobuf files into the client. By loading a `FileDescriptorSet` at runtime, granc acts as a bridge between human-readable JSON and binary Protobuf wire format.

It is heavily inspired by tools like `grpcurl` but built to leverage the safety and performance of the Rust ecosystem (Tonic + Prost).

## 🚀 Features

* **Dynamic Encoding/Decoding**: Transcodes JSON to Protobuf (and vice versa) on the fly using `prost-reflect`.
* **Smart Dispatch**: Automatically detects if a call is Unary, Server Streaming, Client Streaming, or Bidirectional based on the descriptor.
* **Server Reflection**: Can fetch schemas directly from the server, removing the need to pass a local file descriptor set file (`.bin` or `.pb`).
* **Metadata Support**: Easily attach custom headers (authorization, tracing) to your requests.
* **Fast Fail Validation**: Validates your JSON *before* hitting the network.
* **Zero Compilation Dependencies**: Does not require generating Rust code for your protos. Just point to a descriptor file.
* **Tonic 0.14**: Built on the latest stable Rust gRPC stack.

## 📦 Installation

### From Crates.io

```bash
cargo install granc
```

### From Source

Ensure you have Rust and Cargo installed.

```bash
git clone https://github.com/JasterV/granc
cd granc
cargo install --path .
```

## 🛠️ Prerequisites

Granc needs to know the schema of the service you are calling. It can obtain this in two ways:

1. **Automatic Server Reflection**: If the server has [Server Reflection](https://github.com/grpc/grpc/blob/master/doc/server-reflection.md) enabled, Granc can download the schema automatically.
2. **Local Descriptor File**: You can provide a binary `FileDescriptorSet` (`.bin`) generated by `protoc`.

### Generating Descriptors (Optional)

If your server does not support reflection, you must generate a descriptor file:

```bash
# Generate descriptor.bin including all imports
protoc \
    --include_imports \
    --descriptor_set_out=descriptor.bin \
    --proto_path=. \
    my_service.proto
```

> **Note**: The `--include_imports` flag is crucial. It ensures that types defined in imported files (like `google/protobuf/timestamp.proto`) are available for reflection.

## 📖 Usage

**Syntax:**

```bash
granc [OPTIONS] <URL> <ENDPOINT>
```

### Arguments

| Argument | Description | Required |
| --- | --- | --- |
| `<URL>` | Server address (e.g., `http://[::1]:50051`). | **Yes** |
| `<ENDPOINT>` | Fully qualified method name (e.g., `my.package.Service/Method`). | **Yes** |

### Options

| Flag | Short | Description | Required |
| --- | --- | --- | --- |
| `--proto-set` |  | Path to the binary FileDescriptorSet (`.bin`). | **No** |
| `--body` |  | The request body in JSON format. | **Yes** |
| `--header` | `-H` | Custom header `key:value`. Can be used multiple times. | No |

### Automatic Server Reflection

If you omit the `--proto-set` flag, Granc will automatically attempt to connect to the server's reflection service to download the necessary schemas.

```bash
# Using Reflection (no descriptor file needed)
granc \
  --body '{"name": "Ferris"}' \
  http://localhost:50051 \
  helloworld.Greeter/SayHello
```

This requires the server to have the [`grpc.reflection.v1`](https://github.com/grpc/grpc-proto/blob/master/grpc/reflection/v1/reflection.proto) service enabled.

### JSON Body Format

* **Unary / Server Streaming**: Provide a single JSON object `{ ... }`.
* **Client / Bidirectional Streaming**: Provide a JSON array of objects `[ { ... }, { ... } ]`.

### Examples

**1. Unary Call (using local descriptor)**

```bash
granc \
  --proto-set ./descriptor.bin \
  --body '{"name": "Ferris"}' \
  http://localhost:50051 \
  helloworld.Greeter/SayHello
```

**2. Bidirectional Streaming (Chat)**

```bash
granc \
  --body '[{"text": "Hello"}, {"text": "How are you?"}]' \
  -H "authorization: Bearer token123" \
  http://localhost:50051 \
  chat.ChatService/StreamMessages
```

## 🔮 Roadmap

* **Interactive Mode**: A REPL for streaming requests interactively.
* **Pretty Printing**: Enhanced colored output for JSON responses.
* **TLS Support**: Configurable root certificates and client identity.

## ⚠️ Common Errors

**1. `Service 'x' not found**`

* **Cause:** The service name in the command does not match the package defined in your proto file.
* **Fix:** Check your `.proto` file. If it has `package my.app;` and `service API {}`, the full name is `my.app.API`.

**2. `Method 'y' not found in service 'x'**`

* **Cause:** Typo in the method name or the method doesn't exist.
* **Fix:** Ensure case sensitivity matches (e.g., `GetUser` vs `getUser`).

**3. `h2 protocol error**`

* **Cause:** This often occurs when the JSON payload fails to encode *after* the connection has already been established, or the server rejected the stream structure.
* **Fix:** Double-check your JSON payload against the Protobuf schema.

## 🤝 Contributing

Contributions are welcome! Please run the Makefile checks before submitting a PR:

```bash
cargo make ci # Checks formatting, lints, and runs tests
```

## 📄 License

Licensed under either of:

* Apache License, Version 2.0 ([LICENSE-APACHE](http://www.apache.org/licenses/LICENSE-2.0))
* MIT license ([LICENSE-MIT](http://opensource.org/licenses/MIT))

at your option.

### Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.