Protocol Buffers for Efficient Data Serialization in Go

This challenge focuses on implementing Protocol Buffers (protobuf) in Go for efficient data serialization and deserialization. You will define a protobuf schema, generate Go code from it, and then use that code to send and receive structured data between two Go programs, simulating a common use case in microservices or inter-process communication.

Problem Description

You are tasked with creating a system that uses Protocol Buffers to serialize and deserialize a User data structure. This structure should contain fields for user ID, username, email, and an optional field for a profile picture URL.

Requirements:

1. Define the Protobuf Schema: Create a .proto file that defines the User message with the specified fields.
2. Generate Go Code: Use the protoc compiler with the Go plugin to generate Go source code from your .proto file.
3. Implement Serialization: Create a Go program (sender.go) that creates a User object, serializes it into a byte slice using protobuf.
4. Implement Deserialization: Create a separate Go program (receiver.go) that receives the serialized byte slice, deserializes it back into a User object, and prints the user's details.

Expected Behavior:

• The sender.go program should successfully create a User message and output its serialized byte representation (e.g., to standard output or a file).
• The receiver.go program should successfully read the serialized data, reconstruct the User object, and print its fields correctly, including handling the optional field.

Edge Cases to Consider:

• Optional Fields: Ensure your implementation correctly handles cases where the optional profile_picture_url is not provided.
• Empty Strings: Verify that empty strings for fields like username or email are handled correctly.

Examples

Example 1: Sending and Receiving a User with a Profile Picture

sender.go Input (Conceptual):

User{
  Id: 123,
  Username: "Alice",
  Email: "alice@example.com",
  ProfilePictureUrl: "http://example.com/profiles/alice.jpg",
}

sender.go Output (Serialized Bytes): This will be a raw byte stream. A textual representation is not practical for demonstration here, but the receiver.go should be able to interpret it.

receiver.go Input (Serialized Bytes from sender.go): The program will read these bytes.

receiver.go Output:

User ID: 123
Username: Alice
Email: alice@example.com
Profile Picture URL: http://example.com/profiles/alice.jpg

Explanation: The sender creates a user with all fields populated. The receiver deserializes these bytes and prints all the information.

Example 2: Sending and Receiving a User without a Profile Picture

sender.go Input (Conceptual):

User{
  Id: 456,
  Username: "Bob",
  Email: "bob@example.com",
  // ProfilePictureUrl is omitted
}

sender.go Output (Serialized Bytes): Serialized byte stream.

receiver.go Input (Serialized Bytes from sender.go): The program will read these bytes.

receiver.go Output:

User ID: 456
Username: Bob
Email: bob@example.com
Profile Picture URL: (not provided)

Explanation: The sender creates a user where the optional profile picture URL is not set. The receiver deserializes the data and correctly indicates that the URL was not present.

Constraints

• Protobuf Version: Use Protocol Buffers version 3.
• Go Version: Use Go version 1.18 or later.
• Dependencies: Only official Go protobuf libraries and the protoc compiler are allowed.
• Output Format: The sender.go program should output the raw serialized bytes to standard output. The receiver.go program should print the deserialized user information to standard output, formatted as shown in the examples.
• File Handling: For simplicity, you can pipe the output of sender.go to receiver.go or have sender.go write to a file and receiver.go read from it.

Notes

• Installation: Ensure you have the protoc compiler installed and the Go protobuf plugin (protoc-gen-go). You can typically install the Go plugin with: go install google.golang.org/protobuf/cmd/protoc-gen-go@latest.
• Schema Definition: The .proto file will define the structure of your User message. Pay attention to field numbers and data types.
• Generated Code: The protoc compiler will generate .pb.go files that contain Go types and methods for marshaling (serializing) and unmarshaling (deserializing) your protobuf messages.
• oneof vs. Optional Fields: For simple optional fields like profile_picture_url, you can use the optional keyword (available in proto3) or oneof for more complex scenarios. For this challenge, the optional keyword is sufficient.
• Error Handling: Implement basic error handling for protobuf operations and I/O.
• Communication: For this challenge, you can simulate communication by having the sender print to stdout and the receiver read from stdin.