SOLUTION.md

Sure, I can provide a documentation for the given code. Here's a breakdown of the different components:

main.py

Entry Point

The main.py file serves as the entry point of the project. It imports necessary modules and defines the main function that orchestrates the entire workflow.

Imports

• os: This module provides a way to interact with the operating system, including file operations.
• asyncio: This module is used for writing concurrent code using the async/await syntax.
• json: This module is used for serializing and deserializing JSON data (note the TODO comment suggesting replacement with a different serializer).
• Transaction and TransactionSchema: These are imported from the src.transaction module and are used for handling transaction data and its schema.
• ValidateTransaction: This is imported from the src.validation module and is used for validating transactions.
• ValidationError: This is imported from the marshmallow library and is used for handling validation errors.
• mine_block: This is imported from the src.mine module and is used for mining a block.
• defaultdict: This is imported from the collections module and is used for creating a default dictionary to store transactions by their IDs.

Global Variable

• TRANSACTION_BY_ID: This is a defaultdict that stores transactions by their IDs.

Main Function The main function is an asynchronous function (defined with async def) and is the main entry point of the program. Here's what it does:

1. Read and Deserialize Transactions: It reads transaction data from files in the mempool directory, deserializes them using the TransactionSchema, and stores them in the transactions list. It also populates the TRANSACTION_BY_ID dictionary with transactions indexed by their IDs.

2. Validate Transactions Asynchronously: It creates an instance of the ValidateTransaction class, passing the TRANSACTION_BY_ID dictionary, and calls the validate_transactions method asynchronously to validate the transactions. The valid transactions are stored in the valid_transactions list.

3. Mine the Block: It calls the mine_block function, passing the valid_transactions list, to mine a new block.

4. Write Block Data: It writes the mined block data to the output.txt file.

Entry Point Check The if __name__ == "__main__": block ensures that the main function is executed only when the script is run directly (not imported as a module).

transaction.py

Recieving and Filtering Transactions

Imports

• marshmallow: This is a library used for data serialization and deserialization. The following classes and functions are imported from it:
  • Schema: This is the base class for creating data serialization/deserialization schemas.
  • fields: This module contains various field types used to define the structure of the data.
  • post_load: This is a decorator used to define a method that will be called after the data is deserialized.
  • ValidationError: This exception is raised when data fails to validate against the defined schema.
• typing: This module provides support for type hints. In this case, it's used to specify the type of an optional variable.

Schemas The code defines several schemas using the marshmallow library:

1. PrevOutSchema: This schema defines the structure for the prevout field in a transaction input (vin). It includes fields like scriptpubkey, scriptpubkey_asm, scriptpubkey_type, scriptpubkey_address, and value.

2. VinSchema: This schema defines the structure for a transaction input (vin). It includes fields like txid, vout, prevout (nested PrevOutSchema), scriptsig, scriptsig_asm, witness, is_coinbase, sequence, inner_redeemscript_asm, and inner_witnessscript_asm.

3. VoutSchema: This schema defines the structure for a transaction output (vout). It includes fields like scriptpubkey, scriptpubkey_asm, scriptpubkey_type, scriptpubkey_address, and value.

4. TransactionSchema: This schema defines the overall structure of a transaction. It includes fields like version, locktime, vin (a list of nested VinSchema), and vout (a list of nested VoutSchema).

Transaction Class The Transaction class is defined to hold methods for managing transactions. It has the following components:

• __init__ method: This is the constructor for the Transaction class. It takes four parameters: version, locktime, vin, and vout, and initializes the corresponding attributes of the class.

• make_transaction method: This method is a post_load hook for the TransactionSchema. It is called after the data is deserialized, and it returns an instance of the Transaction class with the deserialized data.

The Transaction class is designed to hold the structure of a transaction, which includes the version, locktime, input transactions (vin), and output transactions (vout). The input and output transactions are represented using nested schemas (VinSchema and VoutSchema, respectively) to define their structure.

Overall, this code defines the data structure and schema for representing transactions in a blockchain system, using the marshmallow library for serialization and deserialization.

validate.py

Validation process

To be documented

mine.py

Block Mining Functions

mine_block(valid_transactions) -> str

This function is responsible for mining a block by including the valid transactions and finding a valid block hash.

Parameters:

• valid_transactions: List of valid transactions to include in the block.

Returns:

• A string representing the block data in the required format.

calculate_merkle_root(transactions) -> hashlib object

This function calculates the Merkle root for the given transactions.

Parameters:

• transactions: List of transactions to include in the Merkle tree.

Returns:

• Hashlib object representing the Merkle root.

calculate_coinbase_transaction(transactions) -> bytes

This function calculates the coinbase transaction for the given block.

Parameters:

• transactions: List of transactions to include in the block.

Returns:

• Bytes representing the coinbase transaction.