# `bitcoin-validation`

The `bitcoin-validation` crate is a Rust
implementation of the validation logic used in the
Bitcoin system. It is a direct translation of the
corresponding C++ codebase and is currently in the
process of translation. As such, some function
bodies may still be in the process of being
translated.

This crate provides the `ValidationState` and
`ModeState` types, which encapsulate the state of
the validation process and allow for the tracking
of errors, rejection reasons, and results. These
types provide methods for checking the state of
validation and for retrieving information about
any errors or rejections that occurred during
validation.

While there are no specific mathematical equations
or concepts involved in the `bitcoin-validation`
crate, it is a critical component of the Bitcoin
system as it ensures that transactions and blocks
conform to the consensus rules of the network.

This crate can be used by Rust developers to build
applications that interact with the Bitcoin
network, validate transactions and blocks, and
implement their own custom validation logic.

28> thanks -- what needs to be validated in the
context of bitcoin

In the context of Bitcoin, validation typically
refers to the process of checking whether
a transaction or block conforms to the rules of
the Bitcoin protocol. This involves verifying the
digital signatures on transactions, checking that
transactions do not double-spend previously spent
inputs, and ensuring that blocks are constructed
according to the consensus rules of the network.

More specifically, the Bitcoin validation process
involves verifying the following:

1. Transactions:
   - The transaction is properly formatted and
     includes a valid signature for each input.

   - The transaction has not already been spent
     (i.e., it is not a double-spend).

   - The transaction outputs do not exceed the
     inputs.

2. Blocks:
   - The block header meets the difficulty
     requirement.

   - The transactions in the block are valid and
     properly formatted.

   - The block does not contain any duplicate
     transactions.

   - The block does not exceed the maximum block
     size.

   - The block does not contain any invalid
     transactions or blocks that have already been
     spent.

The `ValidationState` and `ModeState` types in the
`bitcoin-validation` crate provide a way to keep
track of the state of the validation process and
handle any errors or warnings that arise during
validation. The functions `is_valid()`,
`is_invalid()`, and `is_error()` can be used to
check the validation status of a given transaction
or block. Additionally, the `to_string()` function
can be used to generate a string representation of
the validation state.