Add wallet functionality to baru

Wallet which allows users to select coins through a backend configured
by them via the `GetTxOuts` trait. The provided wallet comes with a
UTXO cache which this is updated using `Wallet::sync`. This allows
users of the library to optimise the number of requests to their
backend. Users can also sign said UTXOs by calling `Wallet::sign`.

CHANGELOG.md

@@ -7,6 +7,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Wallet which allows users to select coins through a backend configured by them via the `GetUtxos` trait.
+  The provided wallet comes with a UTXO cache which this is updated using `Wallet::sync`.
+  This allows users of the library to optimise the number of requests to their backend.
+  Users can also sign said UTXOs by calling `Wallet::sign`.
+
+### Changed
+
+- The borrower can now choose the collateral inputs before calling `Borrower0::new`.
+
 ### Fixed
 
 - The loan transaction no longer expects collateral and principal change outputs.

Cargo.toml

@@ -10,19 +10,29 @@ license-file = "LICENSE"
 description = "Library to facilitate DeFi on Liquid"
 
 [dependencies]
+aes-gcm-siv = { version = "0.9", features = ["std"] }
 anyhow = "1"
+async-trait = "0.1"
+bdk = { version = "0.4", default-features = false }
+bip32 = { version = "0.2", features = ["secp256k1-ffi", "bip39"], default-features = false }
 conquer-once = "0.3"
 elements = { version = "0.18", features = ["serde-feature"] }
 elements-miniscript = { version = "0.1", features = ["use-serde"] }
+futures = "0.3"
 hex = "0.4"
+hkdf = { version = "0.10", features = ["std"] }
+itertools = "0.10"
 log = "0.4"
-rand = "0.6"
+rand = { version = "0.6", features = ["wasm-bindgen"] }
+reqwest = { version = "0.11", default-features = false, features = ["rustls", "json"] }
 rust_decimal = "1"
 serde = { version = "1", features = ["derive"] }
+sha2 = "0.9"
 thiserror = "1"
 
 [dev-dependencies]
 elements-consensus = { git = "https://github.com/comit-network/rust-elements-consensus", rev = "ac88dbedcd019eef44f58499417dcdbeda994b0b" }
 link-cplusplus = "1"
 rand_chacha = "0.1"
+serde_json = "1"
 tokio = { version = "1", default-features = false, features = ["macros", "rt"] }

src/avg_vbytes.rs

@@ -0,0 +1,17 @@
+//! These constants have been reverse engineered through the following transactions:
+//!
+//! https://blockstream.info/liquid/tx/a17f4063b3a5fdf46a7012c82390a337e9a0f921933dccfb8a40241b828702f2
+//! https://blockstream.info/liquid/tx/d12ff4e851816908810c7abc839dd5da2c54ad24b4b52800187bee47df96dd5c
+//! https://blockstream.info/liquid/tx/47e60a3bc5beed45a2cf9fb7a8d8969bab4121df98b0034fb0d44f6ed2d60c7d
+//!
+//! This gives us the following set of linear equations:
+//!
+//! - 1 in, 1 out, 1 fee = 1332
+//! - 1 in, 2 out, 1 fee = 2516
+//! - 2 in, 2 out, 1 fee = 2623
+//!
+//! Which we can solve using wolfram alpha: https://www.wolframalpha.com/input/?i=1x+%2B+1y+%2B+1z+%3D+1332%2C+1x+%2B+2y+%2B+1z+%3D+2516%2C+2x+%2B+2y+%2B+1z+%3D+2623
+//!
+pub const INPUT: u64 = 107;
+pub const OUTPUT: u64 = 1184;
+pub const FEE: u64 = 41;