From d0e0e9462046a49f8f8efba4f120b6613bc27c03 Mon Sep 17 00:00:00 2001
From: Dr Maxim Orlovsky <orlovsky@lnp-bp.org>
Date: Sun, 30 Jul 2023 16:59:09 +0200
Subject: [PATCH] bip32: fix FromStr implementations

---
 Cargo.lock       |  4 ++--
 Cargo.toml       |  2 +-
 std/src/index.rs | 19 +++++++++++--------
 std/src/path.rs  |  8 ++++----
 std/src/xpub.rs  | 18 +++++++++++++++---
 5 files changed, 33 insertions(+), 18 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index db3d1f1..8962c88 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4,9 +4,9 @@ version = 3
 
 [[package]]
 name = "amplify"
-version = "4.0.0"
+version = "4.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f26966af46e0d200e8bf2b7f16230997c1c3f2d141bc27ccc091c012ed527b58"
+checksum = "4707ab08f19a25ba492cbf61713591b7f022b54ee188f35457e6de22f367df4a"
 dependencies = [
  "amplify_apfloat",
  "amplify_derive",
diff --git a/Cargo.toml b/Cargo.toml
index 59c11f3..a342ef4 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,7 +13,7 @@ edition = "2021"
 license = "Apache-2.0"
 
 [workspace.dependencies]
-amplify = "4.0.0"
+amplify = "4.0.1"
 bitcoin_hashes = "0.12.0"
 bech32 = "0.9.1"
 bp-primitives = "0.10.6"
diff --git a/std/src/index.rs b/std/src/index.rs
index f947edd..e251882 100644
--- a/std/src/index.rs
+++ b/std/src/index.rs
@@ -363,13 +363,13 @@ impl Idx for HardenedIndex {
     const MAX: Self = Self(u32::MAX);
 
     #[inline]
-    fn from_child_number(index: impl Into<u16>) -> Self { Self(index.into() as u32) }
+    fn from_child_number(child_no: impl Into<u16>) -> Self { Self(child_no.into() as u32) }
 
     #[inline]
-    fn try_from_child_number(index: impl Into<u32>) -> Result<Self, IndexError> {
-        let index = index.into();
+    fn try_from_child_number(child_no: impl Into<u32>) -> Result<Self, IndexError> {
+        let index = child_no.into();
         if index < HARDENED_INDEX_BOUNDARY {
-            Ok(Self(index - HARDENED_INDEX_BOUNDARY))
+            Ok(Self(index))
         } else {
             Err(IndexError {
                 what: "child number",
@@ -386,10 +386,13 @@ impl Idx for HardenedIndex {
     fn child_number(&self) -> u32 { self.0 }
 
     #[inline]
-    fn try_from_index(value: u32) -> Result<Self, IndexError> {
-        Self::try_from_child_number(value - HARDENED_INDEX_BOUNDARY).map_err(|_| IndexError {
+    fn try_from_index(child_no: u32) -> Result<Self, IndexError> {
+        if child_no < HARDENED_INDEX_BOUNDARY {
+            return Ok(Self(child_no));
+        }
+        Self::try_from_child_number(child_no - HARDENED_INDEX_BOUNDARY).map_err(|_| IndexError {
             what: "index",
-            invalid: value,
+            invalid: child_no,
             start: HARDENED_INDEX_BOUNDARY,
             end: u32::MAX,
         })
@@ -448,7 +451,7 @@ impl DerivationIndex {
     pub fn from_index(value: u32) -> Self {
         match value {
             0..=0x0FFFFFFF => NormalIndex(value).into(),
-            _ => HardenedIndex(value).into(),
+            _ => HardenedIndex(value - HARDENED_INDEX_BOUNDARY).into(),
         }
     }
 
diff --git a/std/src/path.rs b/std/src/path.rs
index 5439e13..cf7e6f8 100644
--- a/std/src/path.rs
+++ b/std/src/path.rs
@@ -65,11 +65,11 @@ where IndexParseError: From<<I as FromStr>::Err>
 {
     type Err = DerivationParseError;
 
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        if !s.starts_with('/') {
-            return Err(DerivationParseError::InvalidFormat(s.to_owned()));
+    fn from_str(mut s: &str) -> Result<Self, Self::Err> {
+        if s.starts_with('/') {
+            s = &s[1..];
         }
-        let inner = s[1..]
+        let inner = s
             .split('/')
             .map(I::from_str)
             .collect::<Result<Vec<_>, I::Err>>()
diff --git a/std/src/xpub.rs b/std/src/xpub.rs
index 7a59efe..e2337dd 100644
--- a/std/src/xpub.rs
+++ b/std/src/xpub.rs
@@ -350,13 +350,25 @@ impl FromStr for XpubDescriptor {
         }
         if !d.origin.derivation.is_empty() {
             let network = if d.xpub.testnet { HardenedIndex::ONE } else { HardenedIndex::ZERO };
-            if d.origin.derivation.last() != Some(&network.into()) {
-                return Err(XpubParseError::DepthMismatch);
+            if d.origin.derivation.get(1) != Some(&network.into()) {
+                return Err(XpubParseError::NetworkMismatch);
             }
             if d.origin.derivation.last() != Some(&d.xpub.meta.child_number) {
-                return Err(XpubParseError::DepthMismatch);
+                return Err(XpubParseError::ParentMismatch);
             }
         }
         Ok(d)
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn display_from_str() {
+        let s = "[643a7adc/86h/1h/0h]tpubDCNiWHaiSkgnQjuhsg9kjwaUzaxQjUcmhagvYzqQ3TYJTgFGJstVaqnu4yhtFktBhCVFmBNLQ5sN53qKzZbMksm3XEyGJsEhQPfVZdWmTE2";
+        let xpub = XpubDescriptor::from_str(s).unwrap();
+        assert_eq!(s, xpub.to_string());
+    }
+}