Take Params instead of Network in difficulty function

What we really want is the maximum target, but since this is a const in
`Params` use an `AsRef<Params>` argument in the `difficulty` functions.

Requires implementation of `AsRef<Params> for Params`.

bitcoin/src/blockdata/block.rs

@@ -16,11 +16,11 @@ use io::{BufRead, Write};
 use super::Weight;
 use crate::blockdata::script;
 use crate::blockdata::transaction::{Transaction, Txid, Wtxid};
-use crate::consensus::{encode, Decodable, Encodable};
+use crate::consensus::{encode, Decodable, Encodable, Params};
 use crate::internal_macros::{impl_consensus_encoding, impl_hashencode};
 use crate::pow::{CompactTarget, Target, Work};
 use crate::prelude::*;
-use crate::{merkle_tree, Network, VarInt};
+use crate::{merkle_tree, VarInt};
 
 hashes::hash_newtype! {
     /// A bitcoin block hash.
@@ -93,7 +93,9 @@ impl Header {
     ///
     /// Difficulty represents how difficult the current target makes it to find a block, relative to
     /// how difficult it would be at the highest possible target (highest target == lowest difficulty).
-    pub fn difficulty(&self, network: Network) -> u128 { self.target().difficulty(network) }
+    pub fn difficulty(&self, params: impl AsRef<Params>) -> u128 {
+        self.target().difficulty(params)
+    }
 
     /// Computes the popular "difficulty" measure for mining and returns a float value of f64.
     pub fn difficulty_float(&self) -> f64 { self.target().difficulty_float() }
@@ -488,6 +490,7 @@ mod tests {
 
     use super::*;
     use crate::consensus::encode::{deserialize, serialize};
+    use crate::Network;
 
     #[test]
     fn test_coinbase_and_bip34() {
@@ -510,7 +513,7 @@ mod tests {
 
     #[test]
     fn block_test() {
-        let network = Network::Bitcoin;
+        let params = Params::new(Network::Bitcoin);
         // Mainnet block 00000000b0c5a240b2a61d2e75692224efd4cbecdf6eaf4cc2cf477ca7c270e7
         let some_block = hex!("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");
         let cutoff_block = hex!("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");
@@ -537,7 +540,7 @@ mod tests {
             real_decode.header.validate_pow(real_decode.header.target()).unwrap(),
             real_decode.block_hash()
         );
-        assert_eq!(real_decode.header.difficulty(network), 1);
+        assert_eq!(real_decode.header.difficulty(&params), 1);
         assert_eq!(real_decode.header.difficulty_float(), 1.0);
 
         assert_eq!(real_decode.total_size(), some_block.len());
@@ -556,7 +559,7 @@ mod tests {
     // Check testnet block 000000000000045e0b1660b6445b5e5c5ab63c9a4f956be7e1e69be04fa4497b
     #[test]
     fn segwit_block_test() {
-        let network = Network::Testnet;
+        let params = Params::new(Network::Testnet);
         let segwit_block = include_bytes!("../../tests/data/testnet_block_000000000000045e0b1660b6445b5e5c5ab63c9a4f956be7e1e69be04fa4497b.raw").to_vec();
 
         let decode: Result<Block, _> = deserialize(&segwit_block);
@@ -579,7 +582,7 @@ mod tests {
             real_decode.header.validate_pow(real_decode.header.target()).unwrap(),
             real_decode.block_hash()
         );
-        assert_eq!(real_decode.header.difficulty(network), 2456598);
+        assert_eq!(real_decode.header.difficulty(&params), 2456598);
         assert_eq!(real_decode.header.difficulty_float(), 2456598.4399242126);
 
         assert_eq!(real_decode.total_size(), segwit_block.len());

bitcoin/src/consensus/params.rs

@@ -147,3 +147,7 @@ impl From<Network> for &'static Params {
 impl From<&Network> for &'static Params {
     fn from(value: &Network) -> Self { value.params() }
 }
+
+impl AsRef<Params> for Params {
+    fn as_ref(&self) -> &Params { self }
+}

bitcoin/src/pow.rs

@@ -16,10 +16,8 @@ use units::parse;
 
 use crate::blockdata::block::BlockHash;
 use crate::consensus::encode::{self, Decodable, Encodable};
-#[cfg(doc)]
 use crate::consensus::Params;
 use crate::error::{ContainsPrefixError, MissingPrefixError, PrefixedHexError, UnprefixedHexError};
-use crate::Network;
 
 /// Implement traits and methods shared by `Target` and `Work`.
 macro_rules! do_impl {
@@ -234,16 +232,11 @@ impl Target {
     /// [max]: Target::max
     /// [target]: crate::blockdata::block::Header::target
     #[cfg_attr(all(test, mutate), mutate)]
-    pub fn difficulty(&self, network: Network) -> u128 {
+    pub fn difficulty(&self, params: impl AsRef<Params>) -> u128 {
         // Panic here may be eaiser to debug than during the actual division.
         assert_ne!(self.0, U256::ZERO, "divide by zero");
 
-        let max = match network {
+        let max = params.as_ref().pow_limit;
-            Network::Bitcoin => Target::MAX_ATTAINABLE_MAINNET,
-            Network::Testnet => Target::MAX_ATTAINABLE_TESTNET,
-            Network::Signet => Target::MAX_ATTAINABLE_SIGNET,
-            Network::Regtest => Target::MAX_ATTAINABLE_REGTEST,
-        };
         let d = max.0 / self.0;
         d.saturating_to_u128()
     }