From ff57bb18e143b2d9197c30738a65b97109cc40d9 Mon Sep 17 00:00:00 2001
From: Andrew Jones <ascjones@gmail.com>
Date: Thu, 25 Jun 2020 11:50:19 +0100
Subject: [PATCH 01/10] add gas argument

---
 core/src/env/engine/on_chain/ext.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/src/env/engine/on_chain/ext.rs b/core/src/env/engine/on_chain/ext.rs
index 72f308bc869..53797bc6947 100644
--- a/core/src/env/engine/on_chain/ext.rs
+++ b/core/src/env/engine/on_chain/ext.rs
@@ -89,7 +89,7 @@ mod sys {
         pub fn ext_block_number();
         pub fn ext_address();
         pub fn ext_balance();
-        pub fn ext_gas_price();
+        pub fn ext_gas_price(gas: u64);
         pub fn ext_gas_left();
         pub fn ext_value_transferred();
         pub fn ext_now();

From 3f829b15a1b005f034f954562f780132911f2cd4 Mon Sep 17 00:00:00 2001
From: Andrew Jones <ascjones@gmail.com>
Date: Thu, 25 Jun 2020 14:56:13 +0100
Subject: [PATCH 02/10] Add gas parameter to ext_gas_price

---
 core/src/env/api.rs                   | 6 +++---
 core/src/env/backend.rs               | 4 ++--
 core/src/env/engine/on_chain/ext.rs   | 5 ++++-
 core/src/env/engine/on_chain/impls.rs | 9 +++++----
 4 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/core/src/env/api.rs b/core/src/env/api.rs
index 3e1c46f035b..3ea53596ed0 100644
--- a/core/src/env/api.rs
+++ b/core/src/env/api.rs
@@ -60,17 +60,17 @@ where
     })
 }
 
-/// Returns the current price for gas.
+/// Returns the price for the specified amount of weight.
 ///
 /// # Errors
 ///
 /// If the returned value cannot be properly decoded.
-pub fn gas_price<T>() -> Result<T::Balance>
+pub fn gas_price<T>(gas: u64) -> Result<T::Balance>
 where
     T: EnvTypes,
 {
     <EnvInstance as OnInstance>::on_instance(|instance| {
-        TypedEnv::gas_price::<T>(instance)
+        TypedEnv::gas_price::<T>(instance, gas)
     })
 }
 
diff --git a/core/src/env/backend.rs b/core/src/env/backend.rs
index a9b11f290ea..1722b66729e 100644
--- a/core/src/env/backend.rs
+++ b/core/src/env/backend.rs
@@ -126,12 +126,12 @@ pub trait TypedEnv: Env {
     /// For more details visit: [`ink_core::env::transferred_balance`]
     fn transferred_balance<T: EnvTypes>(&mut self) -> Result<T::Balance>;
 
-    /// Returns the current price for gas.
+    /// Returns the price for the specified amount of weight.
     ///
     /// # Note
     ///
     /// For more details visit: [`ink_core::env::gas_price`]
-    fn gas_price<T: EnvTypes>(&mut self) -> Result<T::Balance>;
+    fn gas_price<T: EnvTypes>(&mut self, gas: u64) -> Result<T::Balance>;
 
     /// Returns the amount of gas left for the contract execution.
     ///
diff --git a/core/src/env/engine/on_chain/ext.rs b/core/src/env/engine/on_chain/ext.rs
index 53797bc6947..98a27d84f6c 100644
--- a/core/src/env/engine/on_chain/ext.rs
+++ b/core/src/env/engine/on_chain/ext.rs
@@ -285,7 +285,6 @@ impl_ext_wrapper_for! {
     (block_number => ext_block_number),
     (address => ext_address),
     (balance => ext_balance),
-    (gas_price => ext_gas_price),
     (gas_left => ext_gas_left),
     (value_transferred => ext_value_transferred),
     (now => ext_now),
@@ -294,6 +293,10 @@ impl_ext_wrapper_for! {
     (tombstone_deposit => ext_tombstone_deposit),
 }
 
+pub fn gas_price(gas: u64) {
+    unsafe { sys::ext_gas_price(gas) }
+}
+
 pub fn set_rent_allowance(value: &[u8]) {
     unsafe { sys::ext_set_rent_allowance(value.as_ptr() as u32, value.len() as u32) }
 }
diff --git a/core/src/env/engine/on_chain/impls.rs b/core/src/env/engine/on_chain/impls.rs
index 40c8768385c..ea09bec3275 100644
--- a/core/src/env/engine/on_chain/impls.rs
+++ b/core/src/env/engine/on_chain/impls.rs
@@ -208,10 +208,6 @@ impl TypedEnv for EnvInstance {
         self.get_property::<T::Balance>(ext::value_transferred)
     }
 
-    fn gas_price<T: EnvTypes>(&mut self) -> Result<T::Balance> {
-        self.get_property::<T::Balance>(ext::gas_price)
-    }
-
     fn gas_left<T: EnvTypes>(&mut self) -> Result<T::Balance> {
         self.get_property::<T::Balance>(ext::gas_left)
     }
@@ -380,6 +376,11 @@ impl TypedEnv for EnvInstance {
         ext::transfer(destination, value)
     }
 
+    fn gas_price<T: EnvTypes>(&mut self, gas: u64) -> Result<T::Balance> {
+        ext::gas_price(gas);
+        self.decode_scratch_buffer().map_err(Into::into)
+    }
+
     fn random<T>(&mut self, subject: &[u8]) -> Result<T::Hash>
     where
         T: EnvTypes,

From f9d56d1236b6cb5e8b250854d9b1095cdaa54f7e Mon Sep 17 00:00:00 2001
From: Andrew Jones <ascjones@gmail.com>
Date: Fri, 26 Jun 2020 12:27:42 +0100
Subject: [PATCH 03/10] Fix up gas_price offchain api

---
 core/src/env/engine/off_chain/impls.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/src/env/engine/off_chain/impls.rs b/core/src/env/engine/off_chain/impls.rs
index 23af67d2bf4..7be7c833162 100644
--- a/core/src/env/engine/off_chain/impls.rs
+++ b/core/src/env/engine/off_chain/impls.rs
@@ -153,7 +153,7 @@ impl TypedEnv for EnvInstance {
             .map_err(Into::into)
     }
 
-    fn gas_price<T: EnvTypes>(&mut self) -> Result<T::Balance> {
+    fn gas_price<T: EnvTypes>(&mut self, _gas: u64) -> Result<T::Balance> {
         self.chain_spec
             .gas_price::<T>()
             .map_err(|_| scale::Error::from("could not decode gas price"))

From 9b5c99cc857468c87aa2574d8b96d8742feacb5c Mon Sep 17 00:00:00 2001
From: Andrew Jones <ascjones@gmail.com>
Date: Fri, 26 Jun 2020 12:38:06 +0100
Subject: [PATCH 04/10] Fix up env_access api

---
 core/src/env/api.rs     | 2 +-
 core/src/env/backend.rs | 2 +-
 lang/src/env_access.rs  | 6 +++---
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/core/src/env/api.rs b/core/src/env/api.rs
index 3ea53596ed0..5e0f73c8b21 100644
--- a/core/src/env/api.rs
+++ b/core/src/env/api.rs
@@ -60,7 +60,7 @@ where
     })
 }
 
-/// Returns the price for the specified amount of weight.
+/// Returns the price for the specified amount of gas.
 ///
 /// # Errors
 ///
diff --git a/core/src/env/backend.rs b/core/src/env/backend.rs
index 1722b66729e..54599365528 100644
--- a/core/src/env/backend.rs
+++ b/core/src/env/backend.rs
@@ -126,7 +126,7 @@ pub trait TypedEnv: Env {
     /// For more details visit: [`ink_core::env::transferred_balance`]
     fn transferred_balance<T: EnvTypes>(&mut self) -> Result<T::Balance>;
 
-    /// Returns the price for the specified amount of weight.
+    /// Returns the price for the specified amount of gas.
     ///
     /// # Note
     ///
diff --git a/lang/src/env_access.rs b/lang/src/env_access.rs
index 68600fc3c41..2e9793d46c0 100644
--- a/lang/src/env_access.rs
+++ b/lang/src/env_access.rs
@@ -104,13 +104,13 @@ where
         env::transferred_balance::<T>().expect("couldn't decode transferred balance")
     }
 
-    /// Returns the current price for gas.
+    /// Returns the price for the specified amount of gas.
     ///
     /// # Note
     ///
     /// For more details visit: [`ink_core::env::gas_price`]
-    pub fn gas_price(self) -> T::Balance {
-        env::gas_price::<T>().expect("couldn't decode gas price")
+    pub fn gas_price(self, gas: u64) -> T::Balance {
+        env::gas_price::<T>(gas).expect("couldn't decode gas price")
     }
 
     /// Returns the amount of gas left for the contract execution.

From 6a883531d6835be05031e742e00ef138af21853b Mon Sep 17 00:00:00 2001
From: Andrew Jones <ascjones@gmail.com>
Date: Tue, 30 Jun 2020 07:54:03 +0100
Subject: [PATCH 05/10] Emulate gas price calculation

---
 core/src/env/engine/off_chain/impls.rs | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/core/src/env/engine/off_chain/impls.rs b/core/src/env/engine/off_chain/impls.rs
index 7be7c833162..fe56922c646 100644
--- a/core/src/env/engine/off_chain/impls.rs
+++ b/core/src/env/engine/off_chain/impls.rs
@@ -31,6 +31,7 @@ use crate::env::{
     TypedEnv,
 };
 use ink_primitives::Key;
+use core::convert::TryFrom;
 
 impl EnvInstance {
     /// Returns the callee account.
@@ -153,11 +154,18 @@ impl TypedEnv for EnvInstance {
             .map_err(Into::into)
     }
 
-    fn gas_price<T: EnvTypes>(&mut self, _gas: u64) -> Result<T::Balance> {
-        self.chain_spec
+    /// Emulates gas price calculation, scaling price linearly up to `u32::max_value()`.
+    ///
+    /// # Panics
+    ///
+    /// If the resulting gas price overflows `u32::max_value()`
+    fn gas_price<T: EnvTypes>(&mut self, gas: u64) -> Result<T::Balance> {
+        let gas_price = self.chain_spec
             .gas_price::<T>()
-            .map_err(|_| scale::Error::from("could not decode gas price"))
-            .map_err(Into::into)
+            .map_err(|_| scale::Error::from("could not decode gas price"))?;
+
+        let gas = u32::try_from(gas).unwrap_or(u32::max_value().into());
+        Ok(T::Balance::from(gas) * gas_price)
     }
 
     fn gas_left<T: EnvTypes>(&mut self) -> Result<T::Balance> {

From c1c22b465a6f577c8fc8be1bea8b423eb0c13e14 Mon Sep 17 00:00:00 2001
From: Andrew Jones <ascjones@gmail.com>
Date: Tue, 30 Jun 2020 08:12:39 +0100
Subject: [PATCH 06/10] Make clippy happy

---
 core/src/env/engine/off_chain/impls.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/src/env/engine/off_chain/impls.rs b/core/src/env/engine/off_chain/impls.rs
index fe56922c646..36e58b6348f 100644
--- a/core/src/env/engine/off_chain/impls.rs
+++ b/core/src/env/engine/off_chain/impls.rs
@@ -164,7 +164,7 @@ impl TypedEnv for EnvInstance {
             .gas_price::<T>()
             .map_err(|_| scale::Error::from("could not decode gas price"))?;
 
-        let gas = u32::try_from(gas).unwrap_or(u32::max_value().into());
+        let gas = u32::try_from(gas).unwrap_or_else(|_| { u32::max_value() });
         Ok(T::Balance::from(gas) * gas_price)
     }
 

From 787aa151fcd559aef135c6df859f6fcab12d73a1 Mon Sep 17 00:00:00 2001
From: Andrew Jones <ascjones@gmail.com>
Date: Tue, 30 Jun 2020 13:59:21 +0100
Subject: [PATCH 07/10] Use Saturating impl for emulating gas price calculation
 offchain

---
 core/src/env/arithmetic.rs             | 40 +++++++++++++++++---------
 core/src/env/engine/off_chain/impls.rs | 14 ++++-----
 2 files changed, 32 insertions(+), 22 deletions(-)

diff --git a/core/src/env/arithmetic.rs b/core/src/env/arithmetic.rs
index 14c43b10826..5f949717d8a 100644
--- a/core/src/env/arithmetic.rs
+++ b/core/src/env/arithmetic.rs
@@ -24,6 +24,10 @@ use core::ops::{
     Sub,
     SubAssign,
 };
+use core::convert::{
+    TryFrom,
+    TryInto,
+};
 use num_traits::{
     checked_pow,
     Bounded,
@@ -40,7 +44,7 @@ use num_traits::{
 /// if needed.
 pub trait BaseArithmetic:
     Sized
-    + From<u32>
+    + From<u8>
     + Bounded
     + Ord
     + PartialOrd<Self>
@@ -57,21 +61,19 @@ pub trait BaseArithmetic:
     + DivAssign<Self>
     + CheckedMul
     + Saturating
+    + TryFrom<u16>
+    + TryFrom<u32>
+    + TryFrom<u64>
+    + TryFrom<u128>
+    + TryFrom<usize>
+    + TryInto<u16>
+    + TryInto<u32>
+    + TryInto<u64>
+    + TryInto<u128>
+    + TryInto<usize>
 // Further trait bounds from the original BaseArithmetic trait
 // that we could use to extend ink!'s BaseArithmetic trait.
 //
-// From<u8> +
-// From<u16> +
-// From<u32> +
-// TryFrom<u64> +
-// TryFrom<u128> +
-// TryFrom<usize> +
-// TryInto<u8> +
-// TryInto<u16> +
-// TryInto<u32> +
-// TryInto<u64> +
-// TryInto<u128> +
-// TryInto<usize> +
 // UniqueSaturatedInto<u8> +
 // UniqueSaturatedInto<u16> +
 // UniqueSaturatedInto<u32> +
@@ -92,7 +94,7 @@ pub trait BaseArithmetic:
 
 impl<T> BaseArithmetic for T where
     T: Sized
-        + From<u32>
+        + From<u8>
         + Bounded
         + Ord
         + PartialOrd<Self>
@@ -108,6 +110,16 @@ impl<T> BaseArithmetic for T where
         + DivAssign<Self>
         + CheckedMul
         + Saturating
+        + TryFrom<u16>
+        + TryFrom<u32>
+        + TryFrom<u64>
+        + TryFrom<u128>
+        + TryFrom<usize>
+        + TryInto<u16>
+        + TryInto<u32>
+        + TryInto<u64>
+        + TryInto<u128>
+        + TryInto<usize>
 {
 }
 
diff --git a/core/src/env/engine/off_chain/impls.rs b/core/src/env/engine/off_chain/impls.rs
index 36e58b6348f..df41adea4fa 100644
--- a/core/src/env/engine/off_chain/impls.rs
+++ b/core/src/env/engine/off_chain/impls.rs
@@ -31,7 +31,8 @@ use crate::env::{
     TypedEnv,
 };
 use ink_primitives::Key;
-use core::convert::TryFrom;
+use core::convert::TryInto;
+use num_traits::Bounded;
 
 impl EnvInstance {
     /// Returns the callee account.
@@ -154,18 +155,15 @@ impl TypedEnv for EnvInstance {
             .map_err(Into::into)
     }
 
-    /// Emulates gas price calculation, scaling price linearly up to `u32::max_value()`.
-    ///
-    /// # Panics
-    ///
-    /// If the resulting gas price overflows `u32::max_value()`
+    /// Emulates gas price calculation
     fn gas_price<T: EnvTypes>(&mut self, gas: u64) -> Result<T::Balance> {
+        use crate::env::arithmetic::Saturating as _;
+
         let gas_price = self.chain_spec
             .gas_price::<T>()
             .map_err(|_| scale::Error::from("could not decode gas price"))?;
 
-        let gas = u32::try_from(gas).unwrap_or_else(|_| { u32::max_value() });
-        Ok(T::Balance::from(gas) * gas_price)
+        Ok(gas_price.saturating_mul(gas.try_into().unwrap_or_else(|_| Bounded::max_value())))
     }
 
     fn gas_left<T: EnvTypes>(&mut self) -> Result<T::Balance> {

From d216d11b79b1768a5495a3ef2152812bb563a0af Mon Sep 17 00:00:00 2001
From: Andrew Jones <ascjones@gmail.com>
Date: Tue, 30 Jun 2020 14:01:45 +0100
Subject: [PATCH 08/10] Fmt

---
 core/src/env/arithmetic.rs | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/core/src/env/arithmetic.rs b/core/src/env/arithmetic.rs
index 5f949717d8a..75629af84b6 100644
--- a/core/src/env/arithmetic.rs
+++ b/core/src/env/arithmetic.rs
@@ -14,19 +14,21 @@
 
 //! Primitive traits for runtime arithmetic, copied from substrate
 
-use core::ops::{
-    Add,
-    AddAssign,
-    Div,
-    DivAssign,
-    Mul,
-    MulAssign,
-    Sub,
-    SubAssign,
-};
-use core::convert::{
-    TryFrom,
-    TryInto,
+use core::{
+    convert::{
+        TryFrom,
+        TryInto,
+    },
+    ops::{
+        Add,
+        AddAssign,
+        Div,
+        DivAssign,
+        Mul,
+        MulAssign,
+        Sub,
+        SubAssign,
+    },
 };
 use num_traits::{
     checked_pow,

From a6668b7b5528a885801f5a86b4a6291b051f345f Mon Sep 17 00:00:00 2001
From: Andrew Jones <ascjones@gmail.com>
Date: Thu, 2 Jul 2020 12:44:15 +0100
Subject: [PATCH 09/10] Add offchain gas_price test

---
 core/src/env/engine/off_chain/db/chain_spec.rs |  8 ++++++++
 core/src/env/engine/off_chain/mod.rs           |  4 ++++
 core/src/env/engine/off_chain/test_api.rs      | 11 +++++++++++
 core/src/env/engine/off_chain/tests.rs         | 16 ++++++++++++++++
 4 files changed, 39 insertions(+)

diff --git a/core/src/env/engine/off_chain/db/chain_spec.rs b/core/src/env/engine/off_chain/db/chain_spec.rs
index aa5315d74c0..731f2f18ea0 100644
--- a/core/src/env/engine/off_chain/db/chain_spec.rs
+++ b/core/src/env/engine/off_chain/db/chain_spec.rs
@@ -75,6 +75,14 @@ impl ChainSpec {
         self.gas_price.decode().map_err(Into::into)
     }
 
+    /// Set the gas price for the chain.
+    pub fn set_gas_price<T>(&mut self, gas_price: T::Balance)
+    where
+        T: EnvTypes
+    {
+        self.gas_price = OffBalance::new(&gas_price)
+    }
+
     /// Returns the minimum balance for an account on the chain.
     pub fn minimum_balance<T>(&self) -> Result<T::Balance>
     where
diff --git a/core/src/env/engine/off_chain/mod.rs b/core/src/env/engine/off_chain/mod.rs
index 7f586220b87..21013eee161 100644
--- a/core/src/env/engine/off_chain/mod.rs
+++ b/core/src/env/engine/off_chain/mod.rs
@@ -254,6 +254,10 @@ impl EnvInstance {
             .last_mut()
             .ok_or_else(|| OffChainError::UninitializedBlocks)
     }
+
+    fn chain_spec_mut(&mut self) -> &mut ChainSpec {
+        &mut self.chain_spec
+    }
 }
 
 impl OnInstance for EnvInstance {
diff --git a/core/src/env/engine/off_chain/test_api.rs b/core/src/env/engine/off_chain/test_api.rs
index a8427251e48..fe69084ca33 100644
--- a/core/src/env/engine/off_chain/test_api.rs
+++ b/core/src/env/engine/off_chain/test_api.rs
@@ -25,6 +25,7 @@ use super::{
 use crate::env::{
     EnvTypes,
     Result,
+    engine::off_chain::db::ChainSpec,
 };
 use ink_prelude::string::String;
 
@@ -210,6 +211,16 @@ where
     .map_err(Into::into)
 }
 
+/// Update the [ChainSpec](`crate::env::engine::off_chain::db::ChainSpec`) for the test environment
+pub fn update_chain_spec<F>(f: F) -> Result<()>
+where
+    F: FnOnce(&mut ChainSpec) -> ()
+{
+    Ok(<EnvInstance as OnInstance>::on_instance(|instance| {
+        f(instance.chain_spec_mut())
+    }))
+}
+
 /// Returns the contents of the past performed environmental `println` in order.
 pub fn recorded_printlns() -> impl Iterator<Item = String> {
     <EnvInstance as OnInstance>::on_instance(|instance| {
diff --git a/core/src/env/engine/off_chain/tests.rs b/core/src/env/engine/off_chain/tests.rs
index 48b2c39d508..f3979b24592 100644
--- a/core/src/env/engine/off_chain/tests.rs
+++ b/core/src/env/engine/off_chain/tests.rs
@@ -68,3 +68,19 @@ fn key_add_sub() -> Result<()> {
         Ok(())
     })
 }
+
+#[test]
+fn gas_price() -> env::Result<()> {
+    env::test::run_test::<env::DefaultEnvTypes, _>(|_| {
+        let gas_price= 2u32;
+        env::test::update_chain_spec(|chain_spec| {
+            chain_spec.set_gas_price::<env::DefaultEnvTypes>(gas_price.into())
+        })?;
+
+        assert_eq!(2u128, env::gas_price::<env::DefaultEnvTypes>(1).unwrap());
+        assert_eq!(20u128, env::gas_price::<env::DefaultEnvTypes>(10).unwrap());
+        assert_eq!(6u128, env::gas_price::<env::DefaultEnvTypes>(3).unwrap());
+
+        Ok(())
+    })
+}

From d8a7e98e05c6933bf4e21b20005497227aadd8ba Mon Sep 17 00:00:00 2001
From: Andrew Jones <ascjones@gmail.com>
Date: Thu, 2 Jul 2020 13:28:41 +0100
Subject: [PATCH 10/10] Make clippy happy

---
 core/src/env/engine/off_chain/test_api.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/core/src/env/engine/off_chain/test_api.rs b/core/src/env/engine/off_chain/test_api.rs
index fe69084ca33..73bd3da1687 100644
--- a/core/src/env/engine/off_chain/test_api.rs
+++ b/core/src/env/engine/off_chain/test_api.rs
@@ -214,11 +214,12 @@ where
 /// Update the [ChainSpec](`crate::env::engine::off_chain::db::ChainSpec`) for the test environment
 pub fn update_chain_spec<F>(f: F) -> Result<()>
 where
-    F: FnOnce(&mut ChainSpec) -> ()
+    F: FnOnce(&mut ChainSpec)
 {
-    Ok(<EnvInstance as OnInstance>::on_instance(|instance| {
+    <EnvInstance as OnInstance>::on_instance(|instance| {
         f(instance.chain_spec_mut())
-    }))
+    });
+    Ok(())
 }
 
 /// Returns the contents of the past performed environmental `println` in order.