From 390a1544bccfffddcf0202ab88de0b1ed74bdaa7 Mon Sep 17 00:00:00 2001
From: Yaroslav Bolyukin <iam@lach.pw>
Date: Wed, 06 Oct 2021 10:54:39 +0000
Subject: [PATCH] feat: burn_from


---
--- a/pallets/nft/src/lib.rs
+++ b/pallets/nft/src/lib.rs
@@ -987,16 +987,44 @@
 		/// * item_id: ID of NFT to burn.
 		#[weight = <SelfWeightOf<T>>::burn_item()]
 		#[transactional]
-		pub fn burn_item(origin, collection_id: CollectionId, item_id: TokenId, item_owner: T::CrossAccountId, value: u128) -> DispatchResult {
+		pub fn burn_item(origin, collection_id: CollectionId, item_id: TokenId, value: u128) -> DispatchResult {
 
 			let sender = T::CrossAccountId::from_sub(ensure_signed(origin)?);
 			let target_collection = Self::get_collection(collection_id)?;
 
-			Self::burn_item_internal(&sender, &target_collection, item_id, &item_owner, value)?;
+			Self::burn_item_internal(&sender, &target_collection, item_id, value, true)?;
 
 			target_collection.submit_logs()
 		}
 
+		/// Destroys a concrete instance of NFT on behalf of the owner
+		/// See also: [`approve`]
+		///
+		/// # Permissions
+		///
+		/// * Collection Owner.
+		/// * Collection Admin.
+		/// * Current NFT Owner.
+		///
+		/// # Arguments
+		///
+		/// * collection_id: ID of the collection.
+		///
+		/// * item_id: ID of NFT to burn.
+		///
+		/// * from: owner of item
+		#[weight = <SelfWeightOf<T>>::burn_item()]
+		#[transactional]
+		pub fn burn_from(origin, collection_id: CollectionId, from: T::CrossAccountId, item_id: TokenId, value: u128) -> DispatchResult {
+
+			let sender = T::CrossAccountId::from_sub(ensure_signed(origin)?);
+			let target_collection = Self::get_collection(collection_id)?;
+
+			Self::burn_from_internal(&sender, &target_collection, &from, item_id, value)?;
+
+			target_collection.submit_logs()
+		}
+
 		/// Change ownership of the token.
 		///
 		/// # Permissions
@@ -1593,21 +1621,22 @@
 	}
 
 	pub fn burn_item_internal(
-		sender: &T::CrossAccountId,
+		owner: &T::CrossAccountId,
 		collection: &CollectionHandle<T>,
 		item_id: TokenId,
-		item_owner: &T::CrossAccountId,
 		value: u128,
+		allow_escalation: bool,
 	) -> DispatchResult {
 		ensure!(
-			Self::is_item_owner(sender, collection, item_id)?
-				|| (collection.limits.owner_can_transfer
-					&& Self::is_owner_or_admin_permissions(collection, sender)?),
+			Self::is_item_owner(owner, collection, item_id)?
+				|| (allow_escalation
+					&& collection.limits.owner_can_transfer
+					&& Self::is_owner_or_admin_permissions(collection, owner)?),
 			Error::<T>::NoPermission
 		);
 
 		if collection.access == AccessMode::WhiteList {
-			Self::check_white_list(collection, sender)?;
+			Self::check_white_list(collection, owner)?;
 		}
 
 		match collection.mode {
@@ -1617,13 +1646,71 @@
 				_ => fail!(<Error<T>>::TokenValueTooLow),
 			},
 			CollectionMode::Fungible(_) => Self::burn_fungible_item(collection, owner, value)?,
-			CollectionMode::ReFungible => Self::burn_refungible_item(collection, item_id, owner, value)?,
+			CollectionMode::ReFungible => {
+				Self::burn_refungible_item(collection, item_id, owner, value)?
+			}
 			_ => (),
 		};
 
 		Ok(())
 	}
 
+	pub fn burn_from_internal(
+		sender: &T::CrossAccountId,
+		collection: &CollectionHandle<T>,
+		from: &T::CrossAccountId,
+		item_id: TokenId,
+		amount: u128,
+	) -> DispatchResult {
+		if sender == from {
+			// Transfer by `from`, because it is either equal to sender, or derived from him
+			return Self::burn_item_internal(from, collection, item_id, amount, true);
+		}
+
+		// Check approval
+		collection.consume_sload()?;
+		let approval: u128 =
+			<Allowances<T>>::get(collection.id, (item_id, from.as_sub(), sender.as_sub()));
+
+		// Transfer permissions check
+		ensure!(
+			approval >= amount
+				|| (collection.limits.owner_can_transfer
+					&& Self::is_owner_or_admin_permissions(collection, sender)?),
+			Error::<T>::NoPermission
+		);
+
+		if collection.access == AccessMode::WhiteList {
+			Self::check_white_list(collection, sender)?;
+		}
+
+		// Reduce approval by transferred amount or remove if remaining approval drops to 0
+		let allowance = approval.saturating_sub(amount);
+		collection.consume_sstore()?;
+		if allowance > 0 {
+			<Allowances<T>>::insert(
+				collection.id,
+				(item_id, from.as_sub(), sender.as_sub()),
+				allowance,
+			);
+		} else {
+			<Allowances<T>>::remove(collection.id, (item_id, from.as_sub(), sender.as_sub()));
+		}
+
+		// Escalation is disallowed here, because we need to be sure that passed owner is real
+		Self::burn_item_internal(from, collection, item_id, amount, false)?;
+
+		if matches!(collection.mode, CollectionMode::Fungible(_)) {
+			collection.log(ERC20Events::Approval {
+				owner: *from.as_eth(),
+				spender: *sender.as_eth(),
+				value: allowance.into(),
+			})?;
+		}
+
+		Ok(())
+	}
+
 	pub fn toggle_white_list_internal(
 		sender: &T::CrossAccountId,
 		collection: &CollectionHandle<T>,

-- 
gitstuff