standards: add DRC20 primitive and reference

Makefile

@@ -1,4 +1,4 @@
-STANDARDS_EXAMPLES := standards/examples/multisig_controller
+STANDARDS_EXAMPLES := standards/examples/drc20_roles_pausable standards/examples/multisig_controller
 STANDARDS_WASM_CONTRACTS := $(STANDARDS_EXAMPLES)
 LEGACY_SUBDIRS := tests/alice tests/bob tests/charlie genesis/transfer genesis/stake tests/host_fn
 STANDARDS_PROPTEST_CASES ?= 8192

standards/Cargo.toml

@@ -1,6 +1,7 @@
 [workspace]
 members = [
     "dusk-contract-standards",
+    "examples/drc20_roles_pausable",
     "examples/multisig_controller",
 ]
 

standards/dusk-contract-standards/src/lib.rs

@@ -40,3 +40,4 @@ pub mod auth;
 pub mod core;
 pub mod governance;
 pub mod security;
+pub mod token;

standards/dusk-contract-standards/src/token/drc20/events.rs

@@ -0,0 +1,55 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+//
+// Copyright (c) DUSK NETWORK. All rights reserved.
+
+//! DRC20 event payloads.
+
+use bytecheck::CheckBytes;
+use rkyv::{Archive, Deserialize, Serialize};
+
+use crate::core::Principal;
+
+/// Transfer event topic.
+pub const TRANSFER_TOPIC: &str = "drc20/transfer";
+/// Approval event topic.
+pub const APPROVAL_TOPIC: &str = "drc20/approval";
+
+/// Transfer event.
+#[derive(
+    Archive, Serialize, Deserialize, Clone, Copy, Debug, PartialEq, Eq,
+)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[archive_attr(derive(CheckBytes))]
+pub struct Transfer {
+    /// Sender.
+    pub from: Principal,
+    /// Recipient.
+    pub to: Principal,
+    /// Amount.
+    pub amount: u64,
+}
+
+/// Approval event.
+#[derive(
+    Archive, Serialize, Deserialize, Clone, Copy, Debug, PartialEq, Eq,
+)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[archive_attr(derive(CheckBytes))]
+pub struct Approval {
+    /// Owner.
+    pub owner: Principal,
+    /// Spender.
+    pub spender: Principal,
+    /// Amount.
+    pub amount: u64,
+}
+
+impl dusk_forge::ContractEvent for Transfer {
+    const TOPICS: &'static [&'static str] = &[TRANSFER_TOPIC];
+}
+
+impl dusk_forge::ContractEvent for Approval {
+    const TOPICS: &'static [&'static str] = &[APPROVAL_TOPIC];
+}

standards/dusk-contract-standards/src/token/drc20/extensions.rs

@@ -0,0 +1,272 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+//
+// Copyright (c) DUSK NETWORK. All rights reserved.
+
+//! Optional DRC20 policy helpers.
+
+use alloc::collections::BTreeMap;
+use alloc::vec::Vec;
+
+use bytecheck::CheckBytes;
+use rkyv::{Archive, Deserialize, Serialize};
+
+use crate::core::{error, Principal};
+
+/// Supply cap policy.
+#[derive(
+    Archive, Serialize, Deserialize, Clone, Copy, Debug, PartialEq, Eq,
+)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[archive_attr(derive(CheckBytes))]
+pub struct SupplyCap {
+    cap: u64,
+}
+
+impl SupplyCap {
+    /// Creates a supply cap.
+    pub const fn new(cap: u64) -> Self {
+        Self { cap }
+    }
+
+    /// Returns the cap.
+    pub const fn cap(&self) -> u64 {
+        self.cap
+    }
+
+    /// Sets a new cap. The new cap must not be below current supply.
+    pub fn set_cap(&mut self, current_supply: u64, cap: u64) {
+        if cap < current_supply {
+            panic!("DRC20: cap below current supply");
+        }
+        self.cap = cap;
+    }
+
+    /// Returns remaining mintable supply.
+    pub const fn remaining(&self, current_supply: u64) -> u64 {
+        self.cap.saturating_sub(current_supply)
+    }
+
+    /// Panics unless minting `amount` keeps supply within cap.
+    pub fn assert_mint(&self, current_supply: u64, amount: u64) {
+        let next = current_supply.checked_add(amount).expect(error::OVERFLOW);
+        if next > self.cap {
+            panic!("DRC20: cap exceeded");
+        }
+    }
+}
+
+/// Vote or accounting checkpoint.
+#[derive(
+    Archive, Serialize, Deserialize, Clone, Copy, Debug, PartialEq, Eq,
+)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[archive_attr(derive(CheckBytes))]
+pub struct Checkpoint {
+    /// Block height, timestamp, epoch, or app-selected timepoint.
+    pub key: u64,
+    /// Value at that timepoint.
+    pub value: u64,
+}
+
+/// Ordered checkpoint trace.
+#[derive(Clone, Debug, Default, PartialEq, Eq)]
+pub struct Checkpoints {
+    checkpoints: Vec<Checkpoint>,
+}
+
+impl Checkpoints {
+    /// Creates an empty trace.
+    pub const fn new() -> Self {
+        Self {
+            checkpoints: Vec::new(),
+        }
+    }
+
+    /// Returns all checkpoints.
+    pub fn entries(&self) -> &[Checkpoint] {
+        &self.checkpoints
+    }
+
+    /// Returns latest value or zero.
+    pub fn latest(&self) -> u64 {
+        self.checkpoints
+            .last()
+            .map(|checkpoint| checkpoint.value)
+            .unwrap_or(0)
+    }
+
+    /// Writes a checkpoint.
+    pub fn push(&mut self, key: u64, value: u64) {
+        if let Some(last) = self.checkpoints.last_mut() {
+            if key < last.key {
+                panic!("Checkpoints: non-monotonic key");
+            }
+            if key == last.key {
+                last.value = value;
+                return;
+            }
+        }
+        self.checkpoints.push(Checkpoint { key, value });
+    }
+
+    fn assert_can_push(&self, key: u64) {
+        if let Some(last) = self.checkpoints.last() {
+            if key < last.key {
+                panic!("Checkpoints: non-monotonic key");
+            }
+        }
+    }
+
+    /// Returns value at or before `key`.
+    pub fn get_at(&self, key: u64) -> u64 {
+        let mut low = 0usize;
+        let mut high = self.checkpoints.len();
+        while low < high {
+            let mid = (low + high) / 2;
+            if self.checkpoints[mid].key <= key {
+                low = mid + 1;
+            } else {
+                high = mid;
+            }
+        }
+        if low == 0 {
+            0
+        } else {
+            self.checkpoints[low - 1].value
+        }
+    }
+}
+
+/// DRC20 voting-unit checkpoint store.
+///
+/// Composing contracts call `move_units` after mint, burn, and transfer hooks
+/// when they want historical vote/accounting queries.
+#[derive(Clone, Debug, Default)]
+pub struct VotingUnits {
+    accounts: BTreeMap<Principal, Checkpoints>,
+    total_supply: Checkpoints,
+}
+
+impl VotingUnits {
+    /// Creates empty voting-unit state.
+    pub const fn new() -> Self {
+        Self {
+            accounts: BTreeMap::new(),
+            total_supply: Checkpoints::new(),
+        }
+    }
+
+    /// Returns latest account units.
+    pub fn latest_votes(&self, account: Principal) -> u64 {
+        self.accounts
+            .get(&account)
+            .map(Checkpoints::latest)
+            .unwrap_or(0)
+    }
+
+    /// Returns historical account units.
+    pub fn past_votes(&self, account: Principal, timepoint: u64) -> u64 {
+        self.accounts
+            .get(&account)
+            .map(|trace| trace.get_at(timepoint))
+            .unwrap_or(0)
+    }
+
+    /// Returns latest total units.
+    pub fn latest_total_supply(&self) -> u64 {
+        self.total_supply.latest()
+    }
+
+    /// Returns historical total units.
+    pub fn past_total_supply(&self, timepoint: u64) -> u64 {
+        self.total_supply.get_at(timepoint)
+    }
+
+    /// Writes an account checkpoint directly.
+    pub fn write_votes(
+        &mut self,
+        account: Principal,
+        timepoint: u64,
+        value: u64,
+    ) {
+        self.accounts
+            .entry(account)
+            .or_default()
+            .push(timepoint, value);
+    }
+
+    /// Moves units between accounts, minting from `None` or burning to `None`.
+    pub fn move_units(
+        &mut self,
+        from: Option<Principal>,
+        to: Option<Principal>,
+        amount: u64,
+        timepoint: u64,
+    ) {
+        if amount == 0 || from == to {
+            return;
+        }
+
+        let from_next = if let Some(from) = from {
+            let current = self.latest_votes(from);
+            if current < amount {
+                panic!("VotingUnits: insufficient units");
+            }
+            Some((from, current - amount))
+        } else {
+            None
+        };
+
+        let to_next = if let Some(to) = to {
+            let current = self.latest_votes(to);
+            let next = current.checked_add(amount).expect(error::OVERFLOW);
+            Some((to, next))
+        } else {
+            None
+        };
+
+        let total_next = match (from, to) {
+            (None, Some(_)) => Some(
+                self.latest_total_supply()
+                    .checked_add(amount)
+                    .expect(error::OVERFLOW),
+            ),
+            (Some(_), None) => {
+                let current = self.latest_total_supply();
+                if current < amount {
+                    panic!("VotingUnits: total supply underflow");
+                }
+                Some(current - amount)
+            }
+            _ => None,
+        };
+
+        if let Some((from, _)) = from_next {
+            self.assert_can_write_votes(from, timepoint);
+        }
+        if let Some((to, _)) = to_next {
+            self.assert_can_write_votes(to, timepoint);
+        }
+        if total_next.is_some() {
+            self.total_supply.assert_can_push(timepoint);
+        }
+
+        if let Some((from, value)) = from_next {
+            self.write_votes(from, timepoint, value);
+        }
+        if let Some((to, value)) = to_next {
+            self.write_votes(to, timepoint, value);
+        }
+        if let Some(value) = total_next {
+            self.total_supply.push(timepoint, value);
+        }
+    }
+
+    fn assert_can_write_votes(&self, account: Principal, timepoint: u64) {
+        if let Some(trace) = self.accounts.get(&account) {
+            trace.assert_can_push(timepoint);
+        }
+    }
+}