BoundedEnumMultiset

pub fn BoundedEnumMultiset(comptime E: type, comptime CountSize: type) type {
    return struct {
        const Self = @This();

        counts: EnumArray(E, CountSize),

        /// Initializes the multiset using a struct of counts.
        pub fn init(init_counts: EnumFieldStruct(E, CountSize, 0)) Self {
            @setEvalBranchQuota(2 * @typeInfo(E).@"enum".fields.len);
            var self = initWithCount(0);
            inline for (@typeInfo(E).@"enum".fields) |field| {
                const c = @field(init_counts, field.name);
                const key = @as(E, @enumFromInt(field.value));
                self.counts.set(key, c);
            }
            return self;
        }

        /// Initializes the multiset with a count of zero.
        pub fn initEmpty() Self {
            return initWithCount(0);
        }

        /// Initializes the multiset with all keys at the
        /// same count.
        pub fn initWithCount(comptime c: CountSize) Self {
            return .{
                .counts = EnumArray(E, CountSize).initDefault(c, .{}),
            };
        }

        /// Returns the total number of key counts in the multiset.
        pub fn count(self: Self) usize {
            var sum: usize = 0;
            for (self.counts.values) |c| {
                sum += c;
            }
            return sum;
        }

        /// Checks if at least one key in multiset.
        pub fn contains(self: Self, key: E) bool {
            return self.counts.get(key) > 0;
        }

        /// Removes all instance of a key from multiset. Same as
        /// setCount(key, 0).
        pub fn removeAll(self: *Self, key: E) void {
            return self.counts.set(key, 0);
        }

        /// Increases the key count by given amount. Caller asserts
        /// operation will not overflow.
        pub fn addAssertSafe(self: *Self, key: E, c: CountSize) void {
            self.counts.getPtr(key).* += c;
        }

        /// Increases the key count by given amount.
        pub fn add(self: *Self, key: E, c: CountSize) error{Overflow}!void {
            self.counts.set(key, try std.math.add(CountSize, self.counts.get(key), c));
        }

        /// Decreases the key count by given amount. If amount is
        /// greater than the number of keys in multset, then key count
        /// will be set to zero.
        pub fn remove(self: *Self, key: E, c: CountSize) void {
            self.counts.getPtr(key).* -= @min(self.getCount(key), c);
        }

        /// Returns the count for a key.
        pub fn getCount(self: Self, key: E) CountSize {
            return self.counts.get(key);
        }

        /// Set the count for a key.
        pub fn setCount(self: *Self, key: E, c: CountSize) void {
            self.counts.set(key, c);
        }

        /// Increases the all key counts by given multiset. Caller
        /// asserts operation will not overflow any key.
        pub fn addSetAssertSafe(self: *Self, other: Self) void {
            inline for (@typeInfo(E).@"enum".fields) |field| {
                const key = @as(E, @enumFromInt(field.value));
                self.addAssertSafe(key, other.getCount(key));
            }
        }

        /// Increases the all key counts by given multiset.
        pub fn addSet(self: *Self, other: Self) error{Overflow}!void {
            inline for (@typeInfo(E).@"enum".fields) |field| {
                const key = @as(E, @enumFromInt(field.value));
                try self.add(key, other.getCount(key));
            }
        }

        /// Decreases the all key counts by given multiset. If
        /// the given multiset has more key counts than this,
        /// then that key will have a key count of zero.
        pub fn removeSet(self: *Self, other: Self) void {
            inline for (@typeInfo(E).@"enum".fields) |field| {
                const key = @as(E, @enumFromInt(field.value));
                self.remove(key, other.getCount(key));
            }
        }

        /// Returns true iff all key counts are the same as
        /// given multiset.
        pub fn eql(self: Self, other: Self) bool {
            inline for (@typeInfo(E).@"enum".fields) |field| {
                const key = @as(E, @enumFromInt(field.value));
                if (self.getCount(key) != other.getCount(key)) {
                    return false;
                }
            }
            return true;
        }

        /// Returns true iff all key counts less than or
        /// equal to the given multiset.
        pub fn subsetOf(self: Self, other: Self) bool {
            inline for (@typeInfo(E).@"enum".fields) |field| {
                const key = @as(E, @enumFromInt(field.value));
                if (self.getCount(key) > other.getCount(key)) {
                    return false;
                }
            }
            return true;
        }

        /// Returns true iff all key counts greater than or
        /// equal to the given multiset.
        pub fn supersetOf(self: Self, other: Self) bool {
            inline for (@typeInfo(E).@"enum".fields) |field| {
                const key = @as(E, @enumFromInt(field.value));
                if (self.getCount(key) < other.getCount(key)) {
                    return false;
                }
            }
            return true;
        }

        /// Returns a multiset with the total key count of this
        /// multiset and the other multiset. Caller asserts
        /// operation will not overflow any key.
        pub fn plusAssertSafe(self: Self, other: Self) Self {
            var result = self;
            result.addSetAssertSafe(other);
            return result;
        }

        /// Returns a multiset with the total key count of this
        /// multiset and the other multiset.
        pub fn plus(self: Self, other: Self) error{Overflow}!Self {
            var result = self;
            try result.addSet(other);
            return result;
        }

        /// Returns a multiset with the key count of this
        /// multiset minus the corresponding key count in the
        /// other multiset. If the other multiset contains
        /// more key count than this set, that key will have
        /// a count of zero.
        pub fn minus(self: Self, other: Self) Self {
            var result = self;
            result.removeSet(other);
            return result;
        }

        pub const Entry = EnumArray(E, CountSize).Entry;
        pub const Iterator = EnumArray(E, CountSize).Iterator;

        /// Returns an iterator over this multiset. Keys with zero
        /// counts are included. Modifications to the set during
        /// iteration may or may not be observed by the iterator,
        /// but will not invalidate it.
        pub fn iterator(self: *Self) Iterator {
            return self.counts.iterator();
        }
    };
}