pub const Wip = struct {
    maps: Maps = .{},

    const Map = std.AutoArrayHashMapUnmanaged(Attribute.Kind, Attribute.Index);
    const Maps = std.ArrayListUnmanaged(Map);

    pub fn deinit(self: *Wip, builder: *const Builder) void {
        for (self.maps.items) |*map| map.deinit(builder.gpa);
        self.maps.deinit(builder.gpa);
        self.* = undefined;
    }

    pub fn addFnAttr(self: *Wip, attribute: Attribute, builder: *Builder) Allocator.Error!void {
        try self.addAttr(function_index, attribute, builder);
    }

    pub fn addFnAttrIndex(
        self: *Wip,
        attribute_index: Attribute.Index,
        builder: *const Builder,
    ) Allocator.Error!void {
        try self.addAttrIndex(function_index, attribute_index, builder);
    }

    pub fn removeFnAttr(self: *Wip, attribute_kind: Attribute.Kind) Allocator.Error!bool {
        return self.removeAttr(function_index, attribute_kind);
    }

    pub fn addRetAttr(self: *Wip, attribute: Attribute, builder: *Builder) Allocator.Error!void {
        try self.addAttr(return_index, attribute, builder);
    }

    pub fn addRetAttrIndex(
        self: *Wip,
        attribute_index: Attribute.Index,
        builder: *const Builder,
    ) Allocator.Error!void {
        try self.addAttrIndex(return_index, attribute_index, builder);
    }

    pub fn removeRetAttr(self: *Wip, attribute_kind: Attribute.Kind) Allocator.Error!bool {
        return self.removeAttr(return_index, attribute_kind);
    }

    pub fn addParamAttr(
        self: *Wip,
        param_index: usize,
        attribute: Attribute,
        builder: *Builder,
    ) Allocator.Error!void {
        try self.addAttr(params_index + param_index, attribute, builder);
    }

    pub fn addParamAttrIndex(
        self: *Wip,
        param_index: usize,
        attribute_index: Attribute.Index,
        builder: *const Builder,
    ) Allocator.Error!void {
        try self.addAttrIndex(params_index + param_index, attribute_index, builder);
    }

    pub fn removeParamAttr(
        self: *Wip,
        param_index: usize,
        attribute_kind: Attribute.Kind,
    ) Allocator.Error!bool {
        return self.removeAttr(params_index + param_index, attribute_kind);
    }

    pub fn finish(self: *const Wip, builder: *Builder) Allocator.Error!FunctionAttributes {
        const attributes = try builder.gpa.alloc(Attributes, self.maps.items.len);
        defer builder.gpa.free(attributes);
        for (attributes, self.maps.items) |*attribute, map|
            attribute.* = try builder.attrs(map.values());
        return builder.fnAttrs(attributes);
    }

    fn addAttr(
        self: *Wip,
        index: usize,
        attribute: Attribute,
        builder: *Builder,
    ) Allocator.Error!void {
        const map = try self.getOrPutMap(builder.gpa, index);
        try map.put(builder.gpa, attribute.getKind(), try builder.attr(attribute));
    }

    fn addAttrIndex(
        self: *Wip,
        index: usize,
        attribute_index: Attribute.Index,
        builder: *const Builder,
    ) Allocator.Error!void {
        const map = try self.getOrPutMap(builder.gpa, index);
        try map.put(builder.gpa, attribute_index.getKind(builder), attribute_index);
    }

    fn removeAttr(self: *Wip, index: usize, attribute_kind: Attribute.Kind) Allocator.Error!bool {
        const map = self.getMap(index) orelse return false;
        return map.swapRemove(attribute_kind);
    }

    fn getOrPutMap(self: *Wip, allocator: Allocator, index: usize) Allocator.Error!*Map {
        if (index >= self.maps.items.len)
            try self.maps.appendNTimes(allocator, .{}, index + 1 - self.maps.items.len);
        return &self.maps.items[index];
    }

    fn getMap(self: *Wip, index: usize) ?*Map {
        return if (index >= self.maps.items.len) null else &self.maps.items[index];
    }

    fn ensureTotalLength(self: *Wip, new_len: usize) Allocator.Error!void {
        try self.maps.appendNTimes(
            .{},
            std.math.sub(usize, new_len, self.maps.items.len) catch return,
        );
    }
}