const std = @import("std");
const Allocator = std.mem.Allocator;
const flecs = @import("./main.zig");
const c = flecs.c;
const err = @import("./error.zig");
const util = @import("./util.zig");
const Id = @import("./id.zig").Id;
const Lookup = @import("./main.zig").Lookup;
const Path = @import("./path.zig").Path;
const World = @import("./world.zig").World;
pub const EntityError = error{
/// Id is `0`.
IsNone,
/// Id is not valid.
IsInvalid,
/// Id is not an `Entity`.
IsNotEntity,
/// Generation doesn't match.
GenMismatch,
/// Entity is not alive.
IsNotAlive,
};
/// An `Entity` is an `Id` which represents a "thing" within the world. This
/// could be a traditional game object, but is also able to represent other
/// concepts such as component types, relationship types, systems, modules,
/// resources, and anything else you can make fit.
///
/// Each `Entity` can have a number of `Id`s added to it, which could be
/// components (such as `Position`), zero-size tags (such as `Disabled`) or
/// relationship `Pair`s (such as `.{ ChildOf, parent }`).
///
/// Entities can be created using `World.entity()` and deleted with `delete()`.
/// When an entity is deleted it is no longer considered "alive". A world can
/// contain up to 4 billion alive entities.
///
/// An `Id` can be converted to an `Entity` using `Id.asEntity()` (fails if
/// the id isn't an entity), and back again with `asId()` (always succeeds).
pub fn Entity(comptime ctx: anytype) type {
return struct {
world: *World(ctx),
raw: c.ecs_entity_t,
const Self = @This();
/// Returns an `Entity` for the specified world and raw entity id.
///
/// No safety checks are done, so if you pass an invalid id, an
/// invalid `Entity` might be returned that could cause panics if
/// passed to other API functions without ensuring their validity.
pub fn fromRaw(world: *World(ctx), raw: c.ecs_entity_t) Self {
return .{ .world = world, .raw = raw };
}
pub const Config = struct {
// Set to modify an existing entity.
id: ?Self = null,
/// Set to specify the entity's name.
name: ?[:0]const u8 = null,
/// Set to specify the entity's symbol.
symbol: ?[:0]const u8 = null,
/// Whether to use a small id when generating one.
/// These are typically reserved for components.
use_low_id: bool = false,
/// Set to specify the parent to create the entity under.
parent: ?Self = null,
/// Set to specify the `Path` under which to create the entity.
path: ?Path = null,
};
/// Creates or modifies an `Entity` in the specified `World`.
///
/// When the settings in `config` refer to an existing entity, it is
/// modified. When any of these settings conflict, such as when an
/// existing entity `.id` is specified but its `.name` doesn't match,
/// an error is returned.
///
/// `add` is a tuple that specifies `Id`s added to the entity.
/// For example: `.{ Position, Velocity, .{ ChildOf, parent } }`.
///
/// When adding components, they are just default-initialized.
/// To set their values you'll need to use `set(...)` on the
/// `Entity` returned from this function.
pub fn init(world: *World(ctx), config: Config, add: anytype) !Self {
const meta = @typeInfo(@TypeOf(add));
if (meta != .Struct or (meta.Struct.is_tuple == false and meta.Struct.fields.len > 0))
@compileError("Expected tuple or empty struct, got '" ++ @typeName(@TypeOf(add)) ++ "'");
if (meta.Struct.fields.len > c.FLECS_ID_DESC_MAX)
@compileError("Adding more than FLECS_ID_DESC_MAX ids");
var id = if (config.id) |i| i.raw else null;
var name = config.name;
var scope = if (config.parent) |p| p.raw else null;
if (config.path) |path| {
if (path.absolute) {
// Specifying parent with an absolute path is invalid.
if (config.parent != null) return error.ParentMismatch;
scope = 0;
}
// Ensure that if `id` or `name` is used alongside path,
// their values do actually match. Also sets these so they
// can be passed to the `ecs_entity_desc_t` struct.
switch (path.parts[path.parts.len - 1]) {
.id => |path_id| {
if (path_id == 0) return error.InvalidParameter;
if (id) |i| if (path_id != i) return error.IdMismatch;
id = path_id;
},
.name => |path_name| {
if (name) |n| if (!std.mem.eql(u8, path_name, n)) return error.NameMismatch;
name = path_name;
},
}
// Ensure the parent entities specified in `path` exist, or create them.
for (path.parts[0..(path.parts.len - 1)]) |part| {
const parent = scope orelse c.ecs_get_scope(world.raw);
switch (part) {
.id => |i| {
const found = c.ecs_get_alive(world.raw, i);
if (found == 0) return error.EntityNotFound;
if (parent != c.ecs_get_parent(world.raw, found)) return error.ParentMismatch;
scope = found;
},
.name => |n| {
const found = c.ecs_lookup_child(world.raw, parent, n.ptr);
if (found == 0) {
var desc = std.mem.zeroInit(c.ecs_entity_desc_t, .{ .sep = "".ptr, .name = n.ptr });
desc.add[0] = c.ecs_pair(c.EcsChildOf, parent);
scope = c.ecs_entity_init(world.raw, &desc);
if (scope == 0) return err.getLastErrorOrUnknown();
} else scope = found;
},
}
}
}
// Set the scope to create the entity under (its parent).
// This avoids using up an id for a `ChildOf` relationship.
const previous = if (scope) |s| world.setScope(s) else null;
defer _ = if (scope != null) world.setScope(previous);
var desc = std.mem.zeroInit(c.ecs_entity_desc_t, .{
.sep = "".ptr, // Disable tokenization.
.id = if (id) |i| i else 0,
.name = if (name) |n| n.ptr else null,
.symbol = if (config.symbol) |s| s.ptr else null,
.use_low_id = config.use_low_id,
});
inline for (add, 0..) |a, i|
desc.add[i] = util.anyToId(ctx, a);
for (desc.add[0..add.len]) |i|
if (c.ecs_id_is_pair(i) and c.ECS_PAIR_FIRST(i) == c.EcsChildOf)
if (config.parent != null or config.path != null)
return error.FoundChildOf;
const result = c.ecs_entity_init(world.raw, &desc);
if (result == 0) return err.getLastErrorOrUnknown();
return Self.fromRaw(world, result);
}
/// Ensures this `Entity` is valid, returning an error otherwise.
/// Invalid entities may cause panics when used with API functions.
///
/// An `Entity` is valid if ..
/// - .. it is not `0`.
/// - .. it does not have dead bits set.
/// - .. it does not have any `Id` flags set.
/// - .. no entity with this id is alive, but this entity's generation is `0`.
/// - .. an entity with this exact id and generation is alive in the world.
pub fn ensureValid(self: Self) !void {
// `0` is not a valid entity id.
if (self.raw == 0) return EntityError.IsNone;
// Entity ids should not contain data in dead zone bits.
const VALID_BITS_MASK: c.ecs_entity_t = 0xFF00FFFFFFFFFFFF;
if ((self.raw & ~VALID_BITS_MASK) != 0) return EntityError.IsInvalid;
// Entity ids should not contain `Id` flag bits.
if ((self.raw & c.ECS_ID_FLAGS_MASK) != 0) return EntityError.IsNotEntity;
// Get the currently alive entity entity with the same id.
// If entity is alive, the generation has to match.
// If entity is not alive, the generation has to be `0`.
const entity = c.ecs_get_alive(self.world.raw, self.raw);
if (c.ECS_GENERATION(entity) != c.ECS_GENERATION(self.raw))
return EntityError.GenMismatch;
}
/// Ensures this `Entity` is alive in this world, returning an error if not.
pub fn ensureAlive(self: Self) !void {
if (!c.ecs_is_alive(self.world.raw, self.raw)) return EntityError.IsNotAlive;
}
pub fn asId(self: Self) Id(ctx) {
return @bitCast(self);
}
pub fn getEntityId(self: Self) u32 {
return @intCast(self.raw & c.ECS_ENTITY_MASK);
}
pub fn getGeneration(self: Self) u16 {
return @intCast(c.ECS_GENERATION(self.raw));
}
/// Deletes this `Entity` and all of its components.
pub fn delete(self: Self) void {
c.ecs_delete(self.world.raw, self.raw);
}
/// Returns the full, absolute `Path` of this `Entity`.
/// The entity is assumed to be alive.
/// See also: `Path.fromEntity(...)`.
pub fn getPath(self: Self, alloc: Allocator) !Path {
return Path.fromEntity(ctx, null, self, alloc);
}
/// Gets the name of this `Entity`, or `null` if none.
///
/// The returned string is owned by Flecs and may only be valid while
/// the entity is alive and its name doesn't change.
pub fn getName(self: Self) ?[:0]const u8 {
const result = c.ecs_get_name(self.world.raw, self.raw);
return std.mem.sliceTo(result, 0);
}
/// Gets the symbol of this `Entity`, or `null` if none.
///
/// The returned string is owned by Flecs and may only be valid while
/// the entity is alive and its symbol doesn't change.
pub fn getSymbol(self: Self) ?[:0]const u8 {
const result = c.ecs_get_symbol(self.world.raw, self.raw);
return std.mem.sliceTo(result, 0);
}
/// Sets the name of this `Entity` to the specified value, if any.
///
/// Flecs does not take ownership of the provided value.
pub fn setName(self: Self, value: ?[*:0]const u8) void {
_ = c.ecs_set_name(self.world.raw, self.raw, value);
}
/// Sets the symbol of this `Entity` to the specified value, if any.
///
/// Flecs does not take ownership of the provided value.
pub fn setSymbol(self: Self, value: ?[*:0]const u8) void {
_ = c.ecs_set_symbol(self.world.raw, self.raw, value);
}
/// Gets the parent of this `Entity`, or `null` if it has none.
pub fn getParent(self: Self) ?Self {
const result = c.ecs_get_parent(self.world.raw, self.raw);
return if (result != 0) fromRaw(self.world, result) else null;
}
/// Returns whether this `Entity` has the specified value.
///
/// `value` must be convertible to an id. See also: `util.anyToId(...)`.
pub fn has(self: Self, value: anytype) bool {
const id = util.anyToId(ctx, value);
return c.ecs_has_id(self.world.raw, self.raw, id);
}
pub fn get(self: Self, comptime T: type) ?*const T {
const id = Lookup(ctx, T).id;
return @alignCast(@ptrCast(c.ecs_get_id(self.world.raw, self.raw, id)));
}
pub fn set(self: Self, comptime T: type, value: T) void {
const id = Lookup(ctx, T).id;
_ = c.ecs_set_id(self.world.raw, self.raw, id, @sizeOf(T), &value);
}
};
}