From d639e8e5a944eb4a1d4efeb37e96e12d98a1fe20 Mon Sep 17 00:00:00 2001
From: copygirl <copygirl@mcft.net>
Date: Mon, 4 Sep 2023 15:42:59 +0200
Subject: [PATCH] Add Entity.getPath

---
 src/entity.zig  | 15 +++++++++++++++
 src/path.zig    | 35 +++++++++++++++++++++++++++++++++++
 test/entity.zig | 20 ++++++++++----------
 3 files changed, 60 insertions(+), 10 deletions(-)

diff --git a/src/entity.zig b/src/entity.zig
index 4489fa7..ec2efe3 100644
--- a/src/entity.zig
+++ b/src/entity.zig
@@ -1,4 +1,5 @@
 const std = @import("std");
+const Allocator = std.mem.Allocator;
 
 const c = @import("./c.zig");
 const err = @import("./error.zig");
@@ -6,6 +7,7 @@ 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{
@@ -141,6 +143,13 @@ pub fn Entity(comptime ctx: anytype) type {
             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.
         pub fn getName(self: Self) ?[:0]const u8 {
             const result = c.ecs_get_name(self.world.raw, self.raw);
@@ -163,6 +172,12 @@ pub fn Entity(comptime ctx: anytype) type {
             _ = 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;
+        }
+
         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)));
diff --git a/src/path.zig b/src/path.zig
index 0787efd..bde7d38 100644
--- a/src/path.zig
+++ b/src/path.zig
@@ -1,6 +1,8 @@
 const std = @import("std");
 const Allocator = std.mem.Allocator;
 
+const Entity = @import("./entity.zig").Entity;
+
 // TODO: Do something better than just `std.debug.assert`.
 // TODO: Offer a way to validate paths, like checking for empty parts.
 
@@ -103,6 +105,39 @@ pub const Path = struct {
         };
     }
 
+    pub fn fromEntity(comptime ctx: type, parent: ?Entity(ctx), child: Entity(ctx), alloc: Allocator) !Path {
+        if (parent) |p| std.debug.assert(p.raw != 0);
+        std.debug.assert(child.raw != 0);
+
+        const starting_capacity: usize = 12;
+        var parts = try alloc.alloc(EntityPart, starting_capacity);
+        var num_parts: usize = 0;
+
+        // Traverse up the entity hierarchy starting from the specified child
+        // entity up until either the specified parent or root of the hierarchy.
+        var current = child;
+        while (true) {
+            std.debug.assert(num_parts == 0 or current.raw != child.raw); // Cycle detected.
+            parts[num_parts] = if (current.getName()) |name|
+                .{ .name = name }
+            else
+                .{ .id = current.getEntityId() };
+            num_parts += 1;
+            current = current.getParent() orelse break;
+            if (parent != null and current.raw == parent.?.raw) break;
+        }
+
+        parts = try alloc.realloc(parts, num_parts);
+        std.mem.reverse(EntityPart, parts);
+
+        return .{
+            .absolute = parent != null,
+            .parts = parts,
+            .alloc = alloc,
+            .owns_array = true,
+        };
+    }
+
     /// Creates a deep clone of this `Path` using the specified `Allocator`.
     pub fn clone(orig: Path, alloc: Allocator) !Path {
         var parts = try alloc.dupe(EntityPart, orig.parts);
diff --git a/test/entity.zig b/test/entity.zig
index 5066600..ae9296c 100644
--- a/test/entity.zig
+++ b/test/entity.zig
@@ -2,9 +2,11 @@
 // https://github.com/SanderMertens/flecs/blob/master/test/api/src/Entity.c
 
 const std = @import("std");
+const alloc = std.testing.allocator;
 const expect = std.testing.expect;
-const expectEql = std.testing.expectEqual;
-const expectStrEql = std.testing.expectEqualStrings;
+const expectFmt = std.testing.expectFmt;
+const expectEqual = std.testing.expectEqual;
+const expectEqualStrings = std.testing.expectEqualStrings;
 
 const util = @import("./util.zig");
 
@@ -16,7 +18,7 @@ const World = context.World;
 const Entity = context.Entity;
 
 test "Entity_init_id" {
-    var world = try World.initMinimal(std.testing.allocator);
+    var world = try World.initMinimal(alloc);
     defer world.deinit();
 
     const e = try world.entity(.{}, .{});
@@ -25,16 +27,14 @@ test "Entity_init_id" {
 }
 
 test "Entity_init_id_name" {
-    var world = try World.initMinimal(std.testing.allocator);
+    var world = try World.initMinimal(alloc);
     defer world.deinit();
 
     const e = try world.entity(.{ .name = "foo" }, .{});
     // try expect(e.raw != 0); -- Not necessary, world.entity() returns error if result would be 0.
-    try expectStrEql("foo", e.getName().?);
+    try expectEqualStrings("foo", e.getName().?);
 
-    // TODO: Implement EntityPath.
-    const path = c.ecs_get_fullpath(world.raw, e.raw);
-    defer c.ecs_os_api.free_.?(path);
-    try expect(path != null);
-    try expectStrEql("foo", std.mem.sliceTo(path.?, 0));
+    const path2 = try e.getPath(alloc);
+    defer path2.deinit();
+    try expectFmt("foo", "{}", .{path2});
 }