From 1675c3f057cdd73b5cad9df5338e2efe54595741 Mon Sep 17 00:00:00 2001
From: mhawryluk <marcinhawrylukxx@gmail.com>
Date: Tue, 9 Jul 2024 16:38:51 +0200
Subject: [PATCH] Replace WGSLPlaceholder with WGSLSlot

---
 packages/wigsill/src/index.ts           |  2 +-
 packages/wigsill/src/types.ts           | 10 +++-
 packages/wigsill/src/wgsl.ts            |  4 +-
 packages/wigsill/src/wgslPlaceholder.ts | 48 ----------------
 packages/wigsill/src/wgslSlot.ts        | 74 +++++++++++++++++++++++++
 5 files changed, 86 insertions(+), 52 deletions(-)
 delete mode 100644 packages/wigsill/src/wgslPlaceholder.ts
 create mode 100644 packages/wigsill/src/wgslSlot.ts

diff --git a/packages/wigsill/src/index.ts b/packages/wigsill/src/index.ts
index b3ae3aca..2abd9d5e 100644
--- a/packages/wigsill/src/index.ts
+++ b/packages/wigsill/src/index.ts
@@ -12,5 +12,5 @@ export { WGSLConstant } from './wgslConstant';
 export { WGSLFunction } from './wgslFunction';
 export { WGSLIdentifier } from './wgslIdentifier';
 export { WGSLMemory } from './wgslMemory';
-export { WGSLPlaceholder } from './wgslPlaceholder';
+export { WGSLSlot } from './wgslSlot';
 export { WGSLRequire } from './wgslRequire';
diff --git a/packages/wigsill/src/types.ts b/packages/wigsill/src/types.ts
index d6020b76..b39e82eb 100644
--- a/packages/wigsill/src/types.ts
+++ b/packages/wigsill/src/types.ts
@@ -27,9 +27,17 @@ export function isWGSLItem(value: unknown): value is WGSLItem {
   );
 }
 
-export interface WGSLBindableTrait<TBinding> extends WGSLItem {
+export function isWGSLSegment(value: unknown): value is WGSLSegment {
+  return (
+    typeof value === 'number' || typeof value === 'string' || isWGSLItem(value)
+  );
+}
+
+export interface WGSLBindableTrait<TBinding> {
   /** type-token, not available at runtime */
   readonly __bindingType: TBinding;
+
+  readonly debugLabel?: string | undefined;
 }
 
 export type WGSLBindPair<T> = [WGSLBindableTrait<T>, T];
diff --git a/packages/wigsill/src/wgsl.ts b/packages/wigsill/src/wgsl.ts
index f344233e..1bce0014 100644
--- a/packages/wigsill/src/wgsl.ts
+++ b/packages/wigsill/src/wgsl.ts
@@ -4,8 +4,8 @@ import { fn as fun } from './wgslFunction';
 import { fn } from './wgslFunctionOld';
 import { identifier } from './wgslIdentifier';
 import { memory } from './wgslMemory';
-import { placeholder } from './wgslPlaceholder';
 import { require } from './wgslRequire';
+import { slot } from './wgslSlot';
 import { variable } from './wgslVariable';
 
 export default Object.assign(code, {
@@ -14,7 +14,7 @@ export default Object.assign(code, {
   fun,
   identifier,
   memory,
-  placeholder,
+  slot,
   constant,
   require,
   var: variable,
diff --git a/packages/wigsill/src/wgslPlaceholder.ts b/packages/wigsill/src/wgslPlaceholder.ts
deleted file mode 100644
index 09c6530e..00000000
--- a/packages/wigsill/src/wgslPlaceholder.ts
+++ /dev/null
@@ -1,48 +0,0 @@
-import {
-  IResolutionCtx,
-  WGSLBindableTrait,
-  WGSLCompoundTrait,
-  WGSLItem,
-  WGSLSegment,
-  hasCompoundTrait,
-} from './types';
-
-export class WGSLPlaceholder
-  implements WGSLItem, WGSLBindableTrait<WGSLSegment>, WGSLCompoundTrait
-{
-  __bindingType!: WGSLSegment;
-  public debugLabel?: string | undefined;
-
-  constructor(public defaultSegment?: WGSLSegment) {}
-
-  public alias(debugLabel: string) {
-    this.debugLabel = debugLabel;
-    return this;
-  }
-
-  private getSegment(ctx: IResolutionCtx) {
-    if (this.defaultSegment) {
-      return ctx.tryBinding(this, this.defaultSegment);
-    }
-
-    return ctx.requireBinding(this);
-  }
-
-  getChildren(ctx: IResolutionCtx): WGSLItem[] {
-    const segment = this.getSegment(ctx);
-
-    if (hasCompoundTrait(segment)) {
-      return segment.getChildren(ctx);
-    }
-
-    return [];
-  }
-
-  resolve(ctx: IResolutionCtx): string {
-    return ctx.resolve(this.getSegment(ctx));
-  }
-}
-
-export function placeholder(defaultSegment?: WGSLSegment): WGSLPlaceholder {
-  return new WGSLPlaceholder(defaultSegment);
-}
diff --git a/packages/wigsill/src/wgslSlot.ts b/packages/wigsill/src/wgslSlot.ts
new file mode 100644
index 00000000..35df6bae
--- /dev/null
+++ b/packages/wigsill/src/wgslSlot.ts
@@ -0,0 +1,74 @@
+import {
+  IResolutionCtx,
+  WGSLBindableTrait,
+  WGSLCompoundTrait,
+  WGSLItem,
+  WGSLSegment,
+  hasCompoundTrait,
+  isWGSLSegment,
+} from './types';
+
+export interface Slot<T> {
+  __brand: 'Slot';
+  /** type-token, not available at runtime */
+  __bindingType: T;
+}
+
+export interface ResolvableSlot<T extends WGSLSegment> extends WGSLItem {
+  __brand: 'Slot';
+  /** type-token, not available at runtime */
+  __bindingType: T;
+}
+
+export class WGSLSlot<T>
+  implements WGSLItem, WGSLBindableTrait<T>, WGSLCompoundTrait
+{
+  __bindingType!: T;
+  __brand = 'Slot' as const;
+  public debugLabel?: string | undefined;
+
+  constructor(public defaultValue?: T) {}
+
+  public alias(debugLabel: string) {
+    this.debugLabel = debugLabel;
+    return this;
+  }
+
+  private getValue(ctx: IResolutionCtx) {
+    if (this.defaultValue) {
+      return ctx.tryBinding(this, this.defaultValue);
+    }
+
+    return ctx.requireBinding(this);
+  }
+
+  getChildren(ctx: IResolutionCtx): WGSLItem[] {
+    const segment = this.getValue(ctx);
+
+    if (hasCompoundTrait(segment)) {
+      return segment.getChildren(ctx);
+    }
+
+    return [];
+  }
+
+  resolve(ctx: IResolutionCtx): string {
+    const value = this.getValue(ctx);
+    if (!isWGSLSegment(value)) {
+      throw new Error(
+        `Cannot resolve value of type ${typeof value} for slot: ${this.debugLabel ?? '<unnamed>'}, type WGSLSegment required`,
+      );
+    }
+    return ctx.resolve(value);
+  }
+}
+
+export function slot<T extends WGSLSegment>(
+  defaultValue?: T,
+): ResolvableSlot<T>;
+
+export function slot<T>(defaultValue?: T): Slot<T>;
+
+export function slot<T>(defaultValue?: T): Slot<T> {
+  return new WGSLSlot(defaultValue);
+}