1 files changed, 101 insertions, 0 deletions
diff --git a/std/encoding/_yaml/schema.ts b/std/encoding/_yaml/schema.ts
new file mode 100644
index 000000000..579644dbb
--- /dev/null
+++ b/std/encoding/_yaml/schema.ts
@@ -0,0 +1,101 @@
+// Ported from js-yaml v3.13.1:
+// https://github.com/nodeca/js-yaml/commit/665aadda42349dcae869f12040d9b10ef18d12da
+// Copyright 2011-2015 by Vitaly Puzrin. All rights reserved. MIT license.
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import { YAMLError } from "./error.ts";
+import { KindType, Type } from "./type.ts";
+import { ArrayObject, Any } from "./utils.ts";
+
+function compileList(
+  schema: Schema,
+  name: "implicit" | "explicit",
+  result: Type[]
+): Type[] {
+  const exclude: number[] = [];
+
+  for (const includedSchema of schema.include) {
+    result = compileList(includedSchema, name, result);
+  }
+
+  for (const currentType of schema[name]) {
+    for (
+      let previousIndex = 0;
+      previousIndex < result.length;
+      previousIndex++
+    ) {
+      const previousType = result[previousIndex];
+      if (
+        previousType.tag === currentType.tag &&
+        previousType.kind === currentType.kind
+      ) {
+        exclude.push(previousIndex);
+      }
+    }
+
+    result.push(currentType);
+  }
+
+  return result.filter((type, index): unknown => !exclude.includes(index));
+}
+
+export type TypeMap = { [k in KindType | "fallback"]: ArrayObject<Type> };
+function compileMap(...typesList: Type[][]): TypeMap {
+  const result: TypeMap = {
+    fallback: {},
+    mapping: {},
+    scalar: {},
+    sequence: {},
+  };
+
+  for (const types of typesList) {
+    for (const type of types) {
+      if (type.kind !== null) {
+        result[type.kind][type.tag] = result["fallback"][type.tag] = type;
+      }
+    }
+  }
+  return result;
+}
+
+export class Schema implements SchemaDefinition {
+  public static SCHEMA_DEFAULT?: Schema;
+
+  public implicit: Type[];
+  public explicit: Type[];
+  public include: Schema[];
+
+  public compiledImplicit: Type[];
+  public compiledExplicit: Type[];
+  public compiledTypeMap: TypeMap;
+
+  constructor(definition: SchemaDefinition) {
+    this.explicit = definition.explicit || [];
+    this.implicit = definition.implicit || [];
+    this.include = definition.include || [];
+
+    for (const type of this.implicit) {
+      if (type.loadKind && type.loadKind !== "scalar") {
+        throw new YAMLError(
+          // eslint-disable-next-line max-len
+          "There is a non-scalar type in the implicit list of a schema. Implicit resolving of such types is not supported."
+        );
+      }
+    }
+
+    this.compiledImplicit = compileList(this, "implicit", []);
+    this.compiledExplicit = compileList(this, "explicit", []);
+    this.compiledTypeMap = compileMap(
+      this.compiledImplicit,
+      this.compiledExplicit
+    );
+  }
+
+  public static create(): void {}
+}
+
+export interface SchemaDefinition {
+  implicit?: Any[];
+  explicit?: Type[];
+  include?: Schema[];
+}