New decode module

1 files changed, 68 insertions, 0 deletions

diff --git a/src/gleam_stdlib_decode_ffi.mjs b/src/gleam_stdlib_decode_ffi.mjs
new file mode 100644
index 0000000..86c9c60
--- /dev/null
+++ b/src/gleam_stdlib_decode_ffi.mjs
@@ -0,0 +1,68 @@
+import { Ok, Error, List, NonEmpty } from "./gleam.mjs";
+import { default as Dict } from "./dict.mjs";
+import { Some, None } from "./gleam/option.mjs";
+import { DecodeError, classify } from "./gleam/dynamic.mjs";
+
+export function strict_index(data, key) {
+  const int = Number.isInteger(key);
+
+  // Dictionaries and dictionary-like objects can be indexed
+  if (data instanceof Dict || data instanceof WeakMap || data instanceof Map) {
+    const token = {};
+    const entry = data.get(key, token);
+    if (entry === token) return new Ok(new None());
+    return new Ok(new Some(entry));
+  }
+
+  // The first 3 elements of lists can be indexed
+  if ((key === 0 || key === 1 || key === 2) && data instanceof List) {
+    let i = 0;
+    for (const value of data) {
+      if (i === key) return new Ok(new Some(value));
+      i++;
+    }
+    return new Error("Indexable");
+  }
+
+  // Arrays and objects can be indexed
+  if (
+    (int && Array.isArray(data)) ||
+    (data && typeof data === "object") ||
+    (data && Object.getPrototypeOf(data) === Object.prototype)
+  ) {
+    if (key in data) return new Ok(new Some(data[key]));
+    return new Ok(new None());
+  }
+
+  return new Error(int ? "Indexable" : "Dict");
+}
+
+export function list(data, decode, pushPath, index, emptyList) {
+  if (!(data instanceof List || Array.isArray(data))) {
+    let error = new DecodeError("List", classify(data), emptyList);
+    return [emptyList, List.fromArray([error])];
+  }
+
+  const decoded = [];
+
+  for (const element of data) {
+    const layer = decode(element);
+    const [out, errors] = layer;
+
+    if (errors instanceof NonEmpty) {
+      const [_, errors] = pushPath(layer, index.toString());
+      return [emptyList, errors];
+    }
+    decoded.push(out);
+    index++;
+  }
+
+  return [List.fromArray(decoded), emptyList];
+}
+
+export function dict(data) {
+  if (data instanceof Dict) {
+    return new Ok(data);
+  }
+  return new Error();
+}