Implement basic script evaluation

src/3x5.ts

@@ -1,4 +1,6 @@
-import { parse } from "./parser";
+import { parse } from './parser';
+import { runNoctl, Vm } from './vm';
+import { AsHtml } from './words';
 
 /**
  * Basic unit of information, also an "actor" in the programming system
@@ -12,25 +14,6 @@ type Card = {
   code: string;
 };
 
-/**
- * "Mode" of the environment a script runs in; determines access to mutability features and such.
- *
- * "action": response to a UI action; allowed to modify card fields and access time and random numbers.
- *
- * "render": deterministic generation of display markup from card and workspace state; can only modify temporary variables.
- */
-type ScriptType = "action" | "render";
-
-/**
- * State for running a script in.
- */
-type Vm = {
-  /** Mutability status */
-  mode: ScriptType;
-  /** Markup to render / output */
-  output: string;
-};
-
 /**
  * @param state VM state
  * @param code Script to run
@@ -39,7 +22,7 @@ type Vm = {
 function renderCard(state: Vm, code: string) {
   const script = parse(code);
   if (script[0]) {
-    state.output = JSON.stringify(script[1], null, 2);
+    runNoctl(state, script[1], (word) => (state.output += AsHtml(word) + "\n"));
   } else {
     state.output = script[1];
   }
@@ -101,6 +84,7 @@ const debugDisplay = document.createElement("pre");
 function render() {
   const vm: Vm = {
     mode: "render",
+    commands: {},
     output: "",
   };
   const html = renderCard(vm, theCard.code);

src/vm.ts

@@ -0,0 +1,74 @@
+import {
+    AsHtml, AsText, Concat, EnchantedWord, HtmlWord, InterpolatedPiece, Script, TextPiece, TextWord,
+    Word
+} from './words';
+
+/**
+ * "Mode" of the environment a script runs in; determines access to mutability features and such.
+ *
+ * "action": response to a UI action; allowed to modify card fields and access time and random numbers.
+ *
+ * "render": deterministic generation of display markup from card and workspace state; can only modify temporary variables.
+ */
+export type ScriptType = "action" | "render";
+
+export type Proc = (state: Vm, argv: TextPiece[]) => TextPiece;
+
+/**
+ * State for running a script in.
+ */
+export type Vm = {
+  /** Mutability status */
+  mode: ScriptType;
+  /** Implementations of commands scripts can run */
+  commands: Record<string, Proc>;
+  /** Markup to render / output */
+  output: string;
+};
+
+function evaluateWord(
+  state: Vm,
+  word: Word | InterpolatedPiece
+): TextWord | EnchantedWord | HtmlWord {
+  if ("enchanted" in word || "text" in word || "html" in word) {
+    return word;
+  } else if ("variable" in word) {
+    return { text: "" };
+  } else if ("script" in word) {
+    return runNoctl(state, word.script);
+  } else {
+    return (
+      word.pieces
+        .map((piece) => evaluateWord(state, piece))
+        .reduce(Concat, null) ?? { text: "" }
+    );
+  }
+}
+
+/**
+ * Runs a script in the context of a Noctl state. Potentially mutates the state.
+ *
+ * @param onReturn callback optionally invoked with the return word for each top-level command (not triggered by command substitutions)
+ * @returns the return word of the final command in the script, or empty text if the script is empty.
+ */
+export function runNoctl(
+  state: Vm,
+  script: Script,
+  onReturn?: (word: TextPiece) => void
+): TextPiece {
+  let returnWord: TextPiece = { text: "" };
+
+  script.forEach((command) => {
+    const argv = command.map((word) => evaluateWord(state, word));
+    const name = AsText(argv[0]);
+    if (name in state.commands) {
+      returnWord = state.commands[name](state, argv);
+    } else {
+      // TODO: implement error propagation
+      returnWord = { html: `<b>UNKNOWN COMMAND: ${AsHtml(argv[0])}</b>` };
+    }
+    onReturn?.(returnWord);
+  });
+
+  return returnWord;
+}