rea/src/domain/javascript/javascriptSemanticPrimitives.ts

import * as t from "@babel/types";

import type {
  JavaScriptSemanticPrimitive,
  JavaScriptSemanticValue,
} from "./javascriptSemanticIr.js";
import { compareCodePoints } from "../canonicalOrdering.js";
import { semanticPrimitiveKey } from "./javascriptSemanticProvenance.js";
import { readExactJavaScriptLiteral } from "./javascriptAstValues.js";
import {
  SEMANTIC_PRIMITIVE_CANDIDATE_LIMIT,
  exceedsSemanticPrimitiveStringByteBudget,
  semanticResourceLimitUnknown,
} from "./javascriptSemanticResourceLimits.js";

/**
 * Keep eight independent binary choices exact, while bounding the next
 * exponential expansion before it allocates hundreds more alternatives.
 */
export const MAX_SEMANTIC_PRIMITIVE_CANDIDATES =
  SEMANTIC_PRIMITIVE_CANDIDATE_LIMIT;

/** Normalize one bounded collection of possible primitive values. */
export const semanticPrimitiveSet = (
  values: readonly JavaScriptSemanticPrimitive[],
): JavaScriptSemanticValue => {
  const uniqueValues = new Set<JavaScriptSemanticPrimitive>();
  for (const value of values) {
    if (typeof value === "number" && !Number.isFinite(value))
      return {
        status: "unknown",
        reason: "Nonfinite numbers are outside the JSON primitive lattice.",
      };
    uniqueValues.add(value);
    if (uniqueValues.size > MAX_SEMANTIC_PRIMITIVE_CANDIDATES)
      return semanticResourceLimitUnknown("primitive-candidates");
  }
  if (
    exceedsSemanticPrimitiveStringByteBudget(
      [...uniqueValues].flatMap((value) =>
        typeof value === "string" ? [value] : [],
      ),
    )
  )
    return semanticResourceLimitUnknown("primitive-bytes");
  const unique = [...uniqueValues]
    .map((value) => ({ key: semanticPrimitiveKey(value), value }))
    .sort((left, right) => compareCodePoints(left.key, right.key))
    .map(({ value }) => value);
  const only = unique[0];
  return unique.length === 1 && only !== undefined
    ? { status: "literal", value: only }
    : { status: "union", values: unique };
};

/** Read the primitive candidates retained in one lattice value. */
export const semanticPrimitiveCandidates = (
  value: JavaScriptSemanticValue,
): readonly JavaScriptSemanticPrimitive[] | null =>
  value.status === "literal"
    ? [value.value]
    : value.status === "union"
      ? value.values
      : null;

/** Parse one Babel primitive literal without evaluating code. */
export const semanticPrimitiveValue = (
  node: t.Node,
):
  | { readonly found: true; readonly value: JavaScriptSemanticPrimitive }
  | { readonly found: false } => {
  return readExactJavaScriptLiteral(node);
};