reverse-engineering-anything/src/domain/javascript/javascriptSemanticGetterResults.ts

import * as t from "@babel/types";
import {
  unwrapJavaScriptExpression,
  semanticStaticPropertyKey,
} from "./javascriptAstValues.js";
import { semanticCallableResultExpressions } from "./javascriptSemanticCallableResults.js";
import { semanticBindingAtRead } from "./javascriptSemanticMutationInitializers.js";
import { semanticReferenceSourcesInactive } from "./javascriptSemanticReferenceSources.js";
import {
  resolveSemanticBindingState,
  type JavaScriptSemanticBindingState,
  type JavaScriptSemanticAnalysisState,
} from "./javascriptSemanticState.js";
import {
  semanticObjectPropertyReferences,
  semanticArrayPropertyReferences,
  type JavaScriptSemanticObjectReference as Reference,
} from "./javascriptSemanticObjectReferences.js";
import type { JavaScriptSemanticPropertyPath as PropertyPath } from "./javascriptSemanticPropertyPaths.js";
import {
  SemanticGetterQuery,
  type GetterQueryJob,
} from "./javascriptSemanticGetterQueries.js";

type ClassNode = t.ClassDeclaration | t.ClassExpression;
interface AliasVisit {
  readonly identity: string;
  readonly pathLength: number;
  readonly parent?: AliasVisit;
}
interface GetterWork {
  readonly node: t.Node;
  readonly path: PropertyPath;
  readonly aliases?: AliasVisit | undefined;
  readonly escapes?: true;
  readonly privateRead?: {
    readonly node: t.MemberExpression | t.OptionalMemberExpression;
    readonly name: string;
    readonly path: PropertyPath;
  };
}
export interface GetterResultResolvers {
  readonly classReferences: (
    lookup: {
      readonly owner: ClassNode;
      readonly receiver?: ClassNode;
      readonly kind: "static" | "instance" | "prototype";
    },
    path: PropertyPath,
    escapes: boolean,
  ) => readonly Reference[];
  readonly objectReferences: (
    receiver: t.ObjectExpression,
    path: PropertyPath,
  ) => readonly Reference[];
  readonly privateReceiver: (
    receiver: ClassNode,
    owner: ClassNode,
    path: PropertyPath,
    isStatic: boolean,
  ) => boolean;
  readonly bases: (node: t.Node) => readonly ClassNode[];
  readonly containerReferences?: (
    node: t.ObjectExpression | t.ArrayExpression,
    path: PropertyPath,
  ) => readonly Reference[];
}

/** Branch syntax contributes alternatives without evaluating application code. */
const resultBranches = (node: t.Node): readonly t.Node[] | undefined => {
  if (t.isConditionalExpression(node)) return [node.consequent, node.alternate];
  if (t.isLogicalExpression(node)) return [node.left, node.right];
  if (t.isSequenceExpression(node)) {
    const last = node.expressions.at(-1);
    return last === undefined ? [] : [last];
  }
  if (t.isAssignmentExpression(node)) {
    if (node.operator === "=") return [node.right];
    if (["&&=", "||=", "??="].includes(node.operator))
      return [node.left, node.right];
  }
  return undefined;
};

/** Each walk owns local aliases; getter-to-getter traversal belongs to the query worklist. */
class GetterResultWalker {
  readonly #pending: GetterWork[] = [];
  readonly #aliases = new Map<string, Set<string>>();
  readonly #scope: string | undefined;

  constructor(
    readonly job: GetterQueryJob,
    readonly query: SemanticGetterQuery,
    readonly resolvers: GetterResultResolvers,
    roots: readonly {
      readonly node: t.Node | null;
    }[] = semanticCallableResultExpressions(job.invocation.getter),
  ) {
    for (const { node } of roots)
      if (node !== null) this.#enqueue(() => ({ node, path: job.path }));
    this.#scope = query.state.scopeByNode.get(job.invocation.getter)?.scopeId;
  }

  run(): void {
    for (let cursor = 0; cursor < this.#pending.length; cursor++) {
      const current = this.#pending[cursor];
      if (current !== undefined) this.#visit(current);
    }
  }

  #enqueue(create: () => GetterWork): void {
    if (!this.query.reserveResult()) return;
    const work = create();
    // The fallback escapes receiver roots. Keeping local suffix permutations
    // here would repeat the precise expansion inside a single getter.
    this.#pending.push(
      this.query.widening
        ? {
            ...work,
            path: [],
            escapes: true,
            ...(work.privateRead === undefined
              ? {}
              : { privateRead: { ...work.privateRead, path: [] } }),
          }
        : work,
    );
  }

  #retain(current: GetterWork, reference: Reference): void {
    this.query.retain(reference, current.escapes || this.job.escapes);
  }

  #privateRead(current: GetterWork): void {
    if (current.privateRead !== undefined)
      this.#retain(current, {
        node: current.privateRead.node,
        path: current.escapes ? [] : current.privateRead.path,
      });
  }

  #localBinding(expression: t.Identifier) {
    const state = this.query.state;
    const binding = resolveSemanticBindingState(
      state,
      expression,
      expression.name,
    );
    let scope =
      binding === undefined ? undefined : state.scopesById.get(binding.scopeId);
    while (scope !== undefined && scope.scopeId !== this.#scope) {
      if (scope.kind === "function" || scope.parentScopeId === null)
        return undefined;
      scope = state.scopesById.get(scope.parentScopeId);
    }
    return scope !== undefined &&
      binding?.referenceInitializers.every(
        (initializer) => initializer.copyKind === undefined,
      )
      ? binding
      : undefined;
  }

  #cycle(current: GetterWork, identity: string): AliasVisit | undefined {
    for (let visit = current.aliases; visit !== undefined; visit = visit.parent)
      if (visit.identity === identity) return visit;
    return undefined;
  }

  #alias(current: GetterWork, expression: t.Identifier): boolean {
    const binding = this.#localBinding(expression);
    if (binding === undefined) return false;
    const identity = JSON.stringify([
      binding.bindingId,
      expression.start,
      expression.end,
    ]);
    const previous = this.#cycle(current, identity);
    if (previous !== undefined) {
      // Growing aliases can reach arbitrarily deep children of the same roots.
      if (current.path.length > previous.pathLength && !current.escapes)
        this.#enqueue(() => ({
          ...current,
          path: [],
          aliases: undefined,
          escapes: true,
        }));
      return true;
    }
    const key = JSON.stringify([
      current.path,
      current.privateRead?.name,
      current.privateRead?.path,
      current.escapes,
    ]);
    const known = this.#aliases.get(identity) ?? new Set<string>();
    if (!known.has(key)) {
      known.add(key);
      this.#aliases.set(identity, known);
      this.#aliasOrigins(current, expression, binding, identity);
    }
    return true;
  }

  #aliasOrigins(
    current: GetterWork,
    expression: t.Identifier,
    binding: JavaScriptSemanticBindingState,
    identity: string,
  ): void {
    const state = this.query.state;
    const { binding: origins } = semanticBindingAtRead(
      binding,
      expression,
      state.parentsByNode,
    );
    const aliases: AliasVisit = {
      identity,
      pathLength: current.path.length,
      ...(current.aliases === undefined ? {} : { parent: current.aliases }),
    };
    for (const initializer of [
      ...origins.initializers,
      ...origins.referenceInitializers.filter(
        (origin) => !semanticReferenceSourcesInactive(origin, state),
      ),
    ])
      this.#enqueue(() => ({
        ...current,
        node: initializer.node,
        path: [...initializer.projection, ...current.path],
        aliases,
      }));
  }

  #ownsThis(expression: t.ThisExpression): boolean {
    let owner = this.query.state.parentsByNode.get(expression);
    while (
      owner !== undefined &&
      !t.isClass(owner) &&
      !(t.isFunction(owner) && !t.isArrowFunctionExpression(owner))
    )
      owner = this.query.state.parentsByNode.get(owner);
    return owner === this.job.invocation.getter;
  }

  #privateValue(current: GetterWork, owner: ClassNode): void {
    const read = current.privateRead;
    if (read === undefined) return;
    const { getter, receiver = owner } = this.job.invocation;
    const isStatic = t.isClassMethod(getter) && getter.static;
    if (
      !t.isClass(receiver) ||
      !this.resolvers.privateReceiver(receiver, owner, current.path, isStatic)
    ) {
      this.#privateRead(current);
      return;
    }
    for (const member of owner.body.body)
      if (
        t.isClassPrivateProperty(member) &&
        member.static === isStatic &&
        member.key.id.name === read.name &&
        member.value != null
      )
        this.#retain(current, {
          node: member.value,
          path: current.escapes ? [] : read.path,
        });
  }

  #thisValue(current: GetterWork, expression: t.ThisExpression): void {
    if (!this.#ownsThis(expression)) return;
    const { getter, owner, receiver = owner } = this.job.invocation;
    if (current.privateRead !== undefined && t.isClass(owner)) {
      this.#privateValue(current, owner);
      return;
    }
    const references = t.isClass(receiver)
      ? this.resolvers.classReferences(
          {
            owner: receiver,
            kind:
              t.isClassMethod(getter) && getter.static ? "static" : "instance",
          },
          current.path,
          current.escapes || this.job.escapes,
        )
      : this.resolvers.objectReferences(receiver, current.path);
    for (const reference of references) this.#retain(current, reference);
  }

  #superValue(
    current: GetterWork,
    expression: t.MemberExpression | t.OptionalMemberExpression,
  ): boolean {
    const { getter, owner, receiver = owner } = this.job.invocation;
    if (
      !t.isSuper(expression.object) ||
      !t.isClass(owner) ||
      owner.superClass == null
    )
      return false;
    const key = semanticStaticPropertyKey(
      expression.property,
      expression.computed,
    );
    for (const base of this.resolvers.bases(owner.superClass))
      for (const reference of this.resolvers.classReferences(
        {
          owner: base,
          receiver: t.isClass(receiver) ? receiver : owner,
          kind:
            t.isClassMethod(getter) && getter.static ? "static" : "prototype",
        },
        [key, ...current.path],
        current.escapes || this.job.escapes,
      ))
        this.#retain(current, reference);
    return true;
  }

  #member(
    current: GetterWork,
    expression: t.MemberExpression | t.OptionalMemberExpression,
  ): void {
    if (
      current.privateRead !== undefined &&
      t.isPrivateName(expression.property)
    ) {
      this.#privateRead(current);
      return;
    }
    if (
      t.isPrivateName(expression.property) &&
      t.isClass(this.job.invocation.owner)
    ) {
      const name = expression.property.id.name;
      this.#enqueue(() => ({
        ...current,
        node: expression.object,
        path: [],
        privateRead: {
          node: expression,
          name,
          path: current.path,
        },
      }));
      return;
    }
    if (!this.#superValue(current, expression))
      this.#enqueue(() => ({
        ...current,
        node: expression.object,
        path: [
          semanticStaticPropertyKey(expression.property, expression.computed),
          ...current.path,
        ],
      }));
  }

  #visit(current: GetterWork): void {
    const expression = unwrapJavaScriptExpression(current.node).node;
    if (t.isIdentifier(expression) && this.#alias(current, expression)) return;
    if (t.isThisExpression(expression)) this.#thisValue(current, expression);
    else if (
      t.isMemberExpression(expression) ||
      t.isOptionalMemberExpression(expression)
    )
      this.#member(current, expression);
    else {
      const branches = resultBranches(expression);
      if (branches !== undefined)
        for (const node of branches)
          this.#enqueue(() => ({ ...current, node }));
      else if (current.privateRead !== undefined) this.#privateRead(current);
      else if (
        current.path.length > 0 &&
        (t.isObjectExpression(expression) || t.isArrayExpression(expression)) &&
        this.resolvers.containerReferences !== undefined
      ) {
        for (const reference of this.resolvers.containerReferences(
          expression,
          current.path,
        ))
          this.#enqueue(() => ({
            ...current,
            node: reference.node,
            path: reference.path,
          }));
      } else this.#retain(current, { node: expression, path: current.path });
    }
  }
}

export const expandSemanticGetterResult = (
  job: GetterQueryJob,
  query: SemanticGetterQuery,
  resolvers: GetterResultResolvers,
): void => new GetterResultWalker(job, query, resolvers).run();

/** Project an effect operand through the same local aliases and `this` owner as getter results. */
export const semanticGetterReceiverPaths = (
  getter: t.ObjectMethod,
  operand: t.Node,
  state: JavaScriptSemanticAnalysisState,
): readonly PropertyPath[] => {
  const owner = state.parentsByNode.get(getter);
  if (!t.isObjectExpression(owner)) return [];
  const query = new SemanticGetterQuery(state);
  const references = query.run(
    () => {
      query.schedule({ getter, owner }, []);
      return [];
    },
    (job) =>
      new GetterResultWalker(
        job,
        query,
        {
          objectReferences: (_receiver, path) => [{ node: getter, path }],
          classReferences: () => [],
          privateReceiver: () => false,
          bases: () => [],
          containerReferences: (node, path) =>
            t.isObjectExpression(node)
              ? semanticObjectPropertyReferences(node, path, state)
              : semanticArrayPropertyReferences(node, path),
        },
        [{ node: operand }],
      ).run(),
  );
  return references
    .filter(({ node }) => node === getter)
    .map(({ path }) => path);
};