import type { Value } from './types';
import type { AST } from './ast';

export type StoreEntry = {
    value: Value,
    body: AST,
    dependencies: Set<string>;
};

export type Store = Map<string, StoreEntry>;

export function createStore(): Store {
    return new Map();
}

let currentlyEvaluating: string | null = null;
let currentDependencies: Set<string> | null = null;

export function startTracking(name: string): Set<string> {
    currentlyEvaluating = name;
    currentDependencies = new Set();
    return currentDependencies;
}

export function stopTracking() {
    currentlyEvaluating = null;
    currentDependencies = null;
}

export function recordDependency(name: string) {
    if (currentDependencies && name !== currentlyEvaluating) {
        currentDependencies.add(name);
    }
}

export function isTracking(): boolean {
    return currentlyEvaluating !== null;
}

export function buildDependents(store: Store): Map<string, Set<string>> {
    const dependents = new Map<string, Set<string>>();

    for (const name of store.keys()) {
        dependents.set(name, new Set());
    }

    for (const [name, entry] of store) {
        for (const dep of entry.dependencies) {
            if (dependents.has(dep)) {
                dependents.get(dep)!.add(name);
            }
        }
    }

    return dependents;
}