import { describe, it, expect } from 'vitest';
import { DependencyGraph } from '../graph';

/**
 * Helper: build a graph from "cell <- precedent, precedent" lines.
 * Node names are arbitrary strings here (real code uses `keyOf`).
 */
function build(edges: Record<string, string[]>): DependencyGraph {
  const g = new DependencyGraph();
  for (const [cell, precs] of Object.entries(edges)) g.setPrecedents(cell, precs);
  return g;
}

describe('DependencyGraph.affected', () => {
  it('returns dirty cells plus their transitive dependents', () => {
    // A -> B -> C ; A -> D
    const g = build({ B: ['A'], C: ['B'], D: ['A'] });
    expect([...g.affected(['A'])].sort()).toEqual(['A', 'B', 'C', 'D']);
    expect([...g.affected(['B'])].sort()).toEqual(['B', 'C']);
  });
});

describe('DependencyGraph.topoOrder', () => {
  it('orders precedents before dependents', () => {
    const g = build({ B: ['A'], C: ['A', 'B'], D: ['C'] });
    const { order, circular } = g.topoOrder(g.affected(['A']));
    expect(circular.size).toBe(0);
    const pos = (n: string) => order.indexOf(n);
    expect(pos('A')).toBeLessThan(pos('B'));
    expect(pos('B')).toBeLessThan(pos('C'));
    expect(pos('C')).toBeLessThan(pos('D'));
  });

  it('detects a direct self-reference', () => {
    const g = build({ A: ['A'] });
    const { circular } = g.topoOrder(g.affected(['A']));
    expect([...circular]).toEqual(['A']);
  });

  it('detects a 2-cycle and flags both nodes', () => {
    const g = build({ A: ['B'], B: ['A'] });
    const { order, circular } = g.topoOrder(g.affected(['A']));
    expect([...circular].sort()).toEqual(['A', 'B']);
    expect(order).toEqual([]);
  });

  it('detects a longer cycle, leaves acyclic tail evaluable', () => {
    // cycle A->B->C->A ; plus D reads C (D is not on the cycle)
    const g = build({ A: ['C'], B: ['A'], C: ['B'], D: ['C'] });
    const { order, circular } = g.topoOrder(g.affected(['A']));
    expect([...circular].sort()).toEqual(['A', 'B', 'C']);
    expect(order).toEqual(['D']);
  });

  it('rewiring precedents removes stale edges', () => {
    const g = build({ B: ['A'] });
    expect([...g.affected(['A'])].sort()).toEqual(['A', 'B']);
    g.setPrecedents('B', []); // B no longer reads A
    expect([...g.affected(['A'])].sort()).toEqual(['A']);
  });
});