import { describe, expect, it } from "vitest";

import { FactIndex, makeUsageNodeFact } from "../index.js";
import type { UsageNodeFact } from "../index.js";
import { regionsByPrefix, type Region } from "./utils.js";

/**
 * Build a `usage_node` fact and add it to the index. Tests assert container /
 * member *relationships*, never literal `nodePath` strings — segments are
 * opaque (per the usage-node-fact contract).
 */
function node(
  ix: FactIndex,
  nodePath: string,
  element: string,
  file = "src/App.tsx"
): UsageNodeFact {
  const fact = makeUsageNodeFact({
    file,
    nodePath,
    element,
    location: { file, line: 1, column: 1 },
  });
  ix.add(fact);
  return fact;
}

function regionFor(regions: Region[], container: UsageNodeFact): Region {
  const region = regions.find((r) => r.container.id === container.id);
  if (!region) throw new Error(`no region for container ${container.nodePath}`);
  return region;
}

const memberIds = (region: Region) => new Set(region.members.map((m) => m.id));

describe("regionsByPrefix", () => {
  // ACCEPTANCE §1 — sibling grouping under a container.
  it("groups sibling children under their container", () => {
    const ix = new FactIndex();
    const n0 = node(ix, "0:0", "ButtonGroup");
    const n1 = node(ix, "0:0/0", "Button");
    const n2 = node(ix, "0:0/1", "Button");

    const regions = regionsByPrefix(ix);
    const members = memberIds(regionFor(regions, n0));
    expect(members.has(n1.id)).toBe(true);
    expect(members.has(n2.id)).toBe(true);

    // n1 and n2 are siblings: neither contains the other.
    expect(regionFor(regions, n1).members).toHaveLength(0);
    expect(regionFor(regions, n2).members).toHaveLength(0);
  });

  // ACCEPTANCE §2 — opaque conditional segment stays in-region.
  it("keeps an opaque conditional (expr:) child in the container's region", () => {
    const ix = new FactIndex();
    const n0 = node(ix, "0:0", "ButtonGroup");
    const n1 = node(ix, "0:0/0", "Button");
    const n2 = node(ix, "0:0/expr:0/0", "Button"); // {show && <Button/>}

    const members = memberIds(regionFor(regionsByPrefix(ix), n0));
    expect(members.has(n1.id)).toBe(true);
    // `expr:0` is one opaque segment, so `0:0` is still a strict prefix.
    expect(members.has(n2.id)).toBe(true);
  });

  it("compares whole segments — distinct conditional branches stay separate", () => {
    const ix = new FactIndex();
    const branchA = node(ix, "0:0/expr:0/0", "Button");
    const branchB = node(ix, "0:0/expr:1/0", "Button");

    const regions = regionsByPrefix(ix);
    expect(memberIds(regionFor(regions, branchA)).has(branchB.id)).toBe(false);
    expect(memberIds(regionFor(regions, branchB)).has(branchA.id)).toBe(false);
  });

  it("includes all descendants, not only direct children", () => {
    const ix = new FactIndex();
    const root = node(ix, "0:0", "Card");
    const child = node(ix, "0:0/0", "ButtonGroup");
    const grandchild = node(ix, "0:0/0/0", "Button");

    const members = memberIds(regionFor(regionsByPrefix(ix), root));
    expect(members.has(child.id)).toBe(true);
    expect(members.has(grandchild.id)).toBe(true);
  });

  it("scopes regions by file — identical paths in different files do not merge", () => {
    const ix = new FactIndex();
    const a0 = node(ix, "0:0", "ButtonGroup", "src/A.tsx");
    const a1 = node(ix, "0:0/0", "Button", "src/A.tsx");
    const b1 = node(ix, "0:0/0", "Button", "src/B.tsx");

    const members = memberIds(regionFor(regionsByPrefix(ix), a0));
    expect(members.has(a1.id)).toBe(true);
    expect(members.has(b1.id)).toBe(false);
  });

  it("scopes regions by rootIndex — separate root trees in one file do not merge", () => {
    const ix = new FactIndex();
    const r0 = node(ix, "0:0", "ButtonGroup");
    const r0child = node(ix, "0:0/0", "Button");
    // Same segments as r0child but a different leading root index.
    const r1child = node(ix, "1:0/0", "Button");

    const members = memberIds(regionFor(regionsByPrefix(ix), r0));
    expect(members.has(r0child.id)).toBe(true);
    expect(members.has(r1child.id)).toBe(false);
  });
});