// @vitest-environment happy-dom
import { createRoot, type Root } from "react-dom/client";
import { act } from "react";
import { afterEach, describe, expect, it } from "vitest";
import { findGraph } from "@/lib/catalog";
import { browserGraphHistory, type GraphHistory } from "@/lib/graph";
import { GraphExplorer } from "./GraphExplorer";

declare global {
  var IS_REACT_ACT_ENVIRONMENT: boolean;
}

globalThis.IS_REACT_ACT_ENVIRONMENT = true;

let root: Root | null = null;

afterEach(() => {
  act(() => root?.unmount());
  root = null;
  document.body.innerHTML = "";
});

function sessionHistory(): GraphHistory & { back: () => void; forward: () => void; location: () => string } {
  const stack = [""];
  let index = 0;
  const listeners = new Set<() => void>();
  const notify = () => {
    for (const listener of listeners) listener();
  };
  return {
    read: () => (stack[index] ? `?${stack[index]}` : ""),
    push: (search) => {
      stack.splice(index + 1);
      stack.push(search);
      index = stack.length - 1;
    },
    subscribe: (listener) => {
      listeners.add(listener);
      return () => listeners.delete(listener);
    },
    back: () => {
      if (index === 0) return;
      index -= 1;
      notify();
    },
    forward: () => {
      if (index >= stack.length - 1) return;
      index += 1;
      notify();
    },
    location: () => (stack[index] ? `?${stack[index]}` : ""),
  };
}

function focusTitle(): string {
  return document.querySelector("[data-focus]")?.textContent ?? "";
}

function neighborhoodIds(): string[] {
  return [...document.querySelectorAll("[data-neighborhood]")].map((node) => node.getAttribute("data-neighborhood") ?? "");
}

async function renderGraph(history: GraphHistory, initialSearch = "") {
  const model = findGraph("systems-thinking");
  if (!model) throw new Error("missing graph");
  const host = document.createElement("div");
  document.body.appendChild(host);
  root = createRoot(host);
  await act(async () => {
    root?.render(<GraphExplorer model={model} initialSearch={initialSearch} history={history} />);
  });
  return model;
}

describe("graph explorer history", () => {
  it("changes the visible neighborhood with focus and hop distance", async () => {
    const history = sessionHistory();
    const model = await renderGraph(history);
    const feedback = model.nodes.find((node) => node.id.endsWith(":feedback"));
    const causal = model.nodes.find((node) => node.id.endsWith(":causal-loop"));
    const boundary = model.nodes.find((node) => node.id.endsWith(":system-boundary"));
    if (!feedback || !causal || !boundary) throw new Error("missing fixture nodes");
    const wide = neighborhoodIds();
    expect(wide).toContain(feedback.id);
    expect(wide).toContain(boundary.id);
    const excluded = Number(document.querySelector("[data-excluded-count]")?.getAttribute("data-excluded-count"));
    expect(excluded).toBeGreaterThan(0);
    expect(document.body.textContent).toContain(`${excluded} relations outside this neighborhood`);

    await act(async () => {
      document.querySelector("button[aria-pressed='false']")?.dispatchEvent(new MouseEvent("click", { bubbles: true }));
    });
    expect(neighborhoodIds()).not.toContain(boundary.id);
    expect(Number(document.querySelector("[data-excluded-count]")?.getAttribute("data-excluded-count"))).toBeGreaterThan(excluded);

    await act(async () => {
      document.querySelector(`button[data-address="${causal.id}"]`)?.dispatchEvent(new MouseEvent("click", { bubbles: true }));
    });
    expect(focusTitle()).toBe(causal.title);
    expect(neighborhoodIds()).toContain(causal.id);
    expect(neighborhoodIds()).not.toEqual(wide);
    const adjacency = document.querySelector("[data-adjacency]")?.textContent ?? "";
    const exported = JSON.parse(adjacency) as { edges: { id: string; predicate: string; direction: string }[] };
    expect(exported.edges.length).toBeGreaterThan(0);
    expect(exported.edges.every((edge) => edge.id && edge.predicate && edge.direction === "out")).toBe(true);
  });

  it("restores focus and detail on reload, back, and forward", async () => {
    const history = sessionHistory();
    const model = await renderGraph(history);
    const feedback = model.nodes.find((node) => node.id.endsWith(":feedback"));
    const causal = model.nodes.find((node) => node.id.endsWith(":causal-loop"));
    const boundary = model.nodes.find((node) => node.id.endsWith(":system-boundary"));
    if (!feedback || !causal || !boundary) throw new Error("missing fixture nodes");
    expect(focusTitle()).toBe(feedback.title);
    expect(document.body.textContent).toContain("Represented by");
    expect(document.body.textContent).toContain("Modeled by");

    await act(async () => {
      document.querySelector(`button[data-focus-node="${causal.id}"]`)?.dispatchEvent(new MouseEvent("click", { bubbles: true }));
    });
    expect(focusTitle()).toBe(causal.title);
    expect(decodeURIComponent(history.location())).toContain(causal.id);

    await act(async () => {
      document.querySelector(`button[data-open-detail="${feedback.id}"]`)?.dispatchEvent(new MouseEvent("click", { bubbles: true }));
    });
    expect(document.querySelector("[data-detail]")?.getAttribute("data-detail")).toBe(feedback.id);
    expect(focusTitle()).toBe(causal.title);
    const saved = history.location();
    expect(decodeURIComponent(saved)).toContain("detail=");
    expect(decodeURIComponent(saved)).toContain(causal.id);

    act(() => root?.unmount());
    root = null;
    document.body.innerHTML = "";
    await renderGraph(history, saved);
    expect(focusTitle()).toBe(causal.title);
    expect(document.querySelector("[data-detail]")?.getAttribute("data-detail")).toBe(feedback.id);

    await act(async () => {
      history.back();
    });
    expect(focusTitle()).toBe(causal.title);
    expect(document.querySelector("[data-detail]")).toBeNull();

    await act(async () => {
      history.back();
    });
    expect(focusTitle()).toBe(feedback.title);
    expect(neighborhoodIds()).toContain(boundary.id);

    await act(async () => {
      history.forward();
    });
    expect(focusTitle()).toBe(causal.title);
    expect(document.querySelector("[data-detail]")).toBeNull();
  });

  it("reads a pushed query and a popstate traversal", () => {
    const model = findGraph("systems-thinking");
    if (!model) throw new Error("missing graph");
    window.history.replaceState(null, "", "/systems-thinking/graph/");
    const history = browserGraphHistory();
    const seen: string[] = [];
    const stop = history.subscribe(() => seen.push(history.read()));
    const focus = model.defaultFocusId;
    history.push(`focus=${encodeURIComponent(focus)}&detail=${encodeURIComponent(focus)}`);
    expect(window.location.search).toContain("focus=");
    expect(window.location.search).toContain("detail=");
    expect(seen).toEqual([]);
    window.history.pushState(null, "", `/systems-thinking/graph/?focus=${encodeURIComponent(focus)}`);
    window.dispatchEvent(new PopStateEvent("popstate"));
    expect(seen).toEqual([`?focus=${encodeURIComponent(focus)}`]);
    stop();
  });
});