// Watcher Integration Test — proves the FS-watcher → LSP wiring works
// end-to-end against gopls: a stale "undefined symbol" diagnostic clears
// after the missing file is created externally (no LSP query touches it).
//
// This is the canonical staleness scenario from `_scratch/plan-fs-watching.md`.
import { describe, it, before, after } from "node:test";
import * as assert from "node:assert/strict";
import * as fs from "node:fs";
import * as os from "node:os";
import * as path from "node:path";
import {
  setTestSocket,
  stopTestDaemon,
  runCliJson,
  requireServer,
} from "../helpers.ts";

const skip = requireServer("gopls");

// Poll Until - Runs `fn` repeatedly until `predicate(result)` is true or
// the timeout elapses. We need this because gopls reanalysis after a
// workspace/didChangeWatchedFiles is asynchronous; diagnostics arrive on
// a `textDocument/publishDiagnostics` push that we then re-fetch.
async function pollUntil<T>(
  fn: () => Promise<T>,
  predicate: (v: T) => boolean,
  timeoutMs: number,
  intervalMs = 250,
): Promise<T> {
  const deadline = Date.now() + timeoutMs;
  let last: T = await fn();
  while (Date.now() < deadline) {
    if (predicate(last)) return last;
    await new Promise((r) => setTimeout(r, intervalMs));
    last = await fn();
  }
  return last;
}

interface DiagResult {
  [serverId: string]: { diagnostics?: { message: string }[] };
}

describe("watcher: gopls picks up externally-created files", { skip: skip ?? undefined }, () => {
  let tmpDir: string;
  let mainFile: string;
  let helperFile: string;
  const env = { ...process.env };
  let cleanup: () => void;

  before(async () => {
    cleanup = setTestSocket(env);
    await stopTestDaemon(env);

    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "pi-lsp-gopls-watch-"));
    // Minimal Go Module - go.mod is gopls's primary root marker.
    fs.writeFileSync(path.join(tmpDir, "go.mod"), "module example.com/wtest\n\ngo 1.21\n");
    mainFile = path.join(tmpDir, "main.go");
    helperFile = path.join(tmpDir, "helper.go");
    // main.go references Helper() which doesn't exist yet \u2014 should produce
    // an "undefined: Helper" diagnostic.
    fs.writeFileSync(
      mainFile,
      "package main\n\nfunc main() {\n\tHelper()\n}\n",
    );
  });

  after(async () => {
    await stopTestDaemon(env);
    cleanup();
    fs.rmSync(tmpDir, { recursive: true, force: true });
  });

  it("initially reports undefined symbol", async () => {
    // Poll - gopls's workspace load on a fresh tmp dir takes a beat; the
    // first diagnostics call can return "No active builds contain ..."
    // before the real analysis lands. Wait up to 15s for it to settle.
    const result = await pollUntil(
      async () =>
        (await runCliJson(
          [mainFile, "diagnostics", '{"timeoutMs":3000}'],
          env,
        )) as DiagResult,
      (r) => {
        const diags = r["gopls"]?.diagnostics ?? [];
        return diags.some(
          (d) =>
            d.message.toLowerCase().includes("undefined") ||
            d.message.includes("Helper"),
        );
      },
      15000,
      500,
    );
    const diags = result["gopls"]?.diagnostics ?? [];
    const hasUndefined = diags.some((d) =>
      d.message.toLowerCase().includes("undefined") || d.message.includes("Helper"),
    );
    assert.ok(
      hasUndefined,
      `Expected undefined-symbol diagnostic, got: ${JSON.stringify(diags)}`,
    );
  });

  it("clears the diagnostic after helper.go is created externally", async () => {
    // Create The Missing File Without Touching It Via LSP - This is the
    // whole point: only chokidar + workspace/didChangeWatchedFiles can tell
    // gopls about helper.go's existence.
    fs.writeFileSync(
      helperFile,
      "package main\n\nfunc Helper() {}\n",
    );

    // Poll - Allow up to 15s for the watcher to fire, gopls to reanalyze,
    // and the diagnostic to clear. Re-query the same file (main.go) only.
    const result = await pollUntil(
      async () =>
        (await runCliJson(
          [mainFile, "diagnostics", '{"timeoutMs":3000}'],
          env,
        )) as DiagResult,
      (r) => {
        const diags = r["gopls"]?.diagnostics ?? [];
        return !diags.some(
          (d) =>
            d.message.toLowerCase().includes("undefined") ||
            d.message.includes("Helper"),
        );
      },
      15000,
      500,
    );

    const finalDiags = result["gopls"]?.diagnostics ?? [];
    const stillUndefined = finalDiags.some(
      (d) =>
        d.message.toLowerCase().includes("undefined") ||
        d.message.includes("Helper"),
    );
    assert.ok(
      !stillUndefined,
      `Expected diagnostic to clear after creating helper.go, still got: ${JSON.stringify(finalDiags)}`,
    );
  });
});