import { Controller, Get, Param, Res } from "@nestjs/common";
import * as fs from "node:fs";
import * as path from "node:path";
import { createRequire } from "node:module";
import type { Response } from "express";
import { parse as parseYaml } from "yaml";

const req = createRequire(process.cwd());

/**
 * Public API documentation surface (TASK-0127):
 *
 *   GET /api/v1/docs               — interactive swagger-ui (the OFFICIAL
 *                                    swagger-ui-dist bundle served from
 *                                    node_modules — no CDN, works offline).
 *                                    The OpenAPI spec is parsed server-side
 *                                    (YAML → JSON) and inlined into the page.
 *   GET /api/v1/docs/openapi.yaml  — the raw spec (the "Download YAML" link).
 *   GET /api/v1/docs/assets/:file  — the vendored swagger-ui static files
 *                                    (allow-listed: css/js/favicon only).
 *
 * The CANONICAL spec file is `docs/api/openapi.yaml` (hand-maintained; the
 * bidirectional contract test in `tests/integration/api-contract/` keeps it
 * honest — every spec path must have a live route and vice versa).
 *
 * The surface is PUBLIC by design (it serves documentation, not data — no
 * live API calls from the UI; see docs/security/security-architecture.md).
 * The swagger-ui bundle is loaded from node_modules at request time (the
 * API is a modular monolith without a build step — `createRequire` resolves
 * the package exactly as the runtime would).
 */

/**
 * Repo root (same pattern as database-ai.service.ts): `process.cwd()` first
 * (the API boots from the repo root in dev and the test harness), a
 * `__dirname` walk under the CJS compile, then a cwd walk-up (vitest cwd = a
 * subdir). Verified by the spec file's existence where possible.
 */
function repoRoot(): string {
  if (fs.existsSync(path.join(process.cwd(), "docs", "api", "openapi.yaml"))) return process.cwd();
  if (typeof __dirname !== "undefined") {
    // apps/api/src/modules/docs → repo root is four levels up.
    const up = path.resolve(__dirname, "..", "..", "..", "..");
    if (fs.existsSync(path.join(up, "docs", "api", "openapi.yaml"))) return up;
  }
  let dir = process.cwd();
  for (let i = 0; i < 6; i++) {
    const parent = path.dirname(dir);
    if (parent === dir) break;
    dir = parent;
    if (fs.existsSync(path.join(dir, "docs", "api", "openapi.yaml"))) return dir;
  }
  return process.cwd();
}

function specPath(): string {
  return path.join(repoRoot(), "docs", "api", "openapi.yaml");
}

/** swagger-ui-dist static files allowed at /docs/assets/ (no traversal). */
const ASSET_WHITELIST: Record<string, string> = {
  "swagger-ui.css": "text/css; charset=utf-8",
  "index.css": "text/css; charset=utf-8",
  "swagger-ui-bundle.js": "application/javascript; charset=utf-8",
  "swagger-ui-standalone-preset.js": "application/javascript; charset=utf-8",
  "swagger-initializer.js": "application/javascript; charset=utf-8",
  "favicon-16x16.png": "image/png",
  "favicon-32x32.png": "image/png"
};

let swaggerDistDir: string | null = null;
function distDir(): string {
  if (!swaggerDistDir) {
    const entry = req.resolve("swagger-ui-dist");
    swaggerDistDir = path.dirname(entry);
  }
  return swaggerDistDir;
}

function readSpecYaml(): string {
  return fs.readFileSync(specPath(), "utf8");
}

@Controller("docs")
export class DocsController {
  /** Interactive docs — swagger-ui with the inlined (parsed) spec. */
  @Get()
  index(@Res() res: Response): void {
    const specJson = JSON.stringify(parseYaml(readSpecYaml())).replace(/</g, "\\u003c");
    res.setHeader("Content-Type", "text/html; charset=utf-8");
    res.setHeader("Cache-Control", "no-cache");
    res.send(`<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8"/>
  <meta name="viewport" content="width=device-width, initial-scale=1"/>
  <title>AI Software Factory — API v1</title>
  <link rel="icon" type="image/png" href="/api/v1/docs/assets/favicon-32x32.png"/>
  <link rel="stylesheet" href="/api/v1/docs/assets/swagger-ui.css"/>
</head>
<body>
  <div id="app"></div>
  <script id="openapi-spec" type="application/json">${specJson}</script>
  <script src="/api/v1/docs/assets/swagger-ui-bundle.js"></script>
  <script src="/api/v1/docs/assets/swagger-ui-standalone-preset.js"></script>
  <script>
    (function () {
      var spec = JSON.parse(document.getElementById("openapi-spec").textContent);
      window.ui = SwaggerUIBundle({
        spec: spec,
        dom_id: "#app",
        deepLinking: true,
        presets: [SwaggerUIBundle.presets.apis, SwaggerUIStandalonePreset],
        layout: "StandaloneLayout",
        requestInterceptor: function (req) {
          // Docs demo: send NOTHING by default (the "Authorize" panel fills
          // in the Bearer token for interactive calls).
          return req;
        }
      });
    })();
  </script>
</body>
</html>`);
  }

  /** The raw OpenAPI spec (the download link in the UI). */
  @Get("openapi.yaml")
  spec(@Res() res: Response): void {
    res.setHeader("Content-Type", "application/yaml; charset=utf-8");
    res.setHeader("Cache-Control", "no-cache");
    res.send(readSpecYaml());
  }

  /** Vendored swagger-ui static assets (allow-listed by name). */
  @Get("assets/:file")
  asset(@Param("file") file: string, @Res() res: Response): void {
    const contentType = ASSET_WHITELIST[file];
    if (!contentType) {
      res.status(404).send("Not found");
      return;
    }
    const full = path.join(distDir(), file);
    if (!fs.existsSync(full)) {
      res.status(404).send("Not found");
      return;
    }
    res.setHeader("Content-Type", contentType);
    res.setHeader("Cache-Control", "public, max-age=86400");
    res.send(fs.readFileSync(full));
  }
}