/**
 * SSSF visualizer server — JSON API over one or more repos' sssf.db, plus the
 * built UI when ./dist exists. Reads are read-only; the single write is
 * POST /api/sessions/:adw_id/archive, which sets one review flag on a row.
 *
 * There is no ingest endpoint and no websocket. The data path is
 * agents → sqlite → web ui, and the UI gets there by polling.
 *
 * Single repo (legacy):
 *   bun run server/index.ts
 *   bun run server/index.ts --db /path/to/repo/adws/adw_data/sssf.db
 *   SSSF_DB=/path/to/sssf.db PORT=4600 bun run server/index.ts
 *
 * Multi repo:
 *   SSSF_REPOS=/path/to/repos.json PORT=4600 bun run server/index.ts
 *
 * In multi-repo mode every route is prefixed with the repo slug:
 *   /api/repos
 *   /api/:repo/sessions
 *   /api/:repo/sessions/:adw_id
 *   ...
 * The legacy unprefixed routes (/api/sessions, ...) are kept and resolve to
 * the first repo, so a single-repo deployment and the SPA's default view
 * keep working unchanged.
 */
import { existsSync, statSync } from "node:fs";
import { join, resolve, sep } from "node:path";
import { buildRepos, type RepoRuntime } from "./repos.ts";
import type { AgentPrompts, ApiError, HealthResponse } from "../shared/types.ts";
import type { Server } from "bun";
const PORT = Number(process.env.PORT ?? 4600);
const DIST_DIR = resolve(import.meta.dir, "..", "dist");

function json(data: unknown, status = 200): Response {
  return new Response(JSON.stringify(data), {
    status,
    headers: {
      "content-type": "application/json; charset=utf-8",
      "cache-control": "no-store",
    },
  });
}

function notFound(message: string): Response {
  return json({ error: message } satisfies ApiError, 404);
}

/** Guard every handler so a malformed query can't take the server down mid-run. */
function safely(
  handler: (req: Request) => Response | Promise<Response>,
): (req: Request) => Promise<Response> {
  return async (req) => {
    try {
      return await handler(req);
    } catch (error) {
      console.error(`[sssf] ${req.method} ${new URL(req.url).pathname}:`, error);
      return json({ error: (error as Error).message } satisfies ApiError, 500);
    }
  };
}

/**
 * adw_ids and agent names are path segments on disk, so anything that isn't a
 * plain identifier is rejected outright rather than sanitized into something
 * that might still escape the sessions directory.
 */
const SAFE_SEGMENT = /^[A-Za-z0-9._-]+$/;

function isSafeSegment(value: string): boolean {
  return SAFE_SEGMENT.test(value) && value !== "." && value !== "..";
}

function param(req: Request, key: string): string {
  return decodeURIComponent(
    (req as Request & { params: Record<string, string> }).params[key] ?? "",
  );
}

function intQuery(req: Request, key: string, fallback: number): number {
  const raw = new URL(req.url).searchParams.get(key);
  if (raw === null || raw.trim() === "") return fallback;
  const parsed = Number.parseInt(raw, 10);
  return Number.isFinite(parsed) ? parsed : fallback;
}

/** Serve the built SPA if it has been built; otherwise point at the dev server. */
async function serveStatic(req: Request): Promise<Response> {
  const { pathname } = new URL(req.url);

  if (!existsSync(DIST_DIR)) {
    return new Response(
      `SSSF visualizer API is running on :${PORT}.\n\n` +
        `No ./dist build found. Run "bun run dev" for the Vite dev server ` +
        `(it proxies /api here), or "bun run build" to serve the UI from this process.\n`,
      { status: 200, headers: { "content-type": "text/plain; charset=utf-8" } },
    );
  }

  // Reject traversal before touching the filesystem.
  const candidate = resolve(join(DIST_DIR, pathname));
  if (candidate === DIST_DIR || candidate.startsWith(DIST_DIR + "/")) {
    if (existsSync(candidate) && statSync(candidate).isFile()) {
      return new Response(Bun.file(candidate));
    }
  }

  // SPA fallback: breadcrumb routes are client-side.
  const indexHtml = join(DIST_DIR, "index.html");
  if (existsSync(indexHtml)) {
    return new Response(Bun.file(indexHtml), {
      headers: { "content-type": "text/html; charset=utf-8" },
    });
  }
  return notFound("not found");
}

/** Build the route table for one repo, mounted at /api/:repo and /api (default). */
function repoRoutes(repo: RepoRuntime, prefix: string) {
  const db = repo.db;
  const p = (path: string) => `${prefix}${path}`;
  return {
    [p("/health")]: safely(
      () =>
        json({
          ok: true,
          repo: repo.slug,
          db: db.path,
          journal_mode: db.journalMode,
          sessions: db.sessionCount(),
        } satisfies HealthResponse),
    ),

    [p("/sessions")]: safely((req) => json(db.sessions(intQuery(req, "limit", 200)))),

    [p("/sessions/:adw_id")]: safely((req) => {
      const detail = db.sessionDetail(param(req, "adw_id"));
      return detail ? json(detail) : notFound(`no session ${param(req, "adw_id")}`);
    }),

    // The one write. Archiving is review triage — it belongs to the reader, not
    // to the run — so it never touches anything a tracer wrote.
    [p("/sessions/:adw_id/archive")]: {
      POST: safely(async (req) => {
        const adwId = param(req, "adw_id");
        if (!isSafeSegment(adwId)) {
          return json({ error: "invalid adw_id" } satisfies ApiError, 400);
        }
        const body = (await req.json().catch(() => ({}))) as { archived?: unknown };
        const archived = body.archived === undefined ? true : Boolean(body.archived);
        return db.setArchived(adwId, archived)
          ? json({ adw_id: adwId, archived })
          : notFound(`no session ${adwId}`);
      }),
    },

    [p("/sessions/:adw_id/events")]: safely((req) =>
      json(
        db.events(
          param(req, "adw_id"),
          intQuery(req, "after", 0),
          intQuery(req, "limit", 500),
        ),
      ),
    ),

    [p("/sessions/:adw_id/envelopes")]: safely((req) =>
      json(db.envelopes(param(req, "adw_id"))),
    ),

    [p("/sessions/:adw_id/gates")]: safely((req) => json(db.gates(param(req, "adw_id")))),

    // The exact prompts an agent was sent, read from the session dir. Files are
    // the raw record; the db has no copy of them.
    [p("/sessions/:adw_id/agents/:agent/prompts")]: safely(async (req) => {
      const adwId = param(req, "adw_id");
      const agent = param(req, "agent");
      if (!isSafeSegment(adwId) || !isSafeSegment(agent)) {
        return json({ error: "invalid adw_id or agent" } satisfies ApiError, 400);
      }
      if (!db.session(adwId)) return notFound(`no session ${adwId}`);

      const dir = resolve(db.sessionsDir, adwId, agent, "prompts");
      // Defense in depth: the segment check already forbids traversal.
      if (dir !== db.sessionsDir && !dir.startsWith(db.sessionsDir + sep)) {
        return json({ error: "invalid path" } satisfies ApiError, 400);
      }

      // A prompt file is absent whenever the agent never ran in this session —
      // a normal state, so it reads as null rather than an error.
      const read = async (name: string): Promise<string | null> => {
        const file = Bun.file(join(dir, `${name}.md`));
        return (await file.exists()) ? await file.text() : null;
      };
      return json({
        system: await read("system"),
        user: await read("user"),
      } satisfies AgentPrompts);
    }),
  };
}

// The registry is mutable: POST /api/reload re-reads repos.json and swaps the
// route table in place (Bun's server.reload), so new repos appear without a
// process restart. `server` is assigned below; the reload handler only runs on
// a request, by which point it is set.
let repos: RepoRuntime[] = (await buildRepos()).repos;
let server: Server<undefined>;

/** Build the route table for the current registry. */
function buildRoutes(repos: RepoRuntime[]): Record<string, unknown> {
  const routes: Record<string, unknown> = {
    "/api/repos": safely(() =>
      json(repos.map((r) => ({ slug: r.slug, name: r.name, db: r.db.path }))),
    ),
    // Re-read repos.json and swap the registry + routes in place. The UI calls
    // this after a repo is added/removed, so it shows up without a restart.
    "/api/reload": {
      POST: safely(async () => {
        const next = (await buildRepos()).repos;
        repos = next;
        server.reload({ routes: buildRoutes(next) as never });
        return json({
          ok: true,
          repos: next.map((r) => ({ slug: r.slug, name: r.name, db: r.db.path })),
        });
      }),
    },
  };
  for (const repo of repos) {
    Object.assign(routes, repoRoutes(repo, `/api/${repo.slug}`));
  }
  Object.assign(routes, repoRoutes(repos[0], "/api"));
  return routes;
}

const routes = buildRoutes(repos);

server = Bun.serve({
  port: PORT,
  routes: routes as never,
  fetch(req) {
    const { pathname } = new URL(req.url);
    if (pathname.startsWith("/api/")) return notFound(`no route ${pathname}`);
    return serveStatic(req);
  },
});

console.log(`[sssf] visualizer api  http://localhost:${server.port}`);
for (const repo of repos) {
  console.log(`[sssf] repo ${repo.slug}  ${repo.db.path}  [journal_mode=${repo.db.journalMode}]`);
}
console.log(
  existsSync(DIST_DIR)
    ? `[sssf] serving ui from  ${DIST_DIR}`
    : `[sssf] no ./dist — use "bun run dev" for the Vite dev server on :4601`,
);

process.on("SIGINT", () => {
  server.stop();
  process.exit(0);
});