import type { AuthUser, Feature, RequestContext, RouteHandler, ServerContext } from "@stc/contracts";
import type { LoadedCourse } from "@stc/course-format";
import { aclRepo } from "@stc/db";
import { serveMedia } from "./media";

type Method = "GET" | "POST" | "PUT" | "PATCH" | "DELETE";
export type Routes = Record<string, Partial<Record<Method, (req: Request) => Response | Promise<Response>>>>;

export function canView(user: AuthUser | null, course: LoadedCourse, acl: { principal_type: string; principal_id: string }[], isAuthor = false): boolean {
  const vis = course.manifest?.visibility ?? "restricted";
  if (vis === "public") return true;
  if (!user) return false;
  if (vis === "signed-in") return true;
  if (user.roles.includes("owner") || isAuthor) return true;
  return acl.some((a) => (a.principal_type === "user" && a.principal_id === user.id) || (a.principal_type === "group" && user.groups.includes(a.principal_id)));
}

const json = (body: unknown, status = 200) => Response.json(body, { status });

export function createApp(ctx: ServerContext, features: Feature[]): { routes: Routes; fetch(req: Request): Promise<Response> } {
  const acl = aclRepo(ctx.db);

  const core: Feature = {
    name: "core",
    routes: {
      "/api/health": { GET: () => json({ ok: true, courses: ctx.courses.list().length, db: ctx.db.dialect }) },
      "/api/media/:courseId/*": {
        GET: async (req, rc) => {
          // Parse from the pathname so we do not depend on how the server fills params for "*".
          const m = /^\/api\/media\/([^/]+)\/(.*)$/s.exec(rc.url.pathname);
          if (!m) return new Response("Not found", { status: 404 });
          let courseId: string, rel: string;
          try { courseId = decodeURIComponent(m[1]!); rel = decodeURIComponent(m[2]!); } catch { return new Response("Not found", { status: 404 }); }
          const course = ctx.courses.get(courseId);
          if (!course) return new Response("Not found", { status: 404 });
          const visible = canView(rc.user, course, await acl.listForCourse(course.id), rc.user ? await acl.isAuthor(course.id, rc.user.id) : false);
          if (!visible) return new Response("Not found", { status: 404 });
          const abs = ctx.courses.resolvePath(course.id, rel);
          if (!abs) return new Response("Not found", { status: 404 });
          return serveMedia(req, abs, { download: rc.url.searchParams.has("download") });
        },
      },
    },
  };

  const wrap = (h: RouteHandler) => async (req: Request & { params?: Record<string, string> }): Promise<Response> => {
    const url = new URL(req.url);
    const rc: RequestContext = { user: await ctx.auth.userFromRequest(req), params: req.params ?? {}, url };
    return h(req, rc);
  };

  const routes: Routes = {};
  for (const f of [core, ...features]) {
    for (const [path, methods] of Object.entries(f.routes)) {
      const slot = (routes[path] ??= {});
      for (const [m, h] of Object.entries(methods) as [Method, RouteHandler][]) {
        if (slot[m]) throw new Error(`Duplicate route ${m} ${path} (feature "${f.name}")`);
        slot[m] = wrap(h);
      }
    }
  }

  // Matcher for fetch(): same semantics as Bun routes (":name" segment, trailing "*" wildcard).
  const compiled = Object.entries(routes).map(([path, methods]) => {
    const parts = path.split("/");
    return { parts, methods };
  });
  const match = (pathname: string) => {
    const segs = pathname.split("/");
    for (const { parts, methods } of compiled) {
      const params: Record<string, string> = {};
      let ok = true;
      for (let i = 0; i < parts.length && ok; i++) {
        const p = parts[i]!;
        if (p === "*") { params["*"] = segs.slice(i).join("/"); if (i >= segs.length) params["*"] = ""; return { methods, params }; }
        if (segs[i] === undefined) ok = false;
        else if (p.startsWith(":")) params[p.slice(1)] = decodeURIComponent(segs[i]!);
        else if (p !== segs[i]) ok = false;
      }
      if (ok && parts.length === segs.length) return { methods, params };
    }
    return null;
  };

  return {
    routes,
    async fetch(req) {
      const url = new URL(req.url);
      let m: ReturnType<typeof match>;
      try { m = match(url.pathname); } catch { return new Response("Bad request", { status: 400 }); }
      if (!m) return new Response("Not found", { status: 404 });
      const h = m.methods[req.method as Method];
      if (!h) return new Response("Method not allowed", { status: 405 });
      const r = req as Request & { params?: Record<string, string> };
      r.params = m.params;
      return h(r);
    },
  };
}