import fs from "node:fs";
import path from "node:path";
import {
  DOCS,
  DOC_GROUP_ORDER,
  type DocEntry,
  type DocGroup,
} from "../../content/docs";

export type { DocEntry, DocGroup };
export { DOC_GROUP_ORDER };

// Build-time only. `output: "export"` means every one of these reads happens
// during `next build`; nothing here runs per request. Mirrors the
// readFileSync-from-cwd approach in export/app/changelog/page.tsx.
//
// Every path op on a cwd-derived path opts out of Turbopack's asset tracing
// (plans/FACTS.md, "A path joined from `process.cwd()` …").
function docPath(entry: DocEntry): string {
  return path.join(/* turbopackIgnore: true */ process.cwd(), "content", "docs", entry.file);
}

// The manifest entries whose file actually exists.
//
// This filter is the whole safety property of the docs subsystem: it feeds BOTH
// `generateStaticParams()` (with `dynamicParams = false`) AND the /docs/ index,
// so a manifest entry with a missing file 404s quietly instead of crashing the
// build, and the index can never link to a page that isn't there. Those two
// facts have to come from the same call, or they will disagree.
export function listDocs(): DocEntry[] {
  return DOCS.filter((entry) => {
    try {
      return fs.statSync(/* turbopackIgnore: true */ docPath(entry)).isFile();
    } catch {
      return false;
    }
  });
}

export function findDoc(slug: string): DocEntry | null {
  return listDocs().find((d) => d.slug === slug) ?? null;
}

// Read a doc's Markdown, minus its leading `# Title` line. The file keeps that
// heading so it stands alone as a document; the page renders its own <h1> from
// the manifest, and two titles in a row reads as a mistake.
export function readDoc(entry: DocEntry): string {
  const raw = fs.readFileSync(/* turbopackIgnore: true */ docPath(entry), "utf8");
  return raw.replace(/^?\s*#[^\n#][^\n]*\n+/, "");
}

// The index, grouped and ordered by the manifest. Groups with no surviving
// entries are dropped rather than rendered empty.
export function groupedDocs(): { label: string; docs: DocEntry[] }[] {
  const docs = listDocs();
  return DOC_GROUP_ORDER.map((g) => ({
    label: g.label,
    docs: docs.filter((d) => d.group === g.id),
  })).filter((g) => g.docs.length > 0);
}