/**
 * CaseLibrary — public-facing case file library.
 *
 * The Disclosure Bureau's outward face. Reads /data/ufo/case/reports/*.md,
 * parses the YAML frontmatter for the case topic, extracts the opening
 * paragraph as a preview hook, and renders a magazine-style grid. No
 * mention of "detectives" anywhere — the AI pipeline is plumbing, not the
 * brand.
 *
 * Server component. Single fs.readdir + N small readFile calls (one per
 * report). Cheap; reports are O(10).
 */
import Link from "next/link";
import { readdir, readFile, stat } from "node:fs/promises";
import path from "node:path";

interface CaseFile {
  slug: string;
  topic: string;
  topic_pt_br: string | null;
  /** Opening paragraph of the body, trimmed and language-picked. */
  opening: string;
  mtimeMs: number;
}

const CASE_ROOT = process.env.CASE_ROOT || "/data/ufo/case";

function parseFrontmatter(md: string): { fm: Record<string, string>; body: string } {
  const m = md.match(/^---\n([\s\S]+?)\n---\n([\s\S]*)$/);
  if (!m) return { fm: {}, body: md };
  const fm: Record<string, string> = {};
  for (const line of m[1].split("\n")) {
    const kv = line.match(/^([a-z_]+):\s*(.+)$/);
    if (!kv) continue;
    let v = kv[2].trim();
    if (v.startsWith('"') && v.endsWith('"')) v = v.slice(1, -1);
    fm[kv[1]] = v;
  }
  return { fm, body: m[2] };
}

/**
 * Pull the first prose paragraph that looks like a narrative opening.
 * Skips H1, H2, blockquotes, table separators, and the "(EN)" / "(PT-BR)"
 * sub-headers. Prefers PT-BR when locale is pt-br.
 */
function pickOpening(body: string, locale: "pt-br" | "en"): string {
  const lines = body.split("\n");
  const blocks: string[] = [];
  let cur: string[] = [];
  for (const raw of lines) {
    const line = raw.trim();
    if (line.length === 0) {
      if (cur.length > 0) { blocks.push(cur.join(" ")); cur = []; }
      continue;
    }
    if (line.startsWith("#") || line.startsWith(">") || line.startsWith("|")
        || line.startsWith("---") || line.startsWith("```")) {
      if (cur.length > 0) { blocks.push(cur.join(" ")); cur = []; }
      continue;
    }
    cur.push(line);
  }
  if (cur.length > 0) blocks.push(cur.join(" "));

  // For PT-BR locale, prefer a block right after a "(PT-BR)" heading.
  // For EN locale, prefer the first prose block (the EN sub-section usually
  // appears first under each act).
  if (locale === "pt-br") {
    const ptIdx = body.indexOf("(PT-BR)");
    if (ptIdx >= 0) {
      const after = body.slice(ptIdx);
      const m = after.match(/\n\n([^\n#>|`-][^\n]+(?:\n[^\n#>|`-][^\n]+)*)/);
      if (m) return m[1].replace(/\s+/g, " ").trim().slice(0, 400);
    }
  }
  return (blocks[0] ?? "").replace(/\s+/g, " ").trim().slice(0, 400);
}

async function loadCases(locale: "pt-br" | "en"): Promise<CaseFile[]> {
  const dir = path.join(CASE_ROOT, "reports");
  let files: string[];
  try {
    files = await readdir(dir);
  } catch {
    return [];
  }
  const items: CaseFile[] = [];
  for (const f of files) {
    if (!f.endsWith(".md")) continue;
    try {
      const full = path.join(dir, f);
      const md = await readFile(full, "utf-8");
      const st = await stat(full);
      const { fm, body } = parseFrontmatter(md);
      items.push({
        slug: f.replace(/\.md$/, ""),
        topic: fm.topic ?? f,
        topic_pt_br: fm.topic_pt_br ?? null,
        opening: pickOpening(body, locale),
        mtimeMs: st.mtimeMs,
      });
    } catch { /* skip broken file */ }
  }
  return items.sort((a, b) => b.mtimeMs - a.mtimeMs);
}

export async function CaseLibrary({
  locale,
  limit,
  layout = "hero+grid",
}: {
  locale: "pt-br" | "en";
  limit?: number;
  /** "hero+grid" = first case big + rest small (homepage); "grid" = all equal (/bureau) */
  layout?: "hero+grid" | "grid";
}) {
  const allCases = await loadCases(locale);
  const cases = typeof limit === "number" ? allCases.slice(0, limit) : allCases;
  if (cases.length === 0) {
    return (
      <section className="my-8 rounded-lg border border-dashed border-[rgba(224,192,128,0.18)] bg-[#0d1220] p-6 text-center">
        <p className="text-[12px] font-mono text-[#9aa6b8]">
          {locale === "pt-br"
            ? "Nenhum caso narrado ainda. As primeiras histórias chegam em breve."
            : "No case files yet. The first stories arrive soon."}
        </p>
      </section>
    );
  }

  const [hero, ...rest] = cases;

  return (
    <section className="my-8">
      <div className="text-[10px] font-mono uppercase tracking-[0.18em] text-[#5a6678] mb-3">
        {locale === "pt-br" ? "// Casos em destaque" : "// Featured case files"}
      </div>

      {layout === "hero+grid" ? (
        <>
          <CaseHero c={hero} locale={locale} />
          {rest.length > 0 && (
            <div className="grid md:grid-cols-2 gap-4 mt-4">
              {rest.map((c) => <CaseCard key={c.slug} c={c} locale={locale} />)}
            </div>
          )}
        </>
      ) : (
        <div className="grid md:grid-cols-2 gap-4">
          {cases.map((c) => <CaseCard key={c.slug} c={c} locale={locale} />)}
        </div>
      )}
    </section>
  );
}

function CaseHero({ c, locale }: { c: CaseFile; locale: "pt-br" | "en" }) {
  const title = locale === "pt-br" ? (c.topic_pt_br ?? c.topic) : c.topic;
  return (
    <Link
      href={`/c/${c.slug}`}
      className="block rounded-xl border border-[rgba(224,192,128,0.30)] bg-gradient-to-br from-[rgba(224,192,128,0.07)] via-[#0d1220] to-transparent p-6 md:p-8 hover:border-[#e0c080] transition-colors group"
    >
      <div className="text-[10px] font-mono uppercase tracking-[0.18em] text-[#e0c080] mb-2">
        {locale === "pt-br" ? "Arquivo desclassificado" : "Declassified case file"}
      </div>
      <h2 className="font-mono text-2xl md:text-3xl text-[#e7ecf3] leading-tight mb-3 group-hover:text-[#e0c080] transition-colors">
        {title}
      </h2>
      {c.opening && (
        <p className="text-[15px] text-[#cbd2dd] leading-relaxed line-clamp-5">
          {c.opening}
        </p>
      )}
      <div className="mt-4 text-[12px] font-mono text-[#e0c080]">
        {locale === "pt-br" ? "ler o caso completo →" : "read the full case file →"}
      </div>
    </Link>
  );
}

function CaseCard({ c, locale }: { c: CaseFile; locale: "pt-br" | "en" }) {
  const title = locale === "pt-br" ? (c.topic_pt_br ?? c.topic) : c.topic;
  return (
    <Link
      href={`/c/${c.slug}`}
      className="block rounded-lg border border-[rgba(224,192,128,0.18)] bg-[#0d1220] p-4 hover:border-[#e0c080] transition-colors group"
    >
      <h3 className="font-mono text-lg text-[#e7ecf3] leading-tight mb-2 group-hover:text-[#e0c080] transition-colors">
        {title}
      </h3>
      {c.opening && (
        <p className="text-[13px] text-[#9aa6b8] leading-relaxed line-clamp-3">
          {c.opening}
        </p>
      )}
      <div className="mt-3 text-[11px] font-mono text-[#5a6678]">
        /c/{c.slug}
      </div>
    </Link>
  );
}