import { randomUUID, createHash } from "node:crypto";
import { openSiteDatabase } from "./site-database";

export type DocLink = {
  slug: string; sourceSlug: string; category: string; title: string; searchText?: string;
  group: string; collection: string; description: string; draft: boolean; featured: boolean;
  revision: number;
};
export type Doc = DocLink & { content: string };
export type DocInput = Omit<Doc, "revision" | "searchText">;
export type DocumentExport = { format: "tabularium-documents-v1"; documents: Doc[] };
export const validSlug = /^[a-z0-9]+(?:-[a-z0-9]+)*(?:\/[a-z0-9]+(?:-[a-z0-9]+)*)*$/;

function database() {
  const db = openSiteDatabase();
  db.exec(`
    CREATE TABLE IF NOT EXISTS documents (
      id TEXT PRIMARY KEY, slug TEXT NOT NULL UNIQUE, source_slug TEXT NOT NULL UNIQUE,
      revision INTEGER NOT NULL, payload TEXT NOT NULL
    );
    CREATE TABLE IF NOT EXISTS document_aliases (
      alias TEXT PRIMARY KEY, document_id TEXT NOT NULL REFERENCES documents(id)
    );
    CREATE TABLE IF NOT EXISTS document_revisions (
      document_id TEXT NOT NULL REFERENCES documents(id), revision INTEGER NOT NULL,
      payload TEXT NOT NULL, created_at TEXT NOT NULL, PRIMARY KEY(document_id, revision)
    );
    CREATE TABLE IF NOT EXISTS document_imports (
      digest TEXT PRIMARY KEY, document_count INTEGER NOT NULL, created_at TEXT NOT NULL
    );
  `);
  return db;
}

export function validateDocument(input: DocInput): void {
  if (!input || typeof input !== "object") throw Error("Invalid document");
  for (const key of ["slug", "sourceSlug"] as const)
    if (typeof input[key] !== "string" || !validSlug.test(input[key])) throw Error(`Invalid ${key}`);
  if (input.slug.split("/").some((part) => /^\d+-/.test(part))) throw Error("Use a semantic public slug");
  for (const key of ["title", "category", "collection", "group"] as const)
    if (typeof input[key] !== "string" || !input[key].trim()) throw Error(`Missing ${key}`);
  if (typeof input.content !== "string" || typeof input.description !== "string" ||
      typeof input.draft !== "boolean" || typeof input.featured !== "boolean") throw Error("Invalid document fields");
  if (input.content.length > 2_000_000) throw Error("Document exceeds content limit");
  const images = [
    ...input.content.matchAll(/!\[[^\]]*\]\(<?([^\s)>]+)/g),
    ...input.content.matchAll(/<img\b[^>]*\bsrc=["']([^"']+)/gi),
  ];
  if (images.some(([, source]) => /\.(?:png|jpe?g|tiff?|bmp)(?:[?#]|$)/i.test(source)))
    throw Error("Use compressed WebP images instead of original rasters");
}

function write(db: ReturnType<typeof database>, input: DocInput, expectedRevision: number): Doc {
  validateDocument(input);
  const existing = db.prepare("SELECT id, revision FROM documents WHERE source_slug=?")
    .get(input.sourceSlug) as { id: string; revision: number } | undefined;
  if ((existing?.revision ?? 0) !== expectedRevision) throw Error("Document revision conflict");
  const id = existing?.id ?? randomUUID();
  const doc: Doc = { slug: input.slug, sourceSlug: input.sourceSlug, category: input.category,
    title: input.title, group: input.group, collection: input.collection, description: input.description,
    draft: input.draft, featured: input.featured, content: input.content, revision: expectedRevision + 1 };
  const payload = JSON.stringify(doc);
  // Aliases remain reserved after renaming; collision rolls back the whole write.
  db.prepare(`INSERT INTO documents VALUES (?,?,?,?,?) ON CONFLICT(id) DO UPDATE SET
    slug=excluded.slug, revision=excluded.revision, payload=excluded.payload`)
    .run(id, doc.slug, doc.sourceSlug, doc.revision, payload);
  for (const alias of new Set([doc.slug, doc.sourceSlug])) {
    const prior = db.prepare("SELECT document_id FROM document_aliases WHERE alias=?")
      .get(alias) as { document_id: string } | undefined;
    if (prior && prior.document_id !== id) throw Error(`Document alias collision: ${alias}`);
    db.prepare("INSERT OR IGNORE INTO document_aliases VALUES (?,?)").run(alias, id);
  }
  db.prepare("INSERT INTO document_revisions VALUES (?,?,?,?)")
    .run(id, doc.revision, payload, new Date().toISOString());
  return doc;
}

export function saveDocument(input: DocInput, expectedRevision: number): Doc {
  if (!Number.isSafeInteger(expectedRevision) || expectedRevision < 0) throw Error("Provide expected revision");
  const db = database();
  try {
    db.exec("BEGIN IMMEDIATE");
    try { const doc = write(db, input, expectedRevision); db.exec("COMMIT"); return doc; }
    catch (error) { db.exec("ROLLBACK"); throw error; }
  } finally { db.close(); }
}

export function readDocument(slug: string): Doc | null {
  if (!validSlug.test(slug)) return null;
  const db = database();
  try {
    const row = db.prepare(`SELECT d.payload FROM documents d JOIN document_aliases a
      ON a.document_id=d.id WHERE a.alias=?`).get(slug) as { payload: string } | undefined;
    return row ? JSON.parse(row.payload) as Doc : null;
  } finally { db.close(); }
}

export function allDocuments(): Doc[] {
  const db = database();
  try {
    return (db.prepare("SELECT payload FROM documents ORDER BY source_slug").all() as { payload: string }[])
      .map((row) => JSON.parse(row.payload) as Doc);
  } finally { db.close(); }
}

export async function readDoc(slug: string): Promise<Doc> {
  const doc = readDocument(slug);
  if (!doc) throw Error("Document not found");
  return doc;
}

export async function listDocs(): Promise<DocLink[]> {
  return allDocuments().map(({ content: _, ...doc }) => { void _; return doc; });
}

// Explicit, atomic bootstrap only. Runtime reads never import repository data.
export function importDocuments(bundle: DocumentExport, onlyIfEmpty = false): number {
  if (bundle?.format !== "tabularium-documents-v1" || !Array.isArray(bundle.documents) || !bundle.documents.length)
    throw Error("Invalid or empty document export");
  bundle.documents.forEach(validateDocument);
  const digest = createHash("sha256").update(JSON.stringify(bundle)).digest("hex");
  const db = database();
  try {
    db.exec("BEGIN IMMEDIATE");
    try {
      const imported = db.prepare("SELECT digest FROM document_imports WHERE digest=?").get(digest);
      if (imported) { db.exec("COMMIT"); return 0; }
      const count = (db.prepare("SELECT COUNT(*) AS n FROM documents").get() as { n: number }).n;
      if (count) {
        if (!onlyIfEmpty) throw Error("Bootstrap requires an empty document database");
        db.exec("COMMIT"); return 0;
      }
      for (const doc of bundle.documents) write(db, doc, 0);
      db.prepare("INSERT INTO document_imports VALUES (?,?,?)").run(digest, bundle.documents.length, new Date().toISOString());
      db.exec("COMMIT"); return bundle.documents.length;
    } catch (error) { db.exec("ROLLBACK"); throw error; }
  } finally { db.close(); }
}

export function documentHistory(sourceSlug: string): Doc[] {
  const db = database();
  try {
    return (db.prepare(`SELECT r.payload FROM document_revisions r JOIN documents d
      ON r.document_id=d.id WHERE d.source_slug=? ORDER BY r.revision`).all(sourceSlug) as { payload: string }[])
      .map((row) => JSON.parse(row.payload) as Doc);
  } finally { db.close(); }
}