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 class DocumentValidationError extends Error {}
export class DocumentConflictError extends Error {}
export type DocumentReceipt = Pick<Doc, "slug" | "sourceSlug" | "revision">;
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_write_requests (
      namespace TEXT NOT NULL, request_id TEXT NOT NULL, digest TEXT NOT NULL,
      response TEXT NOT NULL, PRIMARY KEY(namespace, request_id)
    );
    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 new DocumentValidationError("Invalid document");
  for (const key of ["slug", "sourceSlug"] as const)
    if (typeof input[key] !== "string" || !validSlug.test(input[key])) throw new DocumentValidationError(`Invalid ${key}`);
  if (input.slug.split("/").some((part) => /^\d+-/.test(part))) throw new DocumentValidationError("Use a semantic public slug");
  for (const key of ["title", "category", "collection", "group"] as const)
    if (typeof input[key] !== "string" || !input[key].trim()) throw new DocumentValidationError(`Missing ${key}`);
  if (typeof input.content !== "string" || typeof input.description !== "string" ||
      typeof input.draft !== "boolean" || typeof input.featured !== "boolean") throw new DocumentValidationError("Invalid document fields");
  if (input.content.length > 2_000_000) throw new DocumentValidationError("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 new DocumentValidationError("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 new DocumentConflictError("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);
  // Reserve both canonical and historical names before updating any rows.
  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 new DocumentConflictError(`Document alias collision: ${alias}`);
  }
  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]))
    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 new DocumentValidationError("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(); }
}

// API batches commit entirely or not at all; receipts make lost-response retries safe.
export function saveDocumentBatch(documents: Doc[], request?: { namespace: string; id: string }) {
  if (!Array.isArray(documents) || !documents.length || documents.length > 100)
    throw new DocumentValidationError("Provide 1 to 100 documents");
  const seen = new Set<string>();
  for (const doc of documents) {
    validateDocument(doc);
    if (!Number.isSafeInteger(doc.revision) || doc.revision < 0)
      throw new DocumentValidationError("Provide expected revision");
    if (seen.has(doc.sourceSlug)) throw new DocumentValidationError("Duplicate sourceSlug in batch");
    seen.add(doc.sourceSlug);
  }
  if (request && (!request.namespace || !/^[A-Za-z0-9._:-]{1,128}$/.test(request.id)))
    throw new DocumentValidationError("Invalid Idempotency-Key");
  const digest = createHash("sha256").update(JSON.stringify(documents)).digest("hex");
  const db = database();
  try {
    db.exec("BEGIN IMMEDIATE");
    try {
      if (request) {
        const prior = db.prepare("SELECT digest,response FROM document_write_requests WHERE namespace=? AND request_id=?")
          .get(request.namespace, request.id) as { digest: string; response: string } | undefined;
        if (prior) {
          if (prior.digest !== digest) throw new DocumentConflictError("Idempotency-Key was used with different content");
          db.exec("COMMIT");
          return { documents: JSON.parse(prior.response) as DocumentReceipt[], replayed: true };
        }
      }
      const receipts = documents.map((input) => {
        const { slug, sourceSlug, revision } = write(db, input, input.revision);
        return { slug, sourceSlug, revision };
      });
      if (request) db.prepare("INSERT INTO document_write_requests VALUES (?,?,?,?)")
        .run(request.namespace, request.id, digest, JSON.stringify(receipts));
      db.exec("COMMIT");
      return { documents: receipts, replayed: false };
    } catch (error) { db.exec("ROLLBACK"); throw error; }
  } finally { db.close(); }
}

export function documentPage(limit = 50, offset = 0) {
  if (!Number.isSafeInteger(limit) || limit < 1 || limit > 100 || !Number.isSafeInteger(offset) || offset < 0)
    throw new DocumentValidationError("Invalid pagination");
  const db = database();
  try {
    db.exec("BEGIN");
    const total = (db.prepare("SELECT COUNT(*) AS n FROM documents").get() as { n: number }).n;
    const documents = (db.prepare("SELECT json_remove(payload,'$.content') AS payload FROM documents ORDER BY source_slug LIMIT ? OFFSET ?")
      .all(limit, offset) as { payload: string }[]).map((row) => JSON.parse(row.payload) as DocLink);
    db.exec("COMMIT");
    return { documents, total, limit, offset, nextOffset: offset + documents.length < total ? offset + documents.length : null };
  } finally { db.close(); }
}

export function documentHistoryPage(sourceSlug: string, limit = 50, offset = 0) {
  if (!Number.isSafeInteger(limit) || limit < 1 || limit > 100 || !Number.isSafeInteger(offset) || offset < 0)
    throw new DocumentValidationError("Invalid pagination");
  const db = database();
  try {
    db.exec("BEGIN");
    const total = (db.prepare(`SELECT COUNT(*) AS n FROM document_revisions r JOIN documents d
      ON d.id=r.document_id WHERE d.source_slug=?`).get(sourceSlug) as { n: number }).n;
    const revisions = (db.prepare(`SELECT json_remove(r.payload,'$.content') AS payload, r.created_at AS createdAt
      FROM document_revisions r JOIN documents d ON d.id=r.document_id
      WHERE d.source_slug=? ORDER BY r.revision DESC LIMIT ? OFFSET ?`)
      .all(sourceSlug, limit, offset) as { payload: string; createdAt: string }[])
      .map((row) => ({ ...JSON.parse(row.payload) as DocLink, createdAt: row.createdAt }));
    db.exec("COMMIT");
    return { revisions, total, limit, offset, nextOffset: offset + revisions.length < total ? offset + revisions.length : null };
  } finally { db.close(); }
}

export function documentRevision(sourceSlug: string, revision: number): Doc | null {
  if (!Number.isSafeInteger(revision) || revision < 1) throw new DocumentValidationError("Invalid revision");
  const db = database();
  try {
    const row = db.prepare(`SELECT r.payload FROM document_revisions r JOIN documents d
      ON d.id=r.document_id WHERE d.source_slug=? AND r.revision=?`).get(sourceSlug, revision) as { payload: string } | undefined;
    return row ? JSON.parse(row.payload) as Doc : null;
  } finally { db.close(); }
}