import { createPrivateKey, type KeyObject, X509Certificate } from 'node:crypto';
import * as forge from 'node-forge';
import { buildChains } from './cert-chain';
import { csrItemFromDer } from './cert-csr';
import { exportKey, type KeyExportFormat } from './cert-keys';
import { certItemFromDer } from './cert-model';
import { safeBaseName } from './cert-names';
import { writePkcs12 } from './cert-pkcs12';
import { buildTemplate, isTemplateId } from './cert-templates';
import {
  type BuildContent,
  type BuildFile,
  type BuildInput,
  type BuildResult,
  type CertItem,
  type CsrItem,
  certError,
} from './cert-types';

/**
 * Ausgabe-Bausteine des Zertifikat-Managers (quick-261009-ikt, D-19).
 * Jeder Inhalt in jedem Format laeuft durch die eine Funktion buildOutput. Die Reihenfolge baut die API
 * immer selbst aus den gesendeten Zertifikaten (buildChains); eine vom Browser mitgeschickte Reihenfolge
 * wird nie uebernommen. Schluessel und Passwoerter werden nur verarbeitet, nie gespeichert oder
 * protokolliert, und erscheinen in keiner Fehlermeldung.
 */

export { safeBaseName };

const MIME = {
  pem: 'application/x-pem-file',
  der: 'application/pkix-cert',
  pkcs7: 'application/x-pkcs7-certificates',
  pfx: 'application/x-pkcs12',
  binary: 'application/octet-stream',
  csr: 'application/pkcs10',
} as const;

/** Erlaubte Formate je Inhalt; das erste ist die Vorgabe. */
const FORMATS: Record<BuildContent, readonly string[]> = {
  leaf: ['pem', 'der', 'p7b', 'p7c'],
  fullchain: ['pem', 'p7b', 'p7c'],
  chain: ['pem', 'p7b', 'p7c'],
  leafKey: ['pem'],
  pfx: ['pfx'],
  key: ['pkcs8', 'traditional', 'pkcs8-der'],
  csr: ['pem', 'der'],
  template: ['template'],
};

function parseCertificate(pem: unknown): CertItem {
  if (typeof pem !== 'string' || pem.trim() === '') {
    certError('notACertificate', 400, 'Value is not a certificate');
  }
  try {
    return certItemFromDer(new X509Certificate(pem).raw, { file: 0, path: '' });
  } catch {
    return certError('notACertificate', 400, 'Value is not a certificate');
  }
}

function parseKey(pem: string | undefined): KeyObject {
  if (typeof pem !== 'string' || pem.trim() === '') {
    certError('keyMissing', 400, 'A private key is required');
  }
  try {
    return createPrivateKey(pem);
  } catch {
    return certError('invalidInput', 400, 'keyPem is not a readable private key');
  }
}

const CSR_BLOCK =
  /-----BEGIN (?:NEW )?CERTIFICATE REQUEST-----([\s\S]*?)-----END (?:NEW )?CERTIFICATE REQUEST-----/;

function parseCsr(pem: string | undefined): { der: Buffer; item: CsrItem } {
  const body = typeof pem === 'string' ? CSR_BLOCK.exec(pem)?.[1] : undefined;
  if (!body) certError('invalidInput', 400, 'csrPem is not a certificate request');
  try {
    const der = Buffer.from(body.replace(/\s+/g, ''), 'base64');
    return { der, item: csrItemFromDer(der, { file: 0, path: '' }) };
  } catch {
    return certError('invalidInput', 400, 'csrPem is not a certificate request');
  }
}

function pemBlock(label: string, der: Buffer): string {
  const lines = der.toString('base64').match(/.{1,64}/g) ?? [];
  return `-----BEGIN ${label}-----\n${lines.join('\n')}\n-----END ${label}-----\n`;
}

/** PEM-Bloecke in Kettenreihenfolge, jeder genau einmal mit abschliessendem Zeilenumbruch. */
function joinPem(certs: CertItem[]): string {
  return certs.map((c) => `${c.pem.trim()}\n`).join('');
}

function derOf(cert: CertItem): Buffer {
  return new X509Certificate(cert.pem).raw;
}

const { asn1 } = forge;

function sequence(value: forge.asn1.Asn1[]): forge.asn1.Asn1 {
  return asn1.create(asn1.Class.UNIVERSAL, asn1.Type.SEQUENCE, true, value);
}

function oid(value: string): forge.asn1.Asn1 {
  return asn1.create(asn1.Class.UNIVERSAL, asn1.Type.OID, false, asn1.oidToDer(value).getBytes());
}

/**
 * PKCS#7 „certs only“ (signedData ohne Inhalt und ohne Unterschriften, wie .p7b/.p7c von CAs), von Hand
 * aus ASN.1 gebaut: ContentInfo { signedData, [0] { version 1, leere Verfahrensliste, data, [0] Zertifikate,
 * leere Unterschriftenliste } }. Jedes Zertifikat geht mit seinen eigenen Bytes hinein; forges
 * Zertifikatobjekte (nur RSA) kommen nie vor.
 */
function pkcs7Der(certs: CertItem[]): Buffer {
  const options = { decodeBitStrings: false } as unknown as boolean;
  const certAsn1 = certs.map((c) =>
    asn1.fromDer(forge.util.createBuffer(derOf(c).toString('binary')), options),
  );
  const signedData = sequence([
    asn1.create(asn1.Class.UNIVERSAL, asn1.Type.INTEGER, false, asn1.integerToDer(1).getBytes()),
    asn1.create(asn1.Class.UNIVERSAL, asn1.Type.SET, true, []),
    sequence([oid('1.2.840.113549.1.7.1')]),
    asn1.create(asn1.Class.CONTEXT_SPECIFIC, 0, true, certAsn1),
    asn1.create(asn1.Class.UNIVERSAL, asn1.Type.SET, true, []),
  ]);
  const contentInfo = sequence([
    oid('1.2.840.113549.1.7.2'),
    asn1.create(asn1.Class.CONTEXT_SPECIFIC, 0, true, [signedData]),
  ]);
  return Buffer.from(asn1.toDer(contentInfo).getBytes(), 'binary');
}

function file(filename: string, data: Buffer | string, mimeType: string): BuildFile {
  const bytes = typeof data === 'string' ? Buffer.from(data, 'utf8') : data;
  return { filename, content: bytes.toString('base64'), mimeType };
}

/** Zertifikatsliste als PEM, PKCS#7 PEM (.p7b) oder PKCS#7 DER (.p7c) unter dem Namen `<stem>.<endung>`. */
function certListFile(stem: string, pemName: string, format: string, certs: CertItem[]): BuildFile {
  if (format === 'p7b') {
    return file(`${stem}.p7b`, pemBlock('PKCS7', pkcs7Der(certs)), MIME.pkcs7);
  }
  if (format === 'p7c') return file(`${stem}.p7c`, pkcs7Der(certs), MIME.pkcs7);
  return file(pemName, joinPem(certs), MIME.pem);
}

/** Baut die gewuenschte Ausgabe. Wirft Nest-Ausnahmen mit Code (D-24); nie mit Passwort oder Schluessel im Text. */
export function buildOutput(input: BuildInput): BuildResult {
  const allowed = FORMATS[input.content];
  if (!allowed) certError('invalidInput', 400, 'Unknown content');
  const format = input.format ?? allowed[0];
  if (!allowed.includes(format)) certError('invalidInput', 400, 'Format is not available here');

  if (input.content === 'key') return buildKey(input, format as KeyExportFormat);
  if (input.content === 'csr') return buildCsr(input, format);

  if (!input.certPem) certError('invalidInput', 400, 'certPem is required');
  const head = parseCertificate(input.certPem);
  const pool = (input.poolPems ?? []).map(parseCertificate);

  const unique = new Map<string, CertItem>();
  for (const c of [head, ...pool]) if (!unique.has(c.id)) unique.set(c.id, c);
  const all = [...unique.values()];

  const chain = buildChains(all, [head.id]).chains[0];
  const byId = new Map(all.map((c) => [c.id, c]));
  const path = chain.path.map((id) => byId.get(id) as CertItem);
  const includeRoot = input.includeRoot === true;
  const withoutRoot = path.filter((c) => !(c.role === 'root' && c.id !== head.id));
  const shown = includeRoot ? path : withoutRoot;
  const base = safeBaseName(input.baseName ?? '', head.baseName);

  let files: BuildFile[];
  let snippet: string | null = null;
  switch (input.content) {
    case 'leaf':
      if (format === 'der') files = [file(`${base}.cer`, derOf(head), MIME.der)];
      else files = [certListFile(base, `${base}.crt`, format, [head])];
      break;
    case 'fullchain':
      files = [certListFile(`${base}-fullchain`, `${base}-fullchain.pem`, format, shown)];
      break;
    case 'chain': {
      const issuers = shown.filter((c) => c.id !== head.id);
      if (issuers.length === 0) {
        certError('noChain', 400, 'No intermediate or root certificate available');
      }
      files = [certListFile(`${base}-chain`, `${base}-chain.pem`, format, issuers)];
      break;
    }
    case 'leafKey': {
      const key = matchingKey(head, input.keyPem);
      const certs = input.includeChain === false ? [head] : shown;
      const keyPem = key.export({ type: 'pkcs8', format: 'pem' }) as string;
      files = [file(`${base}-bundle.pem`, joinPem(certs) + keyPem, MIME.pem)];
      break;
    }
    case 'pfx': {
      if (!input.password) certError('passwordRequired', 400, 'A password is required');
      const key = input.keyPem ? matchingKey(head, input.keyPem) : null;
      const der = writePkcs12({
        keyObject: key,
        certDers: shown.map(derOf),
        password: input.password,
        profile: input.pfxEncryption === 'modern' ? 'modern' : 'compat',
        friendlyName: base,
      });
      files = [file(`${base}.pfx`, der, MIME.pfx)];
      break;
    }
    case 'template': {
      if (!isTemplateId(input.template)) certError('invalidInput', 400, 'Unknown template');
      // Eine Vorlage ohne passenden Schluessel gibt es nicht (templateNeedsKey); ein falscher Schluessel ist keyMismatch.
      if (!input.keyPem || input.keyPem.trim() === '') {
        certError('templateNeedsKey', 400, 'The template needs the matching private key');
      }
      const key = matchingKey(head, input.keyPem);
      const built = buildTemplate(input.template, {
        head,
        shown,
        key,
        base,
        password: input.password,
        pfxProfile: input.pfxEncryption === 'modern' ? 'modern' : 'compat',
      });
      files = built.files;
      snippet = built.snippet;
      break;
    }
    default:
      return certError('invalidInput', 400, 'Unknown content');
  }

  return {
    files,
    chainComplete: chain.complete,
    missingIssuerCn: chain.gap?.missingIssuerCn ?? null,
    ...(input.content === 'template' ? { snippet } : {}),
  };
}

/** Liest den Schluessel und prueft, dass er zum Serverzertifikat gehoert (sonst keyMismatch). */
function matchingKey(head: CertItem, keyPem: string | undefined): KeyObject {
  const key = parseKey(keyPem);
  if (!new X509Certificate(head.pem).checkPrivateKey(key)) {
    certError('keyMismatch', 400, 'The key does not belong to the certificate');
  }
  return key;
}

function buildKey(input: BuildInput, format: KeyExportFormat): BuildResult {
  const key = parseKey(input.keyPem);
  const base = safeBaseName(input.baseName ?? '', 'schluessel');
  const data = exportKey(key, format, input.password || undefined);
  let filename: string;
  let mime: string = MIME.pem;
  if (format === 'pkcs8') filename = `${base}.key`;
  else if (format === 'traditional') {
    filename = key.asymmetricKeyType === 'rsa' ? `${base}.rsa.key` : `${base}.ec.key`;
  } else {
    filename = `${base}.key.der`;
    mime = MIME.binary;
  }
  return { files: [file(filename, data, mime)], chainComplete: true, missingIssuerCn: null };
}

function buildCsr(input: BuildInput, format: string): BuildResult {
  const { der, item } = parseCsr(input.csrPem);
  const base = safeBaseName(input.baseName ?? '', item.baseName);
  const out =
    format === 'der'
      ? file(`${base}.csr.der`, der, MIME.csr)
      : file(`${base}.csr`, item.pem, MIME.csr);
  return { files: [out], chainComplete: true, missingIssuerCn: null };
}