import { createHash } from 'node:crypto';
import type { ChatwootWebhookPayload } from '../types/chatwoot.js';

/**
 * Channel-agnostic event the rest of the pipeline works on. New channels
 * (webchat, Allegro, …) only need to produce this shape.
 */
export interface SupportMessageEvent {
  source: 'chatwoot';
  channel: string;
  conversationId: number;
  messageId: string;
  inboxId: number;
  content: string;
  subject: string | null;
  messageCreatedAt: string | null;
  senderEmail: string;
  senderName: string;
  senderId: string | null;
  labels: string[];
  customAttributes: Record<string, unknown>;
  additionalAttributes: Record<string, unknown>;
  attachmentCount: number;
  attachments: NormalizedAttachment[];
  formMail: FormMailInfo | null;
  /** true when the webhook did not carry labels/custom attributes. */
  needsConversationFetch: boolean;
}

export interface NormalizedAttachment {
  fileName: string;
  contentType: string;
  fileSize: number | null;
  inline: boolean;
  contentId: string | null;
}

export interface FormMailInfo {
  customerEmail: string;
  customerName: string;
  phone: string;
  technicalSender: string;
  formSource: string;
}

export type NormalizeResult =
  | { ok: true; event: SupportMessageEvent }
  | { ok: false; reason: string };

const EMAIL_RE = /^[^\s@]+@[^\s@]+\.[^\s@]{2,}$/;

/** Strips quoted replies, signatures and HTML so the LLM sees only new text. */
export function cleanEmailBody(raw: string): string {
  let text = raw.replace(/\r\n/g, '\n');

  if (/<[a-z][\s\S]*>/i.test(text)) {
    text = text
      .replace(/<style[\s\S]*?<\/style>/gi, ' ')
      .replace(/<script[\s\S]*?<\/script>/gi, ' ')
      .replace(/<br\s*\/?>/gi, '\n')
      .replace(/<\/p>/gi, '\n')
      .replace(/<[^>]+>/g, ' ');
  }

  const cutMarkers = [
    /^\s*-{2,}\s*Original Message\s*-{2,}/im,
    /^\s*-{2,}\s*Wiadomość oryginalna\s*-{2,}/im,
    /^\s*_{5,}\s*$/m,
    /^\s*(On|W dniu)\b.*\b(wrote|napisał|napisała|pisze):\s*$/im,
  ];
  for (const marker of cutMarkers) {
    const m = marker.exec(text);
    if (m && m.index > 0) text = text.slice(0, m.index);
  }

  return text
    .split('\n')
    .filter((line) => !/^\s*>/.test(line))
    .join('\n')
    .replace(/\n{3,}/g, '\n\n')
    .trim();
}

function firstEmail(...candidates: (string | undefined | null)[]): string {
  for (const c of candidates) {
    const v = (c ?? '').trim();
    if (v && EMAIL_RE.test(v)) return v.toLowerCase();
  }
  return '';
}

/**
 * Turns a raw Chatwoot webhook into a SupportMessageEvent, or explains why the
 * payload is not something the AI pipeline should act on.
 */
export function normalizeChatwootWebhook(payload: ChatwootWebhookPayload): NormalizeResult {
  if (payload.event !== 'message_created') {
    return { ok: false, reason: `unsupported_event:${payload.event ?? 'none'}` };
  }
  if (payload.message_type !== 'incoming') {
    return { ok: false, reason: `not_incoming:${payload.message_type ?? 'none'}` };
  }
  if (payload.private === true) {
    return { ok: false, reason: 'private_note' };
  }

  const conversation = payload.conversation ?? {};
  const conversationId = Number(conversation.id ?? 0);
  if (!Number.isFinite(conversationId) || conversationId <= 0) {
    return { ok: false, reason: 'missing_conversation_id' };
  }

  const rawContent = typeof payload.content === 'string' ? payload.content : '';
  const content = cleanEmailBody(rawContent);
  const attachments = Array.isArray(payload.attachments) ? payload.attachments : [];
  const normalizedAttachments = attachments.map(normalizeAttachment);

  if (content === '' && attachments.length === 0) {
    return { ok: false, reason: 'empty_message' };
  }

  const metaSender = conversation.meta?.sender;
  const senderEmail = firstEmail(
    metaSender?.email,
    payload.sender?.email,
    conversation.contact_inbox?.source_id,
    payload.source_id ?? undefined,
  );
  const senderName = String(metaSender?.name ?? payload.sender?.name ?? '').trim();
  const senderIdRaw = metaSender?.id ?? payload.sender?.id;

  const labels = Array.isArray(conversation.labels) ? conversation.labels : [];
  const customAttributes = conversation.custom_attributes ?? {};
  const additionalAttributes = conversation.additional_attributes ?? {};

  const messageId =
    payload.id !== undefined && payload.id !== null
      ? String(payload.id)
      : // No message id (older Chatwoot / some channels): derive a stable
        // surrogate so retries still deduplicate.
        `hash:${conversationId}:${createHash('sha256').update(rawContent).digest('hex').slice(0, 32)}`;

  const subject =
    (additionalAttributes.mail_subject as string | undefined) ??
    (additionalAttributes.subject as string | undefined) ??
    null;
  const formMail = detectFormMail({ content, subject, senderEmail, senderName, additionalAttributes });
  const effectiveSenderEmail = formMail?.customerEmail || senderEmail;
  const effectiveSenderName = formMail?.customerName || senderName;
  const messageCreatedAt = parseMessageCreatedAt((payload as Record<string, unknown>).created_at);

  return {
    ok: true,
    event: {
      source: 'chatwoot',
      channel: mapChannel(conversation.channel),
      conversationId,
      messageId,
      inboxId: Number(conversation.inbox_id ?? payload.inbox?.id ?? 0),
      content,
      subject,
      messageCreatedAt,
      senderEmail: effectiveSenderEmail,
      senderName: effectiveSenderName,
      senderId: senderIdRaw !== undefined && senderIdRaw !== null ? String(senderIdRaw) : null,
      labels,
      customAttributes,
      additionalAttributes,
      attachmentCount: attachments.length,
      attachments: normalizedAttachments,
      formMail,
      needsConversationFetch:
        conversation.labels === undefined || conversation.custom_attributes === undefined,
    },
  };
}

function mapChannel(channel?: string): string {
  if (!channel) return 'email';
  if (channel.includes('Email')) return 'email';
  if (channel.includes('Api')) return 'api';
  if (channel.includes('WebWidget')) return 'webchat';
  return channel.replace('Channel::', '').toLowerCase();
}

function parseMessageCreatedAt(value: unknown): string | null {
  if (typeof value === 'number') {
    const ms = value > 10_000_000_000 ? value : value * 1000;
    return new Date(ms).toISOString();
  }
  if (typeof value === 'string' && value.trim() !== '') {
    const n = Number(value);
    const d = Number.isFinite(n) ? new Date(n > 10_000_000_000 ? n : n * 1000) : new Date(value);
    if (Number.isFinite(d.getTime())) return d.toISOString();
  }
  return null;
}

function normalizeAttachment(a: unknown): NormalizedAttachment {
  const o = (a && typeof a === 'object') ? (a as Record<string, unknown>) : {};
  const fileName = String(o.file_name ?? o.filename ?? o.name ?? o.data_url ?? '').slice(0, 200);
  const contentType = String(o.content_type ?? o.contentType ?? o.mime_type ?? o.file_type ?? '').toLowerCase();
  const sizeRaw = o.file_size ?? o.filesize ?? o.size ?? o.byte_size;
  const fileSize = Number.isFinite(Number(sizeRaw)) ? Number(sizeRaw) : null;
  const inline = Boolean(o.inline ?? o.is_inline ?? o.content_id ?? o.contentId);
  const contentId = o.content_id || o.contentId ? String(o.content_id ?? o.contentId) : null;
  return { fileName, contentType, fileSize, inline, contentId };
}

function detectFormMail(input: {
  content: string;
  subject: string | null;
  senderEmail: string;
  senderName: string;
  additionalAttributes: Record<string, unknown>;
}): FormMailInfo | null {
  const subject = input.subject ?? '';
  const headers = flattenHeaders(input.additionalAttributes);
  const replyTo = firstEmail(headers['reply-to'], headers.reply_to, headers.replyto);
  const bodyEmail = extractField(input.content, /(?:e-?mail|email address|adres e-?mail)\s*[:：]\s*([^\s<>]+@[^\s<>]+)/i);
  const name = extractField(input.content, /(?:imi[ęe]|name|nazwisko)\s*[:：]\s*(.+)/i);
  const phone = extractField(input.content, /(?:telefon|phone|tel\.)\s*[:：]\s*([+\d][\d\s().-]{5,})/i);
  const looksLikeForm =
    /(formularz|contact form|zapytanie ze strony|wiadomo[śs][ćc] ze strony|web form)/i.test(subject) ||
    /(?:e-?mail|telefon|imi[ęe]|name)\s*[:：]/i.test(input.content);
  const technicalSender = /^(no-?reply|wordpress|sklep|www|formularz|kontakt|notification)/i.test(input.senderEmail.split('@')[0] ?? '');
  const customerEmail = replyTo || bodyEmail;
  if (!looksLikeForm || !customerEmail || (!technicalSender && customerEmail === input.senderEmail)) return null;
  return {
    customerEmail,
    customerName: name || input.senderName,
    phone,
    technicalSender: input.senderEmail,
    formSource: subject || 'www_form',
  };
}

function extractField(content: string, re: RegExp): string {
  const m = re.exec(content);
  if (!m?.[1]) return '';
  return m[1].split('\n')[0]?.trim().replace(/[<>;,]+$/g, '') ?? '';
}

function flattenHeaders(attrs: Record<string, unknown>): Record<string, string> {
  const out: Record<string, string> = {};
  const raw = (attrs.email as Record<string, unknown> | undefined) ?? attrs;
  const headers = (raw?.headers as Record<string, unknown> | undefined) ?? raw;
  if (!headers || typeof headers !== 'object') return out;
  for (const [k, v] of Object.entries(headers)) {
    if (typeof v === 'string' || typeof v === 'number') out[k.toLowerCase()] = String(v);
  }
  return out;
}