// src/services/ticketClassifier.js
//
// AI-based classifier for Jira poller. Reads a single Jira issue and
// returns a strict `{ kind, storeNum, reason, tokensUsed }` shape.
//
// Design decisions (locked with the operator up front):
//   - Full-auto: whatever the model returns is what runs. No confidence
//     gate. The Webex summary post exposes the model's `reason` per
//     ticket so a human can spot-check bad classifications.
//   - Skip-until-recovery: any failure (network, timeout, malformed
//     JSON, missing required field) throws `TicketClassifierError`.
//     The poller's per-ticket try/catch catches it, logs, and skips
//     without labeling — that ticket comes back next hour.
//   - Closed output taxonomy: kind ∈ {'phone', 'av', 'skip'}. Not
//     'unknown', not 'other'. Every ticket falls into one bucket, and
//     'skip' is a valid, safe non-action.
//   - JSON mode (`response_format: json_object`) is on so we don't fight
//     markdown-wrapped output. Fallback: `parseAndValidate` still
//     tolerates fenced code blocks if the model ignores the hint.
//
// Store Number extraction: because your Jira's Store Number custom
// field is an opaque Atlassian Assets object reference (see comment on
// the poller's `extractStore` for context), the AI is the ONLY reliable
// way to get a numeric store id. The prompt tells the model to look at
// summary + description, where techs consistently type "Store 3860".

import { callGrok } from '../utils/grokClient.js';
import { logger } from '../utils/logger.js';

const MAX_DESCRIPTION_CHARS = 2000;
const MAX_REASON_CHARS = 200;
const VALID_KINDS = new Set(['phone', 'av', 'skip']);

// Optional per-call model override. When unset, defers to XAI_MODEL
// via callGrok. Classification is a small structured task that runs
// well on a cheaper/faster model than long-form summaries.
const CLASSIFIER_MODEL = process.env.JIRA_POLLER_MODEL || undefined;

const SYSTEM_PROMPT =
  "You are triaging unassigned IT support tickets at American Eagle Outfitters (retail stores + corporate).\n" +
  "\n" +
  "Classify the ticket into EXACTLY one category:\n" +
  '- "phone": SIP desk phones, DECT wireless handsets/basestations, extension routing,\n' +
  "  voicemail, dial tone, call quality, telephony provisioning, Webex Calling on desk\n" +
  "  phones. NOT general Webex account access.\n" +
  '- "av": Cisco Webex Room devices, cameras, microphones, digital signage,\n' +
  "  audio amplifiers, in-store music playback, conference-room A/V technology.\n" +
  '- "skip": anything else — laptops, mobile devices, printers, iPhones/iPads,\n' +
  "  account/access requests, Webex account requests (unrelated to phones),\n" +
  "  general networking, hardware orders, non-technical requests, or store\n" +
  "  requests we don't have a matching tool for yet.\n" +
  "\n" +
  "Extract a store number ONLY if the ticket is store-scoped. Store numbers are\n" +
  "2-6 digit integers and usually appear in the summary as 'Store NNNN - ...' but\n" +
  "may also be in the description or the 'Store Number' field. If the ticket is\n" +
  "not clearly for a specific retail store, return null.\n" +
  "\n" +
  "Respond with a SINGLE JSON object matching this schema EXACTLY (no markdown,\n" +
  "no code fences, no extra keys, no prose before or after):\n" +
  '{"kind":"phone"|"av"|"skip","storeNum":"<digits>"|null,"reason":"<one sentence, max 200 chars>"}';

/**
 * Custom error type so the poller's catch block can tell a classifier
 * failure apart from a `collectPhoneStatus` / `collectDeviceStatus`
 * failure — both should skip the ticket, but they have different
 * operator-facing meanings in the log.
 */
export class TicketClassifierError extends Error {
  constructor(message, cause) {
    super(message);
    this.name = 'TicketClassifierError';
    if (cause) this.cause = cause;
  }
}

/**
 * Build the per-ticket user message. Kept as a pure helper so it can
 * be unit-tested without a live X.AI call.
 *
 * The summary is intentionally NOT truncated — store numbers almost
 * always live in the title and truncating there would defeat the whole
 * point. Description gets a 2000-char cap to keep the payload cheap.
 *
 * The raw Store Number field value is included even though it's usually
 * an opaque Assets reference — sometimes it IS a plain string on other
 * tenants / older tickets, and giving the model a chance to use it
 * doesn't cost anything.
 */
export function buildUserMessage(ticket) {
  const key = ticket?.key || '(unknown)';
  const summary = ticket?.summary || '(no summary)';
  const description = truncate(ticket?.description || '', MAX_DESCRIPTION_CHARS);
  const components = Array.isArray(ticket?.components)
    ? ticket.components.map((c) => c?.name).filter(Boolean).join(', ')
    : '';
  const status = ticket?.status || '';
  const reporter = ticket?.reporter || '';
  const storeFieldRaw = ticket?.storeFieldRaw;

  let storeFieldDisplay = '(empty)';
  if (storeFieldRaw !== null && storeFieldRaw !== undefined && storeFieldRaw !== '') {
    if (typeof storeFieldRaw === 'object') {
      // Compact JSON so the model isn't drowning in whitespace but still
      // sees whatever primitive fell out of the Jira response.
      storeFieldDisplay = JSON.stringify(storeFieldRaw);
    } else {
      storeFieldDisplay = String(storeFieldRaw);
    }
  }

  return (
    `Ticket: ${key}\n` +
    `Component(s): ${components || '(none)'}\n` +
    `Status: ${status || '(none)'}\n` +
    `Store Number field: ${storeFieldDisplay}\n` +
    `Reporter: ${reporter || '(unknown)'}\n` +
    `\n` +
    `Summary:\n${summary}\n` +
    `\n` +
    `Description:\n${description || '(none)'}`
  );
}

/**
 * Parse and validate the model's response. Handles:
 *   - naked JSON object (JSON-mode happy path)
 *   - JSON object wrapped in ```json ... ``` fences (model ignoring hint)
 *   - leading/trailing prose
 *
 * Throws `TicketClassifierError` on any shape violation.
 */
export function parseAndValidate(rawContent) {
  if (typeof rawContent !== 'string' || rawContent.trim() === '') {
    throw new TicketClassifierError('empty response from model');
  }

  // Strip optional markdown code fences the model might sneak in.
  const cleaned = rawContent
    .trim()
    .replace(/^```(?:json)?\s*/i, '')
    .replace(/```\s*$/i, '')
    .trim();

  // Extract the first {...} block if there's stray prose around it.
  const firstBrace = cleaned.indexOf('{');
  const lastBrace = cleaned.lastIndexOf('}');
  if (firstBrace === -1 || lastBrace === -1 || lastBrace <= firstBrace) {
    throw new TicketClassifierError(`no JSON object found in response: ${cleaned.slice(0, 120)}`);
  }
  const jsonSlice = cleaned.slice(firstBrace, lastBrace + 1);

  let obj;
  try {
    obj = JSON.parse(jsonSlice);
  } catch (err) {
    throw new TicketClassifierError(`JSON.parse failed: ${err.message} (raw: ${jsonSlice.slice(0, 120)})`);
  }

  if (obj === null || typeof obj !== 'object' || Array.isArray(obj)) {
    throw new TicketClassifierError(`response is not a JSON object (got ${Array.isArray(obj) ? 'array' : typeof obj})`);
  }

  if (!VALID_KINDS.has(obj.kind)) {
    throw new TicketClassifierError(`invalid or missing 'kind' (got ${JSON.stringify(obj.kind)}, expected phone|av|skip)`);
  }

  let storeNum = obj.storeNum;
  if (storeNum === undefined) {
    throw new TicketClassifierError("missing 'storeNum' field (must be a string of digits or null)");
  }
  if (storeNum !== null) {
    // Accept numbers too — some models can't help themselves and
    // return `"storeNum": 3860` instead of `"3860"`.
    const asString = String(storeNum).trim();
    if (!/^\d{2,6}$/.test(asString)) {
      throw new TicketClassifierError(`invalid 'storeNum' (got ${JSON.stringify(storeNum)}, expected 2-6 digit string or null)`);
    }
    storeNum = asString;
  }

  const reason = typeof obj.reason === 'string' ? obj.reason.trim() : '';
  if (!reason) {
    throw new TicketClassifierError("missing or empty 'reason' string");
  }
  const truncatedReason = reason.length > MAX_REASON_CHARS ? reason.slice(0, MAX_REASON_CHARS - 1) + '…' : reason;

  return { kind: obj.kind, storeNum, reason: truncatedReason };
}

/**
 * Classify a single Jira ticket via X.AI.
 *
 * @param {object} ticket
 * @param {string} ticket.key
 * @param {string} ticket.summary
 * @param {string} [ticket.description]
 * @param {Array<{name: string}>} [ticket.components]
 * @param {string} [ticket.status]
 * @param {string} [ticket.reporter]
 * @param {*}      [ticket.storeFieldRaw]  Raw value of the Store Number custom field.
 *
 * @returns {Promise<{ kind: 'phone'|'av'|'skip', storeNum: string|null, reason: string, tokensUsed: number }>}
 * @throws {TicketClassifierError} on any failure — network, timeout, malformed JSON, invalid shape.
 */
export async function classifyTicket(ticket) {
  const userMessage = buildUserMessage(ticket);

  let response;
  try {
    response = await callGrok(userMessage, {
      system: SYSTEM_PROMPT,
      response_format: { type: 'json_object' },
      model: CLASSIFIER_MODEL,
      // Classification wants determinism, not creativity.
      temperature: 0.0,
      // JSON payloads for our schema are ~50 tokens — 200 is plenty of headroom.
      max_tokens: 200,
      // Slightly tighter than the default 15s: classification is a small
      // structured task, and long hangs starve the hourly cron.
      timeout: 10000,
      includeUsage: true,
    });
  } catch (err) {
    throw new TicketClassifierError(`X.AI call failed: ${err.message}`, err);
  }

  const parsed = parseAndValidate(response?.content || '');
  const tokensUsed = response?.usage?.total_tokens || 0;

  logger(
    'ticket:classifier',
    `${ticket?.key || '?'}: kind=${parsed.kind} store=${parsed.storeNum || 'null'} tokens=${tokensUsed}`,
    'debug'
  );

  return { ...parsed, tokensUsed };
}

// Private helper — string truncation with an ellipsis. Also exported so
// smoke tests can exercise it if we ever add stronger edge-case cover.
function truncate(s, max) {
  if (typeof s !== 'string') return '';
  if (s.length <= max) return s;
  return s.slice(0, max - 1) + '…';
}