import { requestJson } from '../lib/httpClient.js';
import { cleanSlackText } from '../lib/slackText.js';
import type { NormalizedDelivery } from '../types/integration.js';
import type { NoteInput } from '../types/domain.js';

const SLACK_API_BASE = 'https://slack.com/api';

export type SlackErrorKind = 'permanent' | 'retryable';

/**
 * Errors a retry cannot fix: a bad credential, a missing scope, or a message
 * that is gone. Everything absent from this list is treated as retryable,
 * including error strings we do not recognize, so a transient failure Slack
 * adds tomorrow is not silently dropped today. The queue bounds attempts, so
 * an unknown-but-really-permanent error wastes a few calls rather than looping.
 */
const PERMANENT_ERRORS: ReadonlySet<string> = new Set([
  'no_token',
  'invalid_auth',
  'not_authed',
  'account_inactive',
  'token_revoked',
  'token_expired',
  'no_permission',
  'missing_scope',
  'channel_not_found',
  'not_in_channel',
  'message_not_found',
  'user_not_found',
  'invalid_arguments',
  'invalid_form_data',
  'is_archived',
]);

export class SlackApiError extends Error {
  readonly method: string;
  readonly slackError: string;
  readonly kind: SlackErrorKind;
  /** The flag lib/queue.ts reads to stop retrying a settled failure. */
  readonly permanent: boolean;

  constructor(method: string, slackError: string) {
    super(`Slack API ${method} failed: ${slackError}`);
    this.name = 'SlackApiError';
    this.method = method;
    this.slackError = slackError;
    this.kind = PERMANENT_ERRORS.has(slackError) ? 'permanent' : 'retryable';
    this.permanent = this.kind === 'permanent';
  }
}

export const isSlackApiError = (err: unknown): err is SlackApiError =>
  err instanceof SlackApiError;

const asRecord = (value: unknown): Record<string, unknown> | undefined =>
  typeof value === 'object' && value !== null && !Array.isArray(value)
    ? (value as Record<string, unknown>)
    : undefined;

const asNonEmptyString = (value: unknown): string | undefined =>
  typeof value === 'string' && value.length > 0 ? value : undefined;

/**
 * Posts a form-encoded Web API call and unwraps Slack's envelope.
 *
 * Slack answers HTTP 200 even for failures, putting the outcome in the body as
 * `{ ok: false, error: "invalid_auth" }`. requestJson cannot see that, so the
 * `ok` field is checked here; transport-level failures (429, 5xx, timeouts) are
 * left to requestJson's retry loop and surface as HttpRequestError unchanged.
 */
export const callSlack = async <T>(
  method: string,
  params: Record<string, string> = {}
): Promise<T> => {
  // Read at call time, never at module load: the token may be rotated into the
  // environment after import, and tests set and unset it per case.
  // Trimmed because a token pasted into a .env file often carries a newline.
  const token = process.env.SLACK_BOT_TOKEN?.trim();
  if (token === undefined || token === '') {
    throw new SlackApiError(method, 'no_token');
  }

  const body = await requestJson<unknown>(`${SLACK_API_BASE}/${method}`, {
    method: 'POST',
    headers: {
      authorization: `Bearer ${token}`,
      'content-type': 'application/x-www-form-urlencoded; charset=utf-8',
    },
    body: new URLSearchParams(params).toString(),
  });

  const envelope = asRecord(body);
  if (envelope === undefined || envelope.ok !== true) {
    const slackError = asNonEmptyString(envelope?.error) ?? 'unknown_error';
    throw new SlackApiError(method, slackError);
  }

  return body as T;
};

/**
 * Credential health check. `ok: true` means Slack accepted the token, so the
 * identity fields are present in practice; they fall back to empty strings
 * rather than throwing, since a malformed success body is not a credential
 * problem and should not read as one.
 */
export const authTest = async (): Promise<{
  teamId: string;
  teamName: string;
  botUserId: string;
}> => {
  const body = await callSlack<unknown>('auth.test');
  const envelope = asRecord(body) ?? {};

  return {
    teamId: asNonEmptyString(envelope.team_id) ?? '',
    teamName: asNonEmptyString(envelope.team) ?? '',
    botUserId: asNonEmptyString(envelope.user_id) ?? '',
  };
};

/** userId to resolved display name. Only successful lookups are stored. */
const displayNames = new Map<string, string>();

export const resetSlackCaches = (): void => {
  displayNames.clear();
};

const pickDisplayName = (body: unknown, userId: string): string => {
  const user = asRecord(asRecord(body)?.user);
  const profile = asRecord(user?.profile);

  return (
    asNonEmptyString(profile?.display_name) ??
    asNonEmptyString(profile?.real_name) ??
    asNonEmptyString(user?.real_name) ??
    asNonEmptyString(user?.name) ??
    userId
  );
};

/**
 * Resolves a human-readable name for a Slack user, memoized for the process.
 * A permanent failure degrades to the raw user ID: a name we cannot look up is
 * cosmetic, and failing the whole ingest over it would lose the note. Retryable
 * failures propagate so the queue can try again.
 */
export const getUserDisplayName = async (userId: string): Promise<string> => {
  const cached = displayNames.get(userId);
  if (cached !== undefined) {
    return cached;
  }

  let name: string;
  try {
    name = pickDisplayName(await callSlack<unknown>('users.info', { user: userId }), userId);
  } catch (err) {
    if (isSlackApiError(err) && err.kind === 'permanent') {
      // Deliberately not cached: a missing scope can be granted without a
      // restart, and caching the degraded answer would outlive the cause.
      return userId;
    }
    throw err;
  }

  displayNames.set(userId, name);
  return name;
};

/**
 * Slack returns the whole thread when `conversations.replies` is given a reply's
 * ts, so the exact timestamp is preferred over position; the first message is
 * the fallback for `conversations.history`, which returns only the one asked for.
 */
const pickMessage = (body: unknown, ts: string): Record<string, unknown> | undefined => {
  const messages = asRecord(body)?.messages;
  if (!Array.isArray(messages)) {
    return undefined;
  }

  const candidates = messages
    .map(asRecord)
    .filter((entry): entry is Record<string, unknown> => entry !== undefined);

  return candidates.find((entry) => entry.ts === ts) ?? candidates[0];
};

/**
 * Reads one message's text by timestamp. `conversations.history` cannot see a
 * threaded reply, so `conversations.replies` is tried before giving up: a
 * reaction on a reply is otherwise indistinguishable from a deleted message.
 * Returns null when there is nothing worth clustering.
 */
export const getMessageText = async (
  channelId: string,
  ts: string
): Promise<{ text: string; userId?: string } | null> => {
  const history = await callSlack<unknown>('conversations.history', {
    channel: channelId,
    latest: ts,
    oldest: ts,
    inclusive: 'true',
    limit: '1',
  });

  let message = pickMessage(history, ts);

  if (message === undefined) {
    const replies = await callSlack<unknown>('conversations.replies', {
      channel: channelId,
      ts,
      limit: '1',
      inclusive: 'true',
    });
    message = pickMessage(replies, ts);
  }

  if (message === undefined) {
    return null;
  }

  const raw = asNonEmptyString(message.text);
  const text = raw === undefined ? '' : cleanSlackText(raw);
  if (text === '') {
    return null;
  }

  const userId = asNonEmptyString(message.user);
  return userId === undefined ? { text } : { text, userId };
};

/**
 * Fills in what a Slack event referenced but did not carry. Runs after the ack,
 * inside the retry queue, so the network calls here are safe to be slow.
 *
 * Notes are processed in sequence rather than in parallel: a delivery carries
 * one or two of them, and serializing keeps a burst of reactions from spending
 * the per-method rate limit all at once.
 */
export const enrichSlackDelivery = async (
  delivery: NormalizedDelivery,
  _payload: unknown
): Promise<NormalizedDelivery> => {
  const notes: NoteInput[] = [];

  for (const note of delivery.notes) {
    const meta = note.sourceMeta;

    if (meta === undefined || meta.needsMessageText !== true) {
      notes.push(note);
      continue;
    }

    const channelId = asNonEmptyString(meta.channelId);
    const messageTs = asNonEmptyString(meta.messageTs);

    // No usable reference means the placeholder text can never be resolved, so
    // the note is dropped for the same reason an unfetchable message is.
    const message =
      channelId === undefined || messageTs === undefined
        ? null
        : await getMessageText(channelId, messageTs);

    if (message === null) {
      continue;
    }

    // Stripped unconditionally so a stale marker can never reach the database.
    const sourceMeta: Record<string, unknown> = { ...meta };
    delete sourceMeta.needsMessageText;

    const authorUserId = asNonEmptyString(meta.authorUserId) ?? message.userId;
    if (authorUserId === undefined) {
      notes.push({ ...note, text: message.text, sourceMeta });
      continue;
    }

    const author = await getUserDisplayName(authorUserId);
    sourceMeta.authorHandle = author;
    notes.push({ ...note, text: message.text, author, sourceMeta });
  }

  return { ...delivery, notes };
};