import type Anthropic from '@anthropic-ai/sdk';
import { promises as fs } from 'fs';
import path from 'path';
import { pool } from '../db';
import { typeForExtension } from '../uploadTypes';
import { getAnthropicClient } from './anthropicClient';
import { draftListing } from './draftListing';
import { applyDraft } from './applyDraft';
import { notifyDraftReady } from './notifyDraft';
import { removeBackgroundsForItem } from './backgroundRemoval';

/**
 * Turns queued submissions into drafts.
 *
 * Driven from two places: a call at the end of a successful submission, so a
 * draft is usually waiting by the time anybody looks, and a cron sweeper, so a
 * restart mid-draft is recoverable rather than a permanently stalled row.
 *
 * The governing rule is that a submission is the only irreplaceable thing here.
 * The photos are often the only copy of an item no longer in the sender's
 * hands, so every failure below leaves the row and its images intact and merely
 * undrafted. Nothing in this file deletes anything.
 *
 * Background removal (#281) follows drafting rather than running on its own
 * pass. That couples the two: an environment with no ANTHROPIC_API_KEY drafts
 * nothing, so it cuts out nothing either. That is the intended trade — a
 * separate pass would re-attempt an unreachable sidecar on every sweep for a
 * row that is going to sit at 'queued' indefinitely — and the admin's per-photo
 * control in the review queue is the way to do it by hand meanwhile.
 */

/** Three tries, then it waits for a person rather than burning money on a loop. */
export const MAX_ATTEMPTS = 3;

/** Small, because each one is an API call and the sweeper comes round again. */
const DEFAULT_BATCH = 5;

type Photo = { mediaType: string; base64: string };

interface QueuedRow {
  item_id: number;
  submitter_note: string | null;
  remove_background: boolean;
}

export interface SweepResult {
  drafted: number;
  failed: number;
  skipped: number;
}

async function readPhotos(itemId: number): Promise<Photo[]> {
  const { rows } = await pool.query<{ image_path: string }>(
    `SELECT image_path FROM item_images WHERE item_id = $1 ORDER BY sort_order`,
    [itemId]
  );

  const photos: Photo[] = [];
  for (const row of rows) {
    // basename only: image_path is stored as '/uploads/<name>' and the
    // directory it lives in is a server constant. Same rule as handleRow in
    // backfillImageReencode, but using the shared typeForExtension rather than
    // that file's private copy of the map.
    const file = path.join(process.env.UPLOADS_DIR ?? '', path.basename(row.image_path));
    const mediaType = typeForExtension(path.extname(file));
    // Null for anything the app would refuse to serve. Sending it to the model
    // would be paying to have it rejected.
    if (mediaType === null) continue;
    photos.push({ mediaType, base64: (await fs.readFile(file)).toString('base64') });
  }
  return photos;
}

async function namesOf(table: 'categories' | 'tags'): Promise<string[]> {
  // The table name is a closed union, never caller input — there is nothing
  // here to interpolate from a request.
  const { rows } = await pool.query<{ name: string }>(`SELECT name FROM ${table} ORDER BY name`);
  return rows.map((row) => row.name);
}

/**
 * Records a failure without ever losing the submission.
 *
 * The row stays reachable either way: 'queued' while tries remain, so the
 * sweeper picks it up again, and 'failed' once they are spent, so it stops
 * costing money and waits for a person. The item and its photos are untouched
 * in both cases.
 */
async function recordFailure(itemId: number, message: string): Promise<void> {
  await pool.query(
    `UPDATE item_drafts
     SET attempts = attempts + 1,
         ai_error = $2,
         state = CASE WHEN attempts + 1 >= $3 THEN 'failed' ELSE 'queued' END
     WHERE item_id = $1`,
    [itemId, message.slice(0, 500), MAX_ATTEMPTS]
  );
}

/** Photos are passed in rather than re-read: the caller has already loaded them
 * to check there is at least one, and reading every file off disk twice per
 * submission is a cost for nothing. */
async function draftOne(
  client: Anthropic,
  itemId: number,
  note: string | null,
  photos: Photo[]
): Promise<void> {
  const outcome = await draftListing(client, {
    photos,
    note,
    categories: await namesOf('categories'),
    tags: await namesOf('tags')
  });

  const db = await pool.connect();
  try {
    await db.query('BEGIN');
    await applyDraft(db, itemId, outcome);
    await db.query('COMMIT');
  } catch (err) {
    await db.query('ROLLBACK');
    throw err;
  } finally {
    db.release();
  }
}

export async function draftQueued(limit = DEFAULT_BATCH): Promise<SweepResult> {
  const { rows } = await pool.query<QueuedRow>(
    `SELECT item_id, submitter_note, remove_background FROM item_drafts
     WHERE state = 'queued' AND attempts < $2
     ORDER BY created_at
     LIMIT $1`,
    [limit, MAX_ATTEMPTS]
  );

  // Unconfigured is not a failure and must not spend an attempt. A fortnight
  // without a key would otherwise exhaust the retries and mark every waiting
  // submission failed, with nothing wrong with any of them.
  const client = getAnthropicClient();
  if (client === null) {
    return { drafted: 0, failed: 0, skipped: rows.length };
  }

  let drafted = 0;
  let failed = 0;

  for (const row of rows) {
    try {
      const photos = await readPhotos(row.item_id);
      if (photos.length === 0) {
        throw new Error('no readable photos');
      }
      await draftOne(client, row.item_id, row.submitter_note, photos);
      drafted++;

      // Deliberately after the draft is committed, and catching for itself.
      //
      // This is the sender's tick from the submission page, honoured here so
      // they never waited for it — and a failure must not mark a draft that was
      // written correctly as failed. The photo keeps its original in that case,
      // and the admin's per-photo control is still there to do it by hand.
      //
      // Awaited, unlike the notification below, so a sweep that has returned
      // has finished its work. Nothing is waiting on this: the worker is off
      // the request path, which is the whole reason drafting lives here.
      if (row.remove_background) {
        await removeBackgroundsForItem(row.item_id).catch((err) =>
          console.error(`[drafting] background removal for item ${row.item_id}:`, err)
        );
      }

      // Fire and forget, and deliberately after the draft is committed. A mail
      // failure must never mark a draft that was written correctly as failed —
      // the queue is what the admin actually works from, and the email is a
      // convenience on top of it.
      void notifyDraftReady(row.item_id).catch((err) =>
        console.error(`[drafting] notifying for item ${row.item_id}:`, err)
      );
    } catch (err) {
      const message = err instanceof Error ? err.message : String(err);
      console.error(`[drafting] item ${row.item_id}: ${message}`);
      await recordFailure(row.item_id, message);
      failed++;
    }
  }

  return { drafted, failed, skipped: 0 };
}