import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
import { useState } from 'react';

import { ApiError, keys, runOptionsQuery, startRun } from '../api';
import type { CeilingBounds, Id, Run } from '../api';
import { useText, type MessageKey, type Text } from '../i18n/text';
import { Button } from '../ui/Button';
import { Checkbox } from '../ui/Checkbox';
import { Modal } from '../ui/Modal';
import { Slider } from '../ui/Slider';
import { Blank } from './Blank';
import { Loaded } from './Loaded';
import { counted } from './format';
import { chapters as chapterForms } from './units';
import styles from './RunStart.module.css';

interface Props {
  bookId: Id;
  isOpen: boolean;
  onClose: () => void;
}

/**
 * Starting a translation: the ceiling of THIS run and the stop at the bank.
 *
 * The bounds are read right before the form is shown and not taken off the book card, because the
 * maximum belongs to the ACCOUNT and moves while the book does not (contract, `run-options`). They
 * arrive already trimmed and are not clamped again here: a second clamp on the client would be a
 * second copy of a policy that lives on the platform.
 *
 * ⚠ The scale counts CHAPTERS and nothing else. There is no sum, no estimate and no money on this
 * screen in any form — the chapters → money conversion is the platform's whole and only (§4.8).
 */
export function RunStart({ bookId, isOpen, onClose }: Props) {
  const text = useText();
  const client = useQueryClient();
  // Read only while the window is open: bounds fetched behind a closed form are bounds that will be
  // stale by the time it opens.
  const options = useQuery({ ...runOptionsQuery(bookId), enabled: isOpen });

  return (
    <Modal title={text('run.title')} isOpen={isOpen} onClose={onClose}>
      <Loaded query={options} waiting={text('run.waiting')}>
        {(data) => (
          <Form
            bookId={bookId}
            ceiling={data.ceiling}
            onClose={onClose}
            // ⚠ BOTH are re-read, because a 409 is not only a ceiling that moved: the platform
            // answers it for a run already in flight and for a book not ready to be translated as
            // well (`fail` in httpapi/v0.go). The bounds may be intact and the CARD stale — and the
            // card is what decides whether the action is offered at all.
            onConflict={() =>
              Promise.all([
                client.invalidateQueries({ queryKey: keys.runOptions(bookId) }),
                client.invalidateQueries({ queryKey: keys.book(bookId) }),
              ])
            }
          />
        )}
      </Loaded>
    </Modal>
  );
}

/**
 * The form itself, mounted only once the bounds are known.
 *
 * ⚠ When the bounds MOVE — which is what a `409` means — the chosen value goes back to the
 * platform's new preset, because a value picked against bounds that no longer exist is not a
 * choice. Adjusted during the render rather than by remounting the form or by an effect: a remount
 * would take the refusal off the screen at the very moment it has to be read, and an effect would
 * draw the old scale for one frame first.
 */
function Form({
  bookId,
  ceiling,
  onClose,
  onConflict,
}: {
  bookId: Id;
  ceiling: CeilingBounds;
  onClose: () => void;
  onConflict: () => Promise<unknown>;
}) {
  const text = useText();
  const client = useQueryClient();
  const [chapters, setChapters] = useState(ceiling.default_chapters);
  // The bounds the value above was chosen against. The query layer keeps the identity of data that
  // did not change (structural sharing), so this fires on a real move of the bounds and not on
  // every refetch.
  const [chosenAgainst, setChosenAgainst] = useState(ceiling);
  if (chosenAgainst !== ceiling) {
    setChosenAgainst(ceiling);
    setChapters(ceiling.default_chapters);
  }
  // ⚠ OFF by default, and that is a choice about TODAY rather than about the product. With the stop
  // on, a run ends at `awaiting_bank` — and nothing in this build can take it further: the signing
  // screen is S5, the bank has no read channel at all (BACKLOG Ф-43), and `resume` answers 409
  // while the set of decisions is incomplete (contract §resumeRun). Preselecting it would be
  // preselecting a dead end. The checkbox itself stays, because the choice is the user's and belongs
  // to THIS run (owner, 02.08); the default flips back the day S5 gives the stop somewhere to go.
  const [verifyBank, setVerifyBank] = useState(false);

  const run = useMutation<Run, Error>({
    mutationFn: () => startRun(bookId, { ceiling_chapters: chapters, verify_bank: verifyBank }),
    onSuccess: () => {
      // The run lives on the book card — that is where the shell reads the stream's id from.
      void client.invalidateQueries({ queryKey: keys.book(bookId) });
      onClose();
    },
    onError: (error) => {
      // A 409 says the state moved between the read and this call. What moved is the platform's to
      // name (its phrase reaches the screen untouched); ours is to read the state again and let the
      // person look — never a quiet retry with a request the platform has just refused.
      if (error instanceof ApiError && error.status === 409) void onConflict();
    },
  });

  // `max_chapters: 0` is not a scale with nothing on it: no run can start at all, and the honest
  // shape of that is the exhausted state instead of a control that cannot be used.
  if (ceiling.max_chapters === 0) {
    return (
      <Blank title={text('run.exhaustedTitle')} description={text('run.exhaustedDescription')} />
    );
  }

  return (
    <div className={styles.form}>
      <Slider
        label={text('about.ceiling')}
        value={chapters}
        min={ceiling.min_chapters}
        max={ceiling.max_chapters}
        onChange={setChapters}
        valueLabel={counted(chapters, chapterForms)}
        hint={text('run.ceilingHint')}
      />

      <div className={styles.option}>
        <Checkbox label={text('run.verifyBank')} isSelected={verifyBank} onChange={setVerifyBank} />
        <p className={styles.hint}>{text('run.verifyBankHint')}</p>
      </div>

      {/* A permanent live region, as in the intake form: the refusal appears away from the focus,
          and a reader that is not told is a reader who thinks the press did nothing (WCAG 4.1.3). */}
      <div role="status" className={styles.live}>
        {run.isError && <Refused error={run.error} />}
      </div>

      <div className={styles.actions}>
        <Button look="action" onPress={onClose}>
          {text('action.cancel')}
        </Button>
        <Button look="primary" isDisabled={run.isPending} onPress={() => run.mutate()}>
          {text('run.action')}
        </Button>
      </div>
    </div>
  );
}

/**
 * Why the run did not start. As in the intake form, the phrase is the platform's where it sent one
 * and the ADVICE is ours: a moved ceiling and a deployment that cannot run at all end in different
 * next actions, and neither of them is "press it again".
 */
function Refused({ error }: { error: Error }) {
  const text = useText();
  const [phrase, advice] = refusal(error, text);
  return (
    <div className={styles.refused}>
      <p className={styles.phrase}>{phrase}</p>
      <p className={styles.hint}>{text(advice)}</p>
    </div>
  );
}

function refusal(error: Error, text: Text): [string, MessageKey] {
  if (!(error instanceof ApiError)) return [text('loaded.unknownError'), 'upload.refusedAdvice'];
  if (error.status === 0) return [text('loaded.serverUnreachable'), 'upload.retryAdvice'];

  const own: Partial<Record<number, [MessageKey, MessageKey]>> = {
    409: ['run.conflict', 'run.conflictAdvice'],
    503: ['run.unavailable', 'run.unavailableAdvice'],
  };
  const [fallback, advice] = own[error.status] ?? ['run.failedTitle', 'upload.refusedAdvice'];
  return [error.problem?.detail ?? error.problem?.title ?? text(fallback), advice];
}