// The intake world: a library that starts EMPTY and fills up from the form.
//
// It is the one fixture that models a WRITE, and therefore the one that has to model the rules of
// the wire rather than only the shape of the answer: the order of the parts, their number, the
// length of a text field, the cap on the body. A client that broke one of them would otherwise be
// found out by the platform and not here (contract 0.2.3, PD-172/PD-180).
//
// ⚠ HOW A REFUSAL IS ASKED FOR. Everything the platform refuses for a reason of its own — no intake
// on this deployment, a body that missed the deadline, a source it could not read — is chosen by a
// MARKER IN THE FILE NAME (the table below). It is the fixture's own switch, the same job the route
// does for the choice of the world, and it exists because those branches have no other trigger: a
// correct client cannot produce them, so without it the screens for them would be checked by
// nothing. Product code knows nothing about any of this.

import { HttpResponse, delay, http } from 'msw';

import type { components } from '../api/schema';
import { begin, live } from './live';

type Schemas = components['schemas'];

/** The wire rules of the intake, in the platform's own numbers (httpapi/v0.go). */
export const intakeLimits = {
  maxParts: 16,
  maxFieldBytes: 1024,
  /** Small on purpose: a scene has to be able to exceed it without carrying tens of megabytes. */
  maxBodyBytes: 2_000_000,
};

/** How long a book stays `parsing` before the fixture answers what came of it. */
export const parseMs = 1200;

/**
 * How long the answer to the intake is held back.
 *
 * A book is minutes of upload on a domestic connection, and the state that waits for the answer is
 * a state the screen has to have — held for a moment here so that it can be photographed and
 * checked at all. Everything before it is the browser's own doing: the mock network answers the
 * request only after the body has been read.
 */
const answerMs = 600;

/**
 * What a marker in the file name asks the fixture to answer. `null` means "accept and parse".
 *
 * The refusals are the classes the contract names for this call; the reasons are the platform's
 * closed vocabulary for a book that was accepted and then could not be turned into chapters.
 */
const outcomes = [
  // ⚠ The phrases are deliberately NOT the client's own fallbacks word for word: the client shows
  // the server's phrase and keeps its own only for a refusal that carried no body, and two equal
  // strings would make that impossible to tell apart — the scene checking it went blind on exactly
  // the one that matched (found by the adversarial review).
  { marker: 'refuse-400', status: 400, title: 'Загрузка не дошла целиком' },
  { marker: 'refuse-404', status: 404, title: 'Этот сервис книги не принимает' },
  { marker: 'refuse-408', status: 408, title: 'Файл не дошёл за отведённое время' },
  { marker: 'reject-source', reject: 'source_unreadable' },
  { marker: 'reject-config', reject: 'not_configured' },
  { marker: 'reject-parser', reject: 'parser_unavailable' },
] as const;

interface Accepted {
  book: Schemas['Book'];
  chapters: Schemas['Chapter'][];
  /** When the parse ends, in milliseconds of the clock. */
  parsedAt: number;
  reject: Schemas['RejectReason'] | null;
  run: Schemas['Run'] | null;
}

const accepted: Accepted[] = [];

/** Tests and scenes share one module instance; a world left half-filled would leak into the next. */
export function clearIntake(): void {
  accepted.length = 0;
  ceilingMoved = false;
}

/** Moves every unfinished parse into the past — for tests, which must not wait out a delay. */
export function settleIntake(): void {
  for (const row of accepted) row.parsedAt = 0;
}

export function intakeBooks(): Schemas['Book'][] {
  // NEWEST FIRST, as the platform answers (`order by b.added_at desc, b.id desc` — pgstore/books.go):
  // a fixture that listed them the other way round would put the book just uploaded at the bottom of
  // a library the screen reads from the top.
  return accepted.map((row) => shown(row)).reverse();
}

export function intakeChapters(bookId: string): Schemas['Chapter'][] {
  const row = accepted.find((item) => item.book.id === bookId);
  // A book still being parsed has no chapters yet — and that is the honest answer, not an error:
  // the tree shows the book with none until the parse ends.
  return row && parsed(row) && row.reject === null ? row.chapters : [];
}

export function intakeUnits(bookId: string, chapterId: string): Schemas['Unit'][] {
  const chapter = intakeChapters(bookId).find((row) => row.id === chapterId);
  if (!chapter) return [];
  return Array.from({ length: chapter.units_total }, (_, index) => ({
    id: `${chapterId}_u${String(index)}`,
    source: sources[index % sources.length] ?? '',
    target: '',
    state: 'pending' as const,
    note: null,
  }));
}

export function intakeRun(bookId: string): Schemas['Run'] | null {
  const run = accepted.find((row) => row.book.id === bookId)?.run;
  // The revision is taken at READ time: frozen at the start it would fall behind the frames the
  // stream is already emitting, which is the one thing the fixture must never do.
  return run ? { ...run, revision: live.revision } : null;
}

/**
 * One chapter of the running book finishes.
 *
 * The tree draws progress PER CHAPTER, and without this the indicators stood at zero while the
 * book's own counter ran to the end — the tree and the card contradicting each other on the same
 * screen. Mutates the stored chapter so that a re-read agrees with the frame: a fixture whose read
 * takes back what its stream just said is a server the contract forbids.
 */
export function advanceIntakeChapter(): Schemas['EventChapter'] | null {
  const row = accepted.find((item) => item.run !== null);
  const chapter = row?.chapters.find((item) => item.units_done < item.units_total);
  if (!chapter) return null;
  chapter.units_done = chapter.units_total;
  live.revision += 1;
  return {
    chapter_id: chapter.id,
    units_done: chapter.units_done,
    note_count: chapter.note_count,
  };
}

/**
 * The bounds of the ceiling scale, and they MOVE — once, on the first start.
 *
 * The contract says exactly this happens (§startRun): the maximum belongs to the account, a hold
 * taken for another book lowers it between the read and the call, and the answer is 409. It is the
 * one refusal a correct client can meet on a correct form, so the fixture produces it the way the
 * platform does rather than by a marker — and it produces it ONCE, so the second press goes through
 * and the path stays walkable.
 */
export const intakeCeiling = { min_chapters: 1, max_chapters: 8, default_chapters: 4 };
let ceilingMoved = false;

/** The bounds a read answers with. Narrower after the first start attempt was refused. */
export function intakeBounds(): Schemas['CeilingBounds'] {
  return ceilingMoved ? { ...intakeCeiling, max_chapters: 2, default_chapters: 2 } : intakeCeiling;
}

/** The refusal a start meets when the ceiling asked for no longer fits. */
export function intakeCeilingFits(chapters: number): boolean {
  if (!ceilingMoved) {
    ceilingMoved = true;
    return false;
  }
  return chapters <= intakeBounds().max_chapters;
}

/**
 * Starting a run over an uploaded book. The world's own, because here the run does not exist until
 * it is started — in the hand-written worlds it is a fixture that was always there.
 */
export function startIntakeRun(
  bookId: string,
  request: Schemas['RunRequest'],
): Schemas['Run'] | null {
  const row = accepted.find((item) => item.book.id === bookId);
  if (!row || !parsed(row) || row.reject !== null) return null;
  begin(row.book.progress.draft.total);
  row.run = {
    id: `run_${row.book.id}`,
    revision: live.revision,
    status: 'translating',
    verify_bank: request.verify_bank,
    ceiling_chapters: request.ceiling_chapters,
    paused_reason: null,
    started_at: new Date().toISOString(),
    finished_at: null,
  };
  return row.run;
}

/**
 * The run walks into its ceiling and halts.
 *
 * ⚠ Built to the CONTRACT and not to the live platform: a ceiling stop is `paused` with a machine
 * reason, never `failed` (§BookStatus). On the stand today it arrives as `failed` — the consumer
 * half of that seam is not built (platform PD-113) — and a fixture bent to match it would teach the
 * screens the wrong shape. Which ceiling was hit, the run's own or the account's, this frame does
 * not say: whether the two need separate reasons is the owner's question (K-13), so the fixture
 * uses the single value the contract has.
 */
export function haltIntakeRun(): void {
  const row = accepted.find((item) => item.run !== null);
  if (!row?.run) return;
  live.revision += 3;
  row.run = { ...row.run, status: 'paused', paused_reason: 'credit_exhausted' };
}

/** `POST /books` — the whole of it, rules included. */
export const intakeHandler = http.post('*/v0/books', async ({ request }) => {
  if (request.headers.get('X-TM-Client') === null) {
    return problem(403, 'Запрос без заголовка клиента');
  }
  const form = await request.formData();
  const parts = [...form.entries()];
  if (parts.length > intakeLimits.maxParts) return problem(400, 'В форме слишком много частей');
  // ⚠ The platform reads the form as a STREAM and STOPS at the file (httpapi/v0.go): everything
  // after it is never read. So the rule is modelled as the platform's own — parts before the file
  // are taken, parts after it are dropped on the floor — and not as "the file must be last, else
  // 400". The difference is not academic: a form with a trailing `genre` is ACCEPTED by the
  // platform, minus the genre, and a fixture that refused it would refuse a legal request (found by
  // the adversarial review of the assignment itself).
  const fileAt = parts.findIndex(([name, value]) => name === 'file' && value instanceof File);
  if (fileAt < 0) return problem(400, 'Форма пришла без файла');
  const read = parts.slice(0, fileAt);
  const last = parts[fileAt];
  if (!last || !(last[1] instanceof File)) return problem(400, 'Форма пришла без файла');
  // In BYTES, which is what the platform measures (`io.LimitReader` over the part): a Cyrillic
  // character is two bytes and a hanzi three, so counting string units would let through a field
  // three times over the limit.
  const bytesOf = new TextEncoder();
  for (const [name, value] of read) {
    if (typeof value === 'string' && bytesOf.encode(value).length > intakeLimits.maxFieldBytes) {
      return problem(400, `Поле «${name}» длиннее килобайта`);
    }
  }
  const file = last[1];
  if (file.size > intakeLimits.maxBodyBytes) {
    return problem(413, 'Файл больше, чем принимает сервис');
  }

  const outcome = outcomes.find((item) => file.name.includes(item.marker));
  if (outcome && 'status' in outcome) return problem(outcome.status, outcome.title);

  await delay(answerMs);
  // Only what was READ counts — a language sent after the file is a language the platform never
  // saw, and it answers that with the same 400 as one never sent.
  const fields = new Map(
    read.filter(([, value]) => typeof value === 'string') as [string, string][],
  );
  const source = fields.get('source_lang') ?? '';
  const target = fields.get('target_lang') ?? '';
  if (source === '' || target === '') return problem(400, 'Языки не заданы');

  // CHARACTERS and not bytes: the platform counts UTF-8 lead bytes as it streams
  // (books.go `counter.Write`), which is a count of code points — and on CJK that is three times
  // fewer than bytes. The cap above is the other quantity and stays in bytes, as it is on the wire.
  const characters = [...(await file.text())].length;
  const book = create({
    // The title of the intake, or the name of the file when the form left it empty — which is what
    // the platform does today (contract 0.2.3, `BookIntake.title`).
    title: (fields.get('title') ?? '') || file.name.replace(/\.[^.]+$/, ''),
    source,
    target,
    genre: fields.get('genre') ?? '',
    characters,
    reject: outcome?.reject ?? null,
  });
  // The `201` carries `parsing` and never `uploading` (PD-180): by the time an answer can be read,
  // the last byte is in. `uploading` is real and is seen from a SECOND read of the library while
  // the body is still on the wire — which is the mock network's own doing, not this handler's.
  return HttpResponse.json(shown(book), { status: 201 });
});

// Deliberately Russian: the platform words its own `problem+json`, and the client shows those
// phrases as they came (contract §Problem). A fixture that answered in English would be modelling
// a platform we do not have.
function problem(status: number, title: string): Response {
  return HttpResponse.json({ type: 'about:blank', title, status } satisfies Schemas['Problem'], {
    status,
    headers: { 'Content-Type': 'application/problem+json' },
  });
}

function create(intake: {
  title: string;
  source: string;
  target: string;
  genre: string;
  characters: number;
  reject: Schemas['RejectReason'] | null;
}): Accepted {
  const chapters = chaptersOf(accepted.length);
  const row: Accepted = {
    book: {
      id: `bk_up${String(accepted.length + 1)}`,
      title: intake.title,
      source_lang: intake.source,
      target_lang: intake.target,
      genre: intake.genre,
      chapter_count: chapters.length,
      character_count: intake.characters,
      added_at: new Date().toISOString(),
      status: 'parsing',
      // ZERO until a run starts, and it is the contract's shape: `Progress` counts the units of a
      // RUN, so a book that has never been run has nothing to count. A fixture that filled the
      // totals at intake made the card print "0 sections, 12 blocks" while the parse was still on.
      progress: { draft: { done: 0, total: 0 }, edit: { done: 0, total: 0 } },
      note_count: 0,
    },
    chapters,
    parsedAt: Date.now() + parseMs,
    reject: intake.reject,
    run: null,
  };
  accepted.push(row);
  live.revision += 1;
  return row;
}

const parsed = (row: Accepted) => Date.now() >= row.parsedAt;

/**
 * The book as a read must answer it right now: parsing until the deadline, then either the tree it
 * was cut into or the reason it could not be.
 *
 * ⚠ Nothing PUSHES this change: the event stream belongs to a run, and a book being parsed has no
 * run at all. The client learns of it by asking again — which is why the reads of the library and
 * of the card poll while a book is in intake (src/api/queries.ts, BACKLOG Ф-56).
 */
function shown(row: Accepted): Schemas['Book'] {
  // ⚠ NO chapter count until the parse ends, and it is the platform's own shape: the number is
  // written when the engine has cut the book, so a fixture that answered it earlier would teach the
  // screen that a book being parsed already knows how many sections it has.
  if (!parsed(row)) return { ...row.book, chapter_count: 0 };
  if (row.reject !== null) {
    return { ...row.book, status: 'rejected', reject_reason: row.reject, chapter_count: 0 };
  }
  if (row.run) {
    return {
      ...row.book,
      status: row.run.status,
      progress: {
        draft: { done: live.draftDone, total: live.draftTotal },
        edit: { done: 0, total: live.draftTotal },
        eta_seconds: live.etaSeconds,
      },
    };
  }
  return { ...row.book, status: 'not_started' };
}

// The book a parse produces: labels of the same shape as the long-tail fixture, and a book without
// headings among them — a book legally has none (K-3), and the intake is where one arrives.
const headings = [
  'Нет раскаяния',
  'Прозрение пятисот лет',
  'Церемония открытия',
  'Класс А',
  'Деревня Гуюэ',
  'Первый гу',
  'Аптека',
  'Кровь на снегу',
];

const sources = [
  '青茅山下，古月家的少年们排成一列，等待开窍。',
  '风从北面吹来，带着雪的气味。',
  '祠堂前的石阶上落满了霜。',
];

function chaptersOf(book: number): Schemas['Chapter'][] {
  return Array.from({ length: headings.length }, (_, index) => ({
    id: `up${String(book)}_ch${String(index + 1)}`,
    number: index + 1,
    heading: index === headings.length - 1 ? null : (headings[index] ?? null),
    units_total: 1 + (index % 2),
    units_done: 0,
    note_count: 0,
  }));
}