import {
  ATTEMPT_STATUSES,
  JOB_ITEM_TERMINAL_STATES,
  JOB_STATUSES,
  MAX_PAGE_SIZE,
  SORT_DIRECTIONS,
  type Attempt,
  type Job,
  type JobItem,
  type JobPage,
  type JobPageQuery,
  type ProblemDetails,
  type ValidationIssue,
} from '@multi-simadmin/contracts';

import type { JobsDataSource } from './jobs-page.js';

const MAX_STRING_LENGTH = 256;
const QUERY_KEYS = [
  'page',
  'pageSize',
  'sort',
  'direction',
  'status',
  'operationId',
  'rootJobId',
  'instanceId',
] as const;
const ITEM_KEYS = ['id', 'targetId', 'state', 'sourceJobItemId', 'error'] as const;
const ATTEMPT_KEYS = ['id', 'state', 'startedAt', 'finishedAt'] as const;
const PROBLEM_KEYS = [
  'type',
  'title',
  'status',
  'detail',
  'code',
  'requestId',
  'validation',
] as const;

function record(value: unknown): Record<string, unknown> | null {
  return value !== null && typeof value === 'object' && !Array.isArray(value)
    ? (value as Record<string, unknown>)
    : null;
}

function hasExactKeys(
  value: Record<string, unknown>,
  required: readonly string[],
  optional: readonly string[] = [],
): boolean {
  const keys = Object.keys(value);
  const allowed = new Set([...required, ...optional]);
  return (
    required.every((key) => Object.hasOwn(value, key)) && keys.every((key) => allowed.has(key))
  );
}

function boundedString(value: unknown): value is string {
  return typeof value === 'string' && value.length > 0 && value.length <= MAX_STRING_LENGTH;
}

function canonicalTimestamp(value: unknown): value is string {
  if (!boundedString(value)) return false;
  const time = Date.parse(value);
  return Number.isFinite(time) && new Date(time).toISOString() === value;
}

function safePositiveInteger(value: unknown, maximum = Number.MAX_SAFE_INTEGER): value is number {
  return Number.isSafeInteger(value) && (value as number) >= 1 && (value as number) <= maximum;
}

function parseValidationIssue(value: unknown): ValidationIssue | null {
  const source = record(value);
  if (
    !source ||
    !hasExactKeys(source, ['field', 'code', 'message']) ||
    !boundedString(source.field) ||
    !boundedString(source.code) ||
    !boundedString(source.message)
  )
    return null;
  return { field: source.field, code: source.code, message: source.message };
}

function parseProblem(value: unknown): ProblemDetails | null {
  const source = record(value);
  if (
    !source ||
    !hasExactKeys(source, PROBLEM_KEYS.slice(0, 6), ['validation']) ||
    !boundedString(source.type) ||
    !boundedString(source.title) ||
    !Number.isSafeInteger(source.status) ||
    (source.status as number) < 400 ||
    (source.status as number) > 599 ||
    !boundedString(source.detail) ||
    !boundedString(source.code) ||
    !boundedString(source.requestId)
  )
    return null;
  let validation: ValidationIssue[] | undefined;
  if (source.validation !== undefined) {
    if (!Array.isArray(source.validation) || source.validation.length > MAX_PAGE_SIZE) return null;
    validation = [];
    for (const candidate of source.validation) {
      const issue = parseValidationIssue(candidate);
      if (!issue) return null;
      validation.push(issue);
    }
  }
  return {
    type: source.type,
    title: source.title,
    status: source.status as number,
    detail: source.detail,
    code: source.code,
    requestId: source.requestId,
    ...(validation === undefined ? {} : { validation }),
  };
}

function parseItem(value: unknown): JobItem | null {
  const source = record(value);
  if (
    !source ||
    !hasExactKeys(source, ITEM_KEYS.slice(0, 3), ['sourceJobItemId', 'error']) ||
    !boundedString(source.id) ||
    !boundedString(source.targetId) ||
    typeof source.state !== 'string' ||
    !(JOB_ITEM_TERMINAL_STATES as readonly string[]).includes(source.state)
  )
    return null;
  const sourceJobItemId = source.sourceJobItemId;
  if (sourceJobItemId !== undefined && !boundedString(sourceJobItemId)) return null;
  const error = source.error === undefined ? undefined : parseProblem(source.error);
  if (source.error !== undefined && !error) return null;
  const result: JobItem = {
    id: source.id,
    targetId: source.targetId,
    state: source.state as JobItem['state'],
    ...(sourceJobItemId === undefined ? {} : { sourceJobItemId }),
  };
  return error ? { ...result, error } : result;
}

function parseAttempt(value: unknown): Attempt | null {
  const source = record(value);
  if (
    !source ||
    !hasExactKeys(source, ATTEMPT_KEYS.slice(0, 3), ['finishedAt']) ||
    !boundedString(source.id) ||
    typeof source.state !== 'string' ||
    !(ATTEMPT_STATUSES as readonly string[]).includes(source.state) ||
    !canonicalTimestamp(source.startedAt) ||
    (source.finishedAt !== undefined && !canonicalTimestamp(source.finishedAt))
  )
    return null;
  return {
    id: source.id,
    state: source.state as Attempt['state'],
    startedAt: source.startedAt,
    ...(source.finishedAt === undefined ? {} : { finishedAt: source.finishedAt as string }),
  };
}

function parseJob(value: unknown): Job | null {
  const source = record(value);
  if (
    !source ||
    !hasExactKeys(
      source,
      ['id', 'operationId', 'status', 'rootJobId', 'items', 'attempts', 'createdAt'],
      ['retryOfJobId'],
    ) ||
    !boundedString(source.id) ||
    !boundedString(source.operationId) ||
    typeof source.status !== 'string' ||
    !(JOB_STATUSES as readonly string[]).includes(source.status) ||
    !boundedString(source.rootJobId) ||
    !Array.isArray(source.items) ||
    source.items.length > MAX_PAGE_SIZE ||
    !Array.isArray(source.attempts) ||
    source.attempts.length > MAX_PAGE_SIZE ||
    !canonicalTimestamp(source.createdAt) ||
    (source.retryOfJobId !== undefined && !boundedString(source.retryOfJobId))
  )
    return null;
  const items: JobItem[] = [];
  for (const candidate of source.items) {
    const item = parseItem(candidate);
    if (!item) return null;
    items.push(item);
  }
  const attempts: Attempt[] = [];
  for (const candidate of source.attempts) {
    const attempt = parseAttempt(candidate);
    if (!attempt) return null;
    attempts.push(attempt);
  }
  return {
    id: source.id,
    operationId: source.operationId,
    status: source.status as Job['status'],
    ...(source.retryOfJobId === undefined ? {} : { retryOfJobId: source.retryOfJobId as string }),
    rootJobId: source.rootJobId,
    items,
    attempts,
    createdAt: source.createdAt,
  };
}

function parseJobPage(value: unknown): JobPage {
  const source = record(value);
  if (!source || !hasExactKeys(source, ['items', 'page']) || !Array.isArray(source.items))
    throw new Error('Jobs response is invalid.');
  const page = record(source.page);
  if (
    !page ||
    !hasExactKeys(page, ['page', 'pageSize', 'total']) ||
    !safePositiveInteger(page.page) ||
    !safePositiveInteger(page.pageSize, MAX_PAGE_SIZE) ||
    !Number.isSafeInteger(page.total) ||
    (page.total as number) < 0 ||
    source.items.length > MAX_PAGE_SIZE ||
    source.items.length > (page.pageSize as number) ||
    source.items.length > (page.total as number)
  )
    throw new Error('Jobs response is invalid.');
  const items: Job[] = [];
  for (const candidate of source.items) {
    const item = parseJob(candidate);
    if (!item) throw new Error('Jobs response is invalid.');
    items.push(item);
  }
  return {
    items,
    page: {
      page: page.page as number,
      pageSize: page.pageSize as number,
      total: page.total as number,
    },
  };
}

function queryString(query: JobPageQuery): string {
  if (Object.keys(query).some((key) => !(QUERY_KEYS as readonly string[]).includes(key)))
    throw new Error('Jobs query is invalid.');
  const params = new URLSearchParams();
  for (const key of QUERY_KEYS) {
    const value = query[key];
    if (value === undefined) continue;
    const valid =
      (key === 'page' && safePositiveInteger(value)) ||
      (key === 'pageSize' && safePositiveInteger(value, MAX_PAGE_SIZE)) ||
      (key === 'sort' && ['createdAt', 'status', 'operationId'].includes(value as string)) ||
      (key === 'direction' && (SORT_DIRECTIONS as readonly unknown[]).includes(value)) ||
      (key === 'status' && (JOB_STATUSES as readonly unknown[]).includes(value)) ||
      (['operationId', 'rootJobId', 'instanceId'].includes(key) && boundedString(value));
    if (!valid) throw new Error('Jobs query is invalid.');
    params.set(key, String(value));
  }
  const serialized = params.toString();
  return serialized ? `?${serialized}` : '';
}

export class JobsApiError extends Error {
  readonly status: number;
  readonly code: string;
  readonly requestId: string;

  constructor(status: number, code: string, requestId: string) {
    super(`Jobs request failed (${status}; code=${code}; requestId=${requestId}).`);
    this.name = 'JobsApiError';
    this.status = status;
    this.code = code;
    this.requestId = requestId;
  }
}

async function responseError(response: Response): Promise<JobsApiError> {
  let code = 'UNKNOWN';
  let requestId = 'unavailable';
  try {
    const problem = parseProblem(await response.json());
    if (problem && problem.status === response.status) {
      code = problem.code;
      requestId = problem.requestId;
    }
  } catch {
    // Never read or expose raw response text or Problem detail/title.
  }
  return new JobsApiError(response.status, code, requestId);
}

export function createJobsApiDataSource(fetcher: typeof fetch = fetch): JobsDataSource {
  return {
    async load(query, signal): Promise<JobPage> {
      const response = await fetcher(`/api/v1/jobs${queryString(query)}`, {
        method: 'GET',
        credentials: 'same-origin',
        headers: { accept: 'application/json' },
        signal,
      });
      if (!response.ok) throw await responseError(response);
      let body: unknown;
      try {
        body = await response.json();
      } catch {
        throw new Error('Jobs response is invalid.');
      }
      return parseJobPage(body);
    },
  };
}