import type { TaxonomyAsset } from '@/lib/server/taxonomy/types';

type FilingAssetDiscoveryInput = {
  cik: string;
  accessionNumber: string;
  filingUrl: string | null;
  primaryDocument: string | null;
  fetchImpl?: typeof fetch;
};

type FilingDirectoryJson = {
  directory?: {
    item?: Array<{
      name?: string;
      type?: string;
      size?: string | number;
    }>;
  };
};

function envUserAgent() {
  return process.env.SEC_USER_AGENT || 'Fiscal Clone <support@fiscal.local>';
}

function compactAccessionNumber(value: string) {
  return value.replace(/-/g, '');
}

function normalizeCikForPath(value: string) {
  const digits = value.replace(/\D/g, '');
  if (!digits) {
    return null;
  }

  const numeric = Number(digits);
  if (!Number.isFinite(numeric)) {
    return null;
  }

  return String(numeric);
}

function resolveFilingDirectoryUrl(input: {
  filingUrl: string | null;
  cik: string;
  accessionNumber: string;
}) {
  const direct = input.filingUrl?.trim();
  if (direct) {
    const lastSlash = direct.lastIndexOf('/');
    if (lastSlash > 'https://'.length) {
      return direct.slice(0, lastSlash + 1);
    }
  }

  const cikPath = normalizeCikForPath(input.cik);
  const accessionPath = compactAccessionNumber(input.accessionNumber);
  if (!cikPath || !accessionPath) {
    return null;
  }

  return `https://www.sec.gov/Archives/edgar/data/${cikPath}/${accessionPath}/`;
}

function classifyAssetType(name: string): TaxonomyAsset['asset_type'] {
  const lower = name.toLowerCase();

  if (lower.endsWith('.pdf')) {
    return 'pdf';
  }

  if (lower.endsWith('.xsd')) {
    return 'schema';
  }

  if (lower.endsWith('.xml')) {
    if (/(_|-)pre\.xml$/.test(lower) || /presentation/.test(lower)) {
      return 'presentation';
    }

    if (/(_|-)lab\.xml$/.test(lower) || /label/.test(lower)) {
      return 'label';
    }

    if (/(_|-)cal\.xml$/.test(lower) || /calculation/.test(lower)) {
      return 'calculation';
    }

    if (/(_|-)def\.xml$/.test(lower) || /definition/.test(lower)) {
      return 'definition';
    }

    return 'instance';
  }

  return 'other';
}

function scorePdf(name: string, sizeBytes: number | null) {
  const lower = name.toLowerCase();
  let score = 0;

  if (/financial|statement|annual|quarter|10k|10q/.test(lower)) {
    score += 8;
  }

  if (/exhibit|ex-\d+/.test(lower)) {
    score -= 2;
  }

  if (sizeBytes && sizeBytes > 100_000) {
    score += 1;
  }

  return score;
}

function scoreInstance(name: string, primaryDocument: string | null) {
  const lower = name.toLowerCase();
  let score = 1;

  if (/_htm\.xml$/.test(lower)) {
    score += 4;
  }

  if (/_ins\.xml$/.test(lower)) {
    score += 4;
  }

  const basePrimary = (primaryDocument ?? '').replace(/\.[a-z0-9]+$/i, '').toLowerCase();
  if (basePrimary && lower.includes(basePrimary)) {
    score += 5;
  }

  if (/cal|def|lab|pre/.test(lower)) {
    score -= 3;
  }

  return score;
}

function parseSize(raw: unknown) {
  if (typeof raw === 'number') {
    return Number.isFinite(raw) ? raw : null;
  }

  if (typeof raw === 'string') {
    const parsed = Number(raw);
    return Number.isFinite(parsed) ? parsed : null;
  }

  return null;
}

async function fetchJson<T>(url: string, fetchImpl: typeof fetch): Promise<T> {
  const response = await fetchImpl(url, {
    headers: {
      'User-Agent': envUserAgent(),
      Accept: 'application/json'
    },
    cache: 'no-store'
  });

  if (!response.ok) {
    throw new Error(`SEC request failed (${response.status})`);
  }

  return await response.json() as T;
}

export async function discoverFilingAssets(input: FilingAssetDiscoveryInput): Promise<{
  directoryUrl: string | null;
  assets: TaxonomyAsset[];
}> {
  const fetchImpl = input.fetchImpl ?? fetch;
  const directoryUrl = resolveFilingDirectoryUrl({
    filingUrl: input.filingUrl,
    cik: input.cik,
    accessionNumber: input.accessionNumber
  });

  if (!directoryUrl) {
    return {
      directoryUrl: null,
      assets: []
    };
  }

  let payload: FilingDirectoryJson | null = null;
  try {
    payload = await fetchJson<FilingDirectoryJson>(`${directoryUrl}index.json`, fetchImpl);
  } catch {
    payload = null;
  }

  const discovered: TaxonomyAsset[] = [];
  for (const item of payload?.directory?.item ?? []) {
    const name = (item.name ?? '').trim();
    if (!name) {
      continue;
    }

    const url = `${directoryUrl}${name.replace(/^\/+/, '')}`;
    const asset_type = classifyAssetType(name);
    const size_bytes = parseSize(item.size);

    discovered.push({
      asset_type,
      name,
      url,
      size_bytes,
      score: null,
      is_selected: false
    });
  }

  if (discovered.length === 0 && input.filingUrl) {
    const fallbackName = input.primaryDocument ?? input.filingUrl.split('/').pop() ?? 'primary_document';
    discovered.push({
      asset_type: fallbackName.toLowerCase().endsWith('.xml') ? 'instance' : 'other',
      name: fallbackName,
      url: input.filingUrl,
      size_bytes: null,
      score: null,
      is_selected: true
    });
  }

  const instanceCandidates = discovered
    .filter((asset) => asset.asset_type === 'instance')
    .map((asset) => ({
      asset,
      score: scoreInstance(asset.name, input.primaryDocument)
    }))
    .sort((a, b) => b.score - a.score);

  const selectedInstanceUrl = instanceCandidates[0]?.asset.url ?? null;

  const selectedPdfUrls = discovered
    .filter((asset) => asset.asset_type === 'pdf')
    .map((asset) => ({
      asset,
      score: scorePdf(asset.name, asset.size_bytes)
    }))
    .sort((a, b) => b.score - a.score)
    .slice(0, 3)
    .map((entry) => entry.asset.url);

  const assets = discovered.map((asset) => {
    if (asset.asset_type === 'instance') {
      const score = scoreInstance(asset.name, input.primaryDocument);
      return {
        ...asset,
        score,
        is_selected: asset.url === selectedInstanceUrl
      };
    }

    if (asset.asset_type === 'pdf') {
      const score = scorePdf(asset.name, asset.size_bytes);
      return {
        ...asset,
        score,
        is_selected: selectedPdfUrls.includes(asset.url)
      };
    }

    return {
      ...asset,
      score: null,
      is_selected: asset.asset_type === 'presentation'
        || asset.asset_type === 'label'
        || asset.asset_type === 'calculation'
        || asset.asset_type === 'definition'
        || asset.asset_type === 'schema'
    };
  });

  return {
    directoryUrl,
    assets
  };
}