#!/usr/bin/env node
// Validates that every translation file under src/i18n is complete and consistent.
//
// Checks:
//   1. Locales declared in SUPPORTED_LANGUAGES (index.ts) match the files in locales/
//      and the language records in descriptions.ts / details.ts.
//   2. Every leaf key in en.ts is present and non-empty in every other locale.
//   3. Every {{placeholder}} and HTML tag in an English string also appears,
//      with the same multiset, in the translated string.
//   4. descriptions.ts and details.ts: the union of feature-name keys across
//      languages is treated as canonical; every language must cover all of them.
//   5. The lazy locale loader map covers every non-English supported language.
//   6. Selected visible UI strings that previously slipped through are not
//      hardcoded outside the i18n files.
//
// The script parses the TypeScript source with the compiler API and walks the
// AST — no runtime import, no transpilation, no temp files. Run it with:
//   node frontend/scripts/check-translations.mjs

import { readFileSync, readdirSync } from 'fs';
import { dirname, join, relative } from 'path';
import { fileURLToPath } from 'url';
import ts from 'typescript';

const __dirname = dirname(fileURLToPath(import.meta.url));
const I18N_DIR = join(__dirname, '..', 'src', 'i18n');
const LOCALES_DIR = join(I18N_DIR, 'locales');
const SRC_DIR = join(__dirname, '..', 'src');

const PLACEHOLDER_RE = /\{\{\s*[a-zA-Z_][\w]*\s*\}\}/g;
const HTML_TAG_RE = /<\/?[a-zA-Z][\w]*\b[^>]*>/g;

const errors = [];
const warnings = [];
const fail = (msg) => errors.push(msg);
const warn = (msg) => warnings.push(msg);

const SAME_AS_EN_PATH_ALLOWLIST = new Set([
  'streetView.title',
  'home.showcaseMinutes',
  'home.showcaseStep2Sources',
  'format.lessThanMin',
  'format.moreThanMin',
  'learnPage.attrOglLink',
  'learnPage.attrOsmContrib',
  'learnPage.attrOsmLicenseLink',
  'home.showcaseTopThree',
  'learnPage.dsTravelOrigin',
  'learnPage.dsParkOrigin',
  'learnPage.dsCrimeOrigin',
  'learnPage.dsDemographicsOrigin',
  'learnPage.dsElectionOrigin',
  'learnPage.dsPoiOrigin',
  'learnPage.dsEthnicityOrigin',
  'learnPage.dsBroadbandOrigin',
]);

const SAME_AS_EN_PATH_ALLOWLIST_RE = [/^learnPage\.ds[A-Za-z0-9]+Origin$/];

const SAME_AS_EN_VALUE_ALLOWLIST = new Set([
  'Perfect Postcode',
  'Land Registry',
  'HM Land Registry',
  'ONS',
  'OpenStreetMap',
  'Ofsted',
  'Rightmove',
  'Zoopla',
  'Google',
  'Excel',
  'UK',
  'Reform UK',
  'Labour',
  'Conservative',
  'Liberal Democrat',
]);

const FORBIDDEN_VISIBLE_STRINGS = [
  ['without this filter', 'filters.withoutThisFilter'],
  ['Connecting to server...', 'common.connectingToServer'],
  ['Property saved!', 'toasts.propertySaved'],
  ['View saved', 'toasts.viewSaved'],
  ["Don't show again", 'toasts.dontShowAgain'],
  ['Close pane', 'common.closePane'],
  ['Points of interest', 'poiPane.pointsOfInterest'],
  ['No data', 'common.noData'],
  ['All low', 'common.allLow'],
  ['School type', 'filters.schoolType'],
  ['School rating', 'filters.schoolRating'],
  ['School distance', 'filters.schoolDistance'],
  ['Crime type', 'filters.crimeType'],
  ['POI type', 'filters.poiType'],
  ['Matching homes', 'home.showcaseMatchingHomesLabel'],
  ['Journey routes', 'home.showcaseJourneyRoutes'],
  ['...and lots more', 'home.showcaseLotsMore'],
  ['Send the shortlist', 'home.showcaseSendShortlist'],
  ['Download .xlsx', 'home.showcaseDownloadXlsx'],
  ['Product demo', 'home.productDemoLabel'],
  ['Play product demo', 'home.playProductDemo'],
  ['Scroll to product demo', 'home.scrollToProductDemo'],
];

function parseFile(path) {
  const src = readFileSync(path, 'utf8');
  return ts.createSourceFile(path, src, ts.ScriptTarget.Latest, true);
}

// Recursively turn a TS literal expression into a plain JS value.
// Returns undefined for nodes we don't understand — callers must check.
function literalToJs(node) {
  if (!node) return undefined;
  if (ts.isStringLiteral(node) || ts.isNoSubstitutionTemplateLiteral(node)) return node.text;
  if (ts.isAsExpression(node) || ts.isParenthesizedExpression(node)) {
    return literalToJs(node.expression);
  }
  if (ts.isSatisfiesExpression?.(node)) {
    return literalToJs(node.expression);
  }
  if (ts.isObjectLiteralExpression(node)) {
    const out = {};
    for (const prop of node.properties) {
      if (!ts.isPropertyAssignment(prop)) continue;
      const k = prop.name;
      let key;
      if (ts.isIdentifier(k)) key = k.text;
      else if (ts.isStringLiteral(k) || ts.isNoSubstitutionTemplateLiteral(k)) key = k.text;
      else continue;
      out[key] = literalToJs(prop.initializer);
    }
    return out;
  }
  if (ts.isArrayLiteralExpression(node)) {
    return node.elements.map((e) => literalToJs(e));
  }
  return undefined;
}

function findVarInitializer(sourceFile, name) {
  let result;
  function visit(node) {
    if (ts.isVariableStatement(node)) {
      for (const decl of node.declarationList.declarations) {
        if (ts.isIdentifier(decl.name) && decl.name.text === name) {
          result = decl.initializer;
        }
      }
    }
    ts.forEachChild(node, visit);
  }
  visit(sourceFile);
  return result;
}

function propertyNameText(name) {
  if (ts.isIdentifier(name)) return name.text;
  if (ts.isStringLiteral(name) || ts.isNoSubstitutionTemplateLiteral(name)) return name.text;
  return undefined;
}

function objectLiteralKeys(node) {
  if (!node) return undefined;
  if (ts.isAsExpression(node) || ts.isParenthesizedExpression(node)) {
    return objectLiteralKeys(node.expression);
  }
  if (ts.isSatisfiesExpression?.(node)) {
    return objectLiteralKeys(node.expression);
  }
  if (!ts.isObjectLiteralExpression(node)) return undefined;
  const keys = [];
  for (const prop of node.properties) {
    if (ts.isPropertyAssignment(prop)) {
      const key = propertyNameText(prop.name);
      if (key) keys.push(key);
    }
  }
  return keys;
}

function readSupportedLanguages() {
  const sf = parseFile(join(I18N_DIR, 'index.ts'));
  const init = findVarInitializer(sf, 'SUPPORTED_LANGUAGES');
  if (!init) throw new Error('Could not find SUPPORTED_LANGUAGES in index.ts');
  const arr = literalToJs(init);
  if (!Array.isArray(arr)) throw new Error('SUPPORTED_LANGUAGES is not an array literal');
  return arr.map((entry) => entry.code);
}

function readLocaleLoaderCodes() {
  const sf = parseFile(join(I18N_DIR, 'index.ts'));
  const init = findVarInitializer(sf, 'localeLoaders');
  if (!init) throw new Error('Could not find localeLoaders in index.ts');
  const keys = objectLiteralKeys(init);
  if (!keys) throw new Error('localeLoaders is not an object literal');
  return keys;
}

function readLocale(code) {
  const path = join(LOCALES_DIR, `${code}.ts`);
  const sf = parseFile(path);
  const init = findVarInitializer(sf, code);
  if (!init) throw new Error(`Could not find const ${code} in ${path}`);
  const obj = literalToJs(init);
  if (!obj || typeof obj !== 'object') throw new Error(`${code}.ts: not an object literal`);
  return obj;
}

function readNamedRecord(file, varName) {
  const sf = parseFile(join(I18N_DIR, file));
  const init = findVarInitializer(sf, varName);
  if (!init) throw new Error(`Could not find ${varName} in ${file}`);
  const obj = literalToJs(init);
  if (!obj || typeof obj !== 'object') throw new Error(`${file}: ${varName} is not an object`);
  return obj;
}

function flatten(obj, prefix = '', out = new Map()) {
  for (const [k, v] of Object.entries(obj)) {
    const path = prefix ? `${prefix}.${k}` : k;
    if (v !== null && typeof v === 'object' && !Array.isArray(v)) {
      flatten(v, path, out);
    } else {
      out.set(path, v);
    }
  }
  return out;
}

function tokenMultiset(s, re) {
  const matches = String(s).match(re) || [];
  // Normalise whitespace inside placeholders so '{{ count }}' == '{{count}}'.
  return matches.map((t) => t.replace(/\s+/g, '')).sort();
}

function multisetsEqual(a, b) {
  if (a.length !== b.length) return false;
  for (let i = 0; i < a.length; i++) if (a[i] !== b[i]) return false;
  return true;
}

function checkLeafConsistency(path, enValue, trValue, lang) {
  if (typeof trValue !== 'string') {
    fail(`[${lang}] ${path}: missing translation`);
    return;
  }
  if (trValue.trim() === '') {
    fail(`[${lang}] ${path}: empty translation`);
    return;
  }
  if (isSuspiciousSameAsEnglish(path, enValue, trValue)) {
    warn(`[${lang}] ${path}: same as English; verify this is intentional`);
  }
  for (const [re, label] of [
    [PLACEHOLDER_RE, 'placeholder'],
    [HTML_TAG_RE, 'HTML tag'],
  ]) {
    const want = tokenMultiset(enValue, re);
    const got = tokenMultiset(trValue, re);
    if (!multisetsEqual(want, got)) {
      fail(
        `[${lang}] ${path}: ${label} mismatch — en=${JSON.stringify(want)} ` +
          `${lang}=${JSON.stringify(got)}`
      );
    }
  }
}

function isSuspiciousSameAsEnglish(path, enValue, trValue) {
  if (typeof enValue !== 'string' || typeof trValue !== 'string') return false;
  if (enValue.trim() !== trValue.trim()) return false;
  if (SAME_AS_EN_PATH_ALLOWLIST.has(path)) return false;
  if (SAME_AS_EN_PATH_ALLOWLIST_RE.some((re) => re.test(path))) return false;
  if (SAME_AS_EN_VALUE_ALLOWLIST.has(enValue.trim())) return false;
  if (path.startsWith('server.')) return false;

  const text = enValue.trim();
  if (text.length < 8) return false;
  if (!/[A-Za-z]/.test(text) || !/[a-z]/.test(text)) return false;
  if (!/\s/.test(text)) return false;
  if (/^https?:\/\//i.test(text)) return false;
  if (/^[A-Z0-9 .&/()%+-]+$/.test(text)) return false;
  return true;
}

function checkLocaleLoaders(supportedCodes) {
  let loaderCodes;
  try {
    loaderCodes = readLocaleLoaderCodes();
  } catch (e) {
    fail(e.message);
    return;
  }

  const expected = supportedCodes.filter((code) => code !== 'en');
  for (const code of expected) {
    if (!loaderCodes.includes(code)) {
      fail(`localeLoaders is missing non-English supported language "${code}"`);
    }
  }
  for (const code of loaderCodes) {
    if (code === 'en') {
      fail('localeLoaders should not include "en"; English is imported eagerly');
    } else if (!expected.includes(code)) {
      fail(`localeLoaders includes "${code}" but it is not in SUPPORTED_LANGUAGES`);
    }
  }
}

function checkLocales(supportedCodes) {
  const localeFiles = readdirSync(LOCALES_DIR)
    .filter((f) => f.endsWith('.ts'))
    .map((f) => f.replace(/\.ts$/, ''));

  for (const code of supportedCodes) {
    if (!localeFiles.includes(code)) {
      fail(`SUPPORTED_LANGUAGES lists "${code}" but locales/${code}.ts is missing`);
    }
  }
  for (const code of localeFiles) {
    if (!supportedCodes.includes(code)) {
      warn(`locales/${code}.ts exists but is not listed in SUPPORTED_LANGUAGES`);
    }
  }

  const en = flatten(readLocale('en'));
  for (const code of supportedCodes) {
    if (code === 'en') continue;
    if (!localeFiles.includes(code)) continue;
    const tr = flatten(readLocale(code));
    for (const [path, enValue] of en) {
      checkLeafConsistency(path, enValue, tr.get(path), code);
    }
    for (const path of tr.keys()) {
      if (!en.has(path)) warn(`[${code}] ${path}: extra key not in en.ts`);
    }
  }
}

function checkRecordCoverage(file, varName, supportedCodes, serverKeys) {
  const record = readNamedRecord(file, varName);
  const expected = supportedCodes.filter((c) => c !== 'en');
  const present = Object.keys(record);

  for (const code of expected) {
    if (!present.includes(code)) {
      fail(`${file}: missing language record "${code}"`);
    }
  }
  for (const code of present) {
    if (!expected.includes(code)) {
      warn(`${file}: unexpected language record "${code}"`);
    }
  }

  // Use the union of feature-name keys across languages as canonical.
  const union = new Set();
  for (const code of expected) {
    if (record[code]) for (const k of Object.keys(record[code])) union.add(k);
  }

  for (const code of expected) {
    const langKeys = new Set(Object.keys(record[code] ?? {}));
    for (const key of union) {
      if (!langKeys.has(key)) {
        fail(`${file} [${code}]: missing translation for "${key}"`);
      } else {
        const v = record[code][key];
        if (typeof v !== 'string' || v.trim() === '') {
          fail(`${file} [${code}]: empty translation for "${key}"`);
        }
      }
    }
  }

  // Every key here must also be a translatable feature name in en.ts > server.
  // Otherwise the description is unreachable — ts() looks up server.${name}.
  for (const key of union) {
    if (!serverKeys.has(key)) {
      fail(`${file}: key "${key}" has no matching entry in en.ts > server`);
    }
  }
}

function collectSourceFiles(dir, out = []) {
  for (const entry of readdirSync(dir, { withFileTypes: true })) {
    const path = join(dir, entry.name);
    const rel = relative(SRC_DIR, path).replace(/\\/g, '/');
    if (entry.isDirectory()) {
      if (rel === 'i18n' || rel.includes('/__tests__') || entry.name === '__tests__') continue;
      collectSourceFiles(path, out);
      continue;
    }
    if (!entry.isFile()) continue;
    if (!/\.(ts|tsx)$/.test(entry.name)) continue;
    if (/\.d\.ts$/.test(entry.name) || /\.(test|spec)\.(ts|tsx)$/.test(entry.name)) continue;
    out.push(path);
  }
  return out;
}

function lineNumberAt(src, index) {
  return src.slice(0, index).split(/\r\n|\r|\n/).length;
}

function checkForbiddenVisibleStrings() {
  for (const file of collectSourceFiles(SRC_DIR)) {
    const rel = relative(join(__dirname, '..'), file).replace(/\\/g, '/');
    const src = readFileSync(file, 'utf8');
    const sf = ts.createSourceFile(file, src, ts.ScriptTarget.Latest, true, ts.ScriptKind.TSX);

    function checkText(textNode, value) {
      for (const [text, key] of FORBIDDEN_VISIBLE_STRINGS) {
        if (!value.includes(text)) continue;
        fail(
          `${rel}:${lineNumberAt(src, textNode.getStart(sf))}: hardcoded visible string ` +
            `"${text}" should use "${key}"`
        );
      }
    }

    function visit(node) {
      if (ts.isStringLiteral(node) || ts.isNoSubstitutionTemplateLiteral(node)) {
        checkText(node, node.text);
      } else if (ts.isJsxText(node)) {
        checkText(node, node.getText(sf));
      } else if (ts.isTemplateHead(node) || ts.isTemplateMiddle(node) || ts.isTemplateTail(node)) {
        checkText(node, node.text);
      }
      ts.forEachChild(node, visit);
    }
    visit(sf);
  }
}

function main() {
  let supportedCodes;
  try {
    supportedCodes = readSupportedLanguages();
  } catch (e) {
    console.error(`fatal: ${e.message}`);
    process.exit(2);
  }

  checkLocales(supportedCodes);
  checkLocaleLoaders(supportedCodes);
  const en = readLocale('en');
  const serverKeys = new Set(Object.keys(en.server ?? {}));
  checkRecordCoverage('descriptions.ts', 'descriptions', supportedCodes, serverKeys);
  checkRecordCoverage('details.ts', 'details', supportedCodes, serverKeys);
  checkForbiddenVisibleStrings();

  for (const w of warnings) console.warn(`warn: ${w}`);
  if (errors.length > 0) {
    for (const e of errors) console.error(`error: ${e}`);
    console.error(`\n${errors.length} translation error(s).`);
    process.exit(1);
  }
  console.log(`i18n OK — ${supportedCodes.length} languages, ${warnings.length} warning(s).`);
}

main();