import { readdirSync, readFileSync, statSync } from 'node:fs';
import { dirname, isAbsolute, relative, resolve } from 'node:path';
import ts from 'typescript';

const SDK_ALLOWED = /framework[\\/]sdk(?:[\\/]|$)/;
const FRAMEWORK_INTERNAL = /framework[\\/](?:net|protocol|platform|application|domain|presentation|ui|core|compat)(?:[\\/]|$)/;
const LEGACY_RUNTIME = /framework[\\/](?:net[\\/]net-client|platform[\\/](?:session|startup|room-rpc-bus|readonly|stores[\\/](?:app-store|player-store|room-store|types))|protocol[\\/]room-handlers)\.ts$/;
const CONTRACTS_PATH = /framework[\\/]sdk[\\/]contracts(?:[\\/]|$)/;
const MIGRATION_ONLY_NAMES = new Set(['GameContext', 'IGameModule']);

/**
 * Recursively scans TypeScript imports for framework/game layering violations.
 * Paths in violations are normalized for useful, cross-platform diagnostics.
 */
export function scanImportBoundaries(options) {
  const frameworkDir = resolve(options.frameworkDir);
  const gamesDir = resolve(options.gamesDir);
  const violations = [];

  for (const file of [...typescriptFiles(frameworkDir), ...typescriptFiles(gamesDir)]) {
    const source = readFileSync(file, 'utf8');
    for (const imported of extractImports(source, file)) {
      const resolved = imported.specifier.startsWith('.')
        ? resolve(dirname(file), imported.specifier)
        : null;
      const violation = findViolation({
        file,
        specifier: imported.specifier,
        bindings: imported.bindings,
        resolved,
        frameworkDir,
        gamesDir,
      });
      if (violation) violations.push(violation);
    }
  }

  return violations;
}

function* typescriptFiles(directory) {
  let entries;
  try {
    entries = readdirSync(directory);
  } catch (error) {
    if (error && error.code === 'ENOENT') return;
    throw error;
  }
  for (const entry of entries) {
    const file = resolve(directory, entry);
    if (statSync(file).isDirectory()) yield* typescriptFiles(file);
    else if (file.endsWith('.ts')) yield file;
  }
}

function extractImports(source, file) {
  const imports = [];
  const sourceFile = ts.createSourceFile(file, source, ts.ScriptTarget.Latest, false, ts.ScriptKind.TS);

  const visit = (node) => {
    if ((ts.isImportDeclaration(node) || ts.isExportDeclaration(node))
      && node.moduleSpecifier
      && ts.isStringLiteral(node.moduleSpecifier)) {
      imports.push({
        specifier: node.moduleSpecifier.text,
        bindings: ts.isImportDeclaration(node) && node.importClause
          ? node.importClause.getText(sourceFile)
          : '',
      });
    }
    if (ts.isImportTypeNode(node)
      && ts.isLiteralTypeNode(node.argument)
      && ts.isStringLiteral(node.argument.literal)) {
      imports.push({ specifier: node.argument.literal.text, bindings: '' });
    }
    if (ts.isCallExpression(node)
      && node.expression.kind === ts.SyntaxKind.ImportKeyword
      && node.arguments.length === 1
      && ts.isStringLiteral(node.arguments[0])) {
      imports.push({ specifier: node.arguments[0].text, bindings: '' });
    }
    ts.forEachChild(node, visit);
  };
  ts.forEachChild(sourceFile, visit);
  return imports;
}

function findViolation(context) {
  const { file, specifier, bindings, resolved, frameworkDir, gamesDir } = context;
  const filePath = displayPath(file);
  const resolvedPath = resolved ? displayPath(resolved) : specifier;
  const isContract = CONTRACTS_PATH.test(filePath);
  const isGame = isInside(file, gamesDir);
  const isFramework = isInside(file, frameworkDir);

  if (isContract && !resolved) {
    return violation(filePath, specifier, `sdk/contracts may import only sibling contracts; non-relative specifier ${specifier} is forbidden`);
  }

  if (isContract && dirname(resolved) !== dirname(file)) {
    return violation(filePath, specifier, `sdk/contracts may import only sibling contracts; sdk path resolved to ${resolvedPath}`);
  }

  if (isGame && resolved && isFrameworkReference(resolved, frameworkDir) && !SDK_ALLOWED.test(resolvedPath)) {
    return violation(filePath, specifier, `game code may import only framework/sdk; game import resolved to ${resolvedPath}`);
  }

  if (importsMigrationOnlyName(bindings) && !isMigrationOnlyImporter(filePath, frameworkDir)) {
    const importer = isGame ? 'game code' : 'production code';
    return violation(filePath, specifier, `${importer} cannot import ${migrationOnlyName(bindings)}; it is migration-only`);
  }

  if (isFramework && resolved && isInside(resolved, gamesDir)) {
    return violation(filePath, specifier, `framework code cannot import games; framework import resolved to ${resolvedPath}`);
  }

  if (resolved && LEGACY_RUNTIME.test(resolvedPath) && !isLegacyRuntimeImporter(filePath, frameworkDir)) {
    return violation(filePath, specifier, `new production code cannot import quarantined legacy runtime ${resolvedPath}`);
  }

  return null;
}

function isFrameworkReference(path, frameworkDir) {
  return isInside(path, frameworkDir)
    || SDK_ALLOWED.test(path)
    || FRAMEWORK_INTERNAL.test(path)
    || /(?:^|[\\/])framework(?:[\\/]|$)/.test(path);
}

function isLegacyRuntimeImporter(filePath, frameworkDir) {
  const normalizedFrameworkDir = displayPath(frameworkDir);
  return filePath === `${normalizedFrameworkDir}/sdk/index.ts` || LEGACY_RUNTIME.test(filePath);
}

/**
 * ActiveGame is the retained compatibility owner of IGameModule until Task 11
 * removes both it and the migration-only declarations from sdk/index.ts.
 */
function isMigrationOnlyImporter(filePath, frameworkDir) {
  return filePath === `${displayPath(frameworkDir)}/protocol/active-game.ts`;
}

function importsMigrationOnlyName(bindings) {
  return [...MIGRATION_ONLY_NAMES].some((name) => new RegExp(`\\b${name}\\b`).test(bindings));
}

function migrationOnlyName(bindings) {
  return [...MIGRATION_ONLY_NAMES].find((name) => new RegExp(`\\b${name}\\b`).test(bindings));
}

function isInside(file, directory) {
  const pathFromDirectory = relative(directory, file);
  return pathFromDirectory !== '' && !pathFromDirectory.startsWith('..') && !isAbsolute(pathFromDirectory);
}

function displayPath(file) {
  return file.replaceAll('\\', '/');
}

function violation(file, specifier, message) {
  return { file, specifier, message };
}

export { FRAMEWORK_INTERNAL, LEGACY_RUNTIME, SDK_ALLOWED };