import { readdirSync, readFileSync, realpathSync, 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']);
const SDK_INDEX_MIGRATION_DEPENDENCIES = new Set([
  'core/events.ts',
  'core/reactive.ts',
  'platform/readonly.ts',
  'platform/stores/types.ts',
]);

/**
 * 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 compilerOptions = readCompilerOptions(options.tsconfigPath);
  const resolutionBase = options.tsconfigPath
    ? dirname(resolve(options.tsconfigPath))
    : frameworkDir;
  const moduleCache = ts.createModuleResolutionCache(
    resolutionBase,
    (file) => pathKey(canonicalPath(file)),
    compilerOptions,
  );
  const violations = [];

  for (const file of [...typescriptFiles(frameworkDir), ...typescriptFiles(gamesDir)]) {
    const source = readFileSync(file, 'utf8');
    for (const imported of extractImports(source, file)) {
      const resolved = resolveDependency(
        imported.specifier,
        file,
        compilerOptions,
        moduleCache,
      ) ?? (imported.specifier.startsWith('.')
        ? canonicalPath(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;
}

/**
 * Finds the first dependency path from one modern entry into a forbidden
 * compatibility file. Reachable non-static dynamic imports fail closed.
 */
export function findCompatibilityDependency(options) {
  const entry = canonicalPath(options.entry);
  const traversalRoot = canonicalPath(options.traversalRoot);
  const forbiddenFiles = new Set(options.forbiddenFiles.map((file) => pathKey(canonicalPath(file))));
  const compilerOptions = readCompilerOptions(options.tsconfigPath);
  const moduleCache = ts.createModuleResolutionCache(
    options.tsconfigPath ? dirname(resolve(options.tsconfigPath)) : traversalRoot,
    (file) => pathKey(canonicalPath(file)),
    compilerOptions,
  );
  const visited = new Set();

  const visit = (file, path) => {
    const canonicalFile = canonicalPath(file);
    const key = pathKey(canonicalFile);
    const nextPath = [...path, canonicalFile];
    if (forbiddenFiles.has(key)) {
      return { kind: 'forbidden', path: nextPath, file: canonicalFile };
    }
    if (visited.has(key) || !isInsideOrEqual(canonicalFile, traversalRoot)) return null;
    visited.add(key);

    const source = readFileSync(canonicalFile, 'utf8');
    for (const edge of extractDependencyEdges(source, canonicalFile)) {
      if (edge.kind === 'dynamic') {
        return { kind: 'dynamic', path: nextPath, file: canonicalFile };
      }
      const imported = resolveDependency(edge.specifier, canonicalFile, compilerOptions, moduleCache);
      if (imported === null) continue;
      const found = visit(imported, nextPath);
      if (found !== null) return found;
    }
    return null;
  };

  return visit(entry, []);
}

function readCompilerOptions(tsconfigPath) {
  if (!tsconfigPath) {
    return {
      allowImportingTsExtensions: true,
      module: ts.ModuleKind.ESNext,
      moduleResolution: ts.ModuleResolutionKind.Bundler,
      target: ts.ScriptTarget.ES2020,
    };
  }

  const configFile = resolve(tsconfigPath);
  const loaded = ts.readConfigFile(configFile, ts.sys.readFile);
  if (loaded.error) throw new Error(formatTsDiagnostics([loaded.error]));
  const parsed = ts.parseJsonConfigFileContent(
    loaded.config,
    ts.sys,
    dirname(configFile),
    undefined,
    configFile,
  );
  if (parsed.errors.length > 0) throw new Error(formatTsDiagnostics(parsed.errors));
  return parsed.options;
}

function formatTsDiagnostics(diagnostics) {
  return ts.formatDiagnostics(diagnostics, {
    getCanonicalFileName: (file) => file,
    getCurrentDirectory: () => process.cwd(),
    getNewLine: () => '\n',
  });
}

function extractDependencyEdges(source, file) {
  const edges = [];
  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.isStringLiteralLike(node.moduleSpecifier)) {
      edges.push({ kind: 'static', specifier: node.moduleSpecifier.text });
    } else if (ts.isImportTypeNode(node)
      && ts.isLiteralTypeNode(node.argument)
      && ts.isStringLiteralLike(node.argument.literal)) {
      edges.push({ kind: 'static', specifier: node.argument.literal.text });
    } else if (ts.isCallExpression(node)
      && node.expression.kind === ts.SyntaxKind.ImportKeyword) {
      const argument = node.arguments[0];
      if (node.arguments.length === 1 && argument && ts.isStringLiteralLike(argument)) {
        edges.push({ kind: 'static', specifier: argument.text });
      } else {
        edges.push({ kind: 'dynamic' });
      }
    }
    ts.forEachChild(node, visit);
  };
  ts.forEachChild(sourceFile, visit);
  return edges;
}

function resolveDependency(specifier, containingFile, compilerOptions, moduleCache) {
  const result = ts.resolveModuleName(
    specifier,
    containingFile,
    compilerOptions,
    ts.sys,
    moduleCache,
  );
  return result.resolvedModule ? canonicalPath(result.resolvedModule.resolvedFileName) : null;
}

function canonicalPath(file) {
  const absolute = resolve(file);
  try {
    return realpathSync.native(absolute);
  } catch (error) {
    if (error && error.code === 'ENOENT') return absolute;
    throw error;
  }
}

function pathKey(file) {
  return process.platform === 'win32' ? file.toLowerCase() : file;
}

function isInsideOrEqual(file, directory) {
  if (pathKey(file) === pathKey(directory)) return true;
  return isInside(file, directory);
}

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.isStringLiteralLike(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.isStringLiteralLike(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.isStringLiteralLike(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 isSdk = SDK_ALLOWED.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 (isSdk && isCocosSpecifier(specifier)) {
    return violation(filePath, specifier, `sdk cannot import Cocos module ${specifier}`);
  }

  if (isSdk
    && resolved
    && isInside(resolved, frameworkDir)
    && !SDK_ALLOWED.test(resolvedPath)
    && !isSdkIndexMigrationDependency(filePath, resolved, frameworkDir)) {
    return violation(filePath, specifier, `sdk cannot import framework implementation ${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);
}

function isSdkIndexMigrationDependency(filePath, resolved, frameworkDir) {
  if (filePath !== `${displayPath(frameworkDir)}/sdk/index.ts`) return false;
  return SDK_INDEX_MIGRATION_DEPENDENCIES.has(displayPath(relative(frameworkDir, resolved)));
}

function isCocosSpecifier(specifier) {
  return specifier === 'cc' || specifier.startsWith('cc/');
}

/**
 * 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 };