feat: create resolver for ESM files and aliases

src/resolver.js

@@ -0,0 +1,142 @@
+const ospath = require("path");
+const PathFunctions = require("./path");
+
+let instance;
+
+class Resolver {
+    constructor() {
+        this.aliasObj = {};
+        this.from = "";
+        if (instance) {
+          throw new Error("You can only create one instance!");
+        }
+        instance = this;  
+    }
+
+    getTargetPathType(target, from) {
+      if (!PathFunctions.isNodeModule(from) && PathFunctions.isNodeModule(target)) {
+        return "CJS";
+      } else {
+        return "ESM";
+      }
+    }
+
+    resolve(path, from) {
+        const originalPath = PathFunctions.isRegularPath(path) ? path : this.convertAliasToOriginal(path);
+        const fromDir = ospath.dirname(from);
+        const absolutePath = PathFunctions.getAbsolutePath(originalPath, fromDir);
+        if (!absolutePath) return;
+        const extensions = ["", ".js", ".jsx", ".ts", ".tsx"];
+        const filePath = this.getFilePathWithExtension(absolutePath, extensions);
+        if (filePath) {
+          const resolvedPath = new ResolvedPath();
+          if (this.getTargetPathType(absolutePath, from) === "ESM") {
+            resolvedPath.absEsmFile = filePath;
+          } else {
+            resolvedPath.absCjsFile = filePath;
+          }
+          return resolvedPath;
+        }
+        const entryPath = this.getFilePathFromPackageJson(absolutePath);
+        if (entryPath) return entryPath;
+        const indexPath = this.getIndexFilePath(absolutePath);
+        if (indexPath) {
+          const resolvedPath = new ResolvedPath();
+          if (this.getTargetPathType(absolutePath, from) === "ESM") {
+            resolvedPath.absEsmFile = indexPath;
+          } else {
+            resolvedPath.absCjsFile = indexPath;
+          }
+          return resolvedPath;
+        };
+    }    
+
+    getFilePathWithExtension(path, extensions) {
+      const ext = extensions.find((ext)=> PathFunctions.fileExists(path + ext));
+      if (ext === undefined) return null;
+      const resolvedPath = path + ext;
+      return resolvedPath;
+    }  
+
+    getFilePathFromPackageJson(path) {
+      const packageFilename = "package.json";
+      const packagePath = ospath.join(path, packageFilename);
+      if (PathFunctions.fileExists(packagePath)) {
+          const configPackage = require(packagePath);
+          const { main, type, module } = configPackage;
+          const cjsModule = type !== "module" && main;
+          const esmModule = type === "module" ? main : module;
+          const absCjsModule = cjsModule && ospath.join(path, cjsModule);
+          const absEsmModule = esmModule && ospath.join(path, esmModule);
+          const resolvedPath = new ResolvedPath();
+          const extensions = ["", ".js", ".jsx", ".ts", ".tsx"];
+          resolvedPath.absCjsFile = absCjsModule && this.getFilePathWithExtension(absCjsModule, extensions)
+          resolvedPath.absEsmFile = absEsmModule && this.getFilePathWithExtension(absEsmModule, extensions)
+          return resolvedPath;
+      }
+    }  
+
+    getIndexFilePath(path) {
+      const extensions = [".js", ".jsx", ".ts", ".tsx"];
+      let indexFilePath = ospath.join(path, "index");
+      indexFilePath = this.getFilePathWithExtension(indexFilePath, extensions);
+      return indexFilePath;
+    }  
+
+    convertAliasToOriginal(path) {
+      const { aliasObj } = this;
+      const aliases = Object.keys(aliasObj);
+      for (const alias of aliases) {
+        let aliasDestination = aliasObj[alias];
+        const regexPattern = alias;
+        const regex = new RegExp(regexPattern);
+        if (regex.test(path)) {
+          const originalPath = path.replace(regex, aliasDestination);
+          return originalPath;
+        }
+      }
+      return path;
+    }    
+
+    appendAlias(alias) {
+        this.aliasObj = { ...this.aliasObj, ...alias };
+    }
+}
+
+class ResolvedPath {
+  constructor(absEsmFile, absCjsFile) {
+    this.absEsmFile = absEsmFile || "";
+    this.absCjsFile = absCjsFile || "";
+  }
+
+  get esmFile() {
+    return PathFunctions.normalizeModulePath(this.absEsmFile);
+  }
+
+  get cjsFile() {
+    return PathFunctions.normalizeModulePath(this.absCjsFile);
+  }
+
+  get absEsmFolder() {
+    return ospath.dirname(this.absEsmFile);
+  }
+
+  get absCjsFolder() {
+    return ospath.dirname(this.absCjsFile);
+  }
+
+  get isNodeModule() {
+    return (
+      PathFunctions.isNodeModule(this.absEsmFile) || 
+      PathFunctions.isNodeModule(this.absCjsFile)
+    )
+  }
+
+  get isDual() {
+    return (this.absEsmFile && this.absCjsFile);
+  }
+}
+
+const singletonResolver = new Resolver();
+
+module.exports = singletonResolver;