wip: creating discover module for importer feature

src/importer/dependency.ts

@@ -0,0 +1,3 @@
+export default class Dependency {
+  constructor(public readonly id: string, public readonly alias: string) {}
+}

src/importer/discover.test.ts

@@ -0,0 +1,57 @@
+import { Lexer } from "@/lexer";
+import Discover from "./discover";
+import Dependency from "./dependency";
+
+describe("Discover test suite", () => {
+  test("Program that imports only one dependency", () => {
+    const program = `
+    from "github.com/guiferpa/testing" as testing
+    `;
+
+    const expected = [new Dependency("github.com/guiferpa/testing", "testing")];
+
+    const lexer = new Lexer(Buffer.from(program, "utf-8"));
+    const discover = new Discover(lexer);
+    const got = discover.run();
+    expect(got).toStrictEqual(expected);
+  });
+
+  test("Program that imports some dependencies", () => {
+    const program = `
+    from "github.com/guiferpa/testing" as testing
+    from "github.com/guiferpa/tester" as tester
+    from "github.com/guiferpa/test" as test
+    `;
+
+    const expected = [
+      new Dependency("github.com/guiferpa/testing", "testing"),
+      new Dependency("github.com/guiferpa/tester", "tester"),
+      new Dependency("github.com/guiferpa/test", "test"),
+    ];
+
+    const lexer = new Lexer(Buffer.from(program, "utf-8"));
+    const discover = new Discover(lexer);
+    const got = discover.run();
+    expect(got).toStrictEqual(expected);
+  });
+
+  test("Program that imports some duplicated dependencies", () => {
+    const program = `
+    from "github.com/guiferpa/testing" as testing
+    from "github.com/guiferpa/testing" as testing
+    from "github.com/guiferpa/tester" as tester
+    from "github.com/guiferpa/test" as test
+    `;
+
+    const expected = [
+      new Dependency("github.com/guiferpa/testing", "testing"),
+      new Dependency("github.com/guiferpa/tester", "tester"),
+      new Dependency("github.com/guiferpa/test", "test"),
+    ];
+
+    const lexer = new Lexer(Buffer.from(program, "utf-8"));
+    const discover = new Discover(lexer);
+    const got = discover.run();
+    expect(got).toStrictEqual(expected);
+  });
+});

src/importer/discover.ts

@@ -0,0 +1,54 @@
+import { Lexer } from "@/lexer";
+import { TokenTag } from "@/lexer/tokens/tag";
+import { Token } from "@/lexer/tokens/token";
+
+import Dependency from "./dependency";
+
+export default class Discover {
+  private _lookahead: Token | null = null;
+
+  constructor(private readonly _lexer: Lexer) {}
+
+  private _discovery(): Dependency[] {
+    const deps = new Map<string, Dependency>();
+
+    this._lookahead = this._lexer.getNextToken();
+
+    while (this._lookahead?.tag === TokenTag.FROM) {
+      this._lookahead = this._lexer.getNextToken();
+      if (this._lookahead.tag !== TokenTag.STR) {
+        throw new Error(
+          `Missing dependency identifier at line ${this._lookahead.line}`
+        );
+      }
+
+      const id = this._lookahead.value;
+
+      this._lookahead = this._lexer.getNextToken();
+
+      if (this._lookahead.tag !== TokenTag.AS) {
+        throw new SyntaxError(
+          `Unexpected token ${this._lookahead.tag} at line ${this._lookahead.line}`
+        );
+      }
+
+      this._lookahead = this._lexer.getNextToken();
+
+      if (this._lookahead.tag !== TokenTag.IDENT) {
+        throw new Error(`Invalid alias at line ${this._lookahead.line}`);
+      }
+
+      const alias = this._lookahead.value;
+
+      deps.set(id, new Dependency(id, alias));
+
+      this._lookahead = this._lexer.getNextToken();
+    }
+
+    return Array.from(deps.values());
+  }
+
+  public run(): Dependency[] {
+    return this._discovery();
+  }
+}

src/lexer/tokens/tag.ts

@@ -34,5 +34,7 @@ export enum TokenTag {
   DESC_FUNC = "__DESC_FUNC__",
   STR = "__STR__",
   COMMENT = "__COMMENT__",
+  FROM = "__FROM__",
+  AS = "__AS__",
   EOF = "__EOF__",
 }

src/lexer/tokens/terminal.ts

@@ -22,6 +22,8 @@ export const Terminals: [RegExp, TokenTag][] = [
   [new RegExp(/^desc/), TokenTag.DESC_FUNC],
   [new RegExp(/^return void/), TokenTag.RETURN_VOID],
   [new RegExp(/^return/), TokenTag.RETURN],
+  [new RegExp(/^from/), TokenTag.FROM],
+  [new RegExp(/^as/), TokenTag.AS],
   [new RegExp(/^var [a-zA-Z_]+(\s?)=/), TokenTag.ASSIGN],
   [new RegExp(/^func [a-zA-Z_><\-!?]+/), TokenTag.DECL_FN],
   [new RegExp(/^\+/), TokenTag.OP_ADD],