From 9ff3943819064c4982d10cc3571cd05235ecad3c Mon Sep 17 00:00:00 2001
From: lisk77 <lisk77@protonmail.com>
Date: Tue, 1 Jul 2025 23:52:19 +0200
Subject: [PATCH] feat: added simple import support

---
 README.md         |  2 +-
 include/ast.hpp   | 12 +++++++++++-
 include/token.hpp |  3 ++-
 src/lexer.cpp     | 19 +++++++++++++++++++
 src/parser.cpp    | 27 +++++++++++++++++++++++++++
 src/token.cpp     |  1 +
 6 files changed, 61 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 61b72d6..6392d5b 100644
--- a/README.md
+++ b/README.md
@@ -42,5 +42,5 @@ For a file to be able to be run, it needs to define a `main` function.
 ## Future ideas
 
 - [ ] types
-- [ ] imports
+- [x] imports (at least simple)
 - [ ] small standard library
diff --git a/include/ast.hpp b/include/ast.hpp
index fbde70d..8def7ec 100644
--- a/include/ast.hpp
+++ b/include/ast.hpp
@@ -6,7 +6,8 @@
 
 // ast stuff lul
 struct Expr {
-  virtual ~Expr() = default;
+    virtual ~Expr() = default;
+    virtual std::unique_ptr<Expr> clone() const = 0;
 };
 
 // represents a simple symbol like "x" or even "thisIsACoolFunctionTrustme100"
@@ -16,6 +17,9 @@ struct Variable : Expr {
     std::string name;
 
     Variable(std::string n) : name(std::move(n)) {}
+    std::unique_ptr<Expr> clone() const override {
+        return std::make_unique<Variable>(name);
+    }
 };
 
 // represents a function itself like \ x . x
@@ -24,6 +28,9 @@ struct Abstraction : Expr {
     std::unique_ptr<Expr> body;
 
     Abstraction(std::string p, std::unique_ptr<Expr> b) : param(std::move(p)), body(std::move(b)) {}
+    std::unique_ptr<Expr> clone() const override {
+        return std::make_unique<Abstraction>(param, body->clone());
+    }
 };
 
 // wouldnt be turing complete if we couldnt apply to these functions innit
@@ -34,6 +41,9 @@ struct Application : Expr {
     std::unique_ptr<Expr> left, right;
 
     Application(std::unique_ptr<Expr> l, std::unique_ptr<Expr> r) : left(std::move(l)), right(std::move(r)) {}
+    std::unique_ptr<Expr> clone() const override {
+        return std::make_unique<Application>(left->clone(), right->clone());
+    }
 };
 
 #endif // AST_HPP
diff --git a/include/token.hpp b/include/token.hpp
index 2e496b9..e68cac7 100644
--- a/include/token.hpp
+++ b/include/token.hpp
@@ -14,7 +14,8 @@ typedef enum {
     LPAREN,
     RPAREN,
     VARIABLE,
-    EQUALS
+    EQUALS,
+    IMPORT
 } TokenType;
 
 typedef struct {
diff --git a/src/lexer.cpp b/src/lexer.cpp
index f21ba84..ba4c867 100644
--- a/src/lexer.cpp
+++ b/src/lexer.cpp
@@ -55,6 +55,25 @@ std::vector<Token> Lexer::tokenize() {
                 position++;
             }
             std::string lex = src.substr(start, position - start);
+            if (lex == "import") {
+                tokens.push_back({ IMPORT, lex, start, position });
+                position++;
+                size_t startPath = position;
+
+                while (position < len && !IS_SPACE(src[position]) && src[position] != ';')
+                {
+                    position++;
+                }
+                if (position >= len) {
+                    std::cerr << "lexer: import statement was not closed with semicolon" << std::endl;
+                    this->error_flag = true;
+                    continue;
+                }
+
+                std::string path = src.substr(startPath, position - startPath);
+                tokens.push_back({ VARIABLE, path, startPath, position });
+                continue;
+            }
             tokens.push_back({ VARIABLE, lex, start, position });
         }
         else if (IS_SPACE(curr)) {
diff --git a/src/parser.cpp b/src/parser.cpp
index eee0556..93062f2 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -1,4 +1,5 @@
 #include "parser.hpp"
+#include "lexer.hpp"
 #include "ast.hpp"
 
 #include <stdexcept>
@@ -6,6 +7,7 @@
 #include <string>
 #include <memory>
 #include <iostream>
+#include <fstream>
 
 Parser::Parser(std::vector<Token> toks)
     : tokens(std::move(toks))
@@ -88,6 +90,31 @@ std::unique_ptr<Expr> Parser::parseSimple() {
         return e;
     }
 
+    if (peek().type == TokenType::IMPORT) {
+        position++;
+        const auto &path = get();
+
+        std::ifstream file(path.lexeme, std::ios::binary);
+        if (!file) {
+            throw std::runtime_error("import: unable to open file: " + path.lexeme);
+        }
+        std::string content(std::istreambuf_iterator<char>(file), {});
+
+        Lexer    lexImp(content);
+        auto     tokensImp = lexImp.tokenize();
+
+        Parser   parserImp(std::move(tokensImp));
+        parserImp.parseProgram();
+
+        std::cout << "importing " << path.lexeme << std::endl;
+
+        for (const auto &entry : parserImp.definitions()) {
+            defs.emplace(entry.first, entry.second->clone());
+        }
+
+        return nullptr;
+    }
+
     throw std::runtime_error("parser: expected \\, variable, or '(' at position " + std::to_string(peek().start));
 }
 
diff --git a/src/token.cpp b/src/token.cpp
index f1b8ddb..6d384bf 100644
--- a/src/token.cpp
+++ b/src/token.cpp
@@ -14,6 +14,7 @@ std::string display_tokentype(TokenType type) {
         case RPAREN      : return "RPAREN";
         case EQUALS      : return "EQUALS";
         case VARIABLE    : return "VARIABLE";
+        case IMPORT      : return "IMPORT";
         default          : return "";
     }
 }