From 1ef6f0e6b9083748e5b91743f15f10f09c6b8432 Mon Sep 17 00:00:00 2001
From: Elias Haugsbakk <elias.haugsbakk@gmail.com>
Date: Fri, 18 Sep 2026 23:10:31 +0200
Subject: Implement parser creating AST

---
 .../no/eliashaugsbakk/kompilator/parsing/AST.java  |  7 ++
 .../eliashaugsbakk/kompilator/parsing/Parser.java  | 79 ++++++++++++++++++++++
 .../kompilator/parsing/ParserException.java        |  7 ++
 .../kompilator/parsing/node/ASTNode.java           |  7 ++
 .../kompilator/parsing/node/Program.java           | 16 +++++
 .../parsing/node/expression/Expression.java        | 17 +++++
 .../parsing/node/expression/FunctionCall.java      | 16 +++++
 .../parsing/node/expression/StringLiteral.java     | 12 ++++
 .../node/statement/ExpressionStatement.java        | 10 +++
 .../parsing/node/statement/Statement.java          | 15 ++++
 10 files changed, 186 insertions(+)
 create mode 100644 src/main/java/no/eliashaugsbakk/kompilator/parsing/ParserException.java
 create mode 100644 src/main/java/no/eliashaugsbakk/kompilator/parsing/node/ASTNode.java
 create mode 100644 src/main/java/no/eliashaugsbakk/kompilator/parsing/node/Program.java
 create mode 100644 src/main/java/no/eliashaugsbakk/kompilator/parsing/node/expression/Expression.java
 create mode 100644 src/main/java/no/eliashaugsbakk/kompilator/parsing/node/expression/FunctionCall.java
 create mode 100644 src/main/java/no/eliashaugsbakk/kompilator/parsing/node/expression/StringLiteral.java
 create mode 100644 src/main/java/no/eliashaugsbakk/kompilator/parsing/node/statement/ExpressionStatement.java
 create mode 100644 src/main/java/no/eliashaugsbakk/kompilator/parsing/node/statement/Statement.java

(limited to 'src/main/java/no/eliashaugsbakk/kompilator/parsing')

diff --git a/src/main/java/no/eliashaugsbakk/kompilator/parsing/AST.java b/src/main/java/no/eliashaugsbakk/kompilator/parsing/AST.java
index 3f54e3c..95ec77c 100644
--- a/src/main/java/no/eliashaugsbakk/kompilator/parsing/AST.java
+++ b/src/main/java/no/eliashaugsbakk/kompilator/parsing/AST.java
@@ -1,4 +1,11 @@
 package no.eliashaugsbakk.kompilator.parsing;
 
+import no.eliashaugsbakk.kompilator.parsing.node.ASTNode;
+
 public class AST {
+  ASTNode root;
+
+  AST(ASTNode root) {
+    this.root = root;
+  }
 }
diff --git a/src/main/java/no/eliashaugsbakk/kompilator/parsing/Parser.java b/src/main/java/no/eliashaugsbakk/kompilator/parsing/Parser.java
index a41a1bf..53af71c 100644
--- a/src/main/java/no/eliashaugsbakk/kompilator/parsing/Parser.java
+++ b/src/main/java/no/eliashaugsbakk/kompilator/parsing/Parser.java
@@ -1,4 +1,83 @@
 package no.eliashaugsbakk.kompilator.parsing;
 
+import static no.eliashaugsbakk.kompilator.tokenization.TokenType.EOF;
+import static no.eliashaugsbakk.kompilator.tokenization.TokenType.KEYWORD;
+import static no.eliashaugsbakk.kompilator.tokenization.TokenType.LPAREN;
+import static no.eliashaugsbakk.kompilator.tokenization.TokenType.RPAREN;
+import static no.eliashaugsbakk.kompilator.tokenization.TokenType.SEMICOLON;
+import static no.eliashaugsbakk.kompilator.tokenization.TokenType.STRING;
+
+import java.util.ArrayList;
+import java.util.List;
+import no.eliashaugsbakk.kompilator.parsing.node.Program;
+import no.eliashaugsbakk.kompilator.parsing.node.expression.Expression;
+import no.eliashaugsbakk.kompilator.parsing.node.expression.FunctionCall;
+import no.eliashaugsbakk.kompilator.parsing.node.expression.StringLiteral;
+import no.eliashaugsbakk.kompilator.parsing.node.statement.ExpressionStatement;
+import no.eliashaugsbakk.kompilator.tokenization.Token;
+
 public class Parser {
+  private final List<Token> tokens;
+  private int position = 0;
+
+  public Parser(List<Token> tokens) {
+    this.tokens = tokens;
+  }
+
+  public AST parse() throws ParserException {
+    Program rootNode = new Program();
+
+    while (position < tokens.size()) {
+      Token token = tokens.get(position);
+
+      if (token.type() == KEYWORD) {
+        String functionName = token.value();
+        position++;
+
+        List<Expression> arguments = parseArguments();
+
+        FunctionCall functionCall = new FunctionCall(functionName, arguments);
+        rootNode.addStatement(new ExpressionStatement(functionCall));
+      } else if (token.type() == EOF) {
+        break;
+      } else {
+        IO.println("Unknown token: " + token.value() + ". Skipping...");
+        position++;
+      }
+    }
+
+    return new AST(rootNode);
+  }
+
+  List<Expression> parseArguments() throws ParserException {
+    List<Expression> arguments = new ArrayList<>();
+
+    if (position >= tokens.size() || tokens.get(position).type() != LPAREN) {
+      throw new ParserException(tokens.get(position).line(), tokens.get(position).colum(),
+          "Unexpected token:" + tokens.get(position).value() + "\n Expected: (");
+    }
+    position++;
+
+    while (position < tokens.size() && tokens.get(position).type() != RPAREN) {
+      if (tokens.get(position).type() == STRING) {
+        arguments.add(new StringLiteral(tokens.get(position).value()));
+      }
+      position++;
+    }
+
+    if (position >= tokens.size()) {
+      throw new ParserException(-1, -1, "Unexpected end of file, expected )");
+    }
+    position++;
+
+    if (position >= tokens.size() || tokens.get(position).type() != SEMICOLON) {
+      throw new ParserException(position < tokens.size() ? tokens.get(position).line() : -1,
+          position < tokens.size() ? tokens.get(position).colum() : -1,
+          "Unexpected token: " + (position < tokens.size() ? tokens.get(position).value() : "EOF") +
+              "\n" + "Expected: ;");
+    }
+    position++;
+
+    return arguments;
+  }
 }
diff --git a/src/main/java/no/eliashaugsbakk/kompilator/parsing/ParserException.java b/src/main/java/no/eliashaugsbakk/kompilator/parsing/ParserException.java
new file mode 100644
index 0000000..ac96a5c
--- /dev/null
+++ b/src/main/java/no/eliashaugsbakk/kompilator/parsing/ParserException.java
@@ -0,0 +1,7 @@
+package no.eliashaugsbakk.kompilator.parsing;
+
+public class ParserException extends Exception {
+  public ParserException(int line, int column, String message) {
+    super(line + ":" + column + ", " + message);
+  }
+}
diff --git a/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/ASTNode.java b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/ASTNode.java
new file mode 100644
index 0000000..1eb201c
--- /dev/null
+++ b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/ASTNode.java
@@ -0,0 +1,7 @@
+package no.eliashaugsbakk.kompilator.parsing.node;
+
+/**
+ * Base class for all nodes in the Abstract Syntax Tree.
+ */
+public abstract class ASTNode {
+}
diff --git a/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/Program.java b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/Program.java
new file mode 100644
index 0000000..0c7cd32
--- /dev/null
+++ b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/Program.java
@@ -0,0 +1,16 @@
+package no.eliashaugsbakk.kompilator.parsing.node;
+
+import java.util.ArrayList;
+import java.util.List;
+import no.eliashaugsbakk.kompilator.parsing.node.statement.Statement;
+
+/**
+ * Root node of the AST. Contains all top-level statements.
+ */
+public class Program extends ASTNode {
+  public List<Statement> statements = new ArrayList<>();
+
+  public void addStatement(Statement statement) {
+    this.statements.add(statement);
+  }
+}
diff --git a/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/expression/Expression.java b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/expression/Expression.java
new file mode 100644
index 0000000..6ca58b2
--- /dev/null
+++ b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/expression/Expression.java
@@ -0,0 +1,17 @@
+package no.eliashaugsbakk.kompilator.parsing.node.expression;
+
+import no.eliashaugsbakk.kompilator.parsing.node.ASTNode;
+
+/**
+ * Base class for all expression nodes.
+ * An expression is a piece of code that evaluates to a value.
+ * Expressions cannot stand alone as statements; they must be used within statements.
+ * <p>
+ * Examples:
+ * - "Hello"          (string literal expression)
+ * - 42               (number literal expression)
+ * - x + 5            (binary operation expression)
+ * - myFunction()     (function call expression)
+ */
+public abstract class Expression extends ASTNode {
+}
diff --git a/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/expression/FunctionCall.java b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/expression/FunctionCall.java
new file mode 100644
index 0000000..3c46ec4
--- /dev/null
+++ b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/expression/FunctionCall.java
@@ -0,0 +1,16 @@
+package no.eliashaugsbakk.kompilator.parsing.node.expression;
+
+import java.util.List;
+
+/**
+ * Represents a function call statement (e.g., print("Hello, world")).
+ */
+public class FunctionCall extends Expression {
+  public String functionName;
+  public List<Expression> arguments;
+
+  public FunctionCall(String functionName, List<Expression> arguments) {
+    this.functionName = functionName;
+    this.arguments = arguments;
+  }
+}
diff --git a/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/expression/StringLiteral.java b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/expression/StringLiteral.java
new file mode 100644
index 0000000..67ce405
--- /dev/null
+++ b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/expression/StringLiteral.java
@@ -0,0 +1,12 @@
+package no.eliashaugsbakk.kompilator.parsing.node.expression;
+
+/**
+ * Represents a string literal expression (e.g., "Hello, World").
+ */
+public class StringLiteral extends Expression {
+  public final String value;
+
+  public StringLiteral(String value) {
+    this.value = value;
+  }
+}
diff --git a/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/statement/ExpressionStatement.java b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/statement/ExpressionStatement.java
new file mode 100644
index 0000000..64bc0a8
--- /dev/null
+++ b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/statement/ExpressionStatement.java
@@ -0,0 +1,10 @@
+package no.eliashaugsbakk.kompilator.parsing.node.statement;
+
+import no.eliashaugsbakk.kompilator.parsing.node.expression.Expression;
+
+public class ExpressionStatement extends Statement {
+  public Expression expression;
+  public ExpressionStatement(Expression expression) {
+    this.expression = expression;
+  }
+}
diff --git a/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/statement/Statement.java b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/statement/Statement.java
new file mode 100644
index 0000000..fc52f9a
--- /dev/null
+++ b/src/main/java/no/eliashaugsbakk/kompilator/parsing/node/statement/Statement.java
@@ -0,0 +1,15 @@
+package no.eliashaugsbakk.kompilator.parsing.node.statement;
+
+import no.eliashaugsbakk.kompilator.parsing.node.ASTNode;
+
+/**
+ * Base class for all statement nodes.
+ * A statement is a top-level line of code that performs an action.
+ * <p>
+ * Examples:
+ * - print("Hello");  (function call statement)
+ * - var x: int = 5;  (variable declaration statement)
+ * - if (x > 0) { }   (conditional statement)
+ */
+public abstract class Statement extends ASTNode {
+}
-- 
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