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src/main/java/ch/fritteli/gombaila/domain/generator/Generator.java

@@ -14,29 +14,19 @@ import ch.fritteli.gombaila.domain.common.NodeStmt;
 import ch.fritteli.gombaila.domain.common.NodeStmtExit;
 import ch.fritteli.gombaila.domain.common.NodeStmtLet;
 import ch.fritteli.gombaila.domain.common.NodeStmtPrint;
+import ch.fritteli.gombaila.domain.printer.Printer;
 import org.jetbrains.annotations.NotNull;
 
+import java.time.ZonedDateTime;
 import java.util.HashMap;
 import java.util.Map;
 
 public class Generator {
     @NotNull
-    private static final String header = """
-            global _start
-            _start:
-            """;
-    @NotNull
-    private static final String defaultExitStmt = """
-                mov rax, 60
-                mov rdi, 0
-                syscall
-            """;
-
+    private final Printer printer = new Printer();
     @NotNull
     private final NodeProg nodeProg;
     @NotNull
-    private final StringBuilder asm;
-    @NotNull
     private final ExprVisitor exprVisitor;
     @NotNull
     private final StmtVisitor stmtVisitor;
@@ -46,18 +36,43 @@ public class Generator {
 
     public Generator(@NotNull final NodeProg nodeProg) {
         this.nodeProg = nodeProg;
-        this.asm = new StringBuilder(header);
         this.exprVisitor = new ExprVisitor();
         this.stmtVisitor = new StmtVisitor();
     }
 
     @NotNull
     public String generate() {
+        this.generateHeader();
+
         for (final NodeStmt stmt : this.nodeProg.stmts()) {
             this.generateStmt(stmt);
         }
-        this.asm.append(defaultExitStmt);
-        return this.asm.toString();
+
+        this.generateFooter();
+
+        return this.printer.toString();
+    }
+
+    private void generateHeader() {
+        this.printer.comment("Program generated by Gombaila on %1$tF, %1$tT".formatted(ZonedDateTime.now()));
+        this.printer.section(".data");
+        this.printer.line("EXIT_SUCCESS", "equ", 0);
+        this.printer.line("SYSCALL_exit", "equ", 60);
+        this.printer.blank();
+        this.printer.section(".text");
+        this.printer.rawLine("global _start");
+        this.printer.blank();
+        this.printer.label("_start");
+
+    }
+
+    private void generateFooter() {
+        this.printer.commentedLine("Prepare for successful exit", "mov", "rdi, EXIT_SUCCESS");
+        this.printer.commentedLine("Jump to the default exit routine", "jmp", "exit");
+        this.printer.blank();
+        this.printer.label("exit");
+        this.printer.commentedLine("Prepare for the EXIT syscall", "mov", "rax, SYSCALL_exit");
+        this.printer.line("syscall");
     }
 
     private void generateStmt(@NotNull final NodeStmt stmt) {
@@ -69,27 +84,15 @@ public class Generator {
     }
 
     private void push(@NotNull final String reg) {
-        this.line("push %s", reg);
+        this.printer.commentedLine("push %s onto top of the stack".formatted(reg), "push", reg);
         this.stackSize++;
     }
 
     private void pop(@NotNull final String reg) {
-        this.line("pop %s", reg);
+        this.printer.commentedLine("pop top of the stack into %s".formatted(reg), "pop", reg);
         this.stackSize--;
     }
 
-    private void label(@NotNull final String name) {
-        this.asm.append(name)
-                .append(":")
-                .append("\n");
-    }
-
-    private void line(@NotNull final String line, @NotNull final Object... params) {
-        this.asm.append("    ")
-                .append(line.formatted(params))
-                .append("\n");
-    }
-
     private record Variable(int stackLocation) {
     }
 
@@ -108,31 +111,33 @@ public class Generator {
 
         private void visit(@NotNull final NodeStmtExit stmt) {
             generateExpr(stmt.expr());
-            line("mov rax, 60");
             pop("rdi");
-            line("syscall");
+            printer.commentedLine("Jump to the default exit routine", "jmp", "exit");
+//            printer.commentedLine("Prepare for the EXIT syscall", "mov", "rax, SYSCALL_exit");
+//            printer.line("syscall");
         }
 
         private void visit(@NotNull final NodeStmtLet stmt) {
-            if (identifierStackposition.containsKey(stmt.ident().value().get())) {
+            final Variable previousValue = identifierStackposition.put(((String) stmt.ident().value().get()), new Variable(stackSize));
+            if (previousValue != null) {
                 throw new GeneratorException("Identifier already used", stmt);
             }
-            identifierStackposition.put(((String) stmt.ident().value().get()), new Variable(stackSize));
             generateExpr(stmt.expr());
         }
 
         private void visit(@NotNull final NodeStmtPrint stmt) {
-            generateExpr(stmt.nodeExpr());
-            // rdx: length of output
-            line("mov rdx, 8");
-            // rsi: output
-            pop("rsi");
-            // rdi: fd-value (STDOUT=1)
-            line("mov rdi, 1");
-            // rax: syscall (SYS_WRITE=1)
-            line("mov rax, 1");
-            // syscall
-            line("syscall");
+//            generateExpr(stmt.nodeExpr());
+//            // rdx: length of output
+//            line("mov rdx, 8");
+//            // rsi: output
+//            pop("rsi");
+//            // rdi: fd-value (STDOUT=1)
+//            line("mov rdi, 1");
+//            // rax: syscall (SYS_WRITE=1)
+//            line("mov rax, 1");
+//            // syscall
+//            line("syscall");
+            throw new GeneratorException("Not implemented yet", stmt);
         }
     }
 
@@ -158,11 +163,11 @@ public class Generator {
             if (variable == null) {
                 throw new GeneratorException("Undeclared identifier", expr);
             }
-            push("QWORD [rsp+%d]".formatted(8 * (stackSize - variable.stackLocation - 1)));
+            push("qword [rsp+%d]".formatted(8 * (stackSize - variable.stackLocation - 1)));
         }
 
         private void visit(@NotNull final NodeExprIntLit expr) {
-            line("mov rax, %s", expr.value().value().get());
+            printer.commentedLine("store the value in rax", "mov", "rax, %s".formatted(expr.value().value().get()));
             push("rax");
         }
 
@@ -171,7 +176,7 @@ public class Generator {
             generateExpr(expr.rhs());
             pop("rbx");
             pop("rax");
-            line("add rax, rbx");
+            printer.commentedLine("add rbx to rax", "add", "rax, rbx");
             push("rax");
         }
 
@@ -180,20 +185,35 @@ public class Generator {
             generateExpr(expr.rhs());
             pop("rbx");
             pop("rax");
-            line("sub rax, rbx");
+            printer.commentedLine("subtract rbx from rax", "sub", "rax, rbx");
             push("rax");
         }
 
         private void visit(@NotNull final NodeBinExprMult expr) {
-            throw new GeneratorException("Not yet implemented!", expr);
+            generateExpr(expr.lhs());
+            generateExpr(expr.rhs());
+            pop("rbx");
+            pop("rax");
+            printer.commentedLine("multiply rax by rbx", "mul", "rbx");
+            push("rax");
         }
 
         private void visit(@NotNull final NodeBinExprDiv expr) {
-            throw new GeneratorException("Not yet implemented!", expr);
+            generateExpr(expr.lhs());
+            generateExpr(expr.rhs());
+            pop("rbx");
+            pop("rax");
+            printer.commentedLine("divide rax by rbx", "div", "rbx");
+            push("rax");
         }
 
         private void visit(@NotNull final NodeBinExprMod expr) {
-            throw new GeneratorException("Not yet implemented!", expr);
+            generateExpr(expr.lhs());
+            generateExpr(expr.rhs());
+            pop("rbx");
+            pop("rax");
+            printer.commentedLine("divide rax by rbx. The remainder will be in rdx.", "div", "rbx");
+            push("rdx");
         }
 
         private void visit(@NotNull final NodeBinExprExp expr) {

src/main/java/ch/fritteli/gombaila/domain/printer/BlankLine.java

@@ -0,0 +1,21 @@
+package ch.fritteli.gombaila.domain.printer;
+
+import org.jetbrains.annotations.NotNull;
+
+record BlankLine() implements Line {
+
+    @Override
+    public int indentationLevel() {
+        return 0;
+    }
+
+    @Override
+    public void updateWithMap() {
+    }
+
+    @NotNull
+    @Override
+    public String toString() {
+        return "";
+    }
+}

src/main/java/ch/fritteli/gombaila/domain/printer/FormattedLine.java

@@ -0,0 +1,49 @@
+package ch.fritteli.gombaila.domain.printer;
+
+import io.vavr.collection.Seq;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+record FormattedLine(@NotNull Seq<String> tokens, @Nullable String comment, int indentationLevel,
+                     @NotNull WidthMap widthMap) implements Line {
+    @Override
+    public void updateWithMap() {
+        this.tokens
+                .forEachWithIndex((token, index) -> {
+                    this.widthMap.updateWidthForTokenIndex(index, token.length());
+                });
+    }
+
+    @NotNull
+    @Override
+    public String toString() {
+        final Seq<String> lineElements;
+        if (this.comment == null) {
+            lineElements = this.tokens.dropRight(1)
+                    .zipWithIndex()
+                    .map(tuple -> tuple.map2(this.widthMap::getTokenWidthByIndex))
+                    .map(tuple -> {
+                        final String token = tuple._1();
+                        final int width = tuple._2();
+                        return String.format("%-" + width + "s", token);
+                    })
+                    .appendAll(this.tokens.lastOption());
+        } else {
+            lineElements = this.tokens.zipWithIndex()
+                    .map(tuple -> tuple.map2(this.widthMap::getTokenWidthByIndex))
+                    .map(tuple -> {
+                        final String token = tuple._1();
+                        final int width = tuple._2();
+                        return String.format("%-" + width + "s", token);
+                    })
+                    .append(";")
+                    .append(this.comment);
+        }
+        final String line = lineElements.mkString(" ");
+        final int indents = this.widthMap.getIndentationSize() * this.indentationLevel;
+        if (indents == 0) {
+            return line;
+        }
+        return ("%-" + indents + "s").formatted("") + line;
+    }
+}

src/main/java/ch/fritteli/gombaila/domain/printer/Line.java

@@ -0,0 +1,5 @@
+package ch.fritteli.gombaila.domain.printer;
+
+interface Line extends Printable {
+    int indentationLevel();
+}

src/main/java/ch/fritteli/gombaila/domain/printer/Printable.java

@@ -0,0 +1,10 @@
+package ch.fritteli.gombaila.domain.printer;
+
+import org.jetbrains.annotations.NotNull;
+
+public interface Printable {
+    void updateWithMap();
+
+    @NotNull
+    String toString();
+}

src/main/java/ch/fritteli/gombaila/domain/printer/Printer.java

@@ -0,0 +1,69 @@
+package ch.fritteli.gombaila.domain.printer;
+
+import io.vavr.collection.List;
+import lombok.NonNull;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.ArrayList;
+
+public class Printer {
+    private static final int INDENTATION_SIZE = 4;
+    private final java.util.List<Printable> printables = new ArrayList<>();
+    private WidthMap widthMap = new WidthMap(INDENTATION_SIZE);
+    private int indentationLevel = 0;
+
+    public void increaseIndent() {
+        this.indentationLevel++;
+    }
+
+    public void decreaseIndent() {
+        this.indentationLevel--;
+    }
+
+    public void resetIndent() {
+        this.indentationLevel = 0;
+    }
+
+    public void comment(@NotNull final String line) {
+        this.printables.add(new RawLine("; %s".formatted(line), this.indentationLevel, this.widthMap));
+    }
+
+    public void section(@NotNull final String sectionName) {
+        this.resetIndent();
+        this.widthMap = new WidthMap(INDENTATION_SIZE);
+        this.printables.add(new RawLine("section %s".formatted(sectionName), this.indentationLevel, this.widthMap));
+    }
+
+    public void label(@NotNull final String label) {
+        this.resetIndent();
+        this.widthMap = new WidthMap(INDENTATION_SIZE);
+        this.printables.add(new RawLine("%s:".formatted(label), this.indentationLevel, this.widthMap));
+        this.increaseIndent();
+    }
+
+    public void blank() {
+        this.printables.add(new RawLine("", 0, this.widthMap));
+    }
+
+    public void line(@NonNull final Object... instructionTokens) {
+        final List<String> tokens = List.of(instructionTokens)
+                .map(String::valueOf);
+        this.printables.add(new FormattedLine(tokens, null, this.indentationLevel, this.widthMap));
+    }
+
+    public void commentedLine(@NotNull final String comment, @NotNull final Object... instructionTokens) {
+        final List<String> tokens = List.of(instructionTokens)
+                .map(String::valueOf);
+        this.printables.add(new FormattedLine(tokens, comment, this.indentationLevel, this.widthMap));
+    }
+
+    public void rawLine(@NotNull final String line) {
+        this.printables.add(new RawLine(line, this.indentationLevel, this.widthMap));
+    }
+
+    @Override
+    public String toString() {
+        this.printables.forEach(Printable::updateWithMap);
+        return List.ofAll(this.printables).mkString("\n");
+    }
+}

src/main/java/ch/fritteli/gombaila/domain/printer/RawLine.java

@@ -0,0 +1,20 @@
+package ch.fritteli.gombaila.domain.printer;
+
+import org.jetbrains.annotations.NotNull;
+
+record RawLine(@NotNull String line, int indentationLevel, @NotNull WidthMap widthMap) implements Line{
+    @Override
+    public void updateWithMap() {
+        // nop
+    }
+
+    @NotNull
+    @Override
+    public String toString() {
+        final int indents = this.widthMap.getIndentationSize() * this.indentationLevel;
+        if (indents == 0) {
+            return this.line;
+        }
+        return ("%-" + indents + "s%s").formatted("", this.line);
+    }
+}

src/main/java/ch/fritteli/gombaila/domain/printer/WidthMap.java

@@ -0,0 +1,38 @@
+package ch.fritteli.gombaila.domain.printer;
+
+import io.vavr.collection.HashMap;
+import io.vavr.collection.Map;
+import lombok.Getter;
+import org.jetbrains.annotations.NotNull;
+
+public class WidthMap {
+    @Getter
+    private final int indentationSize;
+    @NotNull
+    private Map<Integer, Integer> widthByTokenIndex = HashMap.empty();
+
+    public WidthMap(final int indentationSize) {
+        this.indentationSize = indentationSize;
+    }
+
+    int getMaxLineLengthWithoutComment() {
+        return this.widthByTokenIndex.values()
+                .sum()
+                .intValue();
+    }
+
+    int getTokenWidthByIndex(final int tokenIndex) {
+        return this.widthByTokenIndex.get(tokenIndex).getOrElse(0);
+    }
+
+    void updateWidthForTokenIndex(final int tokenIndex, final int width) {
+        if (!this.hasBiggerWidthAt(tokenIndex, width)) {
+            this.widthByTokenIndex = this.widthByTokenIndex.put(tokenIndex, width);
+        }
+    }
+
+    private boolean hasBiggerWidthAt(final int tokenIndex, final int width) {
+        return this.widthByTokenIndex.get(tokenIndex)
+                .exists(existingWidth -> existingWidth > width);
+    }
+}

src/main/resources/docs/readme.md

@@ -8,7 +8,12 @@ let ident = [Expr];
 int_lit  
 ident  
 [BinExpr]
+([Expr])
 
 [BinExpr] ->  
-[Expr] * [Expr]; prec=1  
-[Expr] + [Expr]; prec=0
+[Expr] ^ [Expr]; prec=3 assoc=right  
+[Expr] * [Expr]; prec=2 assoc=left  
+[Expr] / [Expr]; prec=2 assoc=left  
+[Expr] % [Expr]; prec=2 assoc=left  
+[Expr] + [Expr]; prec=1 assoc=left
+[Expr] - [Expr]; prec=1 assoc=left

src/main/resources/gombaila/simple.gb

@@ -1,3 +1,4 @@
-let x = 1 + 2;
-let y = 8 + 2 * x ^ (2 - 1) ^ 2 - 1 * 0;
-exit(y + x % 2);
+let foo = 10;
+let bar = 2;
+let baz = foo / bar;
+exit(baz);