feat: Minimal conversion of THP->PHP AST

CHANGELOG.md

@@ -25,8 +25,8 @@
 
 ## v0.0.14
 
-- [ ] Define a minimal PHP AST
-- [ ] Transform THP AST into PHP AST
+- [x] Define a minimal PHP AST
+- [x] Transform THP AST into PHP AST
 - [ ] Implement minimal codegen for the PHP AST
 - [ ] Remove old codegen
 - [ ] Finish the workflow for a hello world

src/cli/tokenize.rs

@@ -1,5 +1,5 @@
-use std::io::{self, BufRead};
 use crate::lexic::get_tokens;
+use std::io::{self, BufRead};
 
 pub fn tokenize_command(_options: Vec<String>) -> Result<(), ()> {
     // Get the input from stdin
@@ -8,12 +8,10 @@ pub fn tokenize_command(_options: Vec<String>) -> Result<(), ()> {
     let mut lines = Vec::new();
     for line in stdin.lock().lines() {
         match line {
-            Ok(line) => {
-                lines.push(line)
-            }
+            Ok(line) => lines.push(line),
             Err(reason) => {
                 eprintln!("Error reading input: {}", reason);
-                return Err(())
+                return Err(());
             }
         }
     }

src/codegen/mod.rs

@@ -1,5 +1,5 @@
-use crate::syntax::ast::ModuleAST;
-
+// TODO: These are for the THP AST. Eventually replace this
+// with the PHP AST
 mod binding;
 mod block;
 mod expression;
@@ -9,13 +9,15 @@ mod module_ast;
 mod statement;
 mod top_level_construct;
 
+mod php;
+
 /// Trait that the AST and its nodes implement to support transformation to PHP
-trait Transpilable {
+pub trait Transpilable {
     /// Transforms this struct into PHP
     fn transpile(&self) -> String;
 }
 
 /// Transforms an AST to its representation in PHP
-pub fn codegen<'a>(ast: &'a ModuleAST) -> String {
+pub fn codegen<'a>(ast: &'a impl Transpilable) -> String {
     ast.transpile()
 }

src/codegen/php/mod.rs

@@ -0,0 +1,27 @@
+use crate::php_ast::{PhpAst, PhpStatement};
+
+use super::Transpilable;
+
+impl Transpilable for PhpAst<'_> {
+    fn transpile(&self) -> String {
+        let mut fragments = vec![String::from("<?php\n")];
+        
+        for statement in self.statements.iter() {
+            fragments.push(statement.transpile());
+        }
+
+        fragments.join("")
+    }
+}
+
+impl Transpilable for PhpStatement<'_> {
+    fn transpile(&self) -> String {
+        match self {
+            PhpStatement::PhpEchoStatement(expr_list) => {
+                // TODO: Actually generate parameters from the expr_list
+                "echo \"\";".into()
+            }
+        }
+    }
+}
+

src/php_ast/mod.rs

@@ -1,3 +1,20 @@
 // Follows https://phplang.org/spec/19-grammar.html#syntactic-grammar
 
-struct PhpAst {}
+pub mod transformers;
+
+/// Represents `statement-list` on the grammar
+pub struct PhpAst<'a> {
+    pub statements: Vec<PhpStatement<'a>>,
+}
+
+pub enum PhpStatement<'a> {
+    PhpEchoStatement(PhpExpressionList<'a>),
+}
+
+pub struct PhpExpressionList<'a> {
+    pub expressions: Vec<PhpExpression<'a>>,
+}
+
+pub enum PhpExpression<'a> {
+    String(&'a String),
+}

src/php_ast/transformers/expression.rs

@@ -0,0 +1,16 @@
+use super::super::PhpExpression;
+use crate::syntax::ast::Expression;
+
+use super::PHPTransformable;
+
+/// Transforms a THP expression into a PHP expression
+impl<'a> PHPTransformable<'a> for Expression<'_> {
+    type Item = PhpExpression<'a>;
+
+    fn into_php_ast(&'a self) -> Self::Item {
+        match self {
+            Expression::String(value) => PhpExpression::String(value),
+            _ => todo!("transformation for expression: {:?}", self),
+        }
+    }
+}

src/php_ast/transformers/mod.rs

@@ -0,0 +1,10 @@
+pub mod expression;
+pub mod module_ast;
+pub mod statement;
+
+/// Implemented by AST nodes that can be transformed to PHP
+pub trait PHPTransformable<'a> {
+    type Item;
+
+    fn into_php_ast(&'a self) -> Self::Item;
+}

src/php_ast/transformers/module_ast.rs

@@ -0,0 +1,50 @@
+use super::super::PhpAst;
+use crate::php_ast::{PhpExpressionList, PhpStatement};
+use crate::syntax::ast::{Expression, ModuleAST, ModuleMembers};
+
+use super::PHPTransformable;
+
+/// Transforms a THP AST into a PHP AST
+impl<'a> PHPTransformable<'a> for ModuleAST<'_> {
+    type Item = PhpAst<'a>;
+
+    fn into_php_ast(&'a self) -> Self::Item {
+        let mut php_statements = Vec::<PhpStatement>::new();
+
+        for production in self.productions.iter() {
+            match production {
+                ModuleMembers::Stmt(stmt) => {
+                    php_statements.push(stmt.into_php_ast());
+                }
+                ModuleMembers::Expr(expr) => {
+                    // TODO: a print() function call is technically an
+                    // expression in the AST, but PHP expects it to be an statement.
+                    // transform beforehand?
+
+                    match expr {
+                        Expression::FunctionCall(fc) => {
+                            let function_expr: &Expression = &*fc.function;
+                            match function_expr {
+                                Expression::Identifier(id) if *id == "print" => {
+                                        // transform to print() expression
+                                        // no parameters supported
+                                        php_statements.push(PhpStatement::PhpEchoStatement(PhpExpressionList {
+                                            expressions: vec![]
+                                        }));
+                                },
+                                _ => todo!("Not implemented: AST transformation for function call that is not an identifier")
+                            }
+                        }
+                        _ => {
+                            todo!("not implemented: AST transform for expression {:?}", expr)
+                        }
+                    }
+                }
+            }
+        }
+
+        PhpAst {
+            statements: php_statements,
+        }
+    }
+}

src/php_ast/transformers/statement.rs

@@ -0,0 +1,15 @@
+use super::super::PhpStatement;
+use crate::syntax::ast::Statement;
+
+use super::PHPTransformable;
+
+/// Transforms a THP expression into a PHP expression
+impl<'a> PHPTransformable<'a> for Statement<'_> {
+    type Item = PhpStatement<'a>;
+
+    fn into_php_ast(&'a self) -> Self::Item {
+        match self {
+            _ => todo!("transformation for statement: {:?}", self),
+        }
+    }
+}

src/repl/mod.rs

@@ -2,6 +2,7 @@ use std::io::{self, Write};
 
 use colored::Colorize;
 
+use crate::codegen::Transpilable;
 use crate::error_handling::PrintableError;
 use crate::lexic::token::Token;
 
@@ -9,6 +10,8 @@ use super::codegen;
 use super::lexic;
 use super::syntax;
 
+use crate::php_ast::transformers::PHPTransformable;
+
 /// Executes Lexical analysis, handles errors and calls build_ast for the next phase
 fn compile(input: &String) {
     let tokens = lexic::get_tokens(input);
@@ -32,7 +35,9 @@ fn build_ast(input: &String, tokens: Vec<Token>) {
 
     match ast {
         Ok(ast) => {
+            /*
             let res1 = crate::semantic::check_semantics(&ast);
+            TODO: Disabled to test the PHP codegen. Reenable
             match res1 {
                 Ok(_) => {}
                 Err(reason) => {
@@ -42,8 +47,10 @@ fn build_ast(input: &String, tokens: Vec<Token>) {
                     return;
                 }
             }
+            */
 
-            let js_code = codegen::codegen(&ast);
+            let php_ast = ast.into_php_ast();
+            let js_code = php_ast.transpile();
             println!("{}", js_code)
         }
         Err(reason) => {