From e8b7a9bd832dd2ac4a28b2b2cb30eb5c19ec78c2 Mon Sep 17 00:00:00 2001
From: Romain Goyet <romain.goyet@numworks.com>
Date: Sat, 26 Mar 2016 18:47:08 +0100
Subject: [PATCH] Poincare: Add an ExpressionBuilder class

Change-Id: I5865b712cfe1f8e1cd2e29d0d2b50be8182985b8
---
 poincare/Makefile                            |  1 +
 poincare/src/simplify/expression_builder.cpp | 60 ++++++++++++++++++++
 poincare/src/simplify/expression_builder.h   | 44 ++++++++++++++
 3 files changed, 105 insertions(+)
 create mode 100644 poincare/src/simplify/expression_builder.cpp
 create mode 100644 poincare/src/simplify/expression_builder.h

diff --git a/poincare/Makefile b/poincare/Makefile
index af90ddb10..6047d7b6a 100644
--- a/poincare/Makefile
+++ b/poincare/Makefile
@@ -33,6 +33,7 @@ objs += $(addprefix poincare/src/simplify/,\
   simplify_commutative_merge.o\
   simplify_product_zero.o\
   expression_selector.o\
+  expression_builder.o\
 )
 tests += $(addprefix poincare/test/,\
   addition.cpp\
diff --git a/poincare/src/simplify/expression_builder.cpp b/poincare/src/simplify/expression_builder.cpp
new file mode 100644
index 000000000..64c193de7
--- /dev/null
+++ b/poincare/src/simplify/expression_builder.cpp
@@ -0,0 +1,60 @@
+#include "expression_builder.h"
+#include <poincare/addition.h>
+#include <poincare/integer.h>
+extern "C" {
+#include <assert.h>
+}
+
+/* Our compiler defines two things:
+ * - First, a list of ExpressionBuilder
+ * - Second, a children_expression_buffer[] of the proper size.
+ */
+
+Expression * children_expression_buffer[4]; // This will be defined by our compiler
+
+Expression * ExpressionBuilder::build(Expression * matches[]) {
+  Expression * children_expressions[255]; // FIXME: <- The sized can be given by the compiler
+  //Expression * children_expressions = malloc;
+// That malloc can be avoided: we can give an upper bound
+// Afer we've finished processing the rules
+// That upper bound is likely to be very small (3, currently)
+
+  for (int i=0; i<m_numberOfChildren; i++) {
+    ExpressionBuilder * child = this->child(i);
+    children_expressions[i] = child->build(matches);
+  }
+  Expression * result = nullptr;
+  switch(m_action) {
+    case ExpressionBuilder::Action::Build:
+      switch(m_expressionType) {
+        case Expression::Type::Addition:
+          result = new Addition(children_expressions, m_numberOfChildren, true);
+          break;
+        case Expression::Type::Integer:
+          result = new Integer(m_integerValue);
+          break;
+        default:
+          assert(false);
+          break;
+      }
+      break;
+    case ExpressionBuilder::Action::Clone:
+      result = matches[m_matchIndex]->clone();
+      break;
+    case ExpressionBuilder::Action::FunctionCall:
+      // result = m_functionPointer(children_expressions);
+      break;
+  }
+  return result;
+}
+
+// Extrude in a class
+ExpressionBuilder * ExpressionBuilder::child(int index) {
+  assert(index>=0 && index<m_numberOfChildren);
+  if (index == 0) {
+    return (this+1); // Pointer arithmetics
+  } else {
+    ExpressionBuilder * previousChild = this->child(index-1);
+    return previousChild+previousChild->m_numberOfChildren; // Pointer arithm.
+  }
+}
diff --git a/poincare/src/simplify/expression_builder.h b/poincare/src/simplify/expression_builder.h
new file mode 100644
index 000000000..312c2ceb4
--- /dev/null
+++ b/poincare/src/simplify/expression_builder.h
@@ -0,0 +1,44 @@
+#ifndef POINCARE_SIMPLIFY_EXPRESSION_BUILDER_H
+#define POINCARE_SIMPLIFY_EXPRESSION_BUILDER_H
+
+#include <poincare/expression.h>
+extern "C" {
+#include <stdint.h>
+}
+
+class ExpressionBuilder {
+public:
+  ExpressionBuilder * child(int i);
+  Expression * build(Expression * matches[]);
+
+  /*Expression ** match(Expression * e);*/
+
+  enum class Action {
+    Build,
+    Clone,
+    FunctionCall
+  };
+
+  Action m_action;
+
+  union {
+    // m_action == Build
+    struct {
+      Expression::Type m_expressionType;
+      union {
+        // m_expressionType == Integer
+        int32_t m_integerValue;
+        // m_expressionType == Symbol
+        char const * m_symbolName;
+      };
+    };
+    // m_action == Clone
+    uint8_t m_matchIndex;
+    // m_action == FunctionCall
+    void * m_functionPointer;
+  };
+
+  uint8_t m_numberOfChildren;
+};
+
+#endif