MagicSetEditor2/src/script/context.hpp

//+----------------------------------------------------------------------------+
//| Description:  Magic Set Editor - Program to make card games                |
//| Copyright:    (C) Twan van Laarhoven and the other MSE developers          |
//| License:      GNU General Public License 2 or later (see file COPYING)     |
//+----------------------------------------------------------------------------+

#pragma once

// ----------------------------------------------------------------------------- : Includes

#include <script/script.hpp>

class Dependency;

// ----------------------------------------------------------------------------- : VectorIntMap

/// A map like data structure that stores the elements in a vector.
/** K should be an integer type, the keys should be dense. */
template <typename K, typename V>
class VectorIntMap {
public:
  inline V& operator [] (K key) {
    if (values.size() <= key) {
      values.resize(key + 1);
    }
    return values[key];
  }
  /// Get access to the vector
  inline const vector<V>& get() const { return values; }
private:
  vector<V> values;
};

// ----------------------------------------------------------------------------- : Context

/// Context for script evaluation
class Context {
public:
  Context();
  
  /// Evaluate a script inside this context.
  /** This function is safely reentrant.
   *  @param openScope if false, variables set in this eval call will leak out.
   */
  ScriptValueP eval(const Script& script, bool openScope = true);
  
  /// Analyze the dependencies of a script
  /** All things the script depends on are marked with signalDependent(dep).
   *  The return value of this function should be ignored
   */
  ScriptValueP dependencies(const Dependency& dep, const Script& script);
    
  /// Set a variable to a new value (in the current scope)
  void setVariable(const String& name, const ScriptValueP& value);
  /// Set a variable to a new value (in the current scope)
  void setVariable(Variable name, const ScriptValueP& value);
  void setGlobalVariable(Variable name, const ScriptValueP& value);
  
  /// Get the value of a variable, throws if it not set
  ScriptValueP getVariable(const String& name);
  /// Get the value of a variable, returns ScriptValue() if it is not set
  ScriptValueP getVariableOpt(const String& name);
  /// Get the value of a variable, throws if it not set
  ScriptValueP getVariable(Variable var);
  /// Get the value of a variable, returns ScriptValue() if it is not set
  inline ScriptValueP getVariableOpt(Variable var) { return variables[var].value; }
  /// Get the value of a variable only if it was set in the current scope, returns ScriptValue() if it is not set
  ScriptValueP getVariableInScopeOpt(Variable var);
  /// In what scope was the variable set?
  /** Returns 0 for the current scope and >0 for outer scopes.
   *  Returns -1 if the varible is not set
   */
  int getVariableScope(Variable var);
  
  /// Make a closure of the function with the direct parameters of the current call
  ScriptValueP makeClosure(const ScriptValueP& fun);
  
public:
  
  /// Open a new scope
  /** returns the number of shadowed binding before that scope */
  size_t openScope();
  /// Close a scope, must be passed a value from openScope
  void closeScope(size_t scope);
  friend class LocalScope;
  
public:// public for FOR_EACH
  /// Record of a variable
  struct VariableValue {
    VariableValue() : level(0) {}
    unsigned int level; ///< Scope level on which this variable was set
    ScriptValueP value; ///< Value of this variable
    bool global_scope = false; ///< Is this variable globally scoped? 
  };
  /// Record of a variable binding that is being shadowed (overwritten) by another binding
  struct Binding {
    Variable      variable; ///< Name of the overwritten variable.
    VariableValue value;    ///< Old value of that variable.
  };
private:
  /// Variables, indexed by integer name (using string_to_variable)
  VectorIntMap<unsigned int, VariableValue> variables;
  /// Shadowed variable bindings
  vector<Binding> shadowed;
  /// Number of scopes opened
  unsigned int level;
  /// Stack of values
  vector<ScriptValueP> stack;
  #ifdef _DEBUG
    /// The opened scopes, for sanity checking
    vector<size_t> scopes;
  #endif
  
  // utility types for dependency analysis
  struct Jump;
  struct JumpOrder;
  
  /// Return the bindings in the current scope
  void getBindings(size_t scope, vector<Binding>&);
  /// Remove all bindings made in the current scope
  void resetBindings(size_t scope);
  /// Make an object with n elements, popping 2n values from the stack, and push it onto the stack
  void makeObject(size_t n);
  /// Make a closure with n arguments
  void makeClosure(size_t n, const Instruction*& instr);
  
  /// Get a variable name givin its value, returns (Variable)-1 if not found (slow!)
  Variable lookupVariableValue(const ScriptValueP& value);
  friend class ScriptCompose;
};

/// A class that creates a local scope
class LocalScope {
public:
  inline LocalScope(Context& ctx) : ctx(ctx), scope(ctx.openScope()) {}
  inline ~LocalScope() { ctx.closeScope(scope); }
private:
  Context& ctx;
  size_t scope;
};