BrainScriptParser.h

// ConfigParser.h -- config parser (syntactic only, that is, source -> Expression tree)

#pragma once

#include "Basics.h"
#include "ScriptableObjects.h"
#include "File.h"
#include <string>
#include <vector>
#include <map>
#include <memory>

namespace Microsoft { namespace MSR { namespace BS {

    using namespace std;

    // ---------------------------------------------------------------------------
    // TextLocation -- holds a pointer into a source file
    // ---------------------------------------------------------------------------

    struct SourceFile               // content of one source file  (only in this header because TextLocation's private member uses it)
    {
        /*const*/ wstring path;                     // where it came from
        /*const*/ vector<wstring> lines;            // source code lines
        SourceFile(wstring location, wstring text); // from string, e.g. command line
        SourceFile(wstring path);                   // from file
    };

    struct TextLocation                 // position in the text. Lightweight value struct that we can copy around, even into dictionaries etc., for error messages
    {
        // source-code locations are given by line number, character position, and the source file
        size_t lineNo, charPos;         // line number and character index (0-based)
        const SourceFile & GetSourceFile() const { return sourceFileMap[sourceFileAsIndex]; }    // get the corresponding source-code line

        // helpers for pretty-printing errors: Show source-code line with ...^ under it to mark up the point of error
        static void PrintIssue(const vector<TextLocation> & locations, const wchar_t * errorKind, const wchar_t * kind, const wchar_t * what);
        static void Trace(TextLocation, const wchar_t * traceKind, const wchar_t * op, const wchar_t * exprPath);

        // construction
        TextLocation() : lineNo(SIZE_MAX), charPos(SIZE_MAX), sourceFileAsIndex(SIZE_MAX) { }   // default constructor constructs an unmissably invalid object
        bool IsValid() const;

        // register a new source file and return a TextPosition that points to its start
        static TextLocation NewSourceFile(SourceFile && sourceFile);

    private:
        size_t sourceFileAsIndex;   // source file is remembered in the value struct as an index into the static sourceFileMap[]
        // the meaning of the 'sourceFile' index is global, stored in this static map
        static vector<SourceFile> sourceFileMap;
    };

    // ---------------------------------------------------------------------------
    // ConfigException -- all errors from processing the config files are reported as ConfigException
    // ---------------------------------------------------------------------------

    class ConfigException : public Microsoft::MSR::ScriptableObjects::ScriptingException
    {
        vector<TextLocation> locations;  // error location (front()) and evaluation parents (upper)
    public:
        // Note: All our Error objects use wide strings, which we round-trip through runtime_error as utf8.
        ConfigException(const wstring & msg, TextLocation where) : Microsoft::MSR::ScriptableObjects::ScriptingException(msra::strfun::utf8(msg)) { locations.push_back(where); }

        // these are used in pretty-printing
        TextLocation where() const { return locations.front(); }    // where the error happened
        virtual const wchar_t * kind() const = 0;                   // e.g. "warning" or "error"

        // pretty-print this as an error message
        void /*ScriptingException::*/PrintError() const { TextLocation::PrintIssue(locations, L"error", kind(), msra::strfun::utf16(what()).c_str()); }
        void AddLocation(TextLocation where) { locations.push_back(where); }
    };

    // ---------------------------------------------------------------------------
    // Expression -- the entire config is a tree of Expression types
    // We don't use polymorphism here because C++ is so verbose...
    // ---------------------------------------------------------------------------

    struct Expression
    {
        wstring op;                 // operation, encoded as a string; 'symbol' for punctuation and keywords, otherwise used in constructors below ...TODO: use constexpr
        wstring id;                 // identifier;      op == "id", "new", "array", and "." (if macro then it also has args)
        wstring s;                  // string literal;  op == "s"
        double d;                   // numeric literal; op == "d"
        bool b;                     // boolean literal; op == "b"
        typedef shared_ptr<struct Expression> ExpressionPtr;
        vector<ExpressionPtr> args;             // position-dependent expression/function args
        map<wstring, pair<TextLocation,ExpressionPtr>> namedArgs;  // named expression/function args; also dictionary members (loc is of the identifier)
        TextLocation location;      // where in the source code (for downstream error reporting)
        // constructors
        Expression(TextLocation location) : location(location), d(0.0), b(false) { }
        Expression(TextLocation location, wstring op) : location(location), d(0.0), b(false), op(op) { }
        Expression(TextLocation location, wstring op, double d, wstring s, bool b) : location(location), d(d), s(s), b(b), op(op) { }
        Expression(TextLocation location, wstring op, ExpressionPtr arg) : location(location), d(0.0), b(false), op(op) { args.push_back(arg); }
        Expression(TextLocation location, wstring op, ExpressionPtr arg1, ExpressionPtr arg2) : location(location), d(0.0), b(false), op(op) { args.push_back(arg1); args.push_back(arg2); }
        // diagnostics helper: print the content
        void Dump(int indent = 0) const;
    };
    typedef Expression::ExpressionPtr ExpressionPtr;    // circumvent some circular definition problem

    // access the parser through one of these two functions
    ExpressionPtr ParseConfigString(wstring text);
    ExpressionPtr ParseConfigFile(wstring path);

}}} // namespaces