choc_javascript.h

//
//    ██████ ██   ██  ██████   ██████
//   ██      ██   ██ ██    ██ ██            ** Classy Header-Only Classes **
//   ██      ███████ ██    ██ ██
//   ██      ██   ██ ██    ██ ██           https://github.com/Tracktion/choc
//    ██████ ██   ██  ██████   ██████
//
//   CHOC is (C)2022 Tracktion Corporation, and is offered under the terms of the ISC license:
//
//   Permission to use, copy, modify, and/or distribute this software for any purpose with or
//   without fee is hereby granted, provided that the above copyright notice and this permission
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//   AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
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//   WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
//   CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

#ifndef CHOC_JAVASCRIPT_HEADER_INCLUDED
#define CHOC_JAVASCRIPT_HEADER_INCLUDED

#include <stdexcept>
#include <functional>
#include <optional>
#include "../containers/choc_Value.h"
#include "../text/choc_JSON.h"

/**
    Wrapper classes for encapsulating different javascript engines such as
    Duktape and QuickJS.

    Just use one of the context-creation functions such as
    choc::javascript::createQuickJSContext() to create a context for running
    javascript code.
*/
namespace choc::javascript
{
    /// This is thrown by any javascript functions that need to report an error
    struct Error  : public std::runtime_error
    {
        Error (const std::string& error) : std::runtime_error (error) {}
    };

    //==============================================================================
    /// Helper class to hold and provide access to the arguments in a javascript
    /// function callback.
    struct ArgumentList
    {
        const choc::value::Value* args = nullptr;
        size_t numArgs = 0;

        /// Returns the number of arguments
        size_t size() const noexcept                                    { return numArgs; }
        /// Returns true if there are no arguments
        bool empty() const noexcept                                     { return numArgs == 0; }

        /// Returns an argument, or a nullptr if the index is out of range.
        const choc::value::Value* operator[] (size_t index) const       { return index < numArgs ? args + index : nullptr; }

        /// Gets an argument as a primitive type (or a string).
        /// If the index is out of range or the object isn't a suitable type,
        /// then the default value provided will be returned instead.
        template <typename PrimitiveType>
        PrimitiveType get (size_t argIndex, PrimitiveType defaultValue = {}) const;

        /// Standard iterator
        const choc::value::Value* begin() const noexcept                { return args; }
        const choc::value::Value* end() const noexcept                  { return args + numArgs; }
    };

    //==============================================================================
    /**
        An execution context which you use for running javascript code.

        These are really simple to use: call one of the creation functions such
        as choc::javascript::createQuickJSContext() which will give you a shared_ptr to
        a context. Then you can add any native bindings that you need with
        registerFunction(), and call evaluate() or invoke() to execute code or call
        functions directly.

        These contexts are not thread-safe, so it's up to the caller to handle thread
        synchronisation if using a single context from multiple threads.

        They're also definitely not realtime-safe: any of the methods may allocate,
        block, or make system calls.
    */
    class Context
    {
    public:
        /// To create a Context, use a function such as choc::javascript::createQuickJSContext();
        Context() = default;
        Context (Context&&);
        Context& operator= (Context&&);
        ~Context();

        /// Returns true if the context is valid.
        operator bool() const                               { return pimpl != nullptr; }

        //==============================================================================
        /// This callback is used by the run() method.
        using CompletionHandler = std::function<void(const std::string& error,
                                                     const choc::value::ValueView& result)>;

        /// Executes some javascript asynchronously.
        /// If a CompletionHandler callback is provided, it will be called asynchronously
        /// with the return value and any errors that occurred. Note that if you want to execute
        /// the script as a module, use runModule() instead.
        void run (const std::string& javascriptCode,
                  CompletionHandler handleResult = {});

        /// When parsing modules, this function is expected to take a path to a module, and
        /// to return the content of that module, or an empty optional if not found.
        using ReadModuleContentFn = std::function<std::optional<std::string>(std::string_view)>;

        /// This callback will asynchronously parse the script as a module, and will use the
        /// ReadModuleContentFn functor to resolve any imported modules that it needs. If a
        /// CompletionHandler callback is provided, it will be called asynchronously with the
        /// return value and any errors that occurred.
        /// NB: Not all engines support modules.
        void runModule (const std::string& moduleCode,
                        ReadModuleContentFn,
                        CompletionHandler handleResult = {});

        /// Evaluates a javascript expression synchronously, and returns the result.
        /// If there are any parse errors, this will throw a choc::javascript::Error exception.
        /// Note that if you want to execute the script as a module, use runModule() instead.
        choc::value::Value evaluateExpression (const std::string& javascriptCode);

        /// Attempts to synchronously invoke a global function with no arguments.
        /// Any errors will throw a choc::javascript::Error exception.
        /// None of the methods in this class are either thread-safe or realtime-safe, so you'll
        /// need to organise your own locking if you're calling into a single Context from
        /// multiple threads.
        choc::value::Value invoke (std::string_view functionName);

        /// Attempts to invoke a global function with the arguments provided.
        /// The arguments can be primitives, strings, choc::value::ValueView or
        /// choc::value::Value types.
        /// Any errors will throw a choc::javascript::Error exception.
        /// None of the methods in this class are either thread-safe or realtime-safe, so you'll
        /// need to organise your own locking if you're calling into a single Context from
        /// multiple threads.
        template <typename... Args>
        choc::value::Value invoke (std::string_view functionName, Args&&... args);

        /// Attempts to invoke a global function with an array of arguments.
        /// The objects in the argument list can be primitives, strings, choc::value::ValueView
        /// or choc::value::Value types.
        /// Any errors will throw a choc::javascript::Error exception.
        /// None of the methods in this class are either thread-safe or realtime-safe, so you'll
        /// need to organise your own locking if you're calling into a single Context from
        /// multiple threads.
        template <typename ArgList>
        choc::value::Value invokeWithArgList (std::string_view functionName, const ArgList& args);

        /// This is the prototype for a lambda which can be bound as a javascript function.
        using NativeFunction = std::function<choc::value::Value(ArgumentList)>;

        /// Binds a lambda function to a global name so that javascript code can invoke it.
        void registerFunction (const std::string& name, NativeFunction fn);

        /// Pumps the message loop in an engine-specific way - may have no effect on some platforms.
        void pumpMessageLoop();

        //==============================================================================
        /// @internal
        struct Pimpl;
        /// @internal
        Context (std::unique_ptr<Pimpl>);

    private:
        std::unique_ptr<Pimpl> pimpl;
    };

    //==============================================================================
    /// Creates a QuickJS-based context. If you call this, then you'll need to
    /// include choc_javascript_QuickJS.h in one (and only one!) of your source files.
    Context createQuickJSContext();

    /// Creates a Duktape-based context. If you call this, then you'll need to
    /// include choc_javascript_Duktape.h in one (and only one!) of your source files.
    Context createDuktapeContext();

    /// Creates a V8-based context. If you call this, then you'll need to
    /// make sure that your project also has the V8 header folder in its
    /// search path, and that you statically link the appropriate V8 libs.
    Context createV8Context();

    //==============================================================================
    /// Sanitises a string to provide a version of it that is safe for use as a
    /// javascript identifier. This involves removing/replacing any illegal
    /// characters and modifying the string to avoid clashes with reserved words.
    std::string makeSafeIdentifier (std::string name);
}


//==============================================================================
//        _        _           _  _
//     __| |  ___ | |_   __ _ (_)| | ___
//    / _` | / _ \| __| / _` || || |/ __|
//   | (_| ||  __/| |_ | (_| || || |\__ \ _  _  _
//    \__,_| \___| \__| \__,_||_||_||___/(_)(_)(_)
//
//   Code beyond this point is implementation detail...
//
//==============================================================================

namespace choc::javascript
{

template <typename PrimitiveType>
PrimitiveType ArgumentList::get (size_t index, PrimitiveType defaultValue) const
{
    if (auto a = (*this)[index])
        return a->getWithDefault<PrimitiveType> (defaultValue);

    return defaultValue;
}

struct Context::Pimpl
{
    Pimpl() = default;
    virtual ~Pimpl() = default;

    virtual void registerFunction (const std::string&, NativeFunction) = 0;
    virtual choc::value::Value evaluateExpression (const std::string&) = 0;
    virtual void run (const std::string&, ReadModuleContentFn*, CompletionHandler) = 0;
    virtual void prepareForCall (std::string_view, uint32_t numArgs) = 0;
    virtual choc::value::Value performCall() = 0;
    virtual void pushObjectOrArray (const choc::value::ValueView&) = 0;
    virtual void pushArg (std::string_view) = 0;
    virtual void pushArg (int32_t) = 0;
    virtual void pushArg (int64_t) = 0;
    virtual void pushArg (uint32_t) = 0;
    virtual void pushArg (double) = 0;
    virtual void pushArg (bool) = 0;
    virtual void pumpMessageLoop() = 0;

    void pushArg (const std::string& v)   { pushArg (std::string_view (v)); }
    void pushArg (const char* v)          { pushArg (std::string_view (v)); }
    void pushArg (uint64_t v)             { pushArg (static_cast<int64_t> (v)); }
    void pushArg (float v)                { pushArg (static_cast<double> (v)); }

    void pushArg (const choc::value::ValueView& v)
    {
        if (v.isInt32())    return pushArg (v.getInt32());
        if (v.isInt64())    return pushArg (v.getInt64());
        if (v.isFloat32())  return pushArg (v.getFloat32());
        if (v.isFloat64())  return pushArg (v.getFloat64());
        if (v.isString())   return pushArg (v.getString());
        if (v.isBool())     return pushArg (v.getBool());
        if (v.isVoid())     throw Error ("Function arguments cannot be void!");

        pushObjectOrArray (v);
    }
};

inline Context::Context (std::unique_ptr<Pimpl> p) : pimpl (std::move (p)) {}
inline Context::~Context() = default;
inline Context::Context (Context&&) = default;
inline Context& Context::operator= (Context&&) = default;

inline choc::value::Value Context::invoke (std::string_view functionName)
{
    CHOC_ASSERT (pimpl != nullptr); // cannot call this on a moved-from context!
    pimpl->prepareForCall (functionName, 0);
    return pimpl->performCall();
}

template <typename... Args>
choc::value::Value Context::invoke (std::string_view functionName, Args&&... args)
{
    CHOC_ASSERT (pimpl != nullptr); // cannot call this on a moved-from context!
    pimpl->prepareForCall (functionName, sizeof...(args));
    (pimpl->pushArg (std::forward<Args> (args)), ...);
    return pimpl->performCall();
}

template <typename ArgList>
choc::value::Value Context::invokeWithArgList (std::string_view functionName, const ArgList& args)
{
    CHOC_ASSERT (pimpl != nullptr); // cannot call this on a moved-from context!
    pimpl->prepareForCall (functionName, static_cast<uint32_t> (args.size()));

    for (auto& arg : args)
        pimpl->pushArg (arg);

    return pimpl->performCall();
}

inline void Context::registerFunction (const std::string& name, NativeFunction fn)
{
    CHOC_ASSERT (pimpl != nullptr); // cannot call this on a moved-from context!
    pimpl->registerFunction (name, std::move (fn));
}

inline choc::value::Value Context::evaluateExpression (const std::string& javascriptCode)
{
    CHOC_ASSERT (pimpl != nullptr); // cannot call this on a moved-from context!
    return pimpl->evaluateExpression (javascriptCode);
}

inline void Context::run (const std::string& javascriptCode, CompletionHandler handleResult)
{
    CHOC_ASSERT (pimpl != nullptr); // cannot call this on a moved-from context!
    pimpl->run (javascriptCode, nullptr, std::move (handleResult));
}

inline void Context::runModule (const std::string& moduleCode, ReadModuleContentFn readModule, CompletionHandler handleResult)
{
    CHOC_ASSERT (pimpl != nullptr); // cannot call this on a moved-from context!
    pimpl->run (moduleCode, std::addressof (readModule), std::move (handleResult));
}

inline void Context::pumpMessageLoop()
{
    CHOC_ASSERT (pimpl != nullptr); // cannot call this on a moved-from context!
    pimpl->pumpMessageLoop();
}

inline std::string makeSafeIdentifier (std::string s)
{
    constexpr static std::string_view reservedWords[] =
    {
        "abstract", "arguments", "await", "boolean", "break", "byte", "case", "catch",
        "char", "class", "const", "continue", "debugger", "default", "delete", "do",
        "double", "else", "enum", "eval", "export", "extends", "false", "final",
        "finally", "float", "for", "function", "goto", "if", "implements", "import",
        "in", "instanceof", "int", "interface", "let", "long", "native", "new",
        "null", "package", "private", "protected", "public", "return", "short", "static",
        "super", "switch", "synchronized", "this", "throw", "throws", "transient", "true",
        "try", "typeof", "var", "void", "volatile", "while", "with", "yield"
    };

    for (auto& c : s)
        if (std::string_view (" ,./;:").find (c) != std::string_view::npos)
            c = '_';

    s.erase (std::remove_if (s.begin(), s.end(), [&] (char c)
    {
        return ! ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_' || (c >= '0' && c <= '9'));
    }), s.end());

    if (s[0] >= '0' && s[0] <= '9') // Identifiers can't start with a digit
        s = "_" + s;

    for (auto keyword : reservedWords)
        if (s == keyword)
            return s + "_";

    return s;
}

} // namespace choc::javascript

#endif // CHOC_JAVASCRIPT_HEADER_INCLUDED

#ifdef CHOC_JAVASCRIPT_IMPLEMENTATION
 // The way the javascript classes work has changed: instead of
 // setting CHOC_JAVASCRIPT_IMPLEMENTATION in one of your source files, just
 // include the actual engine that you want to use, e.g. choc_javascript_QuickJS.h
 // in (only!) one of your source files, and use that to create instances of that engine.
 #error "CHOC_JAVASCRIPT_IMPLEMENTATION is deprecated"
#endif