LuaJson.cpp

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// LuaJson.cpp

// Implements the Json exposure bindings to Lua

#include "Globals.h"
#include <sstream>
#include "LuaJson.h"
#include "LuaState.h"
#include "tolua++/include/tolua++.h"
#include "json/json.h"





// fwd:

static void PushJsonValue(const Json::Value & a_Value, cLuaState & a_LuaState);
static Json::Value JsonSerializeValue(cLuaState & a_LuaState);




class CannotSerializeException:
    public std::runtime_error
{
    typedef std::runtime_error Super;
public:
    explicit CannotSerializeException(const AString & a_ValueName, const char * a_ErrorMsg):
        Super(a_ErrorMsg),
        m_ValueName(a_ValueName)
    {
    }

    explicit CannotSerializeException(int a_ValueIndex, const char * a_ErrorMsg):
        Super(a_ErrorMsg),
        m_ValueName(Printf("%d", a_ValueIndex))
    {
    }

    explicit CannotSerializeException(const CannotSerializeException & a_Parent, const AString & a_ValueNamePrefix):
        Super(a_Parent.what()),
        m_ValueName(a_ValueNamePrefix + "." + a_Parent.m_ValueName)
    {
    }

    explicit CannotSerializeException(const CannotSerializeException & a_Parent, int a_ValueNamePrefixIndex):
        Super(a_Parent.what()),
        m_ValueName(Printf("%d", a_ValueNamePrefixIndex) + "." + a_Parent.m_ValueName)
    {
    }

    const AString & GetValueName() const { return m_ValueName; }

protected:
    AString m_ValueName;
};





static void PushJsonArray(const Json::Value & a_Value, cLuaState & a_LuaState)
{
    // Create the appropriately-sized Lua table:
    lua_createtable(a_LuaState, static_cast<int>(a_Value.size()), 0);

    // Insert each value to the appropriate index (1-based):
    int idx = 1;
    for (const auto & v: a_Value)
    {
        // Include Json null values in the array - it will have holes, but indices will stay the same
        PushJsonValue(v, a_LuaState);
        lua_rawseti(a_LuaState, -2, idx);
        idx += 1;
    }  // for v: a_Value[]
}





static void PushJsonObject(const Json::Value & a_Value, cLuaState & a_LuaState)
{
    // Create the appropriately-sized Lua table:
    lua_createtable(a_LuaState, 0, static_cast<int>(a_Value.size()));

    // Json::Value has no means of iterating over children with their names included.
    // We need to iterate over names and "find" them in the object again:
    auto names = a_Value.getMemberNames();
    for (const auto & n: names)
    {
        auto v = a_Value[n];
        if (v.isNull())
        {
            // Skip null values
            continue;
        }

        // Set the value in Lua's table:
        a_LuaState.Push(n);
        PushJsonValue(v, a_LuaState);
        lua_rawset(a_LuaState, -3);
    }  // for itr - a_Value[]
}





void PushJsonValue(const Json::Value & a_Value, cLuaState & a_LuaState)
{
    switch (a_Value.type())
    {
        case Json::nullValue:
        {
            a_LuaState.Push(cLuaState::Nil);
            break;
        }

        case Json::intValue:
        case Json::uintValue:
        case Json::realValue:
        {
            a_LuaState.Push(static_cast<lua_Number>(a_Value.asDouble()));
            break;
        }

        case Json::booleanValue:
        {
            a_LuaState.Push(a_Value.asBool());
            break;
        }

        case Json::stringValue:
        {
            a_LuaState.Push(a_Value.asString());
            break;
        }

        case Json::arrayValue:
        {
            PushJsonArray(a_Value, a_LuaState);
            break;
        }

        case Json::objectValue:
        {
            PushJsonObject(a_Value, a_LuaState);
            break;
        }
    }  // switch (v.type())
}





static Json::Value JsonSerializeTable(cLuaState & a_LuaState)
{
    Json::Value res;
    lua_pushnil(a_LuaState);
    while (lua_next(a_LuaState, -2) != 0)
    {
        if (lua_type(a_LuaState, -2) == LUA_TNUMBER)
        {
            int idx;
            a_LuaState.GetStackValue(-2, idx);
            try
            {
                res[idx - 1] = JsonSerializeValue(a_LuaState);
            }
            catch (const CannotSerializeException & exc)
            {
                throw CannotSerializeException(exc, idx);
            }
            catch (const std::exception & exc)  // Cannot catch Json::Exception, because it's not properly defined
            {
                throw CannotSerializeException(idx, exc.what());
            }
        }
        else
        {
            AString name;
            if (a_LuaState.GetStackValue(-2, name))
            {
                try
                {
                    res[name] = JsonSerializeValue(a_LuaState);
                }
                catch (const CannotSerializeException & exc)
                {
                    throw CannotSerializeException(exc, name);
                }
                catch (const std::exception & exc)  // Cannot catch Json::Exception, because it's not properly defined
                {
                    throw CannotSerializeException(name, exc.what());
                }
            }
        }
        lua_pop(a_LuaState, 1);
    }
    return res;
}





static Json::Value JsonSerializeValue(cLuaState & a_LuaState)
{
    switch (lua_type(a_LuaState, -1))
    {
        case LUA_TBOOLEAN:
        {
            bool v;
            a_LuaState.GetStackValue(-1, v);
            return Json::Value(v);
        }
        case LUA_TNIL:
        {
            return Json::Value(Json::nullValue);
        }
        case LUA_TNUMBER:
        {
            lua_Number v;
            a_LuaState.GetStackValue(-1, v);
            return Json::Value(v);
        }
        case LUA_TSTRING:
        {
            AString v;
            a_LuaState.GetStackValue(-1, v);
            return Json::Value(v);
        }
        case LUA_TTABLE:
        {
            return JsonSerializeTable(a_LuaState);
        }
        default:
        {
            LOGD("Attempting to serialize an unhandled Lua value type: %d", lua_type(a_LuaState, -1));
            return Json::Value(Json::nullValue);
        }
    }
}





static int tolua_cJson_Parse(lua_State * a_LuaState)
{
    // Function signature:
    // cJson:Parse("string") -> table

    // Check the param types:
    cLuaState L(a_LuaState);
    if (
        !L.CheckParamUserTable(1, "cJson") ||
        !L.CheckParamString(2) ||
        !L.CheckParamEnd(3)
    )
    {
        return 0;
    }

    // Get the input string:
    AString input;
    if (!L.GetStackValue(2, input))
    {
        LOGWARNING("cJson:Parse(): Cannot read input string");
        L.LogStackTrace();
        return 0;
    }

    // Parse the string:
    Json::Value root;
    Json::Reader reader;
    if (!reader.parse(input, root, false))
    {
        L.Push(cLuaState::Nil, Printf("Parsing Json failed: %s", reader.getFormattedErrorMessages().c_str()));
        return 2;
    }

    // Push the Json value onto Lua stack:
    PushJsonValue(root, L);
    return 1;
}





static int tolua_cJson_Serialize(lua_State * a_LuaState)
{
    // Function signature:
    // cJson:Serialize({table}, [{option1 = value1, option2 = value2}]) -> string

    // Check the param types:
    cLuaState L(a_LuaState);
    if (
        !L.CheckParamUserTable(1, "cJson") ||
        !L.CheckParamTable(2) ||
        !L.CheckParamEnd(4)
    )
    {
        return 0;
    }

    // Push the table to the top of the Lua stack, and call the serializing function:
    lua_pushvalue(L, 2);
    Json::Value root;
    try
    {
        root = JsonSerializeValue(L);
    }
    catch (const CannotSerializeException & exc)
    {
        lua_pushnil(L);
        L.Push(Printf("Cannot serialize into Json, value \"%s\" caused an error \"%s\"", exc.GetValueName().c_str(), exc.what()));
        return 2;
    }
    lua_pop(L, 1);

    // Create the writer, with all properties (optional param 3) applied to it:
    Json::StreamWriterBuilder builder;
    if (lua_istable(L, 3))
    {
        lua_pushnil(L);
        while (lua_next(L, -2) != 0)
        {
            if (lua_type(L, -2) == LUA_TSTRING)
            {
                AString propName, propValue;
                if (L.GetStackValues(-2, propName, propValue))
                {
                    builder[propName] = propValue;
                }
            }
            lua_pop(L, 1);
        }
        // Check for invalid settings:
        Json::Value invalid;
        if (!builder.validate(&invalid))
        {
            LOGINFO("cJson:Serialize(): detected invalid settings:");
            for (const auto & n: invalid.getMemberNames())
            {
                LOGINFO("  \"%s\" (\"%s\")", n.c_str(), invalid[n].asCString());
            }
        }
    }
    auto writer(builder.newStreamWriter());

    // Serialize the string and push it as the return value:
    std::stringstream ss;
    writer->write(root, &ss);
    L.Push(ss.str());
    return 1;
}





void cLuaJson::Bind(cLuaState & a_LuaState)
{
    tolua_beginmodule(a_LuaState, nullptr);

        // Create the cJson API class:
        tolua_usertype(a_LuaState, "cJson");
        tolua_cclass(a_LuaState, "cJson", "cJson", "", nullptr);

        // Fill in the functions (alpha-sorted):
        tolua_beginmodule(a_LuaState, "cJson");
            tolua_function(a_LuaState, "Parse",     tolua_cJson_Parse);
            tolua_function(a_LuaState, "Serialize", tolua_cJson_Serialize);
        tolua_endmodule(a_LuaState);
    tolua_endmodule(a_LuaState);
}