JavaScriptCore Lua bindings

JavaScriptCore.lua

local ffi = require "ffi"
local lgi = require "lgi"
local WebKit = lgi.WebKit

ffi.cdef [[
typedef struct OpaqueJSValue* JSObjectRef;
typedef struct OpaqueJSValue* JSValueRef;
typedef struct OpaqueJSString* JSStringRef;
typedef struct OpaqueJSClass* JSClassRef;
typedef struct OpaqueJSContext* JSContextRef;
typedef struct OpaqueJSContext* JSGlobalContextRef;

typedef enum {
  kJSTypeUndefined,
  kJSTypeNull,
  kJSTypeBoolean,
  kJSTypeNumber,
  kJSTypeString,
  kJSTypeObject
} JSType;
]]

local Context = {}
Context.__index = Context

ffi.cdef [[
typedef struct GObjectInternal WebKitWebFrame;
JSGlobalContextRef webkit_web_frame_get_global_context(WebKitWebFrame *frame);
]]
function Context:new(web_view)
  local instance = {}
  instance.context = ffi.C.webkit_web_frame_get_global_context(web_view:get_main_frame()._native)
  setmetatable(instance, self)
  return instance
end

ffi.cdef [[
JSValueRef JSEvaluateScript(JSContextRef ctx, JSStringRef script, JSObjectRef thisObject,
  JSStringRef sourceURL, int startingLineNumber, JSValueRef* exception)
]]
function Context:eval(script, url, line)
  local script = Context.make_string(script)
  local url = url and Context.make_string(url)
  local line  = line or 0
  local exception = ffi.new("JSValueRef[1]")

  local result = self:get_value(ffi.C.JSEvaluateScript(self.context, script, nil, url, line, exception))
  
  if exception[0] ~= nil then
    return result, self:get_value(exception[0])
  end

  return result
end

ffi.cdef "JSStringRef JSStringCreateWithUTF8CString(const char* string)"
function Context.make_string(str)
  return ffi.gc(ffi.C.JSStringCreateWithUTF8CString(str), ffi.C.JSStringRelease)
end

ffi.cdef [[
JSValueRef JSValueMakeNull(JSContextRef ctx);
JSValueRef JSValueMakeBoolean(JSContextRef ctx, bool value);
JSValueRef JSValueMakeNumber(JSContextRef ctx, double value);
JSValueRef JSValueMakeString(JSContextRef ctx, JSStringRef string);
]]
function Context:make_value(obj)
  if type(obj) == "nil" then
    return ffi.C.JSValueMakeNull(self.context)
  elseif type(obj) == "boolean" then
    return ffi.C.JSValueMakeBoolean(self.context, obj)
  elseif type(obj) == "number" then
    return ffi.C.JSValueMakeNumber(self.context, obj)
  elseif type(obj) == "string" then
    return ffi.C.JSValueMakeNumber(self.context, Context.make_string(obj))
  end
  -- table is not supported
end

ffi.cdef "JSValueRef JSValueMakeFromJSONString(JSContextRef ctx, JSStringRef string)"
function Context:make_object(json)
  return ffi.C.JSValueMakeFromJSONString(self.context, Context.make_string(json))
end

ffi.cdef "JSType JSValueGetType(JSContextRef ctx, JSValueRef value)"
function Context:value_type(value)
  local type = ffi.C.JSValueGetType(self.context, value)
  if type == ffi.C.kJSTypeUndefined then
    return "undefined"
  elseif type == ffi.C.kJSTypeNull then
    return "nil"
  elseif type == ffi.C.kJSTypeBoolean then
    return "boolean"
  elseif type == ffi.C.kJSTypeNumber then
    return "number"
  elseif type == ffi.C.kJSTypeString then
    return "string"
  elseif type == ffi.C.kJSTypeObject then
    return "object"
  end
end

ffi.cdef [[
size_t JSStringGetMaximumUTF8CStringSize(JSStringRef string);
size_t JSStringGetUTF8CString(JSStringRef string, char* buffer, size_t bufferSize);
void JSStringRelease(JSStringRef string);
]]
function Context.get_string(jsstr)
  local len = ffi.C.JSStringGetMaximumUTF8CStringSize(jsstr)
  local str = ffi.new("char[?]", len)
  ffi.C.JSStringGetUTF8CString(jsstr, str, len)
  return ffi.string(str, len)
end

ffi.cdef [[
bool JSValueToBoolean(JSContextRef ctx, JSValueRef value);
double JSValueToNumber(JSContextRef ctx, JSValueRef value, JSValueRef* exception);
JSStringRef JSValueToStringCopy(JSContextRef ctx, JSValueRef value, JSValueRef* exception);
]]
function Context:get_value(value)
  local type = ffi.C.JSValueGetType(self.context, value)
  local exception = ffi.new("JSValueRef[1]")
  local result

  if type == ffi.C.kJSTypeUndefined or type == ffi.C.kJSTypeNull then
    result = nil
  elseif type == ffi.C.kJSTypeBoolean then
    result = ffi.C.JSValueToBoolean(self.context, value)
  elseif type == ffi.C.kJSTypeNumber then
    result = ffi.C.JSValueToNumber(self.context, value, exception)
  elseif type == ffi.C.kJSTypeString or type == ffi.C.kJSTypeObject then
    local jsstr = ffi.gc(ffi.C.JSValueToStringCopy(self.context, value, exception),
      ffi.C.JSStringRelease)
    result = Context.get_string(jsstr)
  end

  if exception[0] ~= nil then
    return result, self:get_value(exception[0])
  end

  return result
end

local jscore = {}
jscore.Context = Context
return jscore