local IMAGE_SCN_CNT_CODE=0x20
local IMAGE_SCN_MEM_EXECUTE=0x20000000

if compareMemory==nil then
  --6.8.4 has compareMemory, but for now implement this myself (slow as fuck)
  compareMemory=function(a1,a2,size,method)
    if size==0 then
      error('Provide a size>0')
    end

    if method~=1 then
      error('this version of compareMemory does not do other methods besides 1 (target/local)')
    end

    local b1=readBytes(a1,size,true)
    local b2=readBytesLocal(a2,size,true)
    local i
    for i=1,size do
      if b1[i]~=b2[i] then
        return false,i-1
      end
    end
    return true
  end
end

function scanModuleForPatches(modulepath, loadedModuleBase)

  local original=createMemoryStream()
  original.loadFromFile(modulepath)
  original.Position=0


  if (byteTableToString(original.read(2))~='MZ') then
    original.destroy()
    error('Not a valid executable')
  end

  original.Position=60;
  local lfanew=original.readDword();
  original.Position=lfanew;

  if (byteTableToString(original.read(2))~='PE') then
    original.destroy()
    error('Not a valid windows executable')
  end

  original.position=original.Position+2
  local Machine=original.readWord()
  local SectionCount=original.readWord()
  original.Position=original.Position+12
  local OptHeaderSize=original.readWord()
  original.position=original.Position+2

  local OptHeaderStart=original.Position
  local Magic=original.readWord()
  local MajorLinkerVersion=original.readByte()
  local MinorLinkerVersion=original.readByte()

  local SizeOfCode=original.readDword()
  original.Position=original.Position+8
  local EntryPoint=original.readDword()
  local BaseOfCode=original.readDword()

  local BaseOfData
  local ImageBase
  --scan the reloc table
  if Machine==0x8664 then
    BaseOfData=nil
    ImageBase=original.readQword()
    original.Position=original.Position+4+4+2+2+2+2+2+2+4+4+4+4+2+2+8+8+8+8
  else
    BaseOfData=original.readDword()
    ImageBase=original.readDword()
    original.Position=original.Position+4+4+2+2+2+2+2+2+4+4+4+4+2+2+4+4+4+4
  end

  local RelocDistance=loadedModuleBase-ImageBase;


  local LoaderFlags=original.readDword()
  local RVACount=original.readDword()

  if RVACount~=16 then
    original.destroy()
    error('This type of module is currently not supported')
  end

  --DataDirectory follows
  local DataDirPosition=original.Position
  local ImageSectionHeaderPosition=OptHeaderStart+OptHeaderSize

  --parse the sections so VirtualToFile can function
  local sections={}
  original.Position=ImageSectionHeaderPosition

  local i
  for i=1,SectionCount do
    sections[i]={}
    sections[i].name=byteTableToString(original.read(8))
    sections[i].misc=original.readDword()
    sections[i].virtualAddress=original.readDword()
    sections[i].sizeOfRawData=original.readDword()
    sections[i].PointerToRawData=original.readDword()
    original.position=original.position+12;
    sections[i].Characteristics=original.readDword()
    sections[i].Executable=sections[i].Characteristics & IMAGE_SCN_CNT_CODE == IMAGE_SCN_CNT_CODE

  end

  local function VirtualToFile(VA)
    --scan the address in the sections list
    local i
    local offset
    for i=1,#sections do
      if (VA>=sections[i].virtualAddress) and (VA<sections[i].virtualAddress+sections[i].sizeOfRawData) then
        return sections[i].PointerToRawData+(VA-sections[i].virtualAddress)
      end
    end
  end


  local ImportTableRVAInfo=DataDirPosition+1*8
  local RelocationTableRVAInfo=DataDirPosition+5*8


  original.Position=ImportTableRVAInfo
  local ImportTableAddress=original.readDword()
  local ImportTableSize=original.readDword()
  local ImportTablePosition=VirtualToFile(ImportTableAddress)

  original.Position=RelocationTableRVAInfo
  local RelocationTableAddress=original.readDword()
  local RelocationTableSize=original.readDword()
  local RelocationTablePosition=VirtualToFile(RelocationTableAddress)


  local relocs={}
  if RelocationTablePosition then

    original.position=RelocationTablePosition
    repeat
      local oldpos=original.position
      local VABase=original.readDword()
      local Size=original.readDword()

      local Entries=math.floor((Size - 8) / 2)
      --print(string.format("VABase=%x (Size=%d Entries=%d)", VABase, Size, Entries))

      local i
      for i=1,Entries do
        local relinfo=original.readWord()
        local reltype=relinfo >> 12
        local VA=VABase+(relinfo & 0xfff);
        if (reltype == 3) then
          writeIntegerLocal(original.Memory+VirtualToFile(VA),readIntegerLocal(original.Memory+VirtualToFile(VA)+RelocDistance))
        else
          if (reltype == 10) then
            writeQwordLocal(original.Memory+VirtualToFile(VA),readQwordLocal(original.Memory+VirtualToFile(VA)+RelocDistance))
          else
            if reltype ~= 0 then
              relocs[VA]=true --just mark it as a "I don't know"
            end
          end
        end
      end

      oldpos=oldpos+Size
    until original.Position>=RelocationTablePosition+RelocationTableSize
  else

  end

  local imports={}
  if ImportTablePosition then
    original.Position=ImportTablePosition
    repeat
      i=#imports+1
      imports[i]={}
      imports[i].ImportLookupTable=VirtualToFile(original.readDword())
      imports[i].TimeDate=original.readDword()
      imports[i].ForwarderChain=original.readDword()
      imports[i].NamePosition=VirtualToFile(original.readDword())
      imports[i].ImportAddressTable=VirtualToFile(original.readDword())

      if imports[i].ImportLookupTable==nil then
        imports[i]=nil
      end
    until original.Position>=ImportTablePosition+ImportTableSize

    for i=1,#imports do
      local reader

      if Machine==0x8664 then
        reader=original.readQword
      else
        reader=original.readDword
      end

      original.Position=imports[i].ImportAddressTable

      while original.Position<original.Size-8 do
        if reader()==0 then break end
      end

      imports[i].ImportAddressTableSize=original.Position-imports[i].ImportAddressTable

      local name
      name=readStringLocal(original.Memory+imports[i].NamePosition,256);
    end
  end
  --all information is gathered. Now scan the code sections and compare against the target process
  print("Scanning for differences...")
  local foundpatches=false

  for i=1 , #sections do
    if sections[i].Executable then
      local VA=loadedModuleBase+sections[i].virtualAddress
      local FA=original.Memory+sections[i].PointerToRawData
      local bytesLeft=sections[i].sizeOfRawData
      local bytesOK
      local result=false

      print(string.format("Checking section %s ranging from %x to %x", sections[i].name, VA,VA+sections[i].sizeOfRawData))

      while result==false do
        result,bytesOK=compareMemory(VA,FA,bytesLeft,1) --VA in target, FA in CE, so method 1
        if (result==false) then
          local addressString=getNameFromAddress(VA+bytesOK)
          if tonumber('0x'..addressString)==nil then
            print(string.format("Diff found at %x (%s)", VA+bytesOK, addressString))
          else
            print(string.format("Diff found at %x", VA+bytesOK))
          end
          VA=VA+bytesOK+8
          FA=FA+bytesOK+8
          bytesLeft=bytesLeft-bytesOK-8
          foundpatches=true
        end

        if result==nil then
          print("Compare error. "..bytesOK)
          break
        end
      end


    end


  end
  if foundpatches==false then
    print("No patches detected")
  end
  original.destroy()
end

function startPatchScan()
  if getOpenedProcessID()==0 then
    openProcess(getCheatEngineProcessID())
  end
  local sl=createStringlist()
  local l=enumModules()
  for i=1,#l do
    sl.add(l[i].Name)
  end

  local i=showSelectionList('Module patch scanner', 'Select the module you wish to scan for changes',sl)+1
  sl.destroy()

  if i>0 then
    scanModuleForPatches(l[i].PathToFile, l[i].Address)
  end
end

local mv=getMemoryViewForm()
local mi=createMenuItem(mv.Menu)
mi.Caption='Scan for patches'
mi.Shortcut='Ctrl+Shift+P'
mi.OnClick=startPatchScan
mv.Extra1.insert(mv.DissectPEheaders1.MenuIndex+1, mi)