/**
 A simple PE/COFF image format reader.

 Authors:
	Jeremie Pelletier

 References:
	$(LINK http://www.csn.ul.ie/~caolan/publink/winresdump/winresdump/doc/pefile.html)

 License:
	Public Domain
*/
module dbg.image.PE;

version(Windows) {

import std.c.string : strncmp;
import dbg.Debug;
import dbg.symbol.CodeView;
//import dbg.symbol.COFF;
//import sys.windows.FileSystem;
//import sys.windows.Memory;
//import sys.windows.Security : GENERIC_READ;
//import sys.windows.Information : CloseHandle;
//import sys.windows.Image;

import win32.windows;
import win32.winbase;

enum IMAGE_SIZEOF_NT_OPTIONAL64_HEADER = 240;

struct IMAGE_NT_HEADERS64 {
    DWORD Signature;
    IMAGE_FILE_HEADER FileHeader;
    IMAGE_OPTIONAL_HEADER64 OptionalHeader;
}

auto IMAGE_FIRST_SECTION64( const(IMAGE_NT_HEADERS64*) ntheader ) {
	return cast(PIMAGE_SECTION_HEADER) ((cast(UINT_PTR)ntheader) + IMAGE_NT_HEADERS64.OptionalHeader.offsetof + (cast(PIMAGE_NT_HEADERS64)(ntheader)).FileHeader.SizeOfOptionalHeader);
}

auto IMAGE_FIRST_SECTION32( const(IMAGE_NT_HEADERS32*) ntheader ) {
	return cast(PIMAGE_SECTION_HEADER)((cast(UINT_PTR)ntheader) + IMAGE_NT_HEADERS32.OptionalHeader.offsetof + (cast(PIMAGE_NT_HEADERS32)ntheader).FileHeader.SizeOfOptionalHeader);
}

class PEImage : IExecutableImage {
	/**
	 Loads and validate the image file.

	 Params:
		fileName =	Path to the image file.
	*/
	this(string fileName)
	in {
		assert(fileName.length && fileName.ptr);
	}
	body {
		_filename = fileName;

		// Create the file mapping
		_file = CreateFileA((fileName ~ '\0').ptr, GENERIC_READ, FILE_SHARE_READ,
			null, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, null);
		if(_file == INVALID_HANDLE_VALUE) SystemException();

		GetFileSizeEx(_file, &_fileSize);

		_map = CreateFileMapping(_file, null, PAGE_READONLY, 0, 0, null);
		if(!_map) SystemException();

		_view = cast(const(ubyte)*)MapViewOfFile(_map, FILE_MAP_READ, 0, 0, 0);
		if(!_view) SystemException();

		// Verify image headers
		if(_dos.e_magic != IMAGE_DOS_SIGNATURE) goto Error;
		CheckOffset(_dos.e_lfanew);

		_nt = cast(IMAGE_NT_HEADERS32*)(_view + _dos.e_lfanew);
		if(_nt.Signature != IMAGE_NT_SIGNATURE) goto Error;

		_is64 = _nt.FileHeader.SizeOfOptionalHeader == IMAGE_SIZEOF_NT_OPTIONAL64_HEADER;

		if(_is64) {
			if(_nt64.OptionalHeader.Magic != IMAGE_NT_OPTIONAL_HDR64_MAGIC)
				goto Error;
		}
		else {
			if(_nt.OptionalHeader.Magic != IMAGE_NT_OPTIONAL_HDR32_MAGIC)
				goto Error;
		}

		// Create the RVA lookup table
		auto sections = this.sections;
		RVAEntry* e = void;
		_rvaTable.length = sections.length;
		foreach(i, ref s; sections) with(s) {
			e = &_rvaTable[i];
			e.start = VirtualAddress;
			e.end = VirtualAddress + SizeOfRawData;
			e.base = PointerToRawData;
		}

		return;

	Error:
		throw new PEInvalidException(this);
	}

	/**
	 Unloads the PE file.
	*/
	~this() {
		if(_dos && !UnmapViewOfFile(cast(void*)_dos)) SystemException();
		if(_map && !CloseHandle(_map)) SystemException();
		if(_file && !CloseHandle(_file)) SystemException();
	}

	/**
	 Get the filename of the image
	*/
	string filename() const {
		return _filename;
	}

	/**
	 Get whether the image uses the 64bit structures or not
	*/
	bool is64() const {
		return _is64;
	}

	/**
	 Get the base address of the image
	*/
	long imageBase() const {
		return _is64 ? _nt64.OptionalHeader.ImageBase : _nt.OptionalHeader.ImageBase;
	}

	/**
	 Get the raw image data
	*/
	const(ubyte)[] data() const {
		return _view[0 .. cast(size_t)_fileSize.QuadPart];
	}

	/**
	 Get the dos, nt or nt64 headers
	*/
	const(IMAGE_DOS_HEADER)* dosHeader() const { return _dos; }
	const(IMAGE_NT_HEADERS32)* ntHeaders32() const { return _nt; }
	const(IMAGE_NT_HEADERS64)* ntHeaders64() const { return _nt64; }

	/**
	 Get the array of data directories
	*/
	const(IMAGE_DATA_DIRECTORY)[] dataDirectory() const {
		return _is64 ? _nt64.OptionalHeader.DataDirectory : _nt.OptionalHeader.DataDirectory;
	}

	/**
	 Get the array of section headers
	*/
	const(IMAGE_SECTION_HEADER)[] sections() const {
		return (_is64 ? IMAGE_FIRST_SECTION64(_nt64) : IMAGE_FIRST_SECTION32(_nt))
			[0 .. _nt.FileHeader.NumberOfSections];
	}

	/**
	 Translate the given Virtual Address to its corresponding data offset.
	*/
	long LookupVA(long va) const {
		return LookupRVA(va - imageBase);
	}

	/**
	 Translate the given Relative Virtual Address to its corresponding
	 data offset.
	*/
	long LookupRVA(long rva) const {
		foreach(ref e; _rvaTable) with(e) {
			if(rva >= start && rva < end) {
				long offset = base + (rva - start);
				CheckOffset(offset);
				return offset;
			}
		}

		return 0;
	}

	/**
	 Get a data structure in the image from its RVA
	*/
	const(T)* GetDataFromRVA(T : T*)(long rva) const {
		long offset = LookupRVA(rva);
		return offset ? cast(T*)(_view + offset) : null;
	}

	/**
	 Get a data directory in the image from its ID
	*/
	const(T)* GetDirectory(T)(uint id) const {
		const IMAGE_DATA_DIRECTORY* dir = &dataDirectory[id];
		return dir.VirtualAddress && dir.Size ?
			GetDataFromRVA!(T*)(dir.VirtualAddress) : null;
	}

	/**
	 Find the first section matching the given flags mask
	*/
	const(IMAGE_SECTION_HEADER)* FindSection(uint mask) const
	in {
		assert(mask);
	}
	body {
		foreach(ref section; sections)
			if(section.Characteristics & mask)
				return &section;

		return null;
	}

	/**
	 Find a section by its name
	*/
	const(IMAGE_SECTION_HEADER)* FindSection(string name) const
	in {
		assert(name.length && name.ptr);
	}
	body {
		foreach(ref section; sections)
			if(strncmp(cast(char*)section.Name.ptr, name.ptr, section.Name.length) == 0)
				return &section;

		return null;
	}

	/**
	 Get the offset to the code segment
	*/
	uint codeOffset() const {
		const(IMAGE_SECTION_HEADER)* section = FindSection(IMAGE_SCN_MEM_EXECUTE);
		return section ? section.VirtualAddress : 0;
	}

	/**
	 Get the symbolic debug info object for this image
	*/
	ISymbolicDebugInfo debugInfo() {
		uint va = _nt.OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_DEBUG].VirtualAddress;
		if(!va) return null;

		const(IMAGE_DEBUG_DIRECTORY)* dir = void;
		uint size = _nt.OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_DEBUG].Size;
		uint offset = void;

		// Borland directory
		const(IMAGE_SECTION_HEADER)* section = FindSection(".debug");
		if(section && section.VirtualAddress == va) {
			CheckOffset(section.PointerToRawData);

			dir = cast(IMAGE_DEBUG_DIRECTORY*)(_view + section.PointerToRawData);
		}
		// Microsoft directory
		else {
			section = FindSection(".rdata");
			if(!section) goto NoDebug;

			offset = section.PointerToRawData + (va - section.VirtualAddress);
			CheckOffset(offset);

			dir = cast(IMAGE_DEBUG_DIRECTORY*)(_view + offset);
		}

		const(void)* end = cast(void*)dir + size;
		Scan: for(; dir < end; dir++) {
			switch(dir.Type) {
			//case IMAGE_DEBUG_TYPE_COFF:
			case IMAGE_DEBUG_TYPE_CODEVIEW:
			// TODO: support more types
				break Scan;

			default:
			}
		}

		if(dir >= end) goto NoDebug;

		offset = dir.PointerToRawData + dir.SizeOfData;
		CheckOffset(offset);
		auto debugView = _view[dir.PointerToRawData .. offset];

		switch(dir.Type) {
		//case IMAGE_DEBUG_TYPE_COFF:
		//	return new COFFDebugInfo(debugView);
		case IMAGE_DEBUG_TYPE_CODEVIEW:
			return new CodeViewDebugInfo(debugView);
		default:
			assert(0);
		}

	NoDebug:
		// TODO: we have no debug section or directory, but there csould still
		// be external symbol files we can use.
		return null;
	}

private:

	/**
	 Verify a file offset before accessing it
	*/
	void CheckOffset(long offset) const {
		if(offset > _fileSize.QuadPart) throw new PECorruptedException(this);
	}

	string							_filename;
	HANDLE							_file;
	HANDLE							_map;
	LARGE_INTEGER					_fileSize;
	bool							_is64;

	union {
		const(ubyte)*				_view;
		const(IMAGE_DOS_HEADER)*	_dos;
	}
	union {
		const(IMAGE_NT_HEADERS32)*	_nt;
		const(IMAGE_NT_HEADERS64)*	_nt64;
	}

	struct RVAEntry {
		uint start;
		uint end;
		uint base;
	}

	RVAEntry[] _rvaTable;
}

/// Thrown if file open failed.
class PEException : Exception {
	this(string msg) {
		super("PEImage: " ~ msg);
	}
}

/// Thrown if not a valid module file
class PEInvalidException : PEException {
	this(in PEImage img) {
		super("Invalid PE file.");
	}
}

/// Thrown on corrupted module file.
class PECorruptedException : PEException {
	this(in PEImage img) {
		super("Corrupted PE file.");
	}
}

} // version(Windows)