using FileContents = std::shared_ptr<std::vector<unsigned char>>;

#define ElfFileParams class Elf_Ehdr, class Elf_Phdr, class Elf_Shdr, class Elf_Addr, class Elf_Off, class Elf_Dyn, class Elf_Sym, class Elf_Verneed, class Elf_Versym
#define ElfFileParamNames Elf_Ehdr, Elf_Phdr, Elf_Shdr, Elf_Addr, Elf_Off, Elf_Dyn, Elf_Sym, Elf_Verneed, Elf_Versym

template<ElfFileParams>
class ElfFile
{
public:

    const FileContents fileContents;

private:

    std::vector<Elf_Phdr> phdrs;
    std::vector<Elf_Shdr> shdrs;

    bool littleEndian;

    bool changed = false;

    bool isExecutable = false;

    using SectionName = std::string;
    using ReplacedSections = std::map<SectionName, std::string>;

    ReplacedSections replacedSections;

    std::string sectionNames; /* content of the .shstrtab section */

    /* Align on 4 or 8 bytes boundaries on 32- or 64-bit platforms
       respectively. */
    size_t sectionAlignment = sizeof(Elf_Off);

    std::vector<SectionName> sectionsByOldIndex;

public:
    explicit ElfFile(FileContents fileContents);

    bool isChanged()
    {
        return changed;
    }

private:

    struct CompPhdr
    {
        ElfFile * elfFile;
        bool operator ()(const Elf_Phdr & x, const Elf_Phdr & y)
        {
            // A PHDR comes before everything else.
            if (elfFile->rdi(y.p_type) == PT_PHDR) return false;
            if (elfFile->rdi(x.p_type) == PT_PHDR) return true;

            // Sort non-PHDRs by address.
            return elfFile->rdi(x.p_paddr) < elfFile->rdi(y.p_paddr);
        }
    };

    friend struct CompPhdr;

    void sortPhdrs();

    struct CompShdr
    {
        ElfFile * elfFile;
        bool operator ()(const Elf_Shdr & x, const Elf_Shdr & y)
        {
            return elfFile->rdi(x.sh_offset) < elfFile->rdi(y.sh_offset);
        }
    };

    friend struct CompShdr;

    unsigned int getPageSize() const;

    void sortShdrs();

    void shiftFile(unsigned int extraPages, size_t sizeOffset, size_t extraBytes);

    std::string getSectionName(const Elf_Shdr & shdr) const;

    Elf_Shdr & findSectionHeader(const SectionName & sectionName);

    std::optional<std::reference_wrapper<Elf_Shdr>> tryFindSectionHeader(const SectionName & sectionName);

    unsigned int getSectionIndex(const SectionName & sectionName);

    std::string & replaceSection(const SectionName & sectionName,
        unsigned int size);

    bool haveReplacedSection(const SectionName & sectionName) const;

    void writeReplacedSections(Elf_Off & curOff,
        Elf_Addr startAddr, Elf_Off startOffset);

    void rewriteHeaders(Elf_Addr phdrAddress);

    void rewriteSectionsLibrary();

    void rewriteSectionsExecutable();

    void normalizeNoteSegments();

public:

    void rewriteSections();

    std::string getInterpreter();

    typedef enum { printOsAbi, replaceOsAbi } osAbiMode;

    void modifyOsAbi(osAbiMode op, const std::string & newOsAbi);

    typedef enum { printSoname, replaceSoname } sonameMode;

    void modifySoname(sonameMode op, const std::string & newSoname);

    void setInterpreter(const std::string & newInterpreter);

    typedef enum { rpPrint, rpShrink, rpSet, rpAdd, rpRemove } RPathOp;

    void modifyRPath(RPathOp op, const std::vector<std::string> & allowedRpathPrefixes, std::string newRPath);
    std::string shrinkRPath(char* rpath, std::vector<std::string> &neededLibs, const std::vector<std::string> & allowedRpathPrefixes);
    void removeRPath(Elf_Shdr & shdrDynamic);

    void addNeeded(const std::set<std::string> & libs);

    void removeNeeded(const std::set<std::string> & libs);

    void replaceNeeded(const std::map<std::string, std::string> & libs);

    void printNeededLibs() /* should be const */;

    void noDefaultLib();

    void addDebugTag();

    void clearSymbolVersions(const std::set<std::string> & syms);

private:

    /* Convert an integer in big or little endian representation (as
       specified by the ELF header) to this platform's integer
       representation. */
    template<class I>
    I rdi(I i) const;

    /* Convert back to the ELF representation. */
    template<class I>
    I wri(I & t, unsigned long long i) const
    {
        t = rdi((I) i);
        return i;
    }

    Elf_Ehdr *hdr() {
      return (Elf_Ehdr *)fileContents->data();
    }

    const Elf_Ehdr *hdr() const {
      return (const Elf_Ehdr *)fileContents->data();
    }
};