#include "derivations.hh"
#include "globals.hh"
#include "shared.hh"
#include "store-api.hh"
#include <sys/utsname.h>
#include <algorithm>
#include <iostream>
#include <fstream>
#include <sys/mman.h>
#include <fcntl.h>
#include <mach-o/loader.h>
#include <mach-o/swap.h>

#define DO_SWAP(x, y) ((x) ? OSSwapInt32(y) : (y))

using namespace nix;

static auto cacheDir = Path{};

Path resolveCacheFile(Path lib) {
    std::replace(lib.begin(), lib.end(), '/', '%');
    return cacheDir + "/" + lib;
}

std::set<string> readCacheFile(const Path & file) {
    return tokenizeString<set<string>>(readFile(file), "\n");
}

void writeCacheFile(const Path & file, std::set<string> & deps) {
    std::ofstream fp;
    fp.open(file);
    for (auto & d : deps) {
        fp << d << "\n";
    }
    fp.close();
}

std::string findDylibName(bool should_swap, ptrdiff_t dylib_command_start) {
    struct dylib_command *dylc = (struct dylib_command*)dylib_command_start;
    return std::string((char*)(dylib_command_start + DO_SWAP(should_swap, dylc->dylib.name.offset)));
}

std::set<std::string> runResolver(const Path & filename) {
    int fd = open(filename.c_str(), O_RDONLY);
    struct stat s;
    fstat(fd, &s);
    void *obj = mmap(NULL, s.st_size, PROT_READ, MAP_SHARED, fd, 0);

    ptrdiff_t mach64_offset = 0;

    uint32_t magic = ((struct mach_header_64*)obj)->magic;
    if(magic == FAT_CIGAM || magic == FAT_MAGIC) {
        bool should_swap = magic == FAT_CIGAM;
        uint32_t narches = DO_SWAP(should_swap, ((struct fat_header*)obj)->nfat_arch);

        for(uint32_t iter = 0; iter < narches; iter++) {
            ptrdiff_t header_offset = (ptrdiff_t)obj + sizeof(struct fat_header);
            struct fat_arch* arch = (struct fat_arch*)header_offset;
            if(DO_SWAP(should_swap, arch->cputype) == CPU_TYPE_X86_64) {
                mach64_offset = (ptrdiff_t)DO_SWAP(should_swap, arch->offset);
                break;
            }
        }
        if (mach64_offset == 0) {
            printMsg(lvlError, format("Could not find any mach64 blobs in file ‘%1%’, continuing...") % filename);
            return std::set<string>();
        }
    } else if (magic == MH_MAGIC_64 || magic == MH_CIGAM_64) {
        mach64_offset = 0;
    } else {
        printMsg(lvlError, format("Object file has unknown magic number ‘%1%’, skipping it...") % magic);
        return std::set<string>();
    }

    ptrdiff_t mach_header_offset = (ptrdiff_t)obj + mach64_offset;
    struct mach_header_64 *m_header = (struct mach_header_64 *)mach_header_offset;

    bool should_swap = magic == MH_CIGAM_64;
    ptrdiff_t cmd_offset = mach_header_offset + sizeof(struct mach_header_64);

    std::set<string> libs;
    for(uint32_t i = 0; i < DO_SWAP(should_swap, m_header->ncmds); i++) {
        struct load_command *cmd = (struct load_command*)cmd_offset;
        switch(DO_SWAP(should_swap, cmd->cmd)) {
            case LC_LOAD_UPWARD_DYLIB:
            case LC_LOAD_DYLIB:
            case LC_REEXPORT_DYLIB:
                libs.insert(findDylibName(should_swap, cmd_offset));
                break;
        }
        cmd_offset += DO_SWAP(should_swap, cmd->cmdsize);
    }

    return libs;
}

bool isSymlink(const Path & path) {
    struct stat st;
    if(lstat(path.c_str(), &st))
        throw SysError(format("getting attributes of path ‘%1%’") % path);

    return S_ISLNK(st.st_mode);
}

Path resolveSymlink(const Path & path) {
    char buf[PATH_MAX];
    ssize_t len = readlink(path.c_str(), buf, sizeof(buf) - 1);
    if(len != -1) {
        buf[len] = 0;
        return Path(buf);
    } else {
        throw SysError(format("readlink('%1%')") % path);
    }
}

std::set<string> resolveTree(const Path & path, PathSet & deps) {
    std::set<string> results;
    if(deps.find(path) != deps.end()) {
        return std::set<string>();
    }
    deps.insert(path);
    for (auto & lib : runResolver(path)) {
        results.insert(lib);
        for (auto & p : resolveTree(lib, deps)) {
            results.insert(p);
        }
    }
    return results;
}

std::set<string> getPath(const Path & path) {
    Path cacheFile = resolveCacheFile(path);
    if(pathExists(cacheFile)) {
        return readCacheFile(cacheFile);
    }

    std::set<string> deps;
    std::set<string> paths;
    paths.insert(path);

    Path next_path = Path(path);
    while(isSymlink(next_path)) {
        next_path = resolveSymlink(next_path);
        paths.insert(next_path);
    }

    for(auto & t : resolveTree(next_path, deps)) {
        paths.insert(t);
    }

    writeCacheFile(cacheFile, paths);

    return paths;
}

int main(int argc, char ** argv) {
    return handleExceptions(argv[0], [&]() {
        initNix();

        struct utsname _uname;

        uname(&_uname);

        auto cacheParentDir = (format("%1%/dependency-maps") % settings.nixStateDir).str();

        cacheDir = (format("%1%/%2%-%3%-%4%")
                % cacheParentDir
                % _uname.machine
                % _uname.sysname
                % _uname.release).str();

        mkdir(cacheParentDir.c_str(), 0755);
        mkdir(cacheDir.c_str(), 0755);

        auto store = openStore();

        auto drv = store->derivationFromPath(Path(argv[1]));
        Strings impurePaths = tokenizeString<Strings>(get(drv.env, "__impureHostDeps"));

        std::set<string> all_paths;

        for (auto & path : impurePaths) {
            for(auto & p : getPath(path)) {
                all_paths.insert(p);
            }
        }

        std::cout << "extra-chroot-dirs" << std::endl;
        for(auto & path : all_paths) {
            std::cout << path << std::endl;
        }
        std::cout << std::endl;
    });
}