#include "Util.h"
#include "Debug.h"
#include "Error.h"
#include "Introspection.h"
#include <atomic>
#include <chrono>
#include <fstream>
#include <iomanip>
#include <map>
#include <mutex>
#include <sstream>
#include <string>

#ifdef _MSC_VER
#include <io.h>
#else
#include <stdlib.h>
#include <unistd.h>
#endif
#include <sys/stat.h>
#include <sys/types.h>

#ifdef __linux__
#define CAN_GET_RUNNING_PROGRAM_NAME
#include <linux/limits.h>  // For PATH_MAX
#endif
#if defined(_MSC_VER) && !defined(NOMINMAX)
#define NOMINMAX
#endif
#ifdef _WIN32
#include <windows.h>
#include <Objbase.h>  // needed for CoCreateGuid
#include <Shlobj.h>  // needed for SHGetFolderPath
#endif
#ifdef __APPLE__
#define CAN_GET_RUNNING_PROGRAM_NAME
#include <mach-o/dyld.h>
#endif

namespace Halide {
namespace Internal {

using std::map;
using std::ostringstream;
using std::string;
using std::vector;

std::string get_env_variable(char const *env_var_name) {
    if (!env_var_name) {
        return "";
    }

    #ifdef _MSC_VER
    // call getenv_s without a buffer to determine the correct string length:
    size_t length = 0;
    if ((getenv_s(&length, NULL, 0, env_var_name) != 0) || (length == 0)) {
        return "";
    }
    // call it again to retrieve the value of the environment variable;
    // note that 'length' already accounts for the null-terminator
    std::string lvl(length - 1, '@');
    size_t read = 0;
    if ((getenv_s(&read, &lvl[0], length, env_var_name) != 0) || (read != length)) {
        return "";
    }
    return lvl;
    #else
    char *lvl = getenv(env_var_name);
    if (lvl) return std::string(lvl);
    #endif

    return "";
}

string running_program_name() {
    #ifndef CAN_GET_RUNNING_PROGRAM_NAME
        return "";
    #else
        string program_name;
        char path[PATH_MAX] = { 0 };
        uint32_t size = sizeof(path);
        #if defined(__linux__)
            ssize_t len = ::readlink("/proc/self/exe", path, size - 1);
        #elif defined(__APPLE__)
            ssize_t len = ::_NSGetExecutablePath(path, &size);
        #endif
        if (len != -1) {
            #if defined(__linux__)
                path[len] = '\0';
            #endif
            string tmp = std::string(path);
            program_name = tmp.substr(tmp.find_last_of("/") + 1);
        } else {
            return "";
        }
        return program_name;
    #endif
}

namespace {
// We use 64K of memory to store unique counters for the purpose of
// making names unique. Using less memory increases the likelihood of
// hash collisions. This wouldn't break anything, but makes stmts
// slightly confusing to read because names that are actually unique
// will get suffixes that falsely hint that they are not.

const int num_unique_name_counters = (1 << 14);

// We want to init these to zero, but cannot use = {0} because that
// would invoke a (deleted) copy ctor; this syntax should force
// the correct behavior.
std::atomic<int> unique_name_counters[num_unique_name_counters] = {};

int unique_count(size_t h) {
    h = h & (num_unique_name_counters - 1);
    return unique_name_counters[h]++;
}
}  // namespace

void reset_unique_name_counters() {
    for (int i = 0; i < num_unique_name_counters; ++i)
        unique_name_counters[i].store(0);
}

// There are three possible families of names returned by the methods below:
// 1) char pattern: (char that isn't '$') + number (e.g. v234)
// 2) string pattern: (string without '$') + '$' + number (e.g. fr#nk82$42)
// 3) a string that does not match the patterns above
// There are no collisions within each family, due to the unique_count
// done above, and there can be no collisions across families by
// construction.

string unique_name(char prefix) {
    if (prefix == '$') prefix = '_';
    return prefix + std::to_string(unique_count((size_t)(prefix)));
}

string unique_name(const std::string &prefix) {
    string sanitized = prefix;

    // Does the input string look like something returned from unique_name(char)?
    bool matches_char_pattern = true;

    // Does the input string look like something returned from unique_name(string)?
    bool matches_string_pattern = true;

    // Rewrite '$' to '_'. This is a many-to-one mapping, but that's
    // OK, we're about to hash anyway. It just means that some names
    // will share the same counter.
    int num_dollars = 0;
    for (size_t i = 0; i < sanitized.size(); i++) {
        if (sanitized[i] == '$') {
            num_dollars++;
            sanitized[i] = '_';
        }
        if (i > 0 && !isdigit(sanitized[i])) {
            // Found a non-digit after the first char
            matches_char_pattern = false;
            if (num_dollars) {
                // Found a non-digit after a '$'
                matches_string_pattern = false;
            }
        }
    }
    matches_string_pattern &= num_dollars == 1;
    matches_char_pattern &= prefix.size() > 1;

    // Then add a suffix that's globally unique relative to the hash
    // of the sanitized name.
    int count = unique_count(std::hash<std::string>()(sanitized));
    if (count == 0) {
        // We can return the name as-is if there's no risk of it
        // looking like something unique_name has ever returned in the
        // past or will ever return in the future.
        if (!matches_char_pattern && !matches_string_pattern) {
            return prefix;
        }
    }

    return sanitized + "$" + std::to_string(count);
}

bool starts_with(const string &str, const string &prefix) {
    if (str.size() < prefix.size()) return false;
    for (size_t i = 0; i < prefix.size(); i++) {
        if (str[i] != prefix[i]) return false;
    }
    return true;
}

bool ends_with(const string &str, const string &suffix) {
    if (str.size() < suffix.size()) return false;
    size_t off = str.size() - suffix.size();
    for (size_t i = 0; i < suffix.size(); i++) {
        if (str[off+i] != suffix[i]) return false;
    }
    return true;
}

string replace_all(const string &str, const string &find, const string &replace) {
    size_t pos = 0;
    string result = str;
    while ((pos = result.find(find, pos)) != string::npos) {
        result.replace(pos, find.length(), replace);
        pos += replace.length();
    }
    return result;
}

string make_entity_name(void *stack_ptr, const string &type, char prefix) {
    string name = Introspection::get_variable_name(stack_ptr, type);

    if (name.empty()) {
        return unique_name(prefix);
    } else {
        // Halide names may not contain '.'
        for (size_t i = 0; i < name.size(); i++) {
            if (name[i] == '.') {
                name[i] = ':';
            }
        }
        return unique_name(name);
    }
}

std::vector<std::string> split_string(const std::string &source, const std::string &delim) {
    std::vector<std::string> elements;
    size_t start = 0;
    size_t found = 0;
    while ((found = source.find(delim, start)) != std::string::npos) {
        elements.push_back(source.substr(start, found - start));
        start = found + delim.size();
    }

    // If start is exactly source.size(), the last thing in source is a
    // delimiter, in which case we want to add an empty string to elements.
    if (start <= source.size()) {
        elements.push_back(source.substr(start, std::string::npos));
    }
    return elements;
}

std::string extract_namespaces(const std::string &name, std::vector<std::string> &namespaces) {
    namespaces = split_string(name, "::");
    std::string result = namespaces.back();
    namespaces.pop_back();
    return result;
}

bool file_exists(const std::string &name) {
    #ifdef _MSC_VER
    return _access(name.c_str(), 0) == 0;
    #else
    return ::access(name.c_str(), F_OK) == 0;
    #endif
}

void assert_file_exists(const std::string &name) {
    internal_assert(file_exists(name)) << "File not found: " << name;
}

void assert_no_file_exists(const std::string &name) {
    internal_assert(!file_exists(name)) << "File (wrongly) found: " << name;
}

void file_unlink(const std::string &name) {
    #ifdef _MSC_VER
    _unlink(name.c_str());
    #else
    ::unlink(name.c_str());
    #endif
}

void ensure_no_file_exists(const std::string &name) {
    if (file_exists(name)) {
        file_unlink(name);
    }
    assert_no_file_exists(name);
}

void dir_rmdir(const std::string &name) {
    #ifdef _MSC_VER
    BOOL r = RemoveDirectoryA(name.c_str());
    internal_assert(r != 0) << "Unable to remove dir: " << name << ":" << GetLastError() << "\n";
    #else
    int r = ::rmdir(name.c_str());
    internal_assert(r == 0) << "Unable to remove dir: " << name << "\n";
    #endif
}

FileStat file_stat(const std::string &name) {
    #ifdef _MSC_VER
    struct _stat a;
    if (_stat(name.c_str(), &a) != 0) {
        user_error << "Could not stat " << name << "\n";
    }
    #else
    struct stat a;
    if (::stat(name.c_str(), &a) != 0) {
        user_error << "Could not stat " << name << "\n";
    }
    #endif
    return {static_cast<uint64_t>(a.st_size),
            static_cast<uint32_t>(a.st_mtime),
            static_cast<uint32_t>(a.st_uid),
            static_cast<uint32_t>(a.st_gid),
            static_cast<uint32_t>(a.st_mode)};
}

#ifdef _WIN32
namespace {

// GetTempPath() will fail rudely if env vars aren't set properly,
// which is the case when we run under a tool in Bazel. Instead,
// look for the current user's AppData/Local/Temp path, which
// should be valid and writable in all versions of Windows that
// we support for compilation purposes.
std::string get_windows_tmp_dir() {
    // Allow overriding of the tmpdir on Windows via an env var;
    // some Windows configs can (apparently) lock down AppData/Local/Temp
    // via policy, making various things break. (Note that this is intended
    // to be a short-lived workaround; we would prefer to be able to avoid
    // requiring this sort of band-aid if possible.)
    std::string tmp_dir = get_env_variable("HL_WINDOWS_TMP_DIR");
    if (!tmp_dir.empty()) {
        return tmp_dir;
    }
    char local_app_data_path[MAX_PATH];
    DWORD ret = SHGetFolderPathA(NULL, CSIDL_LOCAL_APPDATA, NULL, 0, local_app_data_path);
    internal_assert(ret == 0) << "Unable to get Local AppData folder.";
    std::string tmp = local_app_data_path;
    tmp = replace_all(tmp, "\\", "/");
    if (tmp.back() != '/') tmp += '/';
    tmp += "Temp/";
    return tmp;
}

}  //  namespace
#endif

std::string file_make_temp(const std::string &prefix, const std::string &suffix) {
    internal_assert(prefix.find("/") == string::npos &&
                    prefix.find("\\") == string::npos &&
                    suffix.find("/") == string::npos &&
                    suffix.find("\\") == string::npos);
    #ifdef _WIN32
    // Windows implementations of mkstemp() try to create the file in the root
    // directory, which is... problematic.
    std::string tmp_dir = get_windows_tmp_dir();
    char tmp_file[MAX_PATH];
    // Note that GetTempFileNameA() actually creates the file.
    DWORD ret = GetTempFileNameA(tmp_dir.c_str(), prefix.c_str(), 0, tmp_file);
    internal_assert(ret != 0);
    return std::string(tmp_file);
    #else
    std::string templ = "/tmp/" + prefix + "XXXXXX" + suffix;
    // Copy into a temporary buffer, since mkstemp modifies the buffer in place.
    std::vector<char> buf(templ.size() + 1);
    strcpy(&buf[0], templ.c_str());
    int fd = mkstemps(&buf[0], suffix.size());
    internal_assert(fd != -1) << "Unable to create temp file for (" << &buf[0] << ")\n";
    close(fd);
    return std::string(&buf[0]);
    #endif
}

std::string dir_make_temp() {
    #ifdef _WIN32
    std::string tmp_dir = get_windows_tmp_dir();
    // There's no direct API to do this in Windows;
    // our clunky-but-adequate approach here is to use
    // CoCreateGuid() to create a probably-unique name.
    // Add a limit on the number of tries just in case.
    for (int tries = 0; tries < 100; ++tries) {
        GUID guid;
        HRESULT hr = CoCreateGuid(&guid);
        internal_assert(hr == S_OK);
        std::ostringstream name;
        name << std::hex
             << std::setfill('0')
             << std::setw(8)
             << guid.Data1
             << std::setw(4)
             << guid.Data2
             << guid.Data3
             << std::setw(2);
        for (int i = 0; i < 8; i++) {
            name << (int)guid.Data4[i];
        }
        std::string dir = tmp_dir + name.str();
        BOOL result = CreateDirectoryA(dir.c_str(), nullptr);
        if (result) {
            debug(1) << "temp dir is: " << dir << "\n";
            return dir;
        }
        // If name already existed, just loop and try again.
        // Any other error, break from loop and fail.
        if (GetLastError() != ERROR_ALREADY_EXISTS) {
            break;
        }
    }
    internal_assert(false) << "Unable to create temp directory in " << tmp_dir << "\n";
    return "";
    #else
    std::string templ = "/tmp/XXXXXX";
    // Copy into a temporary buffer, since mkdtemp modifies the buffer in place.
    std::vector<char> buf(templ.size() + 1);
    strcpy(&buf[0], templ.c_str());
    char* result = mkdtemp(&buf[0]);
    internal_assert(result != nullptr) << "Unable to create temp directory.\n";
    return std::string(result);
    #endif
}

std::vector<char> read_entire_file(const std::string &pathname) {
    std::ifstream f(pathname, std::ios::in|std::ios::binary);
    std::vector<char> result;

    f.seekg(0, std::ifstream::end);
    size_t size = f.tellg();
    result.resize(size);
    f.seekg(0, std::ifstream::beg);
    f.read(result.data(), result.size());
    internal_assert(f.good()) << "Unable to read file: " << pathname;
    f.close();
    return result;
}

void write_entire_file(const std::string &pathname, const void *source, size_t source_len) {
    std::ofstream f(pathname, std::ios::out|std::ios::binary);

    f.write(reinterpret_cast<const char*>(source), source_len);
    f.flush();
    internal_assert(f.good()) << "Unable to write file: " << pathname;
    f.close();
}

bool add_would_overflow(int bits, int64_t a, int64_t b) {
    int64_t max_val = 0x7fffffffffffffffLL >> (64 - bits);
    int64_t min_val = -max_val - 1;
    return
        ((b > 0 && a > max_val - b) || // (a + b) > max_val, rewritten to avoid overflow
         (b < 0 && a < min_val - b));  // (a + b) < min_val, rewritten to avoid overflow
}

bool sub_would_overflow(int bits, int64_t a, int64_t b) {
    int64_t max_val = 0x7fffffffffffffffLL >> (64 - bits);
    int64_t min_val = -max_val - 1;
    return
        ((b < 0 && a > max_val + b) || // (a - b) > max_val, rewritten to avoid overflow
         (b > 0 && a < min_val + b));  // (a - b) < min_val, rewritten to avoid overflow
}

bool mul_would_overflow(int bits, int64_t a, int64_t b) {
    int64_t max_val = 0x7fffffffffffffffLL >> (64 - bits);
    int64_t min_val = -max_val - 1;
    if (a == 0) {
        return false;
    } else if (a == -1) {
        return b == min_val;
    } else {
        // Do the multiplication as a uint64, for which overflow is
        // well defined, then cast the bits back to int64 to get
        // multiplication modulo 2^64.
        int64_t ab = (int64_t)((uint64_t)a)*((uint64_t)b);
        // The first two clauses catch overflow mod 2^bits, assuming
        // no 64-bit overflow occurs, and the third clause catches
        // 64-bit overflow.
        return ab < min_val || ab > max_val || (ab / a != b);
    }
}

struct TickStackEntry {
    std::chrono::time_point<std::chrono::high_resolution_clock> time;
    string file;
    int line;
};

vector<TickStackEntry> tick_stack;

void halide_tic_impl(const char *file, int line) {
    string f = file;
    f = split_string(f, "/").back();
    tick_stack.push_back({std::chrono::high_resolution_clock::now(), f, line});
}

void halide_toc_impl(const char *file, int line) {
    auto t1 = tick_stack.back();
    auto t2 = std::chrono::high_resolution_clock::now();
    std::chrono::duration<double> diff = t2 - t1.time;
    tick_stack.pop_back();
    for (size_t i = 0; i < tick_stack.size(); i++) {
        debug(0) << "  ";
    }
    string f = file;
    f = split_string(f, "/").back();
    debug(0) << t1.file << ":" << t1.line << " ... " << f << ":" << line << " : " << diff.count() * 1000 << " ms\n";
}

}  // namespace Internal
}  // namespace Halide