// Always use assert, even if llvm-config defines NDEBUG
#ifdef NDEBUG
#undef NDEBUG
#include <assert.h>
#define NDEBUG
#else
#include <assert.h>
#endif

#ifndef HALIDE_UTIL_H
#define HALIDE_UTIL_H

/** \file
 * Various utility functions used internally Halide. */

#include <cstdint>
#include <cstring>
#include <limits>
#include <string>
#include <utility>
#include <vector>

#include "runtime/HalideRuntime.h"

#ifndef HALIDE_EXPORT
#if defined(_MSC_VER)
#ifdef Halide_EXPORTS
#define HALIDE_EXPORT __declspec(dllexport)
#else
#define HALIDE_EXPORT __declspec(dllimport)
#endif
#else
#define HALIDE_EXPORT
#endif
#endif

// If we're in user code, we don't want certain functions to be inlined.
#if defined(COMPILING_HALIDE) || defined(BUILDING_PYTHON)
#define HALIDE_NO_USER_CODE_INLINE
#else
#define HALIDE_NO_USER_CODE_INLINE HALIDE_NEVER_INLINE
#endif

// On windows, Halide needs a larger stack than the default MSVC provides
#ifdef _MSC_VER
#pragma comment(linker, "/STACK:8388608,1048576")
#endif

namespace Halide {
namespace Internal {

/** Some numeric conversions are UB if the value won't fit in the result;
 * safe_numeric_cast<>() is meant as a drop-in replacement for a C/C++ cast
 * that adds well-defined behavior for the UB cases, attempting to mimic
 * common implementation behavior as much as possible.
 */
template<typename DST, typename SRC,
         typename std::enable_if<std::is_floating_point<SRC>::value>::type * = nullptr>
DST safe_numeric_cast(SRC s) {
    if (std::is_integral<DST>::value) {
        // Treat float -> int as a saturating cast; this is handled
        // in different ways by different compilers, so an arbitrary but safe
        // choice like this is reasonable.
        if (s < (SRC) std::numeric_limits<DST>::min()) {
            return std::numeric_limits<DST>::min();
        }
        if (s > (SRC) std::numeric_limits<DST>::max()) {
            return std::numeric_limits<DST>::max();
        }
    }
    return (DST) s;
}

template<typename DST, typename SRC,
         typename std::enable_if<std::is_integral<SRC>::value>::type * = nullptr>
DST safe_numeric_cast(SRC s) {
    if (std::is_integral<DST>::value) {
        // any-int -> signed-int is technically UB if value won't fit;
        // in practice, common compilers implement such conversions as done below
        // (as verified by exhaustive testing on Clang for x86-64). We could
        // probably continue to rely on that behavior, but making it explicit
        // avoids possible wrather of UBSan and similar debug helpers.
        // (Yes, using sizeof for this comparison is a little odd for the uint->int
        // case, but the intent is to match existing common behavior, which this does.)
        if (std::is_integral<SRC>::value && std::is_signed<DST>::value && sizeof(DST) < sizeof(SRC)) {
            using UnsignedSrc = typename std::make_unsigned<SRC>::type;
            return (DST) (s & (UnsignedSrc) (-1));
        }
    }
    return (DST) s;
}

/** An aggressive form of reinterpret cast used for correct type-punning. */
template<typename DstType, typename SrcType>
DstType reinterpret_bits(const SrcType &src) {
    static_assert(sizeof(SrcType) == sizeof(DstType), "Types must be same size");
    DstType dst;
    memcpy(&dst, &src, sizeof(SrcType));
    return dst;
}

/** Make a unique name for an object based on the name of the stack
 * variable passed in. If introspection isn't working or there are no
 * debug symbols, just uses unique_name with the given prefix. */
std::string make_entity_name(void *stack_ptr, const std::string &type, char prefix);

/** Get value of an environment variable. Returns its value
 * is defined in the environment. If the var is not defined, an empty string
 * is returned.
 */
std::string get_env_variable(char const *env_var_name);

/** Get the name of the currently running executable. Platform-specific.
 * If program name cannot be retrieved, function returns an empty string. */
std::string running_program_name();

/** Generate a unique name starting with the given prefix. It's unique
 * relative to all other strings returned by unique_name in this
 * process.
 *
 * The single-character version always appends a numeric suffix to the
 * character.
 *
 * The string version will either return the input as-is (with high
 * probability on the first time it is called with that input), or
 * replace any existing '$' characters with underscores, then add a
 * '$' sign and a numeric suffix to it.
 *
 * Note that unique_name('f') therefore differs from
 * unique_name("f"). The former returns something like f123, and the
 * latter returns either f or f$123.
 */
// @{
std::string unique_name(char prefix);
std::string unique_name(const std::string &prefix);
// @}

/** Reset the unique name counters to zeros. */
void reset_unique_name_counters();

/** Test if the first string starts with the second string */
bool starts_with(const std::string &str, const std::string &prefix);

/** Test if the first string ends with the second string */
bool ends_with(const std::string &str, const std::string &suffix);

/** Replace all matches of the second string in the first string with the last string */
std::string replace_all(const std::string &str, const std::string &find, const std::string &replace);

/** Split the source string using 'delim' as the divider. */
std::vector<std::string> split_string(const std::string &source, const std::string &delim);

/** Perform a left fold of a vector. Returns a default-constructed
 * vector element if the vector is empty. Similar to std::accumulate
 * but with a less clunky syntax. */
template<typename T, typename Fn>
T fold_left(const std::vector<T> &vec, Fn f) {
    T result;
    if (vec.empty()) {
        return result;
    }
    result = vec[0];
    for (size_t i = 1; i < vec.size(); i++) {
        result = f(result, vec[i]);
    }
    return result;
}

/** Returns a right fold of a vector. Returns a default-constructed
 * vector element if the vector is empty. */
template<typename T, typename Fn>
T fold_right(const std::vector<T> &vec, Fn f) {
    T result;
    if (vec.empty()) {
        return result;
    }
    result = vec.back();
    for (size_t i = vec.size()-1; i > 0; i--) {
        result = f(vec[i-1], result);
    }
    return result;
}

template <typename T1, typename T2, typename T3, typename T4 >
inline HALIDE_NO_USER_CODE_INLINE void collect_paired_args(std::vector<std::pair<T1, T2>> &collected_args,
                                     const T3 &a1, const T4 &a2) {
    collected_args.push_back(std::pair<T1, T2>(a1, a2));
}

template <typename T1, typename T2, typename T3, typename T4, typename ...Args>
inline HALIDE_NO_USER_CODE_INLINE void collect_paired_args(std::vector<std::pair<T1, T2>> &collected_args,
                                   const T3 &a1, const T4 &a2, Args&&... args) {
    collected_args.push_back(std::pair<T1, T2>(a1, a2));
    collect_paired_args(collected_args, std::forward<Args>(args)...);
}

template<typename... T>
struct meta_and : std::true_type {};

template<typename T1, typename... Args>
struct meta_and<T1, Args...> : std::integral_constant<bool, T1::value && meta_and<Args...>::value> {};

template<typename... T>
struct meta_or : std::false_type {};

template<typename T1, typename... Args>
struct meta_or<T1, Args...> : std::integral_constant<bool, T1::value || meta_or<Args...>::value> {};

template<typename To, typename... Args>
struct all_are_convertible : meta_and<std::is_convertible<Args, To>...> {};

/** Returns base name and fills in namespaces, outermost one first in vector. */
std::string extract_namespaces(const std::string &name, std::vector<std::string> &namespaces);

struct FileStat {
    uint64_t file_size;
    uint32_t mod_time;  // Unix epoch time
    uint32_t uid;
    uint32_t gid;
    uint32_t mode;
};

/** Create a unique file with a name of the form prefixXXXXXsuffix in an arbitrary
 * (but writable) directory; this is typically /tmp, but the specific
 * location is not guaranteed. (Note that the exact form of the file name
 * may vary; in particular, the suffix may be ignored on Windows.)
 * The file is created (but not opened), thus this can be called from
 * different threads (or processes, e.g. when building with parallel make)
 * without risking collision. Note that if this file is used as a temporary
 * file, the caller is responsibly for deleting it. Neither the prefix nor suffix
 * may contain a directory separator.
 */
std::string file_make_temp(const std::string &prefix, const std::string &suffix);

/** Create a unique directory in an arbitrary (but writable) directory; this is
 * typically somewhere inside /tmp, but the specific location is not guaranteed.
 * The directory will be empty (i.e., this will never return /tmp itself,
 * but rather a new directory inside /tmp). The caller is responsible for removing the
 * directory after use.
 */
std::string dir_make_temp();

/** Wrapper for access(). Quietly ignores errors. */
bool file_exists(const std::string &name);

/** assert-fail if the file doesn't exist. useful primarily for testing purposes. */
void assert_file_exists(const std::string &name);

/** assert-fail if the file DOES exist. useful primarily for testing purposes. */
void assert_no_file_exists(const std::string &name);

/** Wrapper for unlink(). Asserts upon error. */
void file_unlink(const std::string &name);

/** Wrapper for unlink(). Quietly ignores errors. */
void file_unlink(const std::string &name);

/** Ensure that no file with this path exists. If such a file
 * exists and cannot be removed, assert-fail. */
void ensure_no_file_exists(const std::string &name);

/** Wrapper for rmdir(). Asserts upon error. */
void dir_rmdir(const std::string &name);

/** Wrapper for stat(). Asserts upon error. */
FileStat file_stat(const std::string &name);

/** Read the entire contents of a file into a vector<char>. The file
 * is read in binary mode. Errors trigger an assertion failure. */
std::vector<char> read_entire_file(const std::string &pathname);

/** Create or replace the contents of a file with a given pointer-and-length
 * of memory. If the file doesn't exist, it is created; if it does exist, it
 * is completely overwritten. Any error triggers an assertion failure. */
void write_entire_file(const std::string &pathname, const void *source, size_t source_len);

inline void write_entire_file(const std::string &pathname, const std::vector<char> &source) {
    write_entire_file(pathname, source.data(), source.size());
}

/** A simple utility class that creates a temporary file in its ctor and
 * deletes that file in its dtor; this is useful for temporary files that you
 * want to ensure are deleted when exiting a certain scope. Since this is essentially
 * just an RAII wrapper around file_make_temp() and file_unlink(), it has the same
 * failure modes (i.e.: assertion upon error).
 */
class TemporaryFile final {
public:
    TemporaryFile(const std::string &prefix, const std::string &suffix)
        : temp_path(file_make_temp(prefix, suffix)), do_unlink(true) {}
    const std::string &pathname() const { return temp_path; }
    ~TemporaryFile() { if (do_unlink) { file_unlink(temp_path); } }
    // You can call this if you want to defeat the automatic deletion;
    // this is rarely what you want to do (since it defeats the purpose
    // of this class), but can be quite handy for debugging purposes.
    void detach() { do_unlink = false; }
private:
    const std::string temp_path;
    bool do_unlink;
    TemporaryFile(const TemporaryFile &) = delete;
    void operator=(const TemporaryFile &) = delete;
};

/** Routines to test if math would overflow for signed integers with
 * the given number of bits. */
// @{
bool add_would_overflow(int bits, int64_t a, int64_t b);
bool sub_would_overflow(int bits, int64_t a, int64_t b);
bool mul_would_overflow(int bits, int64_t a, int64_t b);
// @}

/** Helper class for saving/restoring variable values on the stack, to allow
 * for early-exit that preserves correctness */
template<typename T>
struct ScopedValue {
    T &var;
    const T old_value;
    /** Preserve the old value, restored at dtor time */
    ScopedValue(T &var) : var(var), old_value(var) {}
    /** Preserve the old value, then set the var to a new value. */
    ScopedValue(T &var, T new_value) : var(var), old_value(var) { var = new_value; }
    ~ScopedValue() { var = old_value; }
    operator T() const { return old_value; }
    // allow move but not copy
    ScopedValue(const ScopedValue& that) = delete;
    ScopedValue(ScopedValue&& that) = default;
};

// Wrappers for some C++14-isms that are useful and trivially implementable
// in C++11; these are defined in the Halide::Internal namespace. If we
// are compiling under C++14 or later, we just use the standard implementations
// rather than our own.
#if __cplusplus >= 201402L

// C++14: Use the standard implementations
using std::integer_sequence;
using std::make_integer_sequence;
using std::index_sequence;
using std::make_index_sequence;

#else

// C++11: std::integer_sequence (etc) is standard in C++14 but not C++11, but
// is easily written in C++11. This is a simple version that could
// probably be improved.

template<typename T, T... Ints>
struct integer_sequence {
    static constexpr size_t size() { return sizeof...(Ints); }
};

template<typename T>
struct next_integer_sequence;

template<typename T, T... Ints>
struct next_integer_sequence<integer_sequence<T, Ints...>> {
    using type = integer_sequence<T, Ints..., sizeof...(Ints)>;
};

template<typename T, T I, T N>
struct make_integer_sequence_helper {
    using type = typename next_integer_sequence<
        typename make_integer_sequence_helper<T, I+1, N>::type
    >::type;
};

template<typename T, T N>
struct make_integer_sequence_helper<T, N, N> {
    using type = integer_sequence<T>;
};

template<typename T, T N>
using make_integer_sequence = typename make_integer_sequence_helper<T, 0, N>::type;

template<size_t... Ints>
using index_sequence = integer_sequence<size_t, Ints...>;

template<size_t N>
using make_index_sequence = make_integer_sequence<size_t, N>;

#endif

// Helpers for timing blocks of code. Put 'TIC;' at the start and
// 'TOC;' at the end. Timing is reported at the toc via
// debug(0). The calls can be nested and will pretty-print
// appropriately. Took this idea from matlab via Jon Barron.
//
// Note that this uses global state internally, and is not thread-safe
// at all. Only use it for single-threaded debugging sessions.

void halide_tic_impl(const char *file, int line);
void halide_toc_impl(const char *file, int line);
#define HALIDE_TIC Halide::Internal::halide_tic_impl(__FILE__, __LINE__)
#define HALIDE_TOC Halide::Internal::halide_toc_impl(__FILE__, __LINE__)
#ifdef COMPILING_HALIDE
#define TIC HALIDE_TIC
#define TOC HALIDE_TOC
#endif

// statically cast a value from one type to another: this is really just
// some syntactic sugar around static_cast<>() to avoid compiler warnings
// regarding 'bool' in some compliation configurations.
template<typename TO>
struct StaticCast {
    template <typename FROM, typename TO2 = TO, typename std::enable_if<!std::is_same<TO2, bool>::value>::type * = nullptr>
    inline constexpr static TO2 value(const FROM &from) { return static_cast<TO2>(from); }

    template <typename FROM, typename TO2 = TO, typename std::enable_if<std::is_same<TO2, bool>::value>::type * = nullptr>
    inline constexpr static TO2 value(const FROM &from) { return from != 0; }
};

// Like std::is_convertible, but with additional tests for arithmetic types:
// ensure that the value will roundtrip losslessly (e.g., no integer truncation
// or dropping of fractional parts).
template<typename TO>
struct IsRoundtrippable {
    template <typename FROM, typename TO2 = TO, typename std::enable_if<
        !std::is_convertible<FROM, TO>::value
    >::type * = nullptr>
    inline constexpr static bool value(const FROM &from) {
        return false;
    }

    template <typename FROM, typename TO2 = TO, typename std::enable_if<
        std::is_convertible<FROM, TO>::value &&
        std::is_arithmetic<TO>::value && std::is_arithmetic<FROM>::value && !std::is_same<TO, FROM>::value
    >::type * = nullptr>
    inline constexpr static bool value(const FROM &from) {
        return StaticCast<FROM>::value(StaticCast<TO>::value(from)) == from;
    }

    template <typename FROM, typename TO2 = TO, typename std::enable_if<
        std::is_convertible<FROM, TO>::value &&
        !(std::is_arithmetic<TO>::value && std::is_arithmetic<FROM>::value && !std::is_same<TO, FROM>::value)
    >::type * = nullptr>
    inline constexpr static bool value(const FROM &from) {
        return true;
    }
};

}  // namespace Internal
}  // namespace Halide

#endif