/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
   file Copyright.txt or https://cmake.org/licensing for details.  */
#include "cmFileTimeComparison.h"

#include <string>
#include <time.h>
#include <unordered_map>
#include <utility>

// Use a platform-specific API to get file times efficiently.
#if !defined(_WIN32) || defined(__CYGWIN__)
#    include "cm_sys_stat.h"
#    define cmFileTimeComparison_Type struct stat
#else
#    include "cmsys/Encoding.hxx"
#    include <windows.h>
#    define cmFileTimeComparison_Type FILETIME
#endif

class cmFileTimeComparisonInternal
{
public:
    // Internal comparison method.
    inline bool FileTimeCompare(const char* f1, const char* f2, int* result);

    bool FileTimesDiffer(const char* f1, const char* f2);

private:
    typedef std::unordered_map<std::string, cmFileTimeComparison_Type>
                 FileStatsMap;
    FileStatsMap Files;

    // Internal methods to lookup and compare modification times.
    inline bool Stat(const char* fname, cmFileTimeComparison_Type* st);
    inline int  Compare(cmFileTimeComparison_Type* st1,
                        cmFileTimeComparison_Type* st2);
    inline bool TimesDiffer(cmFileTimeComparison_Type* st1,
                            cmFileTimeComparison_Type* st2);
};

bool
cmFileTimeComparisonInternal::Stat(const char*                fname,
                                   cmFileTimeComparison_Type* st)
{
    // Use the stored time if available.
    cmFileTimeComparisonInternal::FileStatsMap::iterator fit =
        this->Files.find(fname);
    if(fit != this->Files.end())
    {
        *st = fit->second;
        return true;
    }

#if !defined(_WIN32) || defined(__CYGWIN__)
    // POSIX version.  Use the stat function.
    int res = ::stat(fname, st);
    if(res != 0)
    {
        return false;
    }
#else
    // Windows version.  Get the modification time from extended file
    // attributes.
    WIN32_FILE_ATTRIBUTE_DATA fdata;
    if(!GetFileAttributesExW(cmsys::Encoding::ToWide(fname).c_str(),
                             GetFileExInfoStandard, &fdata))
    {
        return false;
    }

    // Copy the file time to the output location.
    *st = fdata.ftLastWriteTime;
#endif

    // Store the time for future use.
    this->Files[fname] = *st;
    return true;
}

cmFileTimeComparison::cmFileTimeComparison()
{
    this->Internals = new cmFileTimeComparisonInternal;
}

cmFileTimeComparison::~cmFileTimeComparison() { delete this->Internals; }

bool
cmFileTimeComparison::FileTimeCompare(const char* f1, const char* f2,
                                      int* result)
{
    return this->Internals->FileTimeCompare(f1, f2, result);
}

bool
cmFileTimeComparison::FileTimesDiffer(const char* f1, const char* f2)
{
    return this->Internals->FileTimesDiffer(f1, f2);
}

int
cmFileTimeComparisonInternal::Compare(cmFileTimeComparison_Type* s1,
                                      cmFileTimeComparison_Type* s2)
{
#if !defined(_WIN32) || defined(__CYGWIN__)
#    if CMake_STAT_HAS_ST_MTIM
    // Compare using nanosecond resolution.
    if(s1->st_mtim.tv_sec < s2->st_mtim.tv_sec)
    {
        return -1;
    }
    if(s1->st_mtim.tv_sec > s2->st_mtim.tv_sec)
    {
        return 1;
    }
    if(s1->st_mtim.tv_nsec < s2->st_mtim.tv_nsec)
    {
        return -1;
    }
    if(s1->st_mtim.tv_nsec > s2->st_mtim.tv_nsec)
    {
        return 1;
    }
#    elif CMake_STAT_HAS_ST_MTIMESPEC
    // Compare using nanosecond resolution.
    if(s1->st_mtimespec.tv_sec < s2->st_mtimespec.tv_sec)
    {
        return -1;
    }
    if(s1->st_mtimespec.tv_sec > s2->st_mtimespec.tv_sec)
    {
        return 1;
    }
    if(s1->st_mtimespec.tv_nsec < s2->st_mtimespec.tv_nsec)
    {
        return -1;
    }
    if(s1->st_mtimespec.tv_nsec > s2->st_mtimespec.tv_nsec)
    {
        return 1;
    }
#    else
    // Compare using 1 second resolution.
    if(s1->st_mtime < s2->st_mtime)
    {
        return -1;
    }
    if(s1->st_mtime > s2->st_mtime)
    {
        return 1;
    }
#    endif
    // Files have the same time.
    return 0;
#else
    // Compare using system-provided function.
    return (int) CompareFileTime(s1, s2);
#endif
}

bool
cmFileTimeComparisonInternal::TimesDiffer(cmFileTimeComparison_Type* s1,
                                          cmFileTimeComparison_Type* s2)
{
#if !defined(_WIN32) || defined(__CYGWIN__)
#    if CMake_STAT_HAS_ST_MTIM
    // Times are integers in units of 1ns.
    long long bil = 1000000000;
    long long t1  = s1->st_mtim.tv_sec * bil + s1->st_mtim.tv_nsec;
    long long t2  = s2->st_mtim.tv_sec * bil + s2->st_mtim.tv_nsec;
    if(t1 < t2)
    {
        return (t2 - t1) >= bil;
    }
    if(t2 < t1)
    {
        return (t1 - t2) >= bil;
    }
    return false;
#    elif CMake_STAT_HAS_ST_MTIMESPEC
    // Times are integers in units of 1ns.
    long long bil = 1000000000;
    long long t1  = s1->st_mtimespec.tv_sec * bil + s1->st_mtimespec.tv_nsec;
    long long t2  = s2->st_mtimespec.tv_sec * bil + s2->st_mtimespec.tv_nsec;
    if(t1 < t2)
    {
        return (t2 - t1) >= bil;
    }
    if(t2 < t1)
    {
        return (t1 - t2) >= bil;
    }
    return false;
#    else
    // Times are integers in units of 1s.
    if(s1->st_mtime < s2->st_mtime)
    {
        return (s2->st_mtime - s1->st_mtime) >= 1;
    }
    if(s1->st_mtime > s2->st_mtime)
    {
        return (s1->st_mtime - s2->st_mtime) >= 1;
    }
    return false;
#    endif
#else
    // Times are integers in units of 100ns.
    LARGE_INTEGER t1;
    LARGE_INTEGER t2;
    t1.LowPart  = s1->dwLowDateTime;
    t1.HighPart = s1->dwHighDateTime;
    t2.LowPart  = s2->dwLowDateTime;
    t2.HighPart = s2->dwHighDateTime;
    if(t1.QuadPart < t2.QuadPart)
    {
        return (t2.QuadPart - t1.QuadPart) >= static_cast<LONGLONG>(10000000);
    } else if(t2.QuadPart < t1.QuadPart)
    {
        return (t1.QuadPart - t2.QuadPart) >= static_cast<LONGLONG>(10000000);
    } else
    {
        return false;
    }
#endif
}

bool
cmFileTimeComparisonInternal::FileTimeCompare(const char* f1, const char* f2,
                                              int* result)
{
    // Get the modification time for each file.
    cmFileTimeComparison_Type s1;
    cmFileTimeComparison_Type s2;
    if(this->Stat(f1, &s1) && this->Stat(f2, &s2))
    {
        // Compare the two modification times.
        *result = this->Compare(&s1, &s2);
        return true;
    }
    // No comparison available.  Default to the same time.
    *result = 0;
    return false;
}

bool
cmFileTimeComparisonInternal::FileTimesDiffer(const char* f1, const char* f2)
{
    // Get the modification time for each file.
    cmFileTimeComparison_Type s1;
    cmFileTimeComparison_Type s2;
    if(this->Stat(f1, &s1) && this->Stat(f2, &s2))
    {
        // Compare the two modification times.
        return this->TimesDiffer(&s1, &s2);
    }
    // No comparison available.  Default to different times.
    return true;
}
