/*
 *  Copyright (c) 2020-2022 Thakee Nathees
 *  Copyright (c) 2021-2022 Pocketlang Contributors
 *  Distributed Under The MIT License
 */

#include "modules.h"

// FIXME:
// In windows MinGw support most of the posix libraries. So we only need to
// check if it's MSVC (and tcc in windows) or not for posix headers and
// Refactor the bellow macro includes.

#include "thirdparty/cwalk/cwalk.h"

#include <errno.h>
#include <sys/stat.h>

#if defined(_WIN32)
  #include <windows.h>
#endif

#if defined(_MSC_VER) || (defined(_WIN32) && defined(__TINYC__))
  #include "thirdparty/dirent/dirent.h"
  #include <direct.h>
  #include <io.h>

  // access() function flag defines for windows.
  // Reference :https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/access-waccess?view=msvc-170#remarks
  #define F_OK 0
  #define W_OK 2
  #define R_OK 4

  #define access _access
  #define getcwd _getcwd

#else
  #include <dirent.h>
  #include <unistd.h>
#endif

// The maximum path size that pocketlang's default import system supports
// including the null terminator. To be able to support more characters
// override the functions from the host application. Since this is very much
// platform specific we're defining a more general limit.
// See: https://insanecoding.blogspot.com/2007/11/pathmax-simply-isnt.html
#define MAX_PATH_LEN 4096

// The cstring pointer buffer size used in path.join(p1, p2, ...). Tune this
// value as needed.
#define MAX_JOIN_PATHS 8

static inline size_t pathAbs(const char* path, char* buff, size_t buff_size);
static inline bool pathIsFile(const char* path);
static inline bool pathIsDir(const char* path);

/*****************************************************************************/
/* PATH SHARED FUNCTIONS                                                     */
/*****************************************************************************/

// check if path + ext exists. If not return 0, otherwise path + ext will
// written to the buffer and return the total length.
//
// [path] and [buff] should be char array with size of FILENAME_MAX. This
// function will write path + ext to the buff. If the path exists it'll return
// true.
static inline size_t checkImportExists(char* path, const char* ext,
                                       char* buff) {
  size_t path_size = strlen(path);
  size_t ext_size = strlen(ext);

  // If the path size is too large we're bailing out.
  if (path_size + ext_size + 1 >= FILENAME_MAX) return 0;

  // Now we're safe to use strcpy.
  strcpy(buff, path);
  strcpy(buff + path_size, ext);

  if (!pathIsFile(buff)) return 0;
  return path_size + ext_size;
}

// Try all import paths by appending pocketlang supported extensions to the
// path (ex: path + ".pk", path + ".dll", path + ".so", path + "/_init.pk", ...
// if such a path exists it'll allocate a pocketlang string and return it.
//
// Note that [path] and [buff] should be char array with size of FILENAME_MAX.
// The buffer will be used as a working memory.
static char* tryImportPaths(PKVM* vm, char* path, char* buff) {
  size_t path_size = 0;

  // FIXME: review this code.
  do {
    if ((path_size = checkImportExists(path, "", buff)) != 0) {
      break;

    }  else if ((path_size = checkImportExists(path, ".pk", buff)) != 0) {
      break;

    } else if ((path_size = checkImportExists(path, "/_init.pk", buff)) != 0) {
      break;
    }
  } while (false);

  char* ret = NULL;
  if (path_size != 0) {
    ret = pkAllocString(vm, path_size + 1);
    memcpy(ret, buff, path_size + 1);
  }
  return ret;
}

// replace all the '\\' with '/' to make all the seperator in a path is the
// same this is only used in import path system to make the path of a module
// unique (otherwise same path with different seperator makes them different).
void pathFixWindowsSeperator(char* buff) {
  ASSERT(buff, OOPS);
  while (*buff != '\0') {
    if (*buff == '\\') *buff = '/';
    buff++;
  }
}

// Implementation of pocketlang import path resolving function.
char* pathResolveImport(PKVM* vm, const char* from, const char* path) {

  // Buffers to store intermediate path results.
  char buff1[FILENAME_MAX];
  char buff2[FILENAME_MAX];

  // If the path is absolute, Just normalize and return it. Resolve path will
  // only be absolute when the path is provided from the command line.
  if (cwk_path_is_absolute(path)) {

    // buff1 = normalized path. +1 for null terminator.
    size_t size = cwk_path_normalize(path, buff1, sizeof(buff1)) + 1;
    pathFixWindowsSeperator(buff1);

    return tryImportPaths(vm, buff1, buff2);
  }

  if (from == NULL) { //< [path] is relative to cwd.

    // buff1 = absolute path of [path].
    pathAbs(path, buff1, sizeof(buff1));

    // buff2 = normalized path. +1 for null terminator.
    size_t size = cwk_path_normalize(buff1, buff2, sizeof(buff2)) + 1;
    pathFixWindowsSeperator(buff2);

    return tryImportPaths(vm, buff2, buff1);
  }

  // Import statements doesn't support absolute paths.
  ASSERT(cwk_path_is_absolute(from), "From path should be absolute.");

  // From is a path of a script. Try relative to that script.
  {
    size_t from_dir_length = 0;
    cwk_path_get_dirname(from, &from_dir_length);
    if (from_dir_length == 0) return NULL;

    // buff1 = from directory.
    strncpy(buff1, from, sizeof(buff1));
    buff1[from_dir_length] = '\0';

    // buff2 = absolute joined path.
    cwk_path_join(buff1, path, buff2, sizeof(buff2));

    // buff1 = normalized absolute path. +1 for null terminator
    size_t size = cwk_path_normalize(buff2, buff1, sizeof(buff1)) + 1;
    pathFixWindowsSeperator(buff1);

    return tryImportPaths(vm, buff1, buff2);
  }

  // Cannot resolve the path. Return NULL to indicate failure.
  return NULL;
}

/*****************************************************************************/
/* PATH INTERNAL FUNCTIONS                                                   */
/*****************************************************************************/

static inline bool pathIsFile(const char* path) {
  struct stat path_stat;
  stat(path, &path_stat);
  return (path_stat.st_mode & S_IFMT) == S_IFREG;
}

static inline bool pathIsDir(const char* path) {
  struct stat path_stat;
  stat(path, &path_stat);
  return (path_stat.st_mode & S_IFMT) == S_IFDIR;
}

static inline bool pathIsExists(const char* path) {
  return access(path, F_OK) == 0;
}

static inline size_t pathAbs(const char* path, char* buff, size_t buff_size) {

  char cwd[MAX_PATH_LEN];

  if (getcwd(cwd, sizeof(cwd)) == NULL) {
    // TODO: handle error.
  }

  return cwk_path_get_absolute(cwd, path, buff, buff_size);
}

/*****************************************************************************/
/* PATH MODULE FUNCTIONS                                                     */
/*****************************************************************************/

DEF(_pathGetCWD, "") {
  char cwd[MAX_PATH_LEN];
  if (getcwd(cwd, sizeof(cwd)) == NULL) {
    // TODO: Handle error.
  }
  pkSetSlotString(vm, 0, cwd);
}

DEF(_pathAbspath, "") {
  const char* path;
  if (!pkValidateSlotString(vm, 1, &path, NULL)) return;

  char abspath[MAX_PATH_LEN];
  uint32_t len = (uint32_t) pathAbs(path, abspath, sizeof(abspath));
  pkSetSlotStringLength(vm, 0, abspath, len);
}

DEF(_pathRelpath, "") {
  const char* from, * path;
  if (!pkValidateSlotString(vm, 1, &from, NULL)) return;
  if (!pkValidateSlotString(vm, 2, &path, NULL)) return;

  char abs_from[MAX_PATH_LEN];
  pathAbs(from, abs_from, sizeof(abs_from));

  char abs_path[MAX_PATH_LEN];
  pathAbs(path, abs_path, sizeof(abs_path));

  char result[MAX_PATH_LEN];
  uint32_t len = (uint32_t) cwk_path_get_relative(abs_from, abs_path,
                                                  result, sizeof(result));
  pkSetSlotStringLength(vm, 0, result, len);
}

DEF(_pathJoin, "") {
  const char* paths[MAX_JOIN_PATHS + 1]; // +1 for NULL.
  int argc = pkGetArgc(vm);

  if (argc > MAX_JOIN_PATHS) {
    pkSetRuntimeError(vm, "Cannot join more than " STRINGIFY(MAX_JOIN_PATHS)
                           "paths.");
    return;
  }

  for (int i = 0; i < argc; i++) {
    pkValidateSlotString(vm, i + 1, &paths[i], NULL);
  }
  paths[argc] = NULL;

  char result[MAX_PATH_LEN];
  uint32_t len = (uint32_t) cwk_path_join_multiple(paths, result,
                                                   sizeof(result));
  pkSetSlotStringLength(vm, 0, result, len);
}

DEF(_pathNormalize, "") {
  const char* path;
  if (!pkValidateSlotString(vm, 1, &path, NULL)) return;

  char result[MAX_PATH_LEN];
  uint32_t len = (uint32_t) cwk_path_normalize(path, result, sizeof(result));
  pkSetSlotStringLength(vm, 0, result, len);
}

DEF(_pathBaseName, "") {
  const char* path;
  if (!pkValidateSlotString(vm, 1, &path, NULL)) return;

  const char* base_name;
  size_t length;
  cwk_path_get_basename(path, &base_name, &length);
  pkSetSlotStringLength(vm, 0, base_name, (uint32_t)length);
}

DEF(_pathDirName, "") {
  const char* path;
  if (!pkValidateSlotString(vm, 1, &path, NULL)) return;

  size_t length;
  cwk_path_get_dirname(path, &length);
  pkSetSlotStringLength(vm, 0, path, (uint32_t)length);
}

DEF(_pathIsPathAbs, "") {
  const char* path;
  if (!pkValidateSlotString(vm, 1, &path, NULL)) return;

  pkSetSlotBool(vm, 0, cwk_path_is_absolute(path));
}

DEF(_pathGetExtension, "") {
  const char* path;
  if (!pkValidateSlotString(vm, 1, &path, NULL)) return;

  const char* ext;
  size_t length;
  if (cwk_path_get_extension(path, &ext, &length)) {
    pkSetSlotStringLength(vm, 0, ext, (uint32_t)length);
  } else {
    pkSetSlotStringLength(vm, 0, NULL, 0);
  }
}

DEF(_pathExists, "") {
  const char* path;
  if (!pkValidateSlotString(vm, 1, &path, NULL)) return;
  pkSetSlotBool(vm, 0, pathIsExists(path));
}

DEF(_pathIsFile, "") {
  const char* path;
  if (!pkValidateSlotString(vm, 1, &path, NULL)) return;
  pkSetSlotBool(vm, 0, pathIsFile(path));
}

DEF(_pathIsDir, "") {
  const char* path;
  if (!pkValidateSlotString(vm, 1, &path, NULL)) return;
  pkSetSlotBool(vm, 0, pathIsDir(path));
}

void registerModulePath(PKVM* vm) {
  PkHandle* path = pkNewModule(vm, "path");

  pkModuleAddFunction(vm, path, "getcwd",    _pathGetCWD,       0);
  pkModuleAddFunction(vm, path, "abspath",   _pathAbspath,      1);
  pkModuleAddFunction(vm, path, "relpath",   _pathRelpath,      2);
  pkModuleAddFunction(vm, path, "join",      _pathJoin,        -1);
  pkModuleAddFunction(vm, path, "normalize", _pathNormalize,    1);
  pkModuleAddFunction(vm, path, "basename",  _pathBaseName,     1);
  pkModuleAddFunction(vm, path, "dirname",   _pathDirName,      1);
  pkModuleAddFunction(vm, path, "isabspath", _pathIsPathAbs,    1);
  pkModuleAddFunction(vm, path, "getext",    _pathGetExtension, 1);
  pkModuleAddFunction(vm, path, "exists",    _pathExists,       1);
  pkModuleAddFunction(vm, path, "isfile",    _pathIsFile,       1);
  pkModuleAddFunction(vm, path, "isdir",     _pathIsDir,        1);

  pkRegisterModule(vm, path);
  pkReleaseHandle(vm, path);
}