#ifndef POSTJECT_API_H_

#define POSTJECT_API_H_

#include <stdbool.h>

#include <stddef.h>

#include <stdlib.h>

#include <string.h>

#if defined(__APPLE__) && defined(__MACH__)

#include <mach-o/dyld.h>

#include <mach-o/getsect.h>

#elif defined(__linux__)

#include <elf.h>

#include <link.h>

#include <sys/param.h>

#elif defined(_WIN32)

#include <windows.h>

#endif

#ifndef POSTJECT_SENTINEL_FUSE

#define POSTJECT_SENTINEL_FUSE \

  "POSTJECT_SENTINEL_fce680ab2cc467b6e072b8b5df1996b2"

#endif

struct postject_options {

  const char* elf_section_name;

  const char* macho_framework_name;

  const char* macho_section_name;

  const char* macho_segment_name;

  const char* pe_resource_name;

};

inline void postject_options_init(struct postject_options* options) {

  options->elf_section_name = NULL;

  options->macho_framework_name = NULL;

  options->macho_section_name = NULL;

  options->macho_segment_name = NULL;

  options->pe_resource_name = NULL;

}

static inline bool postject_has_resource() {

  static const volatile char* sentinel = POSTJECT_SENTINEL_FUSE ":0";

  return sentinel[sizeof(POSTJECT_SENTINEL_FUSE)] == '1';

}

#if defined(__linux__)

static int postject__dl_iterate_phdr_callback(struct dl_phdr_info* info,

                                              size_t size,

                                              void* data) {

  // Snag the dl_phdr_info struct for the main program, then stop iterating

  *((struct dl_phdr_info*)data) = *info;

  return 1;

}

#endif

static const void* postject_find_resource(

    const char* name,

    size_t* size,

    const struct postject_options* options) {

  // Always zero out the size pointer to start

  if (size != NULL) {

    *size = 0;

  }

#if defined(__APPLE__) && defined(__MACH__)

  char* section_name = NULL;

  const char* segment_name = "__POSTJECT";

  if (options != NULL && options->macho_segment_name != NULL) {

    segment_name = options->macho_segment_name;

  }

  if (options != NULL && options->macho_section_name != NULL) {

    name = options->macho_section_name;

  } else if (strncmp(name, "__", 2) != 0) {

    // Automatically prepend __ to match naming convention

    section_name = (char*)malloc(strlen(name) + 3);

    if (section_name == NULL) {

      return NULL;

    }

    strcpy(section_name, "__");

    strcat(section_name, name);

  }

  unsigned long section_size;

  char* ptr = NULL;

  if (options != NULL && options->macho_framework_name != NULL) {

#ifdef __clang__

#pragma clang diagnostic push

#pragma clang diagnostic ignored "-Wdeprecated-declarations"

#endif

    ptr = getsectdatafromFramework(options->macho_framework_name, segment_name,

                                   section_name != NULL ? section_name : name,

                                   &section_size);

  } else {

    ptr = getsectdata(segment_name, section_name != NULL ? section_name : name,

                      &section_size);

#ifdef __clang__

#pragma clang diagnostic pop

#endif

    if (ptr != NULL) {

      // Add the "virtual memory address slide" amount to ensure a valid pointer

      // in cases where the virtual memory address have been adjusted by the OS.

      //

      // NOTE - `getsectdataFromFramework` already handles this adjustment for

      //        us, which is why we only do it for `getsectdata`, see:

      //        https://web.archive.org/web/20220613234007/https://opensource.apple.com/source/cctools/cctools-590/libmacho/getsecbyname.c.auto.html

      ptr += _dyld_get_image_vmaddr_slide(0);

    }

  }

  free(section_name);

  if (size != NULL) {

    *size = (size_t)section_size;

  }

  return ptr;

#elif defined(__linux__)

  if (options != NULL && options->elf_section_name != NULL) {

    name = options->elf_section_name;

  }

  struct dl_phdr_info main_program_info;

  dl_iterate_phdr(postject__dl_iterate_phdr_callback, &main_program_info);

  uintptr_t p = (uintptr_t)main_program_info.dlpi_phdr;

  size_t n = main_program_info.dlpi_phnum;

  uintptr_t base_addr = main_program_info.dlpi_addr;

  // iterate program header

  for (; n > 0; n--, p += sizeof(ElfW(Phdr))) {

    ElfW(Phdr)* phdr = (ElfW(Phdr)*)p;

    // skip everything but notes

    if (phdr->p_type != PT_NOTE) {

      continue;

    }

    // note segment starts at base address + segment virtual address

    uintptr_t pos = (base_addr + phdr->p_vaddr);

    uintptr_t end = (pos + phdr->p_memsz);

    // iterate through segment until we reach the end

    while (pos < end) {

      if (pos + sizeof(ElfW(Nhdr)) > end) {

        break;  // invalid

      }

      ElfW(Nhdr)* note = (ElfW(Nhdr)*)(uintptr_t)pos;

      if (note->n_namesz != 0 && note->n_descsz != 0 &&

          strncmp((char*)(pos + sizeof(ElfW(Nhdr))), (char*)name,

                  sizeof(name)) == 0) {

        *size = note->n_descsz;

        // advance past note header and aligned name

        // to get to description data

        return (void*)((uintptr_t)note + sizeof(ElfW(Nhdr)) +

                       roundup(note->n_namesz, 4));

      }

      pos += (sizeof(ElfW(Nhdr)) + roundup(note->n_namesz, 4) +

              roundup(note->n_descsz, 4));

    }

  }

  return NULL;

#elif defined(_WIN32)

  void* ptr = NULL;

  char* resource_name = NULL;

  if (options != NULL && options->pe_resource_name != NULL) {

    name = options->pe_resource_name;

  } else {

    // Automatically uppercase the resource name or it won't be found

    resource_name = (char*)malloc(strlen(name) + 1);

    if (resource_name == NULL) {

      return NULL;

    }

    strcpy_s(resource_name, strlen(name) + 1, name);

    CharUpperA(resource_name);  // Uppercases inplace

  }

  HRSRC resource_handle =

      FindResourceA(NULL, resource_name != NULL ? resource_name : name,

                    MAKEINTRESOURCEA(10) /* RT_RCDATA */);

  if (resource_handle) {

    HGLOBAL global_resource_handle = LoadResource(NULL, resource_handle);

    if (global_resource_handle) {

      if (size != NULL) {

        *size = SizeofResource(NULL, resource_handle);

      }

      ptr = LockResource(global_resource_handle);

    }

  }

  free(resource_name);

  return ptr;

#else

  return NULL;

#endif

}

#endif  // POSTJECT_API_H_