// goal:
// replace "file" + "checksec"

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <stdint.h>
#include <string.h>

#define MAX_FILENAME   256
#define EI_NIDENT      16
#define MAX_HEADER_LEN 2048

#define Elf32_Half uint16_t
#define Elf32_Word uint32_t
#define Elf32_Addr uint32_t
#define Elf32_Off  uint32_t

struct Elf32_Ehdr
{
	unsigned char e_ident[EI_NIDENT];
	Elf32_Half e_type;
	Elf32_Half e_machine;
	Elf32_Word e_version;
	Elf32_Addr e_entry; 
	Elf32_Off e_phoff;
	Elf32_Off e_shoff;
	Elf32_Word e_flags;
	Elf32_Half e_ehsize;
	Elf32_Half e_phentsize;
	Elf32_Half e_phnum;
	Elf32_Half e_shentsize;
	Elf32_Half e_shnum;
	Elf32_Half e_shstrndx;
};

int parse_elf_header32(struct Elf32_Ehdr* header, FILE* fp)
{
	fread(header, sizeof(struct Elf32_Ehdr), 1, fp);
	return EXIT_SUCCESS;
}

int main(int argc, char* argv[])
{	
	// Accessing file arg
	if (argc < 2)
	{
		printf("Usage: %s <elf>\n", argv[0]);
		return -EINVAL;
	}

	char* filename = argv[1];

	// 0. is ELF32 or ELF64 ???
	// 1. create ELF header struct
	// 2. populate ELF header struct
	// 3. display ELF header struct	

	if (!filename)
	{
		printf("Error parsing filename.\n");
		return -EINVAL;
	}
	
	FILE* elf_file = fopen(filename, "rb");

	if (!elf_file)
	{
		printf("Couldn't open file '%s'\n", filename);
		return -ENOENT;
	}

	struct Elf32_Ehdr elf_header = {0};	
	int res = parse_elf_header32(&elf_header, elf_file);
	if (res)
	{
		printf("Error parsing ELF header.\n");
		return -EINVAL;
	}

	if (!(memcmp(elf_header.e_ident, "\177ELF", 4) == 0))
	{
		printf("Not an ELF file..\n");
		return -EINVAL;
	}

	printf("ELF file\n");
	
	return EXIT_SUCCESS;
}