/*
	MIT License

	Copyright (c) 2020 xerox

	Permission is hereby granted, free of charge, to any person obtaining a copy
	of this software and associated documentation files (the "Software"), to deal
	in the Software without restriction, including without limitation the rights
	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	copies of the Software, and to permit persons to whom the Software is
	furnished to do so, subject to the following conditions:

	The above copyright notice and this permission notice shall be included in all
	copies or substantial portions of the Software.

	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
	SOFTWARE.
*/

#pragma once
#include <map>
#include <atomic>
#include <memory>
#include <unistd.h>
#include <sys/mman.h>

#define PAGE_START(ptr) reinterpret_cast<void*>(reinterpret_cast<std::uintptr_t>(ptr) >> 12 << 12)
#define ARM_JMP_CODE 0xE51FF004

namespace shithook
{
	class detour
	{
	public:
		detour(void* addr_to_hook, void* jmp_to, bool enable = true)
			:
			hook_addr(addr_to_hook),
			detour_addr(jmp_to),
			hook_installed(false)
		{
			reinterpret_cast<std::uint32_t*>(jmp_code)[0] = ARM_JMP_CODE; // LDR PC, [PC, #-4]
			reinterpret_cast<void**>(jmp_code)[1] = jmp_to;
			memcpy(org_bytes, hook_addr, sizeof(org_bytes));
			if (enable) install();
		}

		void install()
		{
			if (hook_installed.load())
				return;

			if (!mprotect(PAGE_START(hook_addr), getpagesize(), PROT_READ | PROT_WRITE | PROT_EXEC))
			{
				memcpy((void*)((long)hook_addr), jmp_code, sizeof(jmp_code));
				mprotect(PAGE_START(hook_addr), getpagesize(), PROT_READ | PROT_EXEC);
				cacheflush(reinterpret_cast<long>(hook_addr), reinterpret_cast<long>(hook_addr) + getpagesize(), NULL);
				hook_installed.exchange(true);
			}
		}

		void uninstall()
		{
			if (!hook_installed.load())
				return;

			if (!mprotect(PAGE_START(hook_addr), getpagesize(), PROT_READ | PROT_WRITE | PROT_EXEC))
			{
				memcpy(hook_addr, org_bytes, sizeof(jmp_code));
				mprotect(PAGE_START(hook_addr), getpagesize(), PROT_READ | PROT_EXEC);
				cacheflush(reinterpret_cast<long>(hook_addr), reinterpret_cast<long>(hook_addr) + getpagesize(), NULL);
				hook_installed.exchange(false);
			}
		}

		~detour() { uninstall(); }
		bool installed() { return hook_installed; }
		void* hook_address() { return hook_addr; }
		void* detour_address() { return detour_addr; }
	private:
		std::atomic<bool> hook_installed;
		void* hook_addr, * detour_addr;

		unsigned char jmp_code[8]{};
		std::uint8_t org_bytes[sizeof(jmp_code)];
	};

	// this is jank, but needed because the OS isnt initalizing statics/inlined globals... :|
	inline std::map<void*, std::unique_ptr<detour>>* get_hooks()
	{
		static std::map<void*, std::unique_ptr<detour>> hooks{};
		return &hooks;
	}

	inline void make_hook(void* addr_to_hook, void* jmp_to_addr, bool enable = true)
	{
		if (!addr_to_hook)
			return;

		get_hooks()->insert({
			addr_to_hook,
			std::make_unique<detour>(
				addr_to_hook,
				jmp_to_addr,
				enable
			) }
		);
	}

	inline void enable(void* addr)
	{
		if (!addr)
			return;
		get_hooks()->at(addr)->install();
	}

	inline void disable(void* addr)
	{
		if (!addr)
			return;
		get_hooks()->at(addr)->uninstall();
	}

	inline void remove(void* addr)
	{
		if (!addr)
			return;
		get_hooks()->erase(addr);
	}
}