#include <fxos/os.h>
#include <fxos/target.h>
#include <fxos/memory.h>

#include <cstring>

namespace FxOS {

OS::OS(Target &t): m_target {t}
{
	if(!t.covers(0x80000000))
		throw std::runtime_error("OS requires a target with ROM");

	/* OS files are all at least 1 MB large */
	if(!t.covers(0x80000000, 1000000))
		throw std::runtime_error("OS requires target with >1MB ROM");

	/* Detect OS type by heuristic */
	if(t.read_str(0x80010000, 8).value == "CASIOWIN")
		this->type = FX;
	else if(t.read_str(0x80020000, 8).value == "CASIOWIN")
		this->type = CG;
	else
		throw std::runtime_error("Cannot determine OS type (FX/CG)");

	parse_header();
	parse_syscall_table();
	parse_footer();
}

void OS::parse_header()
{
	Target &t = m_target;

	if(this->type == FX)
	{
		/* Bootcode timestamp at the very end of the bootcode */
		this->bootcode_timestamp = t.read_str(0x8000ffb0, 14);
		this->bootcode_checksum = t.read_u32(0x8000fffc);
		this->version = t.read_str(0x80010020, 10);
		/* Serial numer at 0xffd0... sometimes? */
		this->serial_number = t.read_str(0x8000ffd0, 8);
	}
	else if(this->type == CG)
	{
		this->bootcode_timestamp = t.read_str(0x8001ffb0, 14);
		this->bootcode_checksum = t.read_u32(0x8001fffc);
		this->version = t.read_str(0x80020020, 10);
		this->serial_number = t.read_str(0x8001ffd0, 8);
	}
}

//---
//  Syscall resolution
//---

int OS::syscall_count() const noexcept
{
	return m_syscall_table.size();
}

uint32_t OS::syscall(int id) const
{
	return m_syscall_table[id];
}

int OS::find_syscall(uint32_t entry) const noexcept
{
	try {
		return m_syscall_addresses.at(entry);
	}
	catch(std::out_of_range &e) {
		return -1;
	}
}

uint32_t OS::syscall_table_address() const noexcept
{
	uint32_t address = (this->type == FX) ? 0x8001007c : 0x8002007c;
	return m_target.read_u32(address);
}

void OS::parse_syscall_table()
{
	Target &t = m_target;

	/* Traverse the syscall table */
	uint32_t syscall_table = syscall_table_address();
	int id = 0;

	while(1)
	{
		uint32_t entry = t.read_u32(syscall_table + 4 * id);

		MemoryRegion const *r = MemoryRegion::region_for(entry);
		if(!r) break;

		m_syscall_table.push_back(entry);
		m_syscall_addresses[entry] = id;

		id++;
	}
}

//---
//  Footer search
//---

void OS::parse_footer()
{
	Target &t = m_target;

	/* Find the footer address (occurrence of "CASIOABSLangdata") */
	uint32_t start = MemoryRegion::ROM.start;
	uint32_t end = MemoryRegion::ROM.end;

	this->footer = t.search(start, end, "CASIOABSLangdata", 16);
	if(this->footer == end)
	{
		this->footer = -1;
		this->timestamp = std::string("");
		this->langdata = 0;
		return;
	}

	uint32_t addr = this->footer + 8;
	this->langdata = 0;

	while(!memcmp(t.translate(addr, 8), "Langdata", 8))
	{
		this->langdata++;
		addr += 0x30;
	}

	this->timestamp = t.read_str(addr, 14);
	this->checksum  = t.read_u32(addr + 0x18);
}

} /* namespace FxOS */