#include <AK/Assertions.h>
#include <AK/Types.h>
#include <Kernel/Arch/i386/CPU.h>
#include <Kernel/Arch/i386/APIC.h>
#include <Kernel/IO.h>
#include <Kernel/VM/MemoryManager.h>

#define IRQ_APIC_SPURIOUS 0x1f

#define APIC_BASE_MSR 0x1b

#define APIC_REG_LD 0xd0
#define APIC_REG_DF 0xe0
#define APIC_REG_SIV 0xf0
#define APIC_REG_ICR_LOW 0x300
#define APIC_REG_ICR_HIGH 0x310
#define APIC_REG_LVT_TIMER 0x320
#define APIC_REG_LVT_THERMAL 0x330
#define APIC_REG_LVT_PERFORMANCE_COUNTER 0x340
#define APIC_REG_LVT_LINT0 0x350
#define APIC_REG_LVT_LINT1 0x360
#define APIC_REG_LVT_ERR 0x370

extern "C" void apic_spurious_interrupt_entry();

asm(
    ".globl apic_spurious_interrupt_entry \n"
    "apic_spurious_interrupt_entry: \n"
    "    iret\n");

namespace APIC {

class ICRReg
{
    u32 m_reg{0};
public:
    enum DeliveryMode
    {
        Fixed = 0x0,
        LowPriority = 0x1,
        SMI = 0x2,
        NMI = 0x4,
        INIT = 0x5,
        StartUp = 0x6,
    };
    enum DestinationMode
    {
        Physical = 0x0,
        Logical = 0x0,
    };
    enum Level
    {
        DeAssert = 0x0,
        Assert = 0x1
    };
    enum class TriggerMode
    {
        Edge = 0x0,
        Level = 0x1,
    };
    enum DestinationShorthand
    {
        NoShorthand = 0x0,
        Self = 0x1,
        AllIncludingSelf = 0x2,
        AllExcludingSelf = 0x3,
    };

    ICRReg(u8 vector, DeliveryMode delivery_mode, DestinationMode destination_mode, Level level, TriggerMode trigger_mode, DestinationShorthand destination):
        m_reg(vector | (delivery_mode << 8) | (destination_mode << 11) | (level << 14) | (static_cast<u32>(trigger_mode) << 15) | (destination << 18))
    {
    }

    u32 low() const { return m_reg; }
    u32 high() const { return 0; }
};

static volatile u8* g_apic_base = nullptr;

static PhysicalAddress get_base()
{
    u32 lo, hi;
    MSR msr(APIC_BASE_MSR);
    msr.get(lo, hi);
    return PhysicalAddress(lo & 0xfffff000);
}

static void set_base(const PhysicalAddress& base)
{
    u32 hi = 0;
    u32 lo = base.get() | 0x800;
    MSR msr(APIC_BASE_MSR);
    msr.set(lo, hi);
}

static u32 apic_read(u32 off)
{
    return *(volatile u32*)(&g_apic_base[off]);
}

static void apic_write(u32 off, u32 val)
{
    *reinterpret_cast<volatile u32*>(&g_apic_base[off]) = val;
}

static void apic_write_icr(const ICRReg& icr)
{
    apic_write(APIC_REG_ICR_HIGH, icr.high());
    apic_write(APIC_REG_ICR_LOW, icr.low());
}

#define APIC_LVT_MASKED (1 << 15)
#define APIC_LVT_TRIGGER_LEVEL (1 << 14)
#define APIC_LVT(iv, dm) ((iv & 0xff) | ((dm & 0x7) << 8))

asm(
    ".globl apic_ap_start \n"
    ".type apic_ap_start, @function \n"
    "apic_ap_start: \n"
    ".set begin_apic_ap_start, . \n"
    "    jmp apic_ap_start\n" // TODO: implement
    ".set end_apic_ap_start, . \n"
    "\n"
    ".globl apic_ap_start_size \n"
    "apic_ap_start_size: \n"
    ".word end_apic_ap_start - begin_apic_ap_start \n");

extern "C" void apic_ap_start(void);
extern "C" u16 apic_ap_start_size;

bool init()
{
    if (!MSR::have())
        return false;

    // check if we support local apic
    CPUID id(1);
    if ((id.edx() & (1 << 9)) == 0)
        return false;

    PhysicalAddress apic_base = get_base();
    kprintf("Initializing APIC, base: P%x\n", apic_base);
    set_base(apic_base);

    MM.map_for_kernel(VirtualAddress(apic_base.get()), apic_base, true); // Map memory, disable cache!
    g_apic_base = apic_base.as_ptr();
    
    // copy ap init code to P8000
    MM.map_for_kernel(VirtualAddress(0x8000), PhysicalAddress(0x8000));
    memcpy(reinterpret_cast<u8*>(0x8000), reinterpret_cast<const u8*>(apic_ap_start), apic_ap_start_size);
    return true;
}

void enable(u32 cpu)
{
    kprintf("Enabling local APIC for cpu #%u\n", cpu);
    
    // set spurious interrupt vector
    apic_write(APIC_REG_SIV, apic_read(APIC_REG_SIV) | 0x100);
    
    // local destination mode (flat mode)
    apic_write(APIC_REG_DF, 0xf000000);
    
    // set destination id (note that this limits it to 8 cpus)
    apic_write(APIC_REG_LD, (1 << cpu) << 24);
    
    register_interrupt_handler(IRQ_APIC_SPURIOUS, apic_spurious_interrupt_entry);
    
    apic_write(APIC_REG_LVT_TIMER, APIC_LVT(0xff, 0) | APIC_LVT_MASKED);
    apic_write(APIC_REG_LVT_THERMAL, APIC_LVT(0xff, 0) | APIC_LVT_MASKED);
    apic_write(APIC_REG_LVT_PERFORMANCE_COUNTER, APIC_LVT(0xff, 0) | APIC_LVT_MASKED);
    apic_write(APIC_REG_LVT_LINT0, APIC_LVT(0x1f, 7) | APIC_LVT_MASKED);
    apic_write(APIC_REG_LVT_LINT1, APIC_LVT(0xff, 4) | APIC_LVT_TRIGGER_LEVEL); // nmi
    apic_write(APIC_REG_LVT_ERR, APIC_LVT(0xe3, 0) | APIC_LVT_MASKED);
    
    if (cpu == 0) {
        static volatile u32 foo = 0;
        
        // INIT
        apic_write_icr(ICRReg(0, ICRReg::INIT, ICRReg::Physical, ICRReg::Assert, ICRReg::TriggerMode::Edge, ICRReg::AllExcludingSelf));

        for (foo = 0; foo < 0x800000; foo++); // TODO: 10 millisecond delay

        for (int i = 0; i < 2; i++) {
            // SIPI
            apic_write_icr(ICRReg(0x08, ICRReg::StartUp, ICRReg::Physical, ICRReg::Assert, ICRReg::TriggerMode::Edge, ICRReg::AllExcludingSelf)); // start execution at P8000

            for (foo = 0; foo < 0x80000; foo++); // TODO: 200 microsecond delay
        }
    }
}

}