/*
 * Copyright (c) 2022, Timon Kruiper <timonkruiper@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <Kernel/Arch/Interrupts.h>
#include <Kernel/Arch/aarch64/InterruptManagement.h>
#include <Kernel/Interrupts/GenericInterruptHandler.h>
#include <Kernel/Interrupts/SharedIRQHandler.h>
#include <Kernel/Interrupts/UnhandledInterruptHandler.h>

struct TrapFrame;

namespace Kernel {

static Array<GenericInterruptHandler*, 64> s_interrupt_handlers;

extern "C" void handle_interrupt(TrapFrame const* const);
extern "C" void handle_interrupt(TrapFrame const* const)
{
    for (auto& interrupt_controller : InterruptManagement::the().controllers()) {
        auto pending_interrupts = interrupt_controller->pending_interrupts();

        // TODO: Add these interrupts as a source of entropy for randomness.
        u8 irq = 0;
        while (pending_interrupts) {
            if ((pending_interrupts & 0b1) != 0b1) {
                irq += 1;
                pending_interrupts >>= 1;
                continue;
            }

            // TODO: Consider not passing the RegisterState into the handle_interrupt()
            //       function, since no IRQHandler seems to be using the registers.
            RegisterState regs {};

            auto* handler = s_interrupt_handlers[irq];
            VERIFY(handler);
            handler->increment_invoking_counter();
            handler->handle_interrupt(regs);
            handler->eoi();

            irq += 1;
            pending_interrupts >>= 1;
        }
    }
}

// FIXME: Share the code below with Arch/x86/common/Interrupts.cpp
//        While refactoring, the interrupt handlers can also be moved into the InterruptManagement class.
GenericInterruptHandler& get_interrupt_handler(u8 interrupt_number)
{
    auto*& handler_slot = s_interrupt_handlers[interrupt_number];
    VERIFY(handler_slot != nullptr);
    return *handler_slot;
}

static void revert_to_unused_handler(u8 interrupt_number)
{
    auto handler = new UnhandledInterruptHandler(interrupt_number);
    handler->register_interrupt_handler();
}

void register_generic_interrupt_handler(u8 interrupt_number, GenericInterruptHandler& handler)
{
    auto*& handler_slot = s_interrupt_handlers[interrupt_number];
    if (handler_slot != nullptr) {
        if (handler_slot->type() == HandlerType::UnhandledInterruptHandler) {
            if (handler_slot) {
                auto* unhandled_handler = static_cast<UnhandledInterruptHandler*>(handler_slot);
                unhandled_handler->unregister_interrupt_handler();
                delete unhandled_handler;
            }
            handler_slot = &handler;
            return;
        }
        if (handler_slot->is_shared_handler() && !handler_slot->is_sharing_with_others()) {
            VERIFY(handler_slot->type() == HandlerType::SharedIRQHandler);
            static_cast<SharedIRQHandler*>(handler_slot)->register_handler(handler);
            return;
        }
        if (!handler_slot->is_shared_handler()) {
            if (handler_slot->type() == HandlerType::SpuriousInterruptHandler) {
                // FIXME: Add support for spurious interrupts on aarch64
                VERIFY_NOT_REACHED();
            }
            VERIFY(handler_slot->type() == HandlerType::IRQHandler);
            auto& previous_handler = *handler_slot;
            handler_slot = nullptr;
            SharedIRQHandler::initialize(interrupt_number);
            VERIFY(handler_slot);
            static_cast<SharedIRQHandler*>(handler_slot)->register_handler(previous_handler);
            static_cast<SharedIRQHandler*>(handler_slot)->register_handler(handler);
            return;
        }
        VERIFY_NOT_REACHED();
    } else {
        handler_slot = &handler;
    }
}

void unregister_generic_interrupt_handler(u8 interrupt_number, GenericInterruptHandler& handler)
{
    auto*& handler_slot = s_interrupt_handlers[interrupt_number];
    VERIFY(handler_slot != nullptr);
    if (handler_slot->type() == HandlerType::UnhandledInterruptHandler) {
        return;
    }
    if (handler_slot->is_shared_handler() && !handler_slot->is_sharing_with_others()) {
        VERIFY(handler_slot->type() == HandlerType::SharedIRQHandler);
        auto* shared_handler = static_cast<SharedIRQHandler*>(handler_slot);
        shared_handler->unregister_handler(handler);
        if (!shared_handler->sharing_devices_count()) {
            handler_slot = nullptr;
            revert_to_unused_handler(interrupt_number);
        }
        return;
    }
    if (!handler_slot->is_shared_handler()) {
        VERIFY(handler_slot->type() == HandlerType::IRQHandler);
        handler_slot = nullptr;
        revert_to_unused_handler(interrupt_number);
        return;
    }
}

void initialize_interrupts()
{
    for (u8 i = 0; i < s_interrupt_handlers.size(); ++i) {
        auto* handler = new UnhandledInterruptHandler(i);
        handler->register_interrupt_handler();
    }
}

}