const lib = @import("lib");
const log = lib.log;
const assert = lib.assert;
const birth = @import("birth");
const user = @import("user");

const FPU = birth.arch.FPU;
const Registers = birth.arch.Registers;
const RegisterArena = birth.arch.RegisterArena;

const VirtualAddress = lib.VirtualAddress;

const PhysicalMemoryRegion = user.PhysicalMemoryRegion;
const PhysicalMap = user.PhysicalMap;
const SlotAllocator = user.SlotAllocator;
const Thread = user.Thread;
const VirtualAddressSpace = user.VirtualAddressSpace;

pub const Scheduler = extern struct {
    common: birth.arch.UserScheduler,
    generic: user.Scheduler,

    pub fn initDisabled(scheduler: *Scheduler) void {
        _ = scheduler;
        // TODO:
        // *set entry points?
        // *set tls registers?
    }

    pub noinline fn restore(scheduler: *Scheduler, register_arena: *const RegisterArena) noreturn {
        assert(scheduler.common.generic.disabled);
        assert(scheduler.common.generic.has_work);

        assert(register_arena.registers.rip > lib.arch.valid_page_sizes[0]);
        assert(register_arena.registers.rflags.IF and register_arena.registers.rflags.reserved0);

        register_arena.contextSwitch();
    }
};

// CRT0
pub fn _start() callconv(.Naked) noreturn {
    asm volatile (
        \\push %rbp
        \\jmp *%[startFunction]
        :
        : [startFunction] "r" (user.start),
    );
}

pub inline fn setInitialState(register_arena: *RegisterArena, entry: VirtualAddress, stack_virtual_address: VirtualAddress, arguments: birth.syscall.Arguments) void {
    assert(stack_virtual_address.value() > lib.arch.valid_page_sizes[0]);
    assert(lib.isAligned(stack_virtual_address.value(), lib.arch.stack_alignment));
    var stack_address = stack_virtual_address;
    // x86_64 ABI
    stack_address.subOffset(@sizeOf(usize));

    register_arena.registers.rip = entry.value();
    register_arena.registers.rsp = stack_address.value();
    register_arena.registers.rflags = .{ .IF = true };
    register_arena.registers.rdi = arguments[0];
    register_arena.registers.rsi = arguments[1];
    register_arena.registers.rdx = arguments[2];
    register_arena.registers.rcx = arguments[3];
    register_arena.registers.r8 = arguments[4];
    register_arena.registers.r9 = arguments[5];

    register_arena.fpu = lib.zeroes(FPU);
    // register_arena.fpu.fcw = 0x037f;
    register_arena.fpu.fcw = 0x1f80;
}

pub inline fn maybeCurrentScheduler() ?*user.Scheduler {
    return asm volatile (
        \\mov %fs:0, %[user_scheduler]
        : [user_scheduler] "=r" (-> ?*user.Scheduler),
        :
        : "memory"
    );
}

pub inline fn currentScheduler() *user.Scheduler {
    const result = maybeCurrentScheduler().?;
    return result;
}

/// This is an interface to user.PhysicalMap, providing the architecture-specific functionality
pub const PhysicalMapInterface = struct {
    pub fn determineAddress(physical_map: *PhysicalMap, physical_memory_region: PhysicalMemoryRegion, alignment: usize) !VirtualAddress {
        _ = physical_memory_region;
        _ = alignment;
        assert(physical_map.virtual_address_space.regions != null);
        log.debug("PMap: 0x{x}", .{@intFromPtr(physical_map.virtual_address_space.regions)});
        log.debug("PMap: {?}", .{physical_map.virtual_address_space.regions});
        @panic("TODO: PhysicalMapInterface.determineAddress");
    }

    pub fn initializeCurrent(physical_map: *PhysicalMap) !void {
        _ = physical_map;
        log.warn("TODO: PhysicalMapInterface.initializeCurrent", .{});
    }

    pub fn init(virtual_address_space: *VirtualAddressSpace, page_level: u3, slot_allocator: *SlotAllocator) !PhysicalMap {
        var result = PhysicalMap{
            .virtual_address_space = virtual_address_space,
            .slot_allocator = slot_allocator,
        };
        _ = page_level;

        try result.initPageTableManagement();

        @panic("TODO: PhysicalMap.init");
    }
};