/**
 * ACPI (Advanced Configuration and Power Interface) functionality.
 */
module hulk.acpi;

import hulk.hurl;
import hulk.klog;
import hulk.memory;

struct Acpi
{
    private static uint signature(string s)
    {
        return s[0] | (s[1] << 8) | (s[2] << 16) | (s[3] << 24);
    }

    enum uint APIC_SIGNATURE = signature("APIC");
    enum uint MCFG_SIGNATURE = signature("MCFG");
    enum uint XSDT_SIGNATURE = signature("XSDT");

    static align(4) struct Header
    {
        uint signature;
        uint length;
        ubyte revision;
        ubyte checksum;
        char[6] oemid;
        ulong oemtableid;
        uint oem_revision;
        uint creator_id;
        uint creator_revision;
    }

    static struct XSDT
    {
        Header header;
        /* Table pointers are not ulong-aligned! They begin at offset 36. */
        align(4) ulong[1] tables;
    }

    static struct MADT
    {
        static struct Entry
        {
            enum LOCAL_APIC_ADDRESS_OVERRIDE = 5;

            ubyte type;
            ubyte length;
        }

        Header header;
        uint local_apic_address;
        uint flags;

        void initialize()
        {
            apic_address = local_apic_address;
            const(void) * end = cast(const(void) *)(&this) + header.length;
            const(Entry) * entry = cast(const(Entry) *)(cast(ulong)&this + MADT.sizeof);
            while (entry < end)
            {
                entry = cast(const(Entry) *)(cast(size_t)entry + entry.length);
                if (entry.type == Entry.LOCAL_APIC_ADDRESS_OVERRIDE)
                {
                    /* Found a 64-bit Local APIC Address Override entry. */
                    memcpy(cast(void *)&apic_address, cast(const(void) *)entry + 4u, apic_address.sizeof);
                }
            }
        }
    }

    static struct MCFG
    {
        /* PCI Segment Group Memory Area Descriptor. */
        static struct SGMADesc
        {
            uint[2] base_address_a;
            ushort pci_segment_group_number;
            ubyte start_pci_bus_number;
            ubyte end_pci_bus_number;
            uint _reserved;

            public @property ulong base_address() const
            {
                return base_address_a[0] | (cast(ulong)base_address_a[1] << 32);
            }
        }
        static assert(SGMADesc.sizeof == 16);
        static assert(SGMADesc.alignof == 4);

        Header header;
        uint[2] _reserved;
        SGMADesc[0] sgma_descs;

        size_t n_sgma_descs()
        {
            return (header.length - MCFG.sgma_descs.offsetof) / MCFG.SGMADesc.sizeof;
        }
    }

    public __gshared ulong apic_address;

    public __gshared MADT * madt;

    public __gshared MCFG * mcfg;

    public static void initialize(ulong acpi_xsdt_phys)
    {
        Klog.writefln("\a3Initialize ACPI");

        /* Map the XSDT header. */
        map_table(acpi_xsdt_phys, PAGE_SIZE);
        const(XSDT) * xsdt = cast(const(XSDT) *)acpi_xsdt_phys;
        if (xsdt.header.signature != XSDT_SIGNATURE)
        {
            Klog.fatal_error("XSDT signature invalid");
            return;
        }
        /* Map the entire XSDT. */
        if (xsdt.header.length > PAGE_SIZE)
        {
            map_table(acpi_xsdt_phys, xsdt.header.length);
        }
        size_t n_entries = (xsdt.header.length - xsdt.header.sizeof) / xsdt.tables[0].sizeof;
        for (size_t i = 0u; i < n_entries; i++)
        {
            ulong address = xsdt.tables[i];
            map_table(address, PAGE_SIZE);
            const(Header) * header = cast(const(Header) *)address;
            uint length = header.length;
            if (length > PAGE_SIZE)
            {
                map_table(address, length);
            }
            uint signature = header.signature;
            Klog.writefln("Found ACPI table %08x (%c%c%c%c)",
                    signature,
                    signature & 0xFFu,
                    (signature >> 8u) & 0xFFu,
                    (signature >> 16u) & 0xFFu,
                    (signature >> 24u) & 0xFFu);
            if (signature == APIC_SIGNATURE)
            {
                madt = cast(MADT *)address;
                madt.initialize();
            }
            else if (signature == MCFG_SIGNATURE)
            {
                mcfg = cast(MCFG *)address;
            }
        }
        if (madt == null)
        {
            Klog.fatal_error("MADT table not found");
        }
        if (mcfg == null)
        {
            Klog.fatal_error("MCFG table not found");
        }
    }

    private static void map_table(ulong address, ulong length)
    {
        Hurl.identity_map_range(address, length, PT_WRITABLE | PT_DISABLE_CACHE | PT_NO_EXECUTE);
    }
}