use crate::{sdt::SdtHeader, Acpi, AcpiError, AcpiHandler, GenericAddress, PhysicalMapping};

/// Represents the Fixed ACPI Description Table (FADT). This table contains various fixed hardware
/// details, such as the addresses of the hardware register blocks. It also contains a pointer to
/// the Differentiated Definition Block (DSDT).
///
/// In cases where the FADT contains both a 32-bit and 64-bit field for the same address, we should
/// always prefer the 64-bit one. Only if it's zero or the CPU will not allow us to access that
/// address should the 32-bit one be used.
#[repr(C, packed)]
pub struct Fadt {
    header: SdtHeader,

    firmware_ctrl: u32,
    dsdt_address: u32,

    // used in acpi 1.0; compatibility only, should be zero
    reserved: u8,

    preferred_pm_profile: u8,
    sci_interrupt: u16,
    smi_cmd_port: u32,
    acpi_enable: u8,
    acpi_disable: u8,
    s4bios_req: u8,
    pstate_control: u8,
    pm1a_event_block: u32,
    pm1b_event_block: u32,
    pm1a_control_block: u32,
    pm1b_control_block: u32,
    pm2_control_block: u32,
    pm_timer_block: u32,
    gpe0_block: u32,
    gpe1_block: u32,
    pm1_event_length: u8,
    pm1_control_length: u8,
    pm2_control_length: u8,
    pm_timer_length: u8,
    gpe0_block_length: u8,
    gpe1_block_length: u8,
    gpe1_base: u8,
    c_state_control: u8,
    worst_c2_latency: u16,
    worst_c3_latency: u16,
    flush_size: u16,
    flush_stride: u16,
    duty_offset: u8,
    duty_width: u8,
    day_alarm: u8,
    month_alarm: u8,
    century: u8,
    iapc_boot_arch: u16,
    reserved2: u8, // must be 0
    flags: u32,
    reset_reg: GenericAddress,
    reset_value: u8,
    arm_boot_arch: u16,
    fadt_minor_version: u8,
    x_firmware_control: u64,
    x_dsdt_address: u64,
    x_pm1a_event_block: GenericAddress,
    x_pm1b_event_block: GenericAddress,
    x_pm1a_control_block: GenericAddress,
    x_pm1b_control_block: GenericAddress,
    x_pm2_control_block: GenericAddress,
    x_pm_timer_block: GenericAddress,
    x_gpe0_block: GenericAddress,
    x_gpe1_block: GenericAddress,
    sleep_control_reg: GenericAddress,
    sleep_status_reg: GenericAddress,
    hypervisor_vendor_id: u64,
}

pub(crate) fn parse_fadt<H>(
    acpi: &mut Acpi,
    handler: &mut H,
    mapping: &PhysicalMapping<Fadt>,
) -> Result<(), AcpiError>
where
    H: AcpiHandler,
{
    let fadt = &*mapping;
    fadt.header.validate(b"FACP")?;

    // TODO more generic typesafe way of accessing the x_ fields
    acpi.dsdt_address = Some(if fadt.header.revision() > 1 && fadt.x_dsdt_address != 0 {
        fadt.x_dsdt_address as usize
    } else {
        fadt.dsdt_address as usize
    });

    Ok(())
}