use alloc::string::String;
use log::{debug, info};
use uefi::prelude::*;
use uefi::proto::network::IpAddress;
use uefi::CStr16;
use uefi::{Error, Result};
use uefi_raw::table::runtime::VariableVendor;
use uefi_raw::{Guid, Status};

extern crate alloc;

const HTTP_BOOT_VENDOR: VariableVendor =
    VariableVendor(Guid::parse_or_panic("638a24ce-a0ce-4908-8152-b2a4e8b2f29d"));

pub struct Config {
    pub multicast_group: IpAddress,
    pub multicast_port: u16,
    pub client_uuid: String,
}

fn get_var<'a>(
    runtime_services: &RuntimeServices,
    var_name: &'a CStr16,
    res: &'a mut [u8],
) -> Result<()> {
    match runtime_services.get_variable(var_name, &HTTP_BOOT_VENDOR, res) {
        Err(e) => Err(e),
        Ok(_r) => Ok(()),
    }
}

pub fn read_config(runtime_services: &RuntimeServices) -> Result<Config> {
    info!("Reading EFI configuration from EFI vars");

    let mut conf = Config {
        multicast_group: IpAddress::new_v6([
            0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x01,
        ]),
        multicast_port: 42,
        client_uuid: String::from("24609104-7ec6-423f-b57f-632b99b7566a"),
    };

    let mut port_buf: [u8; 2] = [0; 2]; // port is 16 bytes encoded
    get_var(
        runtime_services,
        cstr16!("HTTP_BOOT_MCAST_PORT"),
        &mut port_buf,
    )?;
    conf.multicast_port = u16::from_ne_bytes(port_buf);
    debug!("Got port {}", conf.multicast_port);

    let mut group_buf: [u8; 16] = [0; 16]; // at most ipv6 is 16 bytes
    get_var(
        runtime_services,
        cstr16!("HTTP_BOOT_MCAST_GROUP"),
        &mut group_buf,
    )?;
    conf.multicast_group = IpAddress::new_v6(group_buf);
    debug!("Got group {:?}", conf.multicast_group);

    let mut uid_buf: [u8; 36] = [0; 36]; // uuid is 36 bytes
    get_var(runtime_services, cstr16!("HTTP_BOOT_UUID"), &mut uid_buf)?;
    conf.client_uuid = match String::from_utf8(uid_buf.to_vec()) {
        Err(_e) => return Err(Error::from(Status::INVALID_PARAMETER)),
        Ok(s) => s,
    };
    debug!("Got uuid {:?}", conf.client_uuid);

    Ok(conf)
}