//! `arpa/inet.h` implementation.
//!
//! See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/arpa_inet.h.html>.

use core::{
    ptr, slice,
    str::{self, FromStr},
};

use crate::{
    c_str::CStr,
    header::{
        bits_arpainet::ntohl,
        bits_socklen_t::socklen_t,
        errno::{EAFNOSUPPORT, ENOSPC},
        netinet_in::{INADDR_NONE, in_addr, in_addr_t},
        sys_socket::constants::AF_INET,
    },
    platform::{
        self,
        types::{c_char, c_int, c_void},
    },
    raw_cell::RawCell,
};

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/inet_addr.html>.
///
/// # Deprecated
/// The `inet_addr()` function was marked obsolescent in the Open Group Base
/// Specifications Issue 8.
#[deprecated]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn inet_addr(cp: *const c_char) -> in_addr_t {
    let mut val: in_addr = in_addr { s_addr: 0 };

    if unsafe { inet_aton(cp, &raw mut val) } > 0 {
        val.s_addr
    } else {
        INADDR_NONE
    }
}

/// Non-POSIX, see <https://www.man7.org/linux/man-pages/man3/inet_aton.3.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn inet_aton(cp: *const c_char, inp: *mut in_addr) -> c_int {
    let cp_cstr = unsafe { CStr::from_ptr(cp) };
    let mut four_parts_decimal_only = false;
    if cp_cstr.contains(b'.') {
        // 2, 3 or 4 part address
        let parts = unsafe { str::from_utf8_unchecked(cp_cstr.to_bytes()).split('.') };
        let mut count = 0;
        for part in parts {
            if let Some(hex_or_oct) = part.strip_prefix('0')
                && part.len() > 1
            {
                match hex_or_oct.bytes().next() {
                    Some(b'x' | b'X') => todo_skip!(0, "parsing hex values unimplemented"),
                    // TODO: C2Y accept `0o` or `0O` as octal prefixes, C23 and below only use `0`
                    _ => todo_skip!(0, "parsing octal values unimplemented"),
                }
            } else {
                count += 1;
            }
        }
        if count == 4 {
            four_parts_decimal_only = true;
        }
    } else if cp_cstr.len() == 4 {
        // 1 part address (32 bit value to be stored directly into address without byte rearrangement)
        let s_addr_bytes: [u8; 4] = cp_cstr.to_bytes().try_into().expect("guaranteed 4 bytes");
        unsafe {
            (*inp.cast::<in_addr>()).s_addr = in_addr_t::from_ne_bytes(s_addr_bytes);
        }
        return 1; // successful
    }
    if four_parts_decimal_only {
        unsafe { inet_pton(AF_INET, cp, inp.cast::<c_void>()) }
    } else {
        todo_skip!(0, "parsing 2 or more non-decimal values unimplemented");
        // TODO convert octal and hexadecimal parts into decimal and feed into `inet_pton`
        0 // indicates `cp` is an invalid string
    }
}

/// See <https://pubs.opengroup.org/onlinepubs/7908799/xns/inet_lnaof.html>.
///
/// # Deprecation
/// The `inet_lnaof()` function was specified in Networking Services Issue 5,
/// but not in the Open Group Base Specifications Issue 6 and later.
#[deprecated]
#[unsafe(no_mangle)]
pub extern "C" fn inet_lnaof(r#in: in_addr) -> in_addr_t {
    if r#in.s_addr >> 24 < 128 {
        r#in.s_addr & 0xff_ffff
    } else if r#in.s_addr >> 24 < 192 {
        r#in.s_addr & 0xffff
    } else {
        r#in.s_addr & 0xff
    }
}

/// See <https://pubs.opengroup.org/onlinepubs/7908799/xns/inet_makeaddr.html>.
///
/// # Deprecation
/// The `inet_makeaddr()` function was specified in Networking Services Issue
/// 5, but not in the Open Group Base Specifications Issue 6 and later.
#[deprecated]
#[unsafe(no_mangle)]
pub extern "C" fn inet_makeaddr(net: in_addr_t, lna: in_addr_t) -> in_addr {
    let mut output: in_addr = in_addr { s_addr: 0 };

    if net < 256 {
        output.s_addr = lna | net << 24;
    } else if net < 65536 {
        output.s_addr = lna | net << 16;
    } else {
        output.s_addr = lna | net << 8;
    }

    output
}

/// See <https://pubs.opengroup.org/onlinepubs/7908799/xns/inet_netof.html>.
///
/// # Deprecation
/// The `inet_netof()` function was specified in Networking Services Issue 5,
/// but not in the Open Group Base Specifications Issue 6 and later.
#[deprecated]
#[unsafe(no_mangle)]
pub extern "C" fn inet_netof(r#in: in_addr) -> in_addr_t {
    if r#in.s_addr >> 24 < 128 {
        r#in.s_addr & 0xff_ffff
    } else if r#in.s_addr >> 24 < 192 {
        r#in.s_addr & 0xffff
    } else {
        r#in.s_addr & 0xff
    }
}

/// See <https://pubs.opengroup.org/onlinepubs/7908799/xns/inet_network.html>.
///
/// # Deprecation
/// The `inet_network()` function was specified in Networking Services Issue 5,
/// but not in the Open Group Base Specifications Issue 6 and later.
#[deprecated]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn inet_network(cp: *const c_char) -> in_addr_t {
    ntohl(unsafe { inet_addr(cp) })
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/inet_addr.html>.
///
/// # Deprecation
/// The `inet_ntoa()` function was marked obsolescent in the Open Group Base
/// Specifications Issue 8.
#[deprecated]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn inet_ntoa(r#in: in_addr) -> *mut c_char {
    static NTOA_ADDR: RawCell<[c_char; 16]> = RawCell::new([0; 16]);

    unsafe {
        let ptr = inet_ntop(
            AF_INET,
            ptr::from_ref::<in_addr>(&r#in).cast::<c_void>(),
            NTOA_ADDR.unsafe_mut().as_mut_ptr(),
            NTOA_ADDR.unsafe_ref().len() as socklen_t,
        );
        // Mutable pointer is required, inet_ntop returns destination as const pointer
        ptr.cast_mut()
    }
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/inet_ntop.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn inet_ntop(
    af: c_int,
    src: *const c_void,
    dst: *mut c_char,
    size: socklen_t,
) -> *const c_char {
    if af != AF_INET {
        platform::ERRNO.set(EAFNOSUPPORT);
        ptr::null()
    } else if size < 16 {
        platform::ERRNO.set(ENOSPC);
        ptr::null()
    } else {
        let s_addr = unsafe {
            slice::from_raw_parts(
                ptr::from_ref(&(*(src.cast::<in_addr>())).s_addr).cast::<u8>(),
                4,
            )
        };
        let addr = format!("{}.{}.{}.{}\0", s_addr[0], s_addr[1], s_addr[2], s_addr[3]);
        unsafe {
            ptr::copy(addr.as_ptr().cast::<c_char>(), dst, addr.len());
        }
        dst
    }
}

/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/inet_ntop.html>.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn inet_pton(af: c_int, src: *const c_char, dst: *mut c_void) -> c_int {
    if af != AF_INET {
        platform::ERRNO.set(EAFNOSUPPORT);
        -1
    } else {
        let s_addr = unsafe {
            slice::from_raw_parts_mut(
                ptr::from_mut(&mut (*dst.cast::<in_addr>()).s_addr).cast::<u8>(),
                4,
            )
        };
        let src_cstr = unsafe { CStr::from_ptr(src) };
        let mut octets = unsafe { str::from_utf8_unchecked(src_cstr.to_bytes()).split('.') };
        for part in s_addr.iter_mut().take(4) {
            if let Some(n) = octets
                .next()
                .filter(|x| !x.len() > 3)
                .and_then(|x| u8::from_str(x).ok())
            {
                *part = n;
            } else {
                return 0;
            }
        }
        if octets.next().is_none() {
            1 // Success
        } else {
            0
        }
    }
}