/// Inline hooks on ws2_32!recv and ws2_32!send only.
///
/// WSARecv/WSASend are NOT hooked — their prologues contain RIP-relative
/// (short conditional jump) instructions that would break trampolines.
/// FIFA's LSX client uses plain recv/send, which is confirmed by prior logs.
///
/// Trampolines allow multiple threads to call the original function
/// concurrently without locks or unhook/rehook races.
use core::sync::atomic::{AtomicUsize, Ordering};

unsafe fn write_jmp(target: *mut u8, dest: u64) {
    use windows_sys::Win32::System::Memory::{VirtualProtect, PAGE_EXECUTE_READWRITE};
    let mut old: u32 = 0;
    VirtualProtect(target as _, 14, PAGE_EXECUTE_READWRITE, &mut old);
    target.write(0xFF); target.add(1).write(0x25);
    (target.add(2) as *mut u32).write(0);
    (target.add(6) as *mut u64).write(dest);
    VirtualProtect(target as _, 14, old, &mut old);
}

unsafe fn make_trampoline(orig: *mut u8, name: &str) -> Option<usize> {
    use windows_sys::Win32::System::Memory::{
        VirtualAlloc, MEM_COMMIT, MEM_RESERVE, PAGE_EXECUTE_READWRITE,
    };
    // Log prologue so we can diagnose if trampolines misbehave
    let bytes: [u8; 14] = core::array::from_fn(|i| *orig.add(i));
    let hex: String = bytes.iter().map(|b| format!("{b:02x} ")).collect();
    crate::write_log(&format!("recv_hook: {name} prologue {hex}\n"));

    // Walk instruction boundaries to find relative branches.
    // Byte-by-byte scanning mis-identifies immediate operands (e.g. `sub rsp, 0x70`)
    // as jump opcodes, so we must parse properly.
    if has_rip_relative_branch(&bytes) {
        crate::write_log(&format!("recv_hook: {name} has relative branch in prologue, skipping trampoline\n"));
        return None;
    }

    let mem = VirtualAlloc(
        core::ptr::null_mut(), 32,
        MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE,
    );
    if mem.is_null() { crate::write_log("recv_hook: VirtualAlloc failed\n"); return None; }

    let t = mem as *mut u8;
    core::ptr::copy_nonoverlapping(orig, t, 14);
    // JMP [RIP+0] → orig+14
    let cont = (orig as u64) + 14;
    t.add(14).write(0xFF); t.add(15).write(0x25);
    (t.add(16) as *mut u32).write(0);
    (t.add(20) as *mut u64).write(cont);
    Some(t as usize)
}

/// Walk x86-64 instruction boundaries and return true if any relative branch
/// (JE/JNE/JCC rel8, JMP rel8, JMP/CALL rel32, Jcc rel32) is encountered.
/// Correctly skips over immediate operands so `sub rsp, 0x70` doesn't trigger.
fn has_rip_relative_branch(bytes: &[u8]) -> bool {
    let mut pos = 0;
    while pos < bytes.len() {
        let (len, branch) = decode_instr_len(&bytes[pos..]);
        if branch { return true; }
        if len == 0 { break; } // unknown/truncated — stop safely
        pos += len;
    }
    false
}

fn modrm_extra(modrm: u8) -> usize {
    let md = (modrm >> 6) & 3;
    let rm = modrm & 7;
    match md {
        0 => if rm == 5 { 4 } else if rm == 4 { 1 } else { 0 },
        1 => if rm == 4 { 2 } else { 1 },
        2 => if rm == 4 { 5 } else { 4 },
        _ => 0,
    }
}

/// Returns (instruction_length_in_bytes, is_rip_relative_branch).
/// Returns (0, false) for unknown/truncated.
fn decode_instr_len(b: &[u8]) -> (usize, bool) {
    if b.is_empty() { return (0, false); }
    let mut i = 0;
    // Legacy prefixes
    while let Some(&p) = b.get(i) {
        if matches!(p, 0x66 | 0x67 | 0xF0 | 0xF2 | 0xF3) { i += 1; } else { break; }
    }
    // REX prefix (40–4F)
    if b.get(i).copied().map(|x| (0x40..=0x4F).contains(&x)).unwrap_or(false) { i += 1; }

    let op = match b.get(i) { Some(&x) => x, None => return (0, false) };
    i += 1;

    match op {
        // push/pop reg (50-5F): no extra bytes
        0x50..=0x5F => (i, false),
        // nop
        0x90 => (i, false),
        // Short Jcc (70-7F): 1 byte operand, IS a relative branch
        x if (0x70..=0x7F).contains(&x) => (i + 1, true),
        // JMP rel8, JMP rel32, CALL rel32
        0xEB => (i + 1, true),
        0xE9 | 0xE8 => (i + 4, true),
        // 0F prefix
        0x0F => {
            let op2 = match b.get(i) { Some(&x) => x, None => return (0, false) };
            i += 1;
            if (0x80..=0x8F).contains(&op2) { return (i + 4, true); } // Jcc rel32
            // Most 0F XX: ModRM
            let modrm = match b.get(i) { Some(&x) => x, None => return (0, false) };
            (i + 1 + modrm_extra(modrm), false)
        }
        // Instructions with ModRM only (no immediate)
        0x85 | 0x87 | 0x88 | 0x89 | 0x8A | 0x8B | 0x8C | 0x8D | 0x8E | 0x8F |
        0x01 | 0x03 | 0x09 | 0x0B | 0x11 | 0x13 | 0x21 | 0x23 | 0x29 | 0x2B |
        0x31 | 0x33 | 0x39 | 0x3B | 0xD3 | 0xFF | 0xF7 => {
            let modrm = match b.get(i) { Some(&x) => x, None => return (0, false) };
            (i + 1 + modrm_extra(modrm), false)
        }
        // ModRM + imm8
        0x6B | 0x80 | 0x83 | 0xC0 | 0xC1 | 0xC6 => {
            let modrm = match b.get(i) { Some(&x) => x, None => return (0, false) };
            (i + 1 + modrm_extra(modrm) + 1, false)
        }
        // ModRM + imm32
        0x69 | 0x81 | 0xC7 => {
            let modrm = match b.get(i) { Some(&x) => x, None => return (0, false) };
            (i + 1 + modrm_extra(modrm) + 4, false)
        }
        // MOV reg, imm8/imm32
        0xB0..=0xB7 => (i + 1, false),
        0xB8..=0xBF => (i + 4, false),
        // PUSH imm
        0x6A => (i + 1, false),
        0x68 => (i + 4, false),
        // RET
        0xC2 => (i + 2, false),
        0xC3 => (i, false),
        _ => (0, false), // unknown — stop
    }
}

unsafe fn get_fn(dll: &[u8], sym: &[u8]) -> Option<*mut u8> {
    use windows_sys::Win32::System::LibraryLoader::{GetModuleHandleA, GetProcAddress};
    let h = GetModuleHandleA(dll.as_ptr());
    if h.is_null() { return None; }
    GetProcAddress(h, sym.as_ptr()).map(|f| f as *mut u8)
}

// ─── recv ──────────────────────────────────────────────────────────────────────

static RECV_TRAMPOLINE: AtomicUsize = AtomicUsize::new(0);

pub unsafe extern "system" fn hooked_recv(s: usize, buf: *mut u8, len: i32, flags: i32) -> i32 {
    if crate::lsx::is_lsx(s) {
        return crate::lsx::on_recv(s, buf, len);
    }
    let t = RECV_TRAMPOLINE.load(Ordering::Relaxed);
    if t == 0 { return -1; }
    let f: unsafe extern "system" fn(usize, *mut u8, i32, i32) -> i32 = core::mem::transmute(t);
    f(s, buf, len, flags)
}

pub unsafe fn install_recv_hook() -> bool {
    let ptr = match get_fn(b"ws2_32.dll\0", b"recv\0") { Some(p) => p, None => return false };
    match make_trampoline(ptr, "recv") {
        Some(t) => { RECV_TRAMPOLINE.store(t, Ordering::Relaxed); }
        None    => { crate::write_log("recv_hook: recv trampoline failed, hook skipped\n"); return false; }
    }
    write_jmp(ptr, hooked_recv as u64);
    true
}

// ─── send ──────────────────────────────────────────────────────────────────────

static SEND_TRAMPOLINE: AtomicUsize = AtomicUsize::new(0);

pub unsafe extern "system" fn hooked_send(s: usize, buf: *const u8, len: i32, flags: i32) -> i32 {
    if crate::lsx::is_lsx(s) {
        return crate::lsx::on_send(s, buf, len);
    }
    let t = SEND_TRAMPOLINE.load(Ordering::Relaxed);
    if t == 0 { return -1; }
    let f: unsafe extern "system" fn(usize, *const u8, i32, i32) -> i32 = core::mem::transmute(t);
    f(s, buf, len, flags)
}

pub unsafe fn install_send_hook() -> bool {
    let ptr = match get_fn(b"ws2_32.dll\0", b"send\0") { Some(p) => p, None => return false };
    match make_trampoline(ptr, "send") {
        Some(t) => { SEND_TRAMPOLINE.store(t, Ordering::Relaxed); }
        None    => { crate::write_log("recv_hook: send trampoline failed, hook skipped\n"); return false; }
    }
    write_jmp(ptr, hooked_send as u64);
    true
}