#![no_std]
#![no_main]
#![allow(unsafe_code)]

use core::panic::PanicInfo;
use rsnix::uefi::*;

extern crate alloc;

// ---------------------------------------------------------------------------
// Panic handler
// ---------------------------------------------------------------------------

// ---------------------------------------------------------------------------
// Panic handler
// ---------------------------------------------------------------------------

#[panic_handler]
fn panic(info: &PanicInfo) -> ! {
    use core::fmt::Write;

    // A background task (id >= 2) panicked: die gracefully — log it,
    // mark the task done, switch away.  The shell keeps running and
    // `jobs` shows the corpse.  Panics in the shell, idle, ISR context,
    // or before the scheduler exists still halt the whole system.
    if rsnix::sched::is_ready() && !rsnix::sched::in_isr() && rsnix::sched::current() >= 2 {
        let mut buf = [0u8; 192];
        let n = {
            let mut w = rsnix::strbuf::FmtBuf::new(&mut buf);
            let _ = write!(&mut w, "{}", info.message());
            if let Some(loc) = info.location() {
                let _ = write!(&mut w, " at {}:{}", loc.file(), loc.line());
            }
            w.len()
        };
        let msg = core::str::from_utf8(&buf[..n]).unwrap_or("task panic");
        rsnix::sched::abort_current(msg);
    }

    rsnix::serial::write_str("\r\n*** PANIC ***\r\n");
    let _ = write!(&mut rsnix::serial::SerialWriter, "{}\r\n", info.message());
    if let Some(loc) = info.location() {
        let _ = write!(
            &mut rsnix::serial::SerialWriter,
            "  at {}:{}\r\n",
            loc.file(),
            loc.line()
        );
    }
    // Real hardware has no serial console — put the panic on the screen
    // too (white-on-red band), so a pre-shell panic is not a silent
    // blank screen.  The last boot stage is appended so the user can
    // see how far boot got before the crash.
    let mut loc_buf = [0u8; 96];
    let mut msg_buf = [0u8; 128];
    let mut stage_buf = [0u8; 96];
    let loc_n = {
        let mut w = rsnix::strbuf::FmtBuf::new(&mut loc_buf);
        if let Some(loc) = info.location() {
            let _ = write!(&mut w, "at {}:{}", loc.file(), loc.line());
        } else {
            let _ = write!(&mut w, "(no location)");
        }
        w.len()
    };
    let msg_n = {
        let mut w = rsnix::strbuf::FmtBuf::new(&mut msg_buf);
        let _ = write!(&mut w, "{}", info.message());
        w.len()
    };
    let stage_n = {
        let s = rsnix::gop::last_boot_stage();
        let n = s.len().min(stage_buf.len());
        stage_buf[..n].copy_from_slice(&s.as_bytes()[..n]);
        n
    };
    let lines = [
        "*** PANIC ***",
        core::str::from_utf8(&msg_buf[..msg_n]).unwrap_or("?"),
        core::str::from_utf8(&loc_buf[..loc_n]).unwrap_or("?"),
        core::str::from_utf8(&stage_buf[..stage_n]).unwrap_or(""),
    ];
    rsnix::gop::dump_lines(&lines);
    // Persist to the disk so the report survives the reboot on real
    // hardware (no serial console).  Best-effort; heap-free lines.
    rsnix::fs::write_crash_log(&lines);
    loop {
        unsafe {
            core::arch::asm!("cli; hlt");
        }
    }
}

// ---------------------------------------------------------------------------
// EFI entry point
// ---------------------------------------------------------------------------
/// EFI entry point.
///
/// # Safety
///
/// The firmware hands us raw pointers (image handle, system table) that
/// must remain valid for the lifetime of the call — a contract guaranteed
/// by the UEFI loader.
#[unsafe(no_mangle)]
pub unsafe extern "efiapi" fn efi_main(image_handle: Handle, system_table: *mut SystemTable) -> ! {
    let st = unsafe { &mut *system_table };
    let bs = unsafe { &mut *st.boot_services };
    let con_out = unsafe { &mut *st.con_out };

    // Keep the runtime-services table for later (ResetSystem → poweroff).
    rsnix::power::init(st.runtime_services);

    // Capture the kernel's own image range BEFORE ExitBootServices: the
    // heap and page allocators must never hand out the running kernel's
    // code/data/bss pages (a heap allocation landing on the .bss corrupts
    // statics like the FAT ACTIVE_VOL — observed as a dead filesystem in
    // the fault path).
    unsafe {
        let mut li: *mut core::ffi::c_void = core::ptr::null_mut();
        let li_guid = rsnix::uefi::EFI_LOADED_IMAGE_PROTOCOL_GUID;
        if (bs.handle_protocol)(image_handle, &li_guid as *const rsnix::uefi::Guid, &mut li)
            == rsnix::uefi::EFI_SUCCESS
            && !li.is_null()
        {
            let p = &*(li as *const rsnix::uefi::LoadedImageProtocol);
            rsnix::memory::set_kernel_image_range(p.image_base as usize, p.image_size as usize);
            rsnix::serial_println!(
                "mem: kernel image 0x{:x}..0x{:x} ({} KiB) reserved",
                p.image_base as usize,
                p.image_base as usize + p.image_size as usize,
                p.image_size as usize / 1024
            );
        } else {
            rsnix::serial_println!("mem: WARNING — kernel image range unknown");
        }
    }

    // ---- Phase 1: UEFI boot services alive ----

    // Print banner via UEFI console
    unsafe {
        let s = concat!("rsnix v", env!("CARGO_PKG_VERSION"), " booting..\n");
        let bytes = s.as_bytes();
        let mut buf: [u16; 48] = [0; 48];
        for (i, &b) in bytes.iter().enumerate().take(47) {
            buf[i] = b as u16;
        }
        (con_out.output_string)(con_out, buf.as_ptr());
    }

    rsnix::serial::init();
    rsnix::serial_println!("=== rsnix boot ===");

    // Locate GOP (Graphics Output Protocol) *before* the memory map is
    // captured: the heap/page allocators need to know the framebuffer
    // region so they never hand out its pages (some real firmware lists
    // it as conventional memory).
    let mut gop_interface: *mut core::ffi::c_void = core::ptr::null_mut();
    let gop_guid = EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID;
    let gop_result = unsafe {
        (bs.locate_protocol)(
            &gop_guid as *const Guid,
            core::ptr::null_mut(),
            &mut gop_interface,
        )
    };
    if gop_result == EFI_SUCCESS {
        let gop = unsafe { &mut *(gop_interface as *mut GraphicsOutputProtocol) };
        rsnix::gop::peek_fb_region(gop);
    }

    // Stash the memory map
    let map_key = match rsnix::memory::capture_memory_map(bs) {
        Ok(k) => k,
        Err(e) => {
            rsnix::serial_println!("mem: capture_memory_map failed 0x{:x}", e);
            0
        }
    };

    if gop_result == EFI_SUCCESS {
        let gop = unsafe { &mut *(gop_interface as *mut GraphicsOutputProtocol) };
        rsnix::serial_println!("gop: framebuffer found");
        rsnix::gop::init(gop);
    } else {
        rsnix::serial_println!("gop: not found (0x{:x})", gop_result);
    }
    rsnix::gop::boot_marker("rsnix v0.5.10 booting..");
    rsnix::vt::init();
    let (rows, cols) = rsnix::vt::size();
    rsnix::serial_println!("vt: terminal ready ({}x{})", rows, cols);
    let (fw, fh) = rsnix::gop::pixel_dims();
    rsnix::gop::boot_marker(&alloc::format!(
        "rsnix: gop {}x{} vt {}x{} ok",
        fw,
        fh,
        cols,
        rows
    ));
    if let Some((ib, ie)) = rsnix::memory::kernel_image_range() {
        rsnix::gop::boot_marker(&alloc::format!(
            "rsnix: img 0x{:x}-0x{:x} ({} KiB)",
            ib,
            ie,
            (ie - ib) / 1024
        ));
    }

    // ExitBootServices — we now own the machine
    // DEBUG (OptiPlex sim): corrupt the first key so EBS fails once and
    // the retry path (capture_memory_map -> init_heap rebuild) runs — the
    // exact condition that wiped the pre-EBS shadow on real hardware.
    let ebs_first_key = if rsnix::memory::simulate_ebs_failure() {
        map_key ^ 1
    } else {
        map_key
    };
    if unsafe { (bs.exit_boot_services)(image_handle, ebs_first_key) } != EFI_SUCCESS {
        rsnix::serial_println!("WARN: ExitBootServices failed, retrying...");
        match unsafe { rsnix::memory::refresh_and_exit(bs, image_handle) } {
            Ok(_) => {}
            Err(e) => {
                rsnix::serial_println!("FATAL: cannot ExitBootServices (0x{:x})", e);
                loop {
                    unsafe {
                        core::arch::asm!("cli; hlt");
                    }
                }
            }
        }
    }

    // ---- Phase 2: Native mode ----
    rsnix::serial::init();
    rsnix::serial_println!("serial: COM1 115200 8N1");
    rsnix::ps2::init();
    rsnix::serial_println!("ps2: keyboard initialized");
    if rsnix::ps2::mouse_init() {
        rsnix::serial_println!("ps2: mouse ready (IRQ12, stream mode)");
    } else {
        rsnix::serial_println!("ps2: mouse not present");
    }
    if rsnix::gdt::init() {
        rsnix::serial_println!("gdt: own GDT + TSS (IST: page-fault/double-fault)");
    } else {
        rsnix::serial_println!("gdt: kept UEFI GDT (IST fault stacks off)");
    }
    rsnix::interrupts::init();
    rsnix::serial_println!("intr: IDT loaded, PIC remapped, timer ~100 Hz");
    // Prove the timer actually ticks before handing the machine to the
    // scheduler: if the PIC/APIC route is broken on real hardware, the
    // first `hlt` (shell input, idle) never wakes and the system silently
    // freezes.  Spin briefly with interrupts on and require uptime to
    // advance; a dead timer becomes a visible panic instead.
    let t0 = rsnix::interrupts::uptime_ms();
    let mut timer_ok = false;
    for _ in 0..2_000_000 {
        core::hint::spin_loop();
        if rsnix::interrupts::uptime_ms() != t0 {
            timer_ok = true;
            break;
        }
    }
    if timer_ok {
        rsnix::serial_println!("intr: timer verified (uptime advances)");
    } else {
        panic!("timer: no PIT tick within 2M spins — interrupt routing broken");
    }
    rsnix::gop::boot_marker("rsnix: serial+ps2+gdt+intr ok");

    dump_memory_summary();

    if rsnix::memory::self_test() {
        let hs = rsnix::memory::heap_stats();
        rsnix::gop::boot_marker(&alloc::format!(
            "rsnix: heap 0x{:x}-0x{:x} ({} MiB) ok",
            hs.heap_start,
            hs.heap_end,
            hs.heap_size / 1024 / 1024
        ));
        rsnix::serial_println!(
            "heap: self-test OK (0x{:x}..0x{:x} {} KiB free={} KiB)",
            hs.heap_start,
            hs.heap_end,
            hs.heap_size / 1024,
            hs.free_bytes / 1024
        );
    } else {
        rsnix::serial_println!("heap: self-test FAILED");
    }

    if rsnix::memory::init_page_allocator() {
        rsnix::serial_println!("pages: bitmap allocator ready");
    } else {
        rsnix::serial_println!("pages: init FAILED");
    }
    rsnix::gop::boot_marker("rsnix: shadow ok");
    if rsnix::memory::page_self_test() {
        rsnix::serial_println!("pages: self-test OK (alloc/free/runs)");
    } else {
        rsnix::serial_println!("pages: self-test FAILED");
    }

    if rsnix::paging::adopt_tables() {
        rsnix::serial_println!(
            "pg: adopted own page tables (cr3={:#x})",
            rsnix::paging::cr3()
        );
    } else {
        rsnix::serial_println!("pg: adopt_tables FAILED");
    }

    if rsnix::paging::self_test() {
        rsnix::serial_println!("pg: self-test OK (map/unmap/split)");
    } else {
        rsnix::serial_println!("pg: self-test FAILED");
    }

    // Scheduler init needs the page allocator (idle task's stack + guard
    // page) and the adopted page tables, so it runs after the memory
    // subsystem is fully up.  The tick (interrupts::init) is already
    // live, which is what `sleep`/wake scheduling depends on.
    rsnix::sched::init();

    let t = rsnix::rtc::now();
    rsnix::serial_println!(
        "rtc: {}-{:02}-{:02} {:02}:{:02}:{:02}",
        t.year,
        t.month,
        t.day,
        t.hour,
        t.minute,
        t.second
    );
    let devices = rsnix::pci::probe();
    rsnix::serial_println!("pci: {} device(s) on all buses", devices.len());

    // Disk: AHCI SATA driver, then mount every FAT32 volume under /disk/<UID>/.
    if !rsnix::ahci::init() {
        rsnix::serial_println!("ahci: no disk attached");
    }
    rsnix::gop::boot_marker(&alloc::format!(
        "rsnix: ahci {} disk(s)",
        rsnix::ahci::disk_count()
    ));
    rsnix::fat::init(); // prints one line per mounted volume
    rsnix::gop::boot_marker(&alloc::format!(
        "rsnix: fat {} volume(s) mounted",
        rsnix::fat::volume_count()
    ));

    let (dirs, files) = rsnix::fs::init();
    rsnix::serial_println!("fs: vfs ready — {} dirs, {} files", dirs, files);
    let fstest = rsnix::fs::self_test();
    if fstest {
        rsnix::serial_println!("fs: self-test OK (create/read/write/remove)");
    } else {
        rsnix::serial_println!("fs: self-test FAILED");
    }
    rsnix::gop::boot_marker(&alloc::format!(
        "rsnix: fs ok {} dirs/{} files self-test {}",
        dirs,
        files,
        if fstest { "ok" } else { "FAILED" }
    ));

    rsnix::serial_println!("boot: entering shell");
    rsnix::gop::boot_marker("rsnix: boot done — shell");
    // USB (xHCI) / EHCI mouse is polled; fall back to PS/2 if no USB mouse.
    // Each stage draws its own marker: a real-hardware freeze leaves the
    // last completed stage on the screen, so the hang point is identifiable
    // without a serial console.
    // STOPGAP: skip ALL USB host-controller init so the BIOS USB-Legacy SMI
    // keeps emulating the keyboard/mouse on the 8042 (PS/2).  Resetting the
    // EHCI without a completed USBLEGSUP ownership handshake killed the
    // firmware's legacy emulation, leaving the OptiPlex 7010 with zero input.
    // While NO_USB is set, USB input is served entirely by the BIOS (IRQ1/
    // IRQ12 + our PS/2 driver) and no EHCI/xHCI/UHCI register is touched.
    const NO_USB: bool = false;
    rsnix::gop::boot_marker("rsnix: usb init");
    if !NO_USB {
        rsnix::usb::init();
    } else {
        rsnix::serial_println!("usb: init skipped (stopgap) — BIOS USB-Legacy owns input");
    }
    rsnix::gop::boot_marker("rsnix: ehci init");
    if !NO_USB {
        rsnix::ehci::init();
    } else {
        rsnix::serial_println!("ehci: init skipped (stopgap)");
    }
    rsnix::gop::boot_marker("rsnix: uhci init");
    if !NO_USB {
        rsnix::uhci::init();
    } else {
        rsnix::serial_println!("uhci: init skipped (stopgap)");
    }
    if rsnix::ps2::mouse_present()
        || rsnix::usb::controller_up()
        || rsnix::ehci::controller_up()
        || rsnix::uhci::controller_up()
    {
        rsnix::gop::boot_marker("rsnix: cursor spawn");
        rsnix::cursor::spawn();
    } else {
        rsnix::serial_println!("cursor: no mouse — overlay disabled");
    }
    rsnix::gop::boot_marker("rsnix: shell run");
    // The shell REPL is about to start: from here on task 0 may legitimately
    // park in poll_key with a fixed frame, so the watchdog's boot-phase spin
    // rule for task 0 is disarmed (boot-phase hangs already panicked).
    rsnix::sched::mark_shell_running();
    // Windowed GUI: initialise the window manager and its input pump.
    // The console (vt) stays layer 0; GUI apps are windows composited on top.
    rsnix::wm::init();
    {
        let t = rsnix::vt::home_terminal();
        let (buf, w, h) = t.window_params();
        let id = rsnix::wm::create_home_window(buf as *mut u32, w, h);
        t.set_window(id);
    }
    rsnix::wm::spawn_input_pump();
    // Register the terminal-spawn callback so F1 in the WM creates a
    // windowed shell.  The task lives here in rsdos (which depends on
    // both rsnix and shell).
    unsafe {
        rsnix::wm::SPAWN_TERMINAL_CB = Some(terminal_task);
    }

    shell::run();
}

/// Callback registered with the WM for F1.  Stores the spawn arguments
/// and spawns the terminal task (can't block the input pump).
static mut TERM_TITLE_BUF: [u8; 64] = [0u8; 64];
static mut TERM_TITLE_LEN: usize = 0;
static mut TERM_W: usize = 0;
static mut TERM_H: usize = 0;

fn terminal_task(title: &str, w: usize, h: usize) {
    rsnix::serial_println!("term: callback invoked title='{}' {}x{}", title, w, h);
    // Copy title into static buffer so the spawned task can see it.
    let bytes = title.as_bytes();
    let n = bytes.len().min(63);
    unsafe {
        TERM_TITLE_BUF[..n].copy_from_slice(&bytes[..n]);
        TERM_TITLE_BUF[n] = 0;
        TERM_TITLE_LEN = n;
        TERM_W = w;
        TERM_H = h;
    }
    match rsnix::sched::spawn(terminal_entry, "term") {
        Some(id) => rsnix::serial_println!("term: spawned task {}", id),
        None => rsnix::serial_println!("term: spawn FAILED"),
    }
}

/// The actual terminal task — reads args from statics, creates a window,
/// and runs the shell.
fn terminal_entry() {
    use rsnix::vt::Terminal;
    let (w, h) = unsafe { (TERM_W, TERM_H) };
    let title = unsafe { core::str::from_utf8_unchecked(&TERM_TITLE_BUF[..TERM_TITLE_LEN]) };
    rsnix::serial_println!("term: entry title='{}' {}x{}", title, w, h);
    let Some(win_id) = rsnix::wm::create_window(title, w, h) else {
        rsnix::serial_println!("term: create_window FAILED");
        return;
    };
    rsnix::serial_println!("term: win_id={}", win_id);
    let Some((buf, ww, hh)) = rsnix::wm::buffer(win_id) else {
        rsnix::serial_println!("term: buffer FAILED");
        rsnix::wm::destroy(win_id);
        return;
    };
    rsnix::serial_println!("term: buffer {:?} {}x{}", buf as *mut u32, ww, hh);

    // Build a Terminal that renders into the WM-allocated buffer.
    let mut term = Terminal::from_buffer(buf as *mut u32, ww, hh);
    term.set_window(win_id);
    rsnix::serial_println!("term: terminal created, entering shell");

    // Redirect all vt output (gop_print!, put_char, …) to this terminal.
    rsnix::vt::set_active(&mut term as *mut Terminal);

    // Run the shell — it owns input, line editing, and command execution.
    shell::run_windowed();

    // Shell exited (^D or window close).  Clean up.
    rsnix::serial_println!("term: shell exited, cleaning up");
    rsnix::vt::set_active(core::ptr::null_mut());
    drop(term);
    rsnix::wm::destroy(win_id);
    rsnix::serial_println!("term: done");
}

// ---------------------------------------------------------------------------
// Print a memory summary from the stashed memory map
// ---------------------------------------------------------------------------
fn dump_memory_summary() {
    let (map, key) = rsnix::memory::get_map();
    let mut conventional_4k = 0u64;
    let mut addr_space_4k = 0u64;
    for desc in map.iter() {
        let pages = desc.number_of_pages;
        addr_space_4k += pages;
        if desc.kind == 7 {
            conventional_4k += pages;
        }
    }
    rsnix::serial_println!(
        "mem: {} entries, key=0x{:x}, usable: {} KB ({} MB)",
        map.len(),
        key,
        conventional_4k * 4,
        (conventional_4k * 4) / 1024,
    );
    rsnix::serial_println!(
        "mem: address space: {} MB (incl. PCIe MMIO)",
        (addr_space_4k * 4) / 1024,
    );
}