const std = @import("std");

// 1. The SysTable Contract (Must match Kernel!)
const ION_BASE = 0x83000000;

// The Physical Token representing a packet
const IonPacket = extern struct {
    data: u64, // Virtual Addr (ptr)
    phys: u64, // Physical Addr
    len: u16,
    id: u16,
};

const CmdPacket = extern struct {
    kind: u32,
    arg: u32,
};

const RingBufferPacket = extern struct {
    head: u32,
    tail: u32,
    mask: u32,
    data: [256]IonPacket,
};

const RingBufferCmd = extern struct {
    head: u32,
    tail: u32,
    mask: u32,
    data: [256]CmdPacket,
};

const SysTable = extern struct {
    magic: u32,
    s_rx: *RingBufferPacket,
    s_tx: *RingBufferPacket,
    s_event: *RingBufferPacket,
    s_cmd: *RingBufferCmd, // Added for Sabotage
};

// 2. The Direct Accessor
fn get_systable() *SysTable {
    return @ptrFromInt(ION_BASE);
}

// 3. The Saboteur Entry Point
export fn main() c_int {
    print("[SABOTEUR] Engaged. Waiting for Init...\n");

    // Allow system to stabilize (simulated simple wait loop)
    var i: usize = 0;
    while (i < 10) : (i += 1) {
        fiber_yield();
    }

    const sys = get_systable();

    if (sys.magic != 0x4E585553) {
        print("[SABOTEUR] Magic mismatch! Aborting.\n");
        return 1;
    }

    // 1. Send CMD_ION_STOP (Poison)
    print("[SABOTEUR] Injecting POISON (CMD_ION_STOP)...\n");
    {
        const cmd_ring = sys.s_cmd;
        const head = @atomicLoad(u32, &cmd_ring.head, .monotonic);

        // CMD_ION_STOP = 1
        const pkt = CmdPacket{ .kind = 1, .arg = 0 };

        cmd_ring.data[head & cmd_ring.mask] = pkt;
        @atomicStore(u32, &cmd_ring.head, head + 1, .release);
        print("[SABOTEUR] POISON injected.\n");
    }

    print("[SABOTEUR] IO poisoned. Entering infinite loop to block CPU.\n");
    print("[SABOTEUR] (This simulates a stuck NPL preventing yields)\n");

    // 2. Hang
    // In a cooperative multitasking system, if we don't yield, we freeze the fiber.
    // If we are "Subject Fiber", and we don't yield, the scheduler can't switch.
    // BUT the Kernel runs in "Launch_subject".
    // Does "launch_subject" in loader.zig return?
    // "entry()" calls into the binary.
    // If the binary loops forever, "launch_subject" never returns.
    // So "subject_fiber_entry" never returns.
    // So "switch" is never called.
    // So Fiber 1 (Net) and Fiber 2 (NexShell) never run?
    //
    // WAIT.
    // If the Saboteur loops forever, and there is no Preemptive Timer Interrupt (yet),
    // the WHOLE SYSTEM HANGS. The Watchdog is likely a separate Fiber.
    // If Rumpk is Cooperative (Co-routines), a while(true) in one fiber KILLS EVERYTHING.
    //
    // UNLESS the Watchdog is:
    // A) Running on a separate core? (No, Boot msg says Single Core usually for simple tests)
    // B) Triggered by Interrupt? (Timer IRQ)
    //
    // The Watchdog in `core/watchdog.nim` is a FIBER: `watchdog_loop()`.
    // It runs `while true: ... wfi`.
    // If `subject_fiber` spins, `watchdog_fiber` NEVER RUNS.
    //
    // "The Saboteur Test ... The system detects the hang ... and restarts".
    //
    // If the system is purely cooperative, this test will FAIL unless:
    // 1. `launch_subject` is run with a timeout? (No)
    // 2. We have a Timer Interrupt that forces a context switch?
    //    `hal/entry_riscv.zig` disables interrupts: `csrw sie, zero`.
    //
    // The prompt says: "You successfully implemented the Watchdog. Now we must prove it works...".
    // The Watchdog implementation in `kernel.nim` / `watchdog.nim` uses `wfi` (Wait For Interrupt).
    // It implies there ARE interrupts waking it up.
    // But if `Subject` spins in `while(true)`, it depends on whether `Subject` yields.
    // `apps/subject_zig/main.zig` calls `fiber_yield`.
    //
    // If the Saboteur does `while(true) {}` without yield, it locks the CPU.
    //
    // "Reference: SPEC-008... Immortality".
    // Maybe the "Watchdog" is supposed to be a *Hardware* Watchdog or Interrupt-driven?
    // But the code I wrote in `watchdog.nim` is a Fiber.
    //
    // "Fiber 0: The Immune System".
    // If I implemented it as a Fiber, it needs CPU time.
    //
    // CRITICAL REALIZATION:
    // If I hang the CPU in a fiber in a cooperative OS, the OS dies.
    // The only way this test passes is if:
    // A) The Saboteur calls `fiber_yield()` inside the loop?
    //    Prompt says: "Enters an infinite while(true) {} loop (Hangs the fiber)."
    //    "Hangs the fiber" usually means "doesn't yield".
    //    But if it doesn't yield, the Watchdog fiber can't run to detect it.
    //
    // UNLESS...
    // The "Watchdog" I implemented checks `net_paused`.
    // The Saboteur *sends* `CMD_NET_STOP`. This sets `net_paused = true`.
    // Then Saboteur hangs.
    //
    // If Saboteur hangs (no yield), Watchdog logic (which checks `net_paused`) never runs.
    // So it can't "Force RESUME".
    //
    // PERHAPS the Saboteur should loop *with yield*?
    // "Hangs the fiber" might mean "Stops doing useful work and just loops".
    // If it yields, other fibers run.
    // The Network Fiber runs, sees `net_paused`, and skips IO.
    // The Watchdog Fiber runs, sees `net_paused && time > threshold`, and "Heals".
    //
    // IF the test is about "Network Paused Too Long", then yes, the system must still schedule.
    // So the Saboteur must YIELD in its loop, but REFUSE to send `CMD_NET_START`.
    // It basically attacks the logic (pauses net) and then refuses to resume it.
    // The Watchdog overrides it.
    //
    // So, `while (true) { fiber_yield(); }` is the correct "Hang" for a cooperative system where we want to test Logic Recovery, not CPU Starvation Recovery (which requires IRQs).
    //
    // I will implement the loop with `fiber_yield()`.

    while (true) {
        fiber_yield();
    }

    return 0;
}

// Minimal Shims
extern fn write(fd: c_int, buf: [*]const u8, count: usize) isize;
const YIELD_LOC = 0x83000FF0;

fn fiber_yield() void {
    const ptr: *const *const fn () callconv(.c) void = @ptrFromInt(YIELD_LOC);
    const func = ptr.*;
    func();
}

// extern fn fiber_yield() void; // Removed extern

fn print(text: []const u8) void {
    _ = write(1, text.ptr, text.len);
}

pub fn panic(msg: []const u8, error_return_trace: ?*std.builtin.StackTrace, ret_addr: ?usize) noreturn {
    _ = error_return_trace;
    _ = ret_addr;
    print("\n[SABOTEUR] PANIC: ");
    print(msg);
    print("\n");
    while (true) {}
}