// Rumpk Layer 0: The Concrete Foundation
// Markus Maiwald (Architect) | Voxis Forge (AI)
//
// This is the hardware floor. Sets up stack and calls Nim.

const uart = @import("uart.zig");

// =========================================================
// Stack Setup (16KB)
// =========================================================

export var stack_bytes: [16 * 1024]u8 align(16) = undefined;

// =========================================================
// Entry Point (Naked - no prologue)
// =========================================================

export fn _start() callconv(.naked) noreturn {
    // ARM64: Set up stack pointer, then call zig_entry
    asm volatile (
        \\  adrp x0, stack_bytes
        \\  add x0, x0, :lo12:stack_bytes
        \\  add sp, x0, #16384
        \\  bl zig_entry
        \\  b .
    );
    unreachable;
}

// =========================================================
// HAL Exports to Nim (The ABI Contract)
// =========================================================

export fn console_write(ptr: [*]const u8, len: usize) void {
    uart.write_bytes(ptr[0..len]);
}

export fn rumpk_halt() noreturn {
    uart.puts("[Rumpk L0] Halting.\n");
    while (true) {
        asm volatile ("wfi");
    }
}

// =========================================================
// Nim Entry Point (extern)
// =========================================================

extern fn kmain() void;

// =========================================================
// Zig Entry (called from _start)
// =========================================================

export fn zig_entry() void {
    uart.init();
    uart.puts("\n");
    uart.puts("╔═══════════════════════════════════════╗\n");
    uart.puts("║          RUMPK UNIKERNEL v0.1         ║\n");
    uart.puts("║     Layer 0: Zig HAL Initialized      ║\n");
    uart.puts("╚═══════════════════════════════════════╝\n");
    uart.puts("\n");
    uart.puts("[Rumpk L0] Stack: 16KB @ stack_bytes\n");
    uart.puts("[Rumpk L0] UART: 0x09000000 (QEMU virt)\n");
    uart.puts("[Rumpk L0] Handing off to Nim L1...\n");
    uart.puts("\n");

    // THE RUBICON CROSSING
    kmain();

    // If Nim returns, halt
    uart.puts("[Rumpk L0] Nim returned unexpectedly.\n");
    rumpk_halt();
}