// Rumpk Layer 0: UART Driver
// Minimal serial output for QEMU 'virt' machine
//
// QEMU virt UART: PL011 @ 0x09000000

const UART0_BASE: usize = 0x09000000;

// PL011 Register Offsets
const UARTDR: usize = 0x00; // Data Register
const UARTFR: usize = 0x18; // Flag Register
const UARTFR_TXFF: u32 = 1 << 5; // TX FIFO Full

pub fn init() void {
    // QEMU PL011 is pre-initialized, no setup needed
}

fn write_char(c: u8) void {
    const dr: *volatile u32 = @ptrFromInt(UART0_BASE + UARTDR);
    const fr: *volatile u32 = @ptrFromInt(UART0_BASE + UARTFR);

    // Wait for TX FIFO to have space
    while ((fr.* & UARTFR_TXFF) != 0) {}

    dr.* = c;
}

pub fn write_bytes(bytes: []const u8) void {
    for (bytes) |b| {
        if (b == '\n') {
            write_char('\r');
        }
        write_char(b);
    }
}

pub fn puts(s: []const u8) void {
    write_bytes(s);
}

pub fn putc(c: u8) void {
    if (c == '\n') {
        write_char('\r');
    }
    write_char(c);
}