#![no_std]
#![no_main]

use embassy_executor::Spawner;
use embassy_mcxa::clocks::config::Div8;
use hal::lpuart::{Blocking, Config, Lpuart};
use {defmt_rtt as _, embassy_mcxa as hal, panic_probe as _};

/// Simple helper to write a byte as hex to UART
fn write_hex_byte(uart: &mut Lpuart<'_, Blocking>, byte: u8) {
    const HEX_DIGITS: &[u8] = b"0123456789ABCDEF";
    let _ = uart.write_byte(HEX_DIGITS[(byte >> 4) as usize]);
    let _ = uart.write_byte(HEX_DIGITS[(byte & 0xF) as usize]);
}

#[embassy_executor::main]
async fn main(_spawner: Spawner) {
    let mut cfg = hal::config::Config::default();
    cfg.clock_cfg.sirc.fro_12m_enabled = true;
    cfg.clock_cfg.sirc.fro_lf_div = Some(Div8::no_div());
    let p = hal::init(cfg);

    defmt::info!("boot");

    // Create UART configuration
    let config = Config {
        baudrate_bps: 115_200,
        ..Default::default()
    };

    // Create UART instance using LPUART2 with P2_2 as TX and P2_3 as RX
    let mut uart = Lpuart::new_blocking(
        p.LPUART2, // Peripheral
        p.P2_2,    // TX pin
        p.P2_3,    // RX pin
        config,
    )
    .unwrap();

    // Print welcome message before any async delays to guarantee early console output
    uart.write_str_blocking("\r\n=== MCXA276 UART Echo Demo ===\r\n");
    uart.write_str_blocking("Available commands:\r\n");
    uart.write_str_blocking("  help     - Show this help\r\n");
    uart.write_str_blocking("  echo <text> - Echo back the text\r\n");
    uart.write_str_blocking("  hex <byte> - Display byte in hex (0-255)\r\n");
    uart.write_str_blocking("Type a command: ");

    let mut buffer = [0u8; 64];
    let mut buf_idx = 0;

    loop {
        // Read a byte from UART
        let byte = uart.read_byte_blocking();

        // Echo the character back
        if byte == b'\r' || byte == b'\n' {
            // Enter pressed - process command
            uart.write_str_blocking("\r\n");

            if buf_idx > 0 {
                let command = &buffer[0..buf_idx];

                if command == b"help" {
                    uart.write_str_blocking("Available commands:\r\n");
                    uart.write_str_blocking("  help     - Show this help\r\n");
                    uart.write_str_blocking("  echo <text> - Echo back the text\r\n");
                    uart.write_str_blocking("  hex <byte> - Display byte in hex (0-255)\r\n");
                } else if command.starts_with(b"echo ") && command.len() > 5 {
                    uart.write_str_blocking("Echo: ");
                    uart.write_str_blocking(core::str::from_utf8(&command[5..]).unwrap_or(""));
                    uart.write_str_blocking("\r\n");
                } else if command.starts_with(b"hex ") && command.len() > 4 {
                    // Parse the byte value
                    let num_str = &command[4..];
                    if let Ok(num) = parse_u8(num_str) {
                        uart.write_str_blocking("Hex: 0x");
                        write_hex_byte(&mut uart, num);
                        uart.write_str_blocking("\r\n");
                    } else {
                        uart.write_str_blocking("Invalid number for hex command\r\n");
                    }
                } else if !command.is_empty() {
                    uart.write_str_blocking("Unknown command: ");
                    uart.write_str_blocking(core::str::from_utf8(command).unwrap_or(""));
                    uart.write_str_blocking("\r\n");
                }
            }

            // Reset buffer and prompt
            buf_idx = 0;
            uart.write_str_blocking("Type a command: ");
        } else if byte == 8 || byte == 127 {
            // Backspace
            if buf_idx > 0 {
                buf_idx -= 1;
                uart.write_str_blocking("\x08 \x08"); // Erase character
            }
        } else if buf_idx < buffer.len() - 1 {
            // Regular character
            buffer[buf_idx] = byte;
            buf_idx += 1;
            let _ = uart.write_byte(byte);
        }
    }
}

/// Simple parser for u8 from ASCII bytes
fn parse_u8(bytes: &[u8]) -> Result<u8, ()> {
    let mut result = 0u8;
    for &b in bytes {
        if b.is_ascii_digit() {
            result = result.checked_mul(10).ok_or(())?;
            result = result.checked_add(b - b'0').ok_or(())?;
        } else {
            return Err(());
        }
    }
    Ok(result)
}