use std::fmt::Write;

/// Everything that can go wrong talking to the instrument.
#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error("serial port: {0}")]
    Serial(#[from] serialport::Error),
    #[error("I/O: {0}")]
    Io(#[from] std::io::Error),
    /// A write command was not acknowledged with `8C <cmd>`.
    #[error("no acknowledge for command 0x{cmd:02X} (got {got})")]
    NoAck { cmd: u8, got: String },
    /// A read command answered with an unexpected header.
    #[error("bad response to command 0x{cmd:02X} (got {got})")]
    BadResponse { cmd: u8, got: String },
    /// A data block ended early.
    #[error("{what} short ({got}/{want} bytes)")]
    Short {
        what: &'static str,
        got: usize,
        want: usize,
    },
    #[error("timeout waiting for measurement data")]
    Timeout,
    /// The cancel flag (Ctrl+C) was raised during a wait.
    #[error("cancelled")]
    Cancelled,
    #[error("HPCS 6500 not found (no serial port with VID 0483 / PID 5741)")]
    NotFound,
    #[error("pcap: {0}")]
    Pcap(String),
}

pub type Result<T, E = Error> = std::result::Result<T, E>;

/// `8c 13 0f` style hex for error messages, `(nothing)` when empty.
pub(crate) fn hex(b: &[u8]) -> String {
    if b.is_empty() {
        return "nothing".into();
    }
    let mut s = String::new();
    for (i, x) in b.iter().take(24).enumerate() {
        if i > 0 {
            s.push(' ');
        }
        let _ = write!(s, "{x:02x}");
    }
    if b.len() > 24 {
        let _ = write!(s, " ... ({} bytes)", b.len());
    }
    s
}