//! CSV output for simulation snapshots.

use std::fs::File;
use std::io::{self, BufWriter, Write};
use std::path::Path;

use crate::model::TickRecord;

/// Write records to CSV. If `path` is None, writes to stdout.
///
/// Columns: node_id, commodity_id, supply, demand, price, tick,
///          shadow_intensity, tractus_mark_rate
pub fn write_csv(records: &[TickRecord], path: Option<&Path>) -> io::Result<()> {
    let header =
        "node_id,commodity_id,supply,demand,price,tick,shadow_intensity,tractus_mark_rate\n";

    let write_record = |w: &mut dyn Write, r: &TickRecord| -> io::Result<()> {
        writeln!(
            w,
            "{},{},{:.4},{:.4},{:.4},{},{:.4},{:.6}",
            r.node_id,
            r.commodity_id,
            r.supply,
            r.demand,
            r.price,
            r.tick,
            r.shadow_intensity,
            r.tractus_mark_rate,
        )
    };

    match path {
        Some(p) => {
            let file = File::create(p)?;
            let mut w = BufWriter::new(file);
            write!(w, "{}", header)?;
            for r in records {
                write_record(&mut w, r)?;
            }
            w.flush()
        }
        None => {
            let stdout = io::stdout();
            let mut w = BufWriter::new(stdout.lock());
            write!(w, "{}", header)?;
            for r in records {
                write_record(&mut w, r)?;
            }
            w.flush()
        }
    }
}