acc 0.7.0

plaintext double-entry accounting command line tool
Documentation 
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//! Rebalance phase — convert every posting's amount into a target
//! commodity using the journal's PriceDB.
//!
//! Each posting is converted at the rate on its own transaction date
//! (historical valuation). Postings whose commodity has no rate path to
//! `target` stay unchanged — downstream reports show them as remainders
//! in their original commodity.

use crate::indexer::Index;
use crate::parser::located::Located;
use crate::parser::posting::Posting;
use crate::parser::transaction::Transaction;

/// Convert every posting's amount to `target` in place, each at the
/// exchange rate on its own transaction date.
pub fn rebalance(
    transactions: &mut [Located<Transaction>],
    target: &str,
    db: &Index,
) {
    for lt in transactions {
        let lookup_date: String = lt.value.date.to_string();
        for lp in &mut lt.value.postings {
            convert(&mut lp.value, target, db, &lookup_date);
        }
    }
}

fn convert(p: &mut Posting, target: &str, db: &Index, date: &str) {
    let Some(amount) = p.amount.as_mut() else { return };
    if amount.commodity == target {
        return;
    }
    let Some(rate) = db.find(&amount.commodity, target, date) else {
        // No rate path — keep the posting in its original commodity.
        return;
    };
    // `mul_rounded` instead of `*` because inverse-rate lookups from
    // the PriceDB can serve a 28-digit tail which would make strict
    // multiplication overflow the scale.
    amount.value = amount.value.mul_rounded(rate);
    amount.commodity = target.to_string();
}