//! Amount and cost formatting.

use super::escape_string;
use crate::{Amount, CostSpec, PriceAnnotation};

/// Format an amount through a config's optional number-display
/// context (#1766).
pub fn format_amount_with(amount: &Amount, config: &super::FormatConfig) -> String {
    format!(
        "{} {}",
        super::render_number(amount.number, amount.currency.as_str(), config),
        amount.currency
    )
}

/// Format a cost specification.
///
/// **Precondition: pre-booking input.** The parser only ever emits
/// `CostNumber::PerUnit` or `CostNumber::Total`, so source-level
/// formatters (`rledger format`) round-trip exactly. The
/// `PerUnitFromTotal` arm is reached only if a caller hands in a
/// post-booking spec — in that case we emit the derived per-unit in
/// single braces (matching Python beancount's post-booking
/// `Position.__str__` output). That collapses the user-written
/// `{{ total }}` source form, so do NOT call this on booked
/// directives if you need the original `{{...}}` to survive.
pub fn format_cost_spec(spec: &CostSpec, config: &super::FormatConfig) -> String {
    // Max 4 elements: amount, date, label, merge.
    let mut parts = Vec::with_capacity(4);

    // Amount (per-unit or total). Currency is required for either
    // shape; the per-unit / total distinction comes from the typed
    // `CostNumber` (post-#1164 the invalid both-set state is
    // unrepresentable). `PerUnitFromTotal` renders in per-unit form
    // to match Python beancount's post-booking output. `Total` uses
    // double braces — pre-fix this short-circuit-returned without
    // emitting date/label/merge, causing `{{1500 USD, 2024-01-15,
    // "lot1"}}` to round-trip as `{{1500 USD}}` (review A-3.9).
    let uses_double_braces = matches!(spec.number, Some(crate::CostNumber::Total { .. }));
    if let Some(curr) = &spec.currency {
        let render = |n| super::render_number(n, curr.as_str(), config);
        match spec.number {
            Some(crate::CostNumber::PerUnit { value: num }) => {
                parts.push(format!("{} {curr}", render(num)));
            }
            Some(crate::CostNumber::PerUnitFromTotal(b)) => {
                parts.push(format!("{} {curr}", render(b.per_unit)));
            }
            Some(crate::CostNumber::Total { value: num }) => {
                parts.push(format!("{} {curr}", render(num)));
            }
            Some(crate::CostNumber::Compound { per_unit, total }) => {
                parts.push(format!("{} # {} {curr}", render(per_unit), render(total)));
            }
            None => {}
        }
    }

    // Date
    if let Some(date) = spec.date {
        parts.push(date.to_string());
    }

    // Label
    if let Some(label) = &spec.label {
        parts.push(format!("\"{}\"", escape_string(label)));
    }

    // Merge marker
    if spec.merge {
        parts.push("*".to_string());
    }

    if uses_double_braces {
        format!("{{{{{}}}}}", parts.join(", "))
    } else {
        format!("{{{}}}", parts.join(", "))
    }
}

/// Format a price annotation through the config's optional
/// number-display context (#1766).
pub fn format_price_annotation(price: &PriceAnnotation, config: &super::FormatConfig) -> String {
    let sigil = price.kind.to_string();
    match &price.amount {
        Some(crate::IncompleteAmount::Complete(amt)) => {
            format!("{sigil} {}", format_amount_with(amt, config))
        }
        Some(inc) => format!("{sigil} {}", super::format_incomplete_amount(inc, config)),
        None => sigil,
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{BookedCost, CostNumber, CostSpec};
    use rust_decimal_macros::dec;

    #[test]
    fn cost_spec_per_unit_renders_single_braces() {
        let spec = CostSpec::empty()
            .with_number(crate::CostNumber::PerUnit { value: dec!(150) })
            .with_currency("USD");
        assert_eq!(
            format_cost_spec(&spec, &crate::format::FormatConfig::default()),
            "{150 USD}"
        );
    }

    #[test]
    fn cost_spec_total_renders_double_braces() {
        let spec = CostSpec::empty()
            .with_number(crate::CostNumber::Total { value: dec!(1500) })
            .with_currency("USD");
        assert_eq!(
            format_cost_spec(&spec, &crate::format::FormatConfig::default()),
            "{{1500 USD}}"
        );
    }

    #[test]
    fn cost_spec_per_unit_from_total_renders_as_per_unit() {
        // Python-compat post-booking rendering: the source `{{...}}`
        // becomes per-unit braces after booking derives a per_unit.
        // This is the load-bearing assertion for matching upstream
        // beancount's `Position.__str__` after booking — the original
        // `{{...}}` form is gone post-booking even in upstream.
        let b = BookedCost::new(dec!(150), dec!(300), dec!(2));
        let spec = CostSpec::empty()
            .with_number(CostNumber::PerUnitFromTotal(b))
            .with_currency("USD");
        assert_eq!(
            format_cost_spec(&spec, &crate::format::FormatConfig::default()),
            "{150 USD}"
        );
    }

    #[test]
    fn cost_spec_empty_renders_braces() {
        let spec = CostSpec::empty();
        assert_eq!(
            format_cost_spec(&spec, &crate::format::FormatConfig::default()),
            "{}"
        );
    }

    #[test]
    fn cost_spec_currency_only_renders_bare() {
        // Pin the existing behavior: `format_cost_spec` only emits
        // currency when a number is present. A currency-only spec
        // renders as `{}` (currency is dropped). This matches Python
        // beancount's `Position.__str__` for currency-only lot
        // matches.
        let spec = CostSpec::empty().with_currency("USD");
        assert_eq!(
            format_cost_spec(&spec, &crate::format::FormatConfig::default()),
            "{}"
        );
    }

    #[test]
    fn cost_spec_total_preserves_date_label_merge() {
        // Pre-A-3.9 the Total arm short-circuited after writing the
        // amount, dropping date/label/merge. A round-trip through the
        // parser would silently lose those fields. Exact-match
        // assertion (review A-4.2) — pins delimiter, order, and
        // whitespace, not just field presence.
        let spec = CostSpec::empty()
            .with_number(CostNumber::Total { value: dec!(1500) })
            .with_currency("USD")
            .with_date(crate::naive_date(2024, 1, 15).unwrap())
            .with_label("lot1")
            .with_merge();
        assert_eq!(
            format_cost_spec(&spec, &crate::format::FormatConfig::default()),
            "{{1500 USD, 2024-01-15, \"lot1\", *}}"
        );
    }

    #[test]
    fn cost_spec_per_unit_preserves_date_label_merge() {
        // Symmetric coverage for the per-unit shape (single braces).
        let spec = CostSpec::empty()
            .with_number(CostNumber::PerUnit { value: dec!(150) })
            .with_currency("USD")
            .with_date(crate::naive_date(2024, 1, 15).unwrap())
            .with_label("lot1")
            .with_merge();
        assert_eq!(
            format_cost_spec(&spec, &crate::format::FormatConfig::default()),
            "{150 USD, 2024-01-15, \"lot1\", *}"
        );
    }
}
