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Merged
shsms merged 2 commits into from
Jun 24, 2025
Merged

Return Formulas from formula generators instead of Strings #10

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aa32718
Implement a `Formula` type for representing generated formulas
shsms Jun 24, 2025
8f60f27
Update the formula generators to return `Formula`s and not `String`s
shsms Jun 24, 2025
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1 change: 1 addition & 0 deletions src/graph.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@ mod formulas;
pub mod iterators;

use crate::{ComponentGraphConfig, Edge, Node};
pub use formulas::Formula;
use petgraph::graph::{DiGraph, NodeIndex};
use std::collections::HashMap;

Expand Down
19 changes: 11 additions & 8 deletions src/graph/formulas.rs
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Expand Up @@ -12,58 +12,61 @@ use crate::Node;

mod expr;
mod fallback;
mod formula;
mod generators;
mod traversal;

pub use formula::Formula;

/// Formulas for various microgrid metrics.
impl<N, E> ComponentGraph<N, E>
where
N: Node,
E: Edge,
{
/// Returns a string representing the consumer formula for the graph.
pub fn consumer_formula(&self) -> Result<String, Error> {
pub fn consumer_formula(&self) -> Result<Formula, Error> {
generators::consumer::ConsumerFormulaBuilder::try_new(self)?.build()
}

/// Returns a string representing the grid formula for the graph.
pub fn grid_formula(&self) -> Result<String, Error> {
pub fn grid_formula(&self) -> Result<Formula, Error> {
generators::grid::GridFormulaBuilder::try_new(self)?.build()
}

/// Returns a string representing the producer formula for the graph.
pub fn producer_formula(&self) -> Result<String, Error> {
pub fn producer_formula(&self) -> Result<Formula, Error> {
generators::producer::ProducerFormulaBuilder::try_new(self)?.build()
}

/// Returns a string representing the battery formula for the graph.
pub fn battery_formula(&self, battery_ids: Option<BTreeSet<u64>>) -> Result<String, Error> {
pub fn battery_formula(&self, battery_ids: Option<BTreeSet<u64>>) -> Result<Formula, Error> {
generators::battery::BatteryFormulaBuilder::try_new(self, battery_ids)?.build()
}

/// Returns a string representing the CHP formula for the graph.
pub fn chp_formula(&self, chp_ids: Option<BTreeSet<u64>>) -> Result<String, Error> {
pub fn chp_formula(&self, chp_ids: Option<BTreeSet<u64>>) -> Result<Formula, Error> {
generators::chp::CHPFormulaBuilder::try_new(self, chp_ids)?.build()
}

/// Returns a string representing the PV formula for the graph.
pub fn pv_formula(&self, pv_inverter_ids: Option<BTreeSet<u64>>) -> Result<String, Error> {
pub fn pv_formula(&self, pv_inverter_ids: Option<BTreeSet<u64>>) -> Result<Formula, Error> {
generators::pv::PVFormulaBuilder::try_new(self, pv_inverter_ids)?.build()
}

/// Returns a string with the coalesce formula for the given component IDs.
///
/// This formula uses the `COALESCE` function to return the first non-null
/// value from the components with the provided IDs.
pub fn coalesce(&self, component_ids: BTreeSet<u64>) -> Result<String, Error> {
pub fn coalesce(&self, component_ids: BTreeSet<u64>) -> Result<Formula, Error> {
generators::generic::CoalesceFormulaBuilder::try_new(self, component_ids)?.build()
}

/// Returns a string representing the EV charger formula for the graph.
pub fn ev_charger_formula(
&self,
ev_charger_ids: Option<BTreeSet<u64>>,
) -> Result<String, Error> {
) -> Result<Formula, Error> {
generators::ev_charger::EVChargerFormulaBuilder::try_new(self, ev_charger_ids)?.build()
}
}
54 changes: 54 additions & 0 deletions src/graph/formulas/formula.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,54 @@
// License: MIT
// Copyright © 2025 Frequenz Energy-as-a-Service GmbH

//! This module defines the `Formula` struct and its operations.

use super::expr::Expr;

// This struct represents the microgrid metric formulas that are generated by
// traversing the component graph.
//
// `Formula` objects can be added or subtracted from each other, and they can
// converted to a string representation, before they are passed to an evaluator.
#[derive(Debug, Clone)]
pub struct Formula {
expr: Expr,
}

impl Formula {
pub(crate) fn new(expr: Expr) -> Self {
Formula { expr }
}
}

impl std::ops::Add for Formula {
type Output = Self;

fn add(self, rhs: Self) -> Self::Output {
Formula {
expr: self.expr + rhs.expr,
}
}
}

impl std::ops::Sub for Formula {
type Output = Self;

fn sub(self, rhs: Self) -> Self::Output {
Formula {
expr: self.expr - rhs.expr,
}
}
}

impl std::fmt::Display for Formula {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
self.expr.fmt(f)
}
}

impl From<Formula> for String {
fn from(formula: Formula) -> Self {
formula.expr.to_string()
}
}
52 changes: 31 additions & 21 deletions src/graph/formulas/generators/battery.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,8 @@
use std::collections::BTreeSet;

use crate::component_category::CategoryPredicates;
use crate::graph::formulas::expr::Expr;
use crate::graph::formulas::Formula;
use crate::{ComponentGraph, Edge, Error, Node};

pub(crate) struct BatteryFormulaBuilder<'a, N, E>
Expand Down Expand Up @@ -47,14 +49,14 @@ where
/// This is the sum of all battery_inverters in the graph. If the
/// battery_ids are provided, only the batteries with the given ids are
/// included in the formula.
pub fn build(self) -> Result<String, Error> {
pub fn build(self) -> Result<Formula, Error> {
if self.inverter_ids.is_empty() {
return Ok("0.0".to_string());
return Ok(Formula::new(Expr::number(0.0)));
}

self.graph
.fallback_expr(self.inverter_ids, false)
.map(|expr| expr.to_string())
.map(Formula::new)
}

fn find_inverter_ids(
Expand Down Expand Up @@ -104,7 +106,7 @@ mod tests {
builder.connect(grid, grid_meter);

let graph = builder.build(None)?;
let formula = graph.battery_formula(None)?;
let formula = graph.battery_formula(None)?.to_string();
assert_eq!(formula, "0.0");

// Add a battery meter with one inverter and one battery.
Expand All @@ -115,7 +117,7 @@ mod tests {
assert_eq!(meter_bat_chain.component_id(), 2);

let graph = builder.build(None)?;
let formula = graph.battery_formula(None)?;
let formula = graph.battery_formula(None)?.to_string();
assert_eq!(formula, "COALESCE(#3, #2, 0.0)");

// Add a second battery meter with one inverter and two batteries.
Expand All @@ -125,18 +127,22 @@ mod tests {
assert_eq!(meter_bat_chain.component_id(), 5);

let graph = builder.build(None)?;
let formula = graph.battery_formula(None)?;
let formula = graph.battery_formula(None)?.to_string();
assert_eq!(formula, "COALESCE(#3, #2, 0.0) + COALESCE(#6, #5, 0.0)");

let formula = graph.battery_formula(Some(BTreeSet::from([4])))?;
let formula = graph
.battery_formula(Some(BTreeSet::from([4])))?
.to_string();
assert_eq!(formula, "COALESCE(#3, #2, 0.0)");

let formula = graph.battery_formula(Some(BTreeSet::from([7, 8])))?;
let formula = graph
.battery_formula(Some(BTreeSet::from([7, 8])))?
.to_string();
assert_eq!(formula, "COALESCE(#6, #5, 0.0)");

let formula = graph
.battery_formula(Some(BTreeSet::from([4, 8, 7])))
.unwrap();
.battery_formula(Some(BTreeSet::from([4, 8, 7])))?
.to_string();
assert_eq!(formula, "COALESCE(#3, #2, 0.0) + COALESCE(#6, #5, 0.0)");

// Add a third battery meter with two inverters with two connected batteries.
Expand All @@ -146,7 +152,7 @@ mod tests {
assert_eq!(meter_bat_chain.component_id(), 9);

let graph = builder.build(None)?;
let formula = graph.battery_formula(None)?;
let formula = graph.battery_formula(None)?.to_string();
assert_eq!(
formula,
concat!(
Expand All @@ -157,8 +163,8 @@ mod tests {
);

let formula = graph
.battery_formula(Some(BTreeSet::from([12, 13])))
.unwrap();
.battery_formula(Some(BTreeSet::from([12, 13])))?
.to_string();
assert_eq!(
formula,
"COALESCE(#11 + #10, #9, COALESCE(#11, 0.0) + COALESCE(#10, 0.0))"
Expand All @@ -171,7 +177,7 @@ mod tests {
assert_eq!(meter_pv_chain.component_id(), 14);

let graph = builder.build(None)?;
let formula = graph.battery_formula(None)?;
let formula = graph.battery_formula(None)?.to_string();
assert_eq!(
formula,
concat!(
Expand Down Expand Up @@ -208,7 +214,7 @@ mod tests {
allow_unspecified_inverters: true,
..Default::default()
}))?;
let formula = graph.battery_formula(None)?;
let formula = graph.battery_formula(None)?.to_string();
assert_eq!(
formula,
concat!(
Expand All @@ -220,22 +226,26 @@ mod tests {
);

let formula = graph
.battery_formula(Some(BTreeSet::from([19, 21])))
.unwrap();
.battery_formula(Some(BTreeSet::from([19, 21])))?
.to_string();
assert_eq!(
formula,
"COALESCE(#20 + #18, #17, COALESCE(#20, 0.0) + COALESCE(#18, 0.0))"
);

let formula = graph.battery_formula(Some(BTreeSet::from([19]))).unwrap();
let formula = graph
.battery_formula(Some(BTreeSet::from([19])))?
.to_string();
assert_eq!(formula, "COALESCE(#18, 0.0)");

let formula = graph.battery_formula(Some(BTreeSet::from([21]))).unwrap();
let formula = graph
.battery_formula(Some(BTreeSet::from([21])))?
.to_string();
assert_eq!(formula, "COALESCE(#20, 0.0)");

let formula = graph
.battery_formula(Some(BTreeSet::from([4, 12, 13, 19])))
.unwrap();
.battery_formula(Some(BTreeSet::from([4, 12, 13, 19])))?
.to_string();
assert_eq!(
formula,
concat!(
Expand Down
34 changes: 20 additions & 14 deletions src/graph/formulas/generators/chp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,8 @@
use std::collections::BTreeSet;

use crate::component_category::CategoryPredicates;
use crate::graph::formulas::expr::Expr;
use crate::graph::formulas::Formula;
use crate::{ComponentGraph, Edge, Error, Node};

pub(crate) struct CHPFormulaBuilder<'a, N, E>
Expand Down Expand Up @@ -43,9 +45,9 @@ where
///
/// This is the sum of all CHPs in the graph. If the chp_ids are provided,
/// only the CHPs with the given ids are included in the formula.
pub fn build(self) -> Result<String, Error> {
pub fn build(self) -> Result<Formula, Error> {
if self.chp_ids.is_empty() {
return Ok("0.0".to_string());
return Ok(Formula::new(Expr::number(0.0)));
}

for id in &self.chp_ids {
Expand All @@ -59,7 +61,7 @@ where

self.graph
.fallback_expr(self.chp_ids, false)
.map(|expr| expr.to_string())
.map(Formula::new)
}
}

Expand All @@ -78,7 +80,7 @@ mod tests {
builder.connect(grid, grid_meter);

let graph = builder.build(None)?;
let formula = graph.chp_formula(None)?;
let formula = graph.chp_formula(None)?.to_string();
assert_eq!(formula, "0.0");

// Add a chp meter with one chp
Expand All @@ -89,7 +91,7 @@ mod tests {
assert_eq!(meter_chp_chain.component_id(), 2);

let graph = builder.build(None)?;
let formula = graph.chp_formula(None)?;
let formula = graph.chp_formula(None)?.to_string();
assert_eq!(formula, "COALESCE(#3, #2, 0.0)");

// Add a battery meter with one inverter and two batteries.
Expand All @@ -99,7 +101,7 @@ mod tests {
assert_eq!(meter_bat_chain.component_id(), 4);

let graph = builder.build(None)?;
let formula = graph.chp_formula(None)?;
let formula = graph.chp_formula(None)?.to_string();
assert_eq!(formula, "COALESCE(#3, #2, 0.0)");

// Add a chp meter with two CHPs.
Expand All @@ -109,7 +111,7 @@ mod tests {
assert_eq!(meter_chp_chain.component_id(), 8);

let graph = builder.build(None)?;
let formula = graph.chp_formula(None)?;
let formula = graph.chp_formula(None)?.to_string();
assert_eq!(
formula,
concat!(
Expand All @@ -118,7 +120,9 @@ mod tests {
)
);

let formula = graph.chp_formula(Some(BTreeSet::from([10, 3]))).unwrap();
let formula = graph
.chp_formula(Some(BTreeSet::from([10, 3])))?
.to_string();
assert_eq!(formula, "COALESCE(#3, #2, 0.0) + COALESCE(#10, 0.0)");

// add a meter direct to the grid with three CHPs
Expand All @@ -128,7 +132,7 @@ mod tests {
assert_eq!(meter_chp_chain.component_id(), 11);

let graph = builder.build(None)?;
let formula = graph.chp_formula(None)?;
let formula = graph.chp_formula(None)?.to_string();
assert_eq!(
formula,
concat!(
Expand All @@ -143,8 +147,8 @@ mod tests {
);

let formula = graph
.chp_formula(Some(BTreeSet::from([3, 9, 10, 12, 13])))
.unwrap();
.chp_formula(Some(BTreeSet::from([3, 9, 10, 12, 13])))?
.to_string();
assert_eq!(
formula,
concat!(
Expand All @@ -155,8 +159,8 @@ mod tests {
);

let formula = graph
.chp_formula(Some(BTreeSet::from([3, 9, 10, 12, 13, 14])))
.unwrap();
.chp_formula(Some(BTreeSet::from([3, 9, 10, 12, 13, 14])))?
.to_string();
assert_eq!(
formula,
concat!(
Expand All @@ -170,7 +174,9 @@ mod tests {
),
);

let formula = graph.chp_formula(Some(BTreeSet::from([10, 14]))).unwrap();
let formula = graph
.chp_formula(Some(BTreeSet::from([10, 14])))?
.to_string();
assert_eq!(formula, "COALESCE(#10, 0.0) + COALESCE(#14, 0.0)");

// Failure cases:
Expand Down
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