knur-app/lib/strength/stats.ts

import type { StrengthExercise, StrengthWorkout } from "@/lib/models/strength";


export function exerciseVolumeKg(exercise: StrengthExercise): number {
  return exercise.sets.reduce((sum, set) => sum + (set.weightKg ?? 0) * (set.reps ?? 0), 0);
}

export function exerciseTopWeightKg(exercise: StrengthExercise): number | undefined {
  const weights = exercise.sets
    .map((set) => set.weightKg)
    .filter((weight): weight is number => weight !== undefined);
  return weights.length > 0 ? Math.max(...weights) : undefined;
}

// Epley formula: weight × (1 + reps / 30). Returns best e1rm across all sets.
export function exerciseE1rm(exercise: StrengthExercise): number | undefined {
  let best: number | undefined;
  for (const set of exercise.sets) {
    if (set.weightKg == null || set.reps == null || set.reps < 1) continue;
    const e1rm = set.weightKg * (1 + set.reps / 30);
    if (best === undefined || e1rm > best) best = e1rm;
  }
  return best !== undefined ? Math.round(best * 10) / 10 : undefined;
}

export function workoutVolumeKg(workout: StrengthWorkout): number {
  return workout.exercises.reduce((sum, exercise) => sum + exerciseVolumeKg(exercise), 0);
}

export type ExerciseHistoryPoint = {
  date: Date;
  volumeKg: number;
  topWeightKg?: number;
  e1rmKg?: number;
};

/**
 * History of a single exercise across past workouts (oldest first, including
 * the workout it was found in), used to chart progression.
 */
export function getExerciseHistory(
  exerciseName: string,
  workouts: StrengthWorkout[],
  limit: number
): ExerciseHistoryPoint[] {
  const points: ExerciseHistoryPoint[] = [];
  for (const workout of workouts) {
    const exercise = workout.exercises.find((e) => e.name === exerciseName);
    if (!exercise) continue;
    points.push({
      date: workout.date,
      volumeKg: exerciseVolumeKg(exercise),
      topWeightKg: exerciseTopWeightKg(exercise),
      e1rmKg: exerciseE1rm(exercise),
    });
  }

  points.sort((a, b) => a.date.getTime() - b.date.getTime());
  return points.slice(-limit);
}