import { todayKey } from "./constants";
import { calcRecipe } from "./nutrition";
import type {
  CatalogFood,
  CoachRecommendation,
  HealthProfile,
  HealthProjection,
  HealthStatsDay,
  HealthStatsSummary,
  HellthData,
  HellthDayStateSnapshot,
  HellthGoals,
  ShoppingItem,
  Store,
  WeeklyBudgetSummary,
} from "./types";
import { uid } from "./constants";

export function startOfWeek(dateKey: string) {
  const date = new Date(`${dateKey}T12:00:00`);
  const day = date.getDay() === 0 ? 7 : date.getDay();
  date.setDate(date.getDate() - day + 1);
  return date.toISOString().slice(0, 10);
}

export function weekDates(dateKey: string) {
  const monday = new Date(`${startOfWeek(dateKey)}T12:00:00`);
  return Array.from({ length: 7 }, (_, index) => {
    const date = new Date(monday);
    date.setDate(monday.getDate() + index);
    return date.toISOString().slice(0, 10);
  });
}

export function addDateDays(dateKey: string, days: number) {
  const date = new Date(`${dateKey}T12:00:00`);
  date.setDate(date.getDate() + days);
  return date.toISOString().slice(0, 10);
}

export function buildWeeklyBudgetSummary(data: HellthData, dateKey = todayKey()): WeeklyBudgetSummary {
  const dates = weekDates(dateKey);
  const dailyGoal = data.goals.calories;
  const planByDate = new Map(data.weeklyCaloriePlans.map((plan) => [plan.date, plan]));
  const recipeById = new Map(data.recipes.map((recipe) => [recipe.id, recipe]));

  const days = dates.map((date) => {
    const plannedCalories = planByDate.get(date)?.plannedCalories ?? dailyGoal;
    const plannedMeals = data.plannedMeals.filter((meal) => meal.date === date);
    const eatenCalories = plannedMeals.reduce((sum, meal) => {
      const recipe = meal.recipeId ? recipeById.get(meal.recipeId) : undefined;
      if (!recipe) return sum;
      return sum + calcRecipe(recipe, data.foods, recipe.portions).kcal * meal.portions;
    }, 0);
    const activityCalories = data.activityLogs
      .filter((log) => log.date === date)
      .reduce((sum, log) => sum + (log.calories ?? 0), 0);
    return {
      date,
      plannedCalories,
      extraCalories: planByDate.get(date)?.extraCalories ?? 0,
      eatenCalories,
      activityCalories,
      balance: plannedCalories + activityCalories - eatenCalories,
      note: planByDate.get(date)?.note,
    };
  });

  const plannedBudget = days.reduce((sum, day) => sum + day.plannedCalories, 0);
  const eatenCalories = days.reduce((sum, day) => sum + day.eatenCalories, 0);
  const activityCalories = days.reduce((sum, day) => sum + day.activityCalories, 0);
  const availableCalories = plannedBudget + activityCalories - eatenCalories;

  return {
    weekStart: dates[0]!,
    dailyGoal,
    baseBudget: dailyGoal * 7,
    plannedBudget,
    eatenCalories,
    activityCalories,
    availableCalories,
    balance: plannedBudget + activityCalories - eatenCalories,
    days,
  };
}

function plannedCaloriesForDate(data: HellthData, date: string) {
  const recipeById = new Map(data.recipes.map((recipe) => [recipe.id, recipe]));
  return data.plannedMeals
    .filter((meal) => meal.date === date)
    .reduce((sum, meal) => {
      const recipe = meal.recipeId ? recipeById.get(meal.recipeId) : undefined;
      if (!recipe) return sum;
      return sum + calcRecipe(recipe, data.foods, recipe.portions).kcal * meal.portions;
    }, 0);
}

function latestStreak<T extends HealthStatsDay>(days: T[], predicate: (day: T) => boolean) {
  let streak = 0;
  for (const day of [...days].reverse()) {
    if (!predicate(day)) break;
    streak += 1;
  }
  return streak;
}

function buildWeightProjection(
  data: HellthData,
  days: HealthStatsDay[],
  referenceDate: string,
): HealthProjection | undefined {
  const entries = days
    .filter((day) => day.weightKg !== undefined)
    .map((day) => ({ date: day.date, weightKg: day.weightKg! }));
  if (entries.length < 3) return undefined;

  const first = entries[0]!;
  const last = entries[entries.length - 1]!;
  const elapsedDays = Math.max(
    1,
    Math.round((new Date(`${last.date}T12:00:00`).getTime() - new Date(`${first.date}T12:00:00`).getTime()) / 86_400_000),
  );
  if (elapsedDays < 7) return undefined;

  const trendKgPerWeek = Math.round(((last.weightKg - first.weightKg) / elapsedDays) * 7 * 10) / 10;
  const targetWeight = data.healthProfile?.targetWeightKg ?? data.goals.weightKg;
  const wantsLowerWeight = targetWeight < last.weightKg;
  const movingTowardTarget = wantsLowerWeight ? trendKgPerWeek < -0.05 : trendKgPerWeek > 0.05;

  if (!movingTowardTarget) {
    return {
      kind: "weight",
      trendKgPerWeek,
      confidence: "low",
      message: "Noch kein stabiler Zieltrend. Das ist normal, einzelne Wochen schwanken stark.",
    };
  }

  const kgPerDay = Math.abs(trendKgPerWeek / 7);
  const remainingKg = Math.abs(last.weightKg - targetWeight);
  const estimatedDays = Math.ceil(remainingKg / Math.max(0.01, kgPerDay));
  const targetDate = addDateDays(referenceDate, estimatedDays);

  return {
    kind: "weight",
    trendKgPerWeek,
    targetDate,
    confidence: elapsedDays >= 14 && entries.length >= 5 ? "medium" : "low",
    message: `Aktueller Trend: ${Math.abs(trendKgPerWeek).toLocaleString("de-DE")} kg pro Woche in Richtung Ziel.`,
  };
}

export function buildHealthStatsSummary(
  data: HellthData,
  dayState: HellthDayStateSnapshot = {},
  referenceDate = todayKey(),
): HealthStatsSummary {
  const days = Array.from({ length: 14 }, (_, index) => addDateDays(referenceDate, index - 13)).map((date) => {
    const snapshot = dayState.days?.[date];
    const loggedCalories = snapshot?.foods?.reduce((sum, food) => sum + (Number(food.calories) || 0), 0) ?? 0;
    const plannedCalories = plannedCaloriesForDate(data, date);
    const activityCalories = data.activityLogs
      .filter((log) => log.date === date)
      .reduce((sum, log) => sum + (log.calories ?? 0), 0);

    return {
      date,
      calories: loggedCalories || (date >= referenceDate ? plannedCalories : 0),
      plannedCalories,
      activityCalories,
      protein: snapshot?.foods?.reduce((sum, food) => sum + (Number(food.protein) || 0), 0) ?? 0,
      drinkMl: snapshot?.drinks?.reduce((sum, drink) => sum + (Number(drink.amountMl) || 0), 0) ?? 0,
      weightKg: snapshot?.weightKg,
    };
  });

  const relevantDays = days.filter((day) => day.date <= referenceDate);
  const divisor = Math.max(1, relevantDays.length);
  const averages = {
    calories: Math.round(relevantDays.reduce((sum, day) => sum + day.calories, 0) / divisor),
    protein: Math.round(relevantDays.reduce((sum, day) => sum + day.protein, 0) / divisor),
    drinkMl: Math.round(relevantDays.reduce((sum, day) => sum + day.drinkMl, 0) / divisor),
    activityCalories: Math.round(relevantDays.reduce((sum, day) => sum + day.activityCalories, 0) / divisor),
  };

  const streaks = {
    waterDays: latestStreak(relevantDays, (day) => day.drinkMl >= data.goals.drinkMl),
    proteinDays: latestStreak(relevantDays, (day) => day.protein >= data.goals.protein * 0.8),
    activityDays: latestStreak(relevantDays, (day) => day.activityCalories > 0),
  };

  const wins = [
    streaks.waterDays > 0 ? `${streaks.waterDays} Tag(e) Trinkziel in Folge` : undefined,
    streaks.proteinDays > 0 ? `${streaks.proteinDays} Tag(e) Protein gut getroffen` : undefined,
    streaks.activityDays > 0 ? `${streaks.activityDays} Tag(e) mit Bewegung in Folge` : undefined,
    averages.activityCalories > 0 ? `Ø ${averages.activityCalories} kcal Sportbonus pro Tag` : undefined,
  ].filter(Boolean) as string[];

  return {
    days,
    week: buildWeeklyBudgetSummary(data, referenceDate),
    averages,
    streaks,
    wins: wins.length ? wins : ["Du sammelst gerade Daten. Jeder Eintrag macht die Auswertung besser."],
    projection: buildWeightProjection(data, days, referenceDate),
  };
}

export function redistributeWeeklyCalories(
  data: HellthData,
  targetDate: string,
  extraCalories: number,
  referenceDate = todayKey(),
) {
  const dates = weekDates(referenceDate);
  const dailyGoal = data.goals.calories;
  const target = targetDate || referenceDate;
  const otherDates = dates.filter((date) => date !== target);
  const savingPerOtherDay = otherDates.length ? Math.ceil(extraCalories / otherDates.length) : 0;
  return dates.map((date) => ({
    date,
    plannedCalories: date === target ? dailyGoal + extraCalories : Math.max(1200, dailyGoal - savingPerOtherDay),
    note: date === target ? "bewusst höher geplant" : extraCalories > 0 ? "Ausgleichstag" : undefined,
  }));
}

export function buildGoalsFromProfile(profile: HealthProfile): HellthGoals {
  const weight = Math.max(45, profile.currentWeightKg || 80);
  const height = Math.max(130, profile.heightCm || 175);
  const age = Math.max(18, profile.age || 40);
  const activityFactor =
    profile.activityLevel === "active" ? 1.55 : profile.activityLevel === "moderate" ? 1.35 : 1.2;

  // Neutral estimate without sex-specific assumptions. Good enough for an onboarding target,
  // later refined by real weight trend and adherence.
  const bmr = 10 * weight + 6.25 * height - 5 * age - 80;
  const maintenance = Math.round(bmr * activityFactor);
  const deficit =
    profile.goal === "lose_weight"
      ? profile.pace === "ambitious"
        ? 700
        : profile.pace === "normal"
          ? 500
          : 300
      : 0;
  const floor = weight > 90 ? 1600 : 1400;
  const calories = Math.max(floor, maintenance - deficit);
  const protein = Math.round(Math.min(220, Math.max(90, weight * (profile.goal === "lose_weight" ? 1.6 : 1.3))));
  const fat = Math.round((calories * 0.3) / 9);
  const carbs = Math.round((calories - protein * 4 - fat * 9) / 4);

  return {
    drinkMl: Math.round(Math.min(3500, Math.max(1800, weight * 35)) / 100) * 100,
    calories,
    carbs: Math.max(80, carbs),
    fat,
    protein,
    weightKg: profile.targetWeightKg || profile.currentWeightKg,
    fastingHours: profile.mealsPerDay <= 3 ? 12 : 10,
  };
}

export function buildCoachRecommendations(profile: HealthProfile, goals: HellthGoals): CoachRecommendation[] {
  const recommendations: CoachRecommendation[] = [
    {
      id: "calorie-deficit",
      title: profile.goal === "lose_weight" ? "Moderates Defizit halten" : "Stabile Routine aufbauen",
      body:
        profile.goal === "lose_weight"
          ? `Starte mit ca. ${goals.calories} kcal pro Tag. Prüfe nach 2 Wochen den Gewichtstrend statt einzelne Tageswerte zu bewerten.`
          : `Starte mit ca. ${goals.calories} kcal pro Tag und bewerte Energie, Hunger und Gewichtstrend wöchentlich.`,
      priority: "high",
    },
    {
      id: "protein",
      title: "Protein als Sattmacher planen",
      body: `Plane pro Tag etwa ${goals.protein} g Protein ein. Praktisch: jede Hauptmahlzeit bekommt eine klare Proteinquelle.`,
      priority: "high",
    },
    {
      id: "water",
      title: "Trinken sichtbar machen",
      body: `Dein Trinkziel liegt bei ${goals.drinkMl} ml. Starte mit 500 ml bis Mittag und nutze die Wasserkarte als einfache Erinnerung.`,
      priority: "medium",
    },
  ];

  if (profile.biggestChallenge.trim()) {
    recommendations.push({
      id: "challenge",
      title: "Haupt-Hürde zuerst entschärfen",
      body: `Du hast "${profile.biggestChallenge.trim()}" als Hürde genannt. Plane dafür eine konkrete Standardlösung, z. B. ein schnelles Notfallgericht oder vorbereitete Snacks.`,
      priority: "high",
    });
  }

  if (profile.cookingTime === "low") {
    recommendations.push({
      id: "simple-meals",
      title: "Kurze Rezepte bevorzugen",
      body: "Nutze Rezepte unter 20 Minuten und wiederhole gute Mahlzeiten bewusst. Abnehmen wird leichter, wenn nicht jede Mahlzeit neu entschieden werden muss.",
      priority: "medium",
    });
  }

  if (profile.budgetFocus) {
    recommendations.push({
      id: "budget",
      title: "Budgetfreundliche Basics",
      body: "Haferflocken, Kartoffeln, Reis, Eier, Quark, TK-Gemüse und Hülsenfrüchte eignen sich gut für planbare, günstige Mahlzeiten.",
      priority: "low",
    });
  }

  if (profile.medicalNote) {
    recommendations.unshift({
      id: "medical",
      title: "Gesundheitliche Situation beachten",
      body: "Bei Diagnosen, Medikamenten, Schwangerschaft oder Essstörungs-Vorgeschichte bitte Ziele mit Arzt oder Ernährungsfachkraft abstimmen. Hellth Hub ersetzt keine medizinische Beratung.",
      priority: "high",
    });
  }

  return recommendations;
}

export function isFoodAvailableInStore(food: CatalogFood | undefined, storeId: string) {
  if (!food) return true;
  if (food.availableEverywhere) return true;
  return Boolean(food.storeIds?.includes(storeId));
}

export function departmentForFood(food: CatalogFood | undefined, store: Store) {
  const explicitId = food?.storeDepartmentIds?.[store.id]?.[0];
  if (explicitId) {
    const explicit = store.departments.find((department) => department.id === explicitId);
    if (explicit) return explicit;
  }

  const category = food?.category.toLowerCase() ?? "";
  const match = store.departments.find((department) => {
    const name = department.name.toLowerCase();
    return (
      (category.includes("obst") && name.includes("obst")) ||
      (category.includes("gemüse") && name.includes("gemüse")) ||
      (category.includes("brot") && name.includes("brot")) ||
      (category.includes("getreide") && (name.includes("cerealien") || name.includes("trocken"))) ||
      (category.includes("milch") && name.includes("milch")) ||
      (category.includes("protein") && (name.includes("protein") || name.includes("fleisch"))) ||
      (category.includes("öl") && (name.includes("trocken") || name.includes("sonst")))
    );
  });

  return match ?? store.departments.find((department) => department.name.toLowerCase().includes("sonst")) ?? store.departments.at(-1);
}

export function buildShoppingItemsFromPlan(data: HellthData, dates?: string[]) {
  const dateSet = dates?.length ? new Set(dates) : null;
  const foodById = new Map(data.foods.map((food) => [food.id, food]));
  const recipeById = new Map(data.recipes.map((recipe) => [recipe.id, recipe]));
  const previousByFoodId = new Map(data.shoppingItems.filter((item) => item.foodId).map((item) => [item.foodId!, item]));
  const previousManualItems = data.shoppingItems.filter((item) => !item.foodId);
  const generated = new Map<string, ShoppingItem>();

  for (const plan of data.plannedMeals) {
    if (dateSet && !dateSet.has(plan.date)) continue;
    const recipe = plan.recipeId ? recipeById.get(plan.recipeId) : undefined;
    if (!recipe) continue;

    for (const ingredient of recipe.ingredients) {
      const food = foodById.get(ingredient.foodId);
      if (!food) continue;

      const previous = previousByFoodId.get(food.id);
      const current = generated.get(food.id);
      const amountG = ingredient.amountG * plan.portions;
      generated.set(food.id, {
        id: current?.id ?? previous?.id ?? uid("shop"),
        foodId: food.id,
        name: food.name,
        category: food.category,
        amountG: (current?.amountG ?? 0) + amountG,
        purchaseAmount: current?.purchaseAmount ?? previous?.purchaseAmount,
        checked: current?.checked ?? previous?.checked,
        recipeIds: Array.from(new Set([...(current?.recipeIds ?? []), recipe.id])),
      });
    }
  }

  return [...generated.values(), ...previousManualItems];
}