import type { Achievement, Equipment, GameState } from "@elysium/types";

/**
 * Checks all achievements against the current game state and returns an updated
 * achievements array, marking newly-met conditions with the current timestamp.
 */
const checkAchievements = (state: GameState): Achievement[] => {
  const now = Date.now();
  return (state.achievements ?? []).map((achievement) => {
    if (achievement.unlockedAt !== null) return achievement;

    const { condition } = achievement;
    let met = false;

    switch (condition.type) {
      case "totalGoldEarned":
        met = state.player.totalGoldEarned >= condition.amount;
        break;
      case "totalClicks":
        met = state.player.totalClicks >= condition.amount;
        break;
      case "bossesDefeated":
        met = state.bosses.filter((b) => b.status === "defeated").length >= condition.amount;
        break;
      case "questsCompleted":
        met = state.quests.filter((q) => q.status === "completed").length >= condition.amount;
        break;
      case "adventurerTotal":
        met = state.adventurers.reduce((sum, a) => sum + a.count, 0) >= condition.amount;
        break;
      case "prestigeCount":
        met = state.prestige.count >= condition.amount;
        break;
      case "equipmentOwned":
        met = (state.equipment ?? []).filter((e) => e.owned).length >= condition.amount;
        break;
    }

    return met ? { ...achievement, unlockedAt: now } : achievement;
  });
};

/** Maximum value any resource can accumulate to. Beyond this JS floats lose all useful precision. */
export const RESOURCE_CAP = 1e300;

const capResource = (value: number): number => Math.min(value, RESOURCE_CAP);

/**
 * Pure function — applies one game tick to the state.
 * deltaSeconds: time elapsed since last tick.
 * Returns a new GameState (does not mutate the original).
 */
export const applyTick = (state: GameState, deltaSeconds: number): GameState => {
  const equippedItems: Equipment[] = (state.equipment ?? []).filter((e) => e.equipped);
  const equipmentGoldMultiplier = equippedItems.reduce(
    (mult, e) => mult * (e.bonus.goldMultiplier ?? 1),
    1,
  );

  const runestonesIncome = state.prestige.runestonesIncomeMultiplier ?? 1;
  const runestonesEssence = state.prestige.runestonesEssenceMultiplier ?? 1;
  const runestonesCrystal = state.prestige.runestonesCrystalMultiplier ?? 1;

  let goldGained = 0;
  let essenceGained = 0;

  for (const adventurer of state.adventurers) {
    if (!adventurer.unlocked || adventurer.count === 0) {
      continue;
    }

    const upgradeMultiplier = state.upgrades
      .filter(
        (u) =>
          u.purchased &&
          (u.target === "global" ||
            (u.target === "adventurer" && u.adventurerId === adventurer.id)),
      )
      .reduce((mult, upgrade) => mult * upgrade.multiplier, 1);

    const prestige = state.prestige.productionMultiplier;

    goldGained +=
      adventurer.goldPerSecond *
      adventurer.count *
      upgradeMultiplier *
      prestige *
      runestonesIncome *
      equipmentGoldMultiplier *
      deltaSeconds;

    essenceGained +=
      adventurer.essencePerSecond *
      adventurer.count *
      upgradeMultiplier *
      prestige *
      runestonesEssence *
      deltaSeconds;
  }

  // Complete active quests and apply their rewards
  const now = Date.now();
  let questGold = 0;
  let questEssence = 0;
  let questCrystals = 0;

  let updatedUpgrades = state.upgrades;
  let updatedAdventurers = state.adventurers;
  let updatedEquipment = state.equipment ?? [];

  const updatedQuests = state.quests.map((quest) => {
    if (
      quest.status !== "active" ||
      quest.startedAt == null ||
      now < quest.startedAt + quest.durationSeconds * 1000
    ) {
      return quest;
    }

    for (const reward of quest.rewards) {
      if (reward.type === "gold" && reward.amount != null) {
        questGold += reward.amount;
      } else if (reward.type === "essence" && reward.amount != null) {
        questEssence += reward.amount;
      } else if (reward.type === "crystals" && reward.amount != null) {
        questCrystals += reward.amount * runestonesCrystal;
      } else if (reward.type === "upgrade" && reward.targetId != null) {
        updatedUpgrades = updatedUpgrades.map((u) =>
          u.id === reward.targetId ? { ...u, unlocked: true } : u,
        );
      } else if (reward.type === "adventurer" && reward.targetId != null) {
        updatedAdventurers = updatedAdventurers.map((a) =>
          a.id === reward.targetId ? { ...a, unlocked: true } : a,
        );
      } else if (reward.type === "equipment" && reward.targetId != null) {
        const targetId = reward.targetId;
        updatedEquipment = updatedEquipment.map((e) => {
          if (e.id !== targetId) return e;
          const slotEmpty = !updatedEquipment.some(
            (other) => other.type === e.type && other.equipped,
          );
          return { ...e, owned: true, equipped: slotEmpty || e.equipped };
        });
      }
    }

    return { ...quest, status: "completed" as const };
  });

  // Unlock quests whose prerequisites are now all completed and whose zone is unlocked
  const completedIds = new Set(
    updatedQuests.filter((q) => q.status === "completed").map((q) => q.id),
  );
  const fullyUpdatedQuests = updatedQuests.map((quest) => {
    if (quest.status !== "locked") return quest;
    const zone = state.zones.find((z) => z.id === quest.zoneId);
    if (zone?.status === "locked") return quest;
    if (quest.prerequisiteIds.every((id) => completedIds.has(id))) {
      return { ...quest, status: "available" as const };
    }
    return quest;
  });

  // Unlock zones whose both conditions are now satisfied after quest completion:
  // (1) the gate boss has been defeated, (2) the gate quest is now completed
  const updatedZones = state.zones.map((zone) => {
    if (zone.status === "unlocked") return zone;
    const bossOk =
      zone.unlockBossId == null ||
      state.bosses.some((b) => b.id === zone.unlockBossId && b.status === "defeated");
    const questOk =
      zone.unlockQuestId == null || completedIds.has(zone.unlockQuestId);
    if (bossOk && questOk) {
      return { ...zone, status: "unlocked" as const };
    }
    return zone;
  });

  // Activate the first boss in any zone that just became unlocked this tick
  const newlyUnlockedZoneIds = new Set(
    updatedZones
      .filter((z) => {
        const wasLocked = state.zones.find((oz) => oz.id === z.id)?.status === "locked";
        return z.status === "unlocked" && wasLocked;
      })
      .map((z) => z.id),
  );
  let updatedBosses = state.bosses;
  if (newlyUnlockedZoneIds.size > 0) {
    updatedBosses = state.bosses.map((boss) => {
      if (!newlyUnlockedZoneIds.has(boss.zoneId ?? "")) return boss;
      const zoneBosses = state.bosses.filter((b) => b.zoneId === boss.zoneId);
      const firstBoss = zoneBosses[0];
      if (firstBoss?.id === boss.id && boss.status === "locked") {
        return { ...boss, status: "available" as const };
      }
      return boss;
    });
  }

  const newGold = capResource(state.resources.gold + goldGained + questGold);
  const newEssence = capResource(state.resources.essence + essenceGained + questEssence);
  const newTotalGoldEarned = state.player.totalGoldEarned + goldGained + questGold;

  const partialState: GameState = {
    ...state,
    resources: {
      ...state.resources,
      gold: newGold,
      essence: newEssence,
      crystals: capResource(state.resources.crystals + questCrystals),
    },
    player: {
      ...state.player,
      totalGoldEarned: newTotalGoldEarned,
    },
    quests: fullyUpdatedQuests,
    upgrades: updatedUpgrades,
    adventurers: updatedAdventurers,
    equipment: updatedEquipment,
    bosses: updatedBosses,
    zones: updatedZones,
    lastTickAt: now,
  };

  // Check achievements and apply crystal rewards for newly unlocked ones
  const updatedAchievements = checkAchievements(partialState);
  const crystalsFromAchievements = updatedAchievements.reduce((sum, a, i) => {
    const wasLocked = (state.achievements ?? [])[i]?.unlockedAt === null;
    const isNowUnlocked = a.unlockedAt !== null;
    if (wasLocked && isNowUnlocked) {
      return sum + (a.reward?.crystals ?? 0);
    }
    return sum;
  }, 0);

  return {
    ...partialState,
    achievements: updatedAchievements,
    resources: {
      ...partialState.resources,
      crystals: capResource(partialState.resources.crystals + crystalsFromAchievements),
    },
  };
};

/**
 * Calculates the effective click power, including upgrades and equipped trinkets.
 */
export const calculateClickPower = (state: GameState): number => {
  const clickMultiplier = state.upgrades
    .filter((u) => u.purchased && u.target === "click")
    .reduce((mult, upgrade) => mult * upgrade.multiplier, 1);

  const equipmentClickMultiplier = (state.equipment ?? [])
    .filter((e) => e.equipped && e.bonus.clickMultiplier != null)
    .reduce((mult, e) => mult * (e.bonus.clickMultiplier ?? 1), 1);

  const runestonesClick = state.prestige.runestonesClickMultiplier ?? 1;

  return (
    state.baseClickPower *
    clickMultiplier *
    state.prestige.productionMultiplier *
    runestonesClick *
    equipmentClickMultiplier
  );
};