import {
  baseClassFor,
  classById,
  type BaseClassId,
  type ClassId,
} from "../app/characterCatalog";
import {
  EMPTY_ITEM_STATS,
  ITEM_STAT_KEYS,
  type ItemStats,
  type NumericItemStatKey,
  type WeaponStats,
} from "./itemStats";
import type { InventoryItem } from "./lootTypes";

export const PLAYER_EQUIPMENT_OWNER_ID = "player";

export const EQUIPMENT_SLOTS = [
  "head",
  "neck",
  "shoulder",
  "back",
  "chest",
  "wrist",
  "hands",
  "waist",
  "legs",
  "feet",
  "finger",
  "trinket",
  "main-hand",
  "off-hand",
  "ranged",
] as const;

export type EquipmentSlot = (typeof EQUIPMENT_SLOTS)[number];
export type EquipmentLoadout = Partial<Record<EquipmentSlot, string>>;
export type EquipmentAssignments = Readonly<Record<string, EquipmentLoadout>>;

export interface EquipmentChange {
  readonly ok: boolean;
  readonly assignments: EquipmentAssignments;
  readonly slot?: EquipmentSlot;
  readonly reason?: string;
}

const equipmentSlotSet = new Set<string>(EQUIPMENT_SLOTS);

const ARMOR_RANK: Readonly<Record<string, number>> = Object.freeze({
  cloth: 1,
  leather: 2,
  mail: 3,
  chain: 3,
  plate: 4,
});

const SHIELD_CLASSES = new Set<ClassId>([
  "warrior", "paladin", "shaman",
  "knight-of-xoroth", "guardian", "cultist", "starcaller", "sun-cleric",
  "rom-warrior", "rom-knight", "rom-warden", "rom-champion",
]);

const WEAPON_CLASSES: Readonly<Record<string, ReadonlySet<BaseClassId>>> = Object.freeze({
  bow: new Set<BaseClassId>(["warrior", "hunter", "rogue"]),
  dagger: new Set<BaseClassId>(["warrior", "hunter", "rogue", "priest", "shaman", "mage", "warlock", "druid"]),
  mace: new Set<BaseClassId>(["warrior", "paladin", "priest", "death-knight", "shaman", "druid"]),
  staff: new Set<BaseClassId>(["warrior", "hunter", "priest", "shaman", "mage", "warlock", "druid"]),
  wand: new Set<BaseClassId>(["priest", "mage", "warlock"]),
});

export function equipmentSlotForItem(item: InventoryItem): EquipmentSlot | null {
  const slot = item.inventorySlot === "one-hand" || item.inventorySlot === "two-hand"
    ? "main-hand"
    : item.inventorySlot;
  return equipmentSlotSet.has(slot) ? slot as EquipmentSlot : null;
}

export function classCanEquipItem(classId: ClassId, item: InventoryItem): boolean {
  if (item.armorType === "shield" && !SHIELD_CLASSES.has(classId)) return false;
  if (item.armorType && item.armorType !== "shield") {
    const requiredRank = ARMOR_RANK[item.armorType] ?? Number.POSITIVE_INFINITY;
    if (requiredRank > ARMOR_RANK[classById(classId).armor]) return false;
  }
  if (item.weaponType) {
    const allowedClasses = WEAPON_CLASSES[item.weaponType];
    if (!allowedClasses?.has(baseClassFor(classId))) return false;
  }
  return equipmentSlotForItem(item) !== null;
}

function mutableAssignments(assignments: EquipmentAssignments): Record<string, EquipmentLoadout> {
  return Object.fromEntries(
    Object.entries(assignments).map(([ownerId, loadout]) => [ownerId, { ...loadout }]),
  );
}

function removeItemAssignment(
  assignments: Record<string, EquipmentLoadout>,
  instanceId: string,
): void {
  for (const [ownerId, loadout] of Object.entries(assignments)) {
    const next = { ...loadout };
    for (const slot of EQUIPMENT_SLOTS) {
      if (next[slot] === instanceId) delete next[slot];
    }
    if (Object.keys(next).length) assignments[ownerId] = next;
    else delete assignments[ownerId];
  }
}

export function equipInventoryItem(
  assignments: EquipmentAssignments,
  inventory: readonly InventoryItem[],
  ownerId: string,
  ownerClassId: ClassId,
  instanceId: string,
): EquipmentChange {
  const item = inventory.find((candidate) => candidate.instanceId === instanceId);
  if (!item) return { ok: false, assignments, reason: "That item is no longer in your inventory." };
  const slot = equipmentSlotForItem(item);
  if (!slot) return { ok: false, assignments, reason: `${item.name} does not use an equippable slot.` };
  if (!classCanEquipItem(ownerClassId, item)) {
    return { ok: false, assignments, reason: `That class cannot equip ${item.name}.` };
  }

  const next = mutableAssignments(assignments);
  removeItemAssignment(next, instanceId);
  const loadout = { ...(next[ownerId] ?? {}) };

  if (slot === "main-hand" && item.inventorySlot === "two-hand") delete loadout["off-hand"];
  if (slot === "off-hand" && loadout["main-hand"]) {
    const mainHand = inventory.find((candidate) => candidate.instanceId === loadout["main-hand"]);
    if (mainHand?.inventorySlot === "two-hand") delete loadout["main-hand"];
  }

  loadout[slot] = instanceId;
  next[ownerId] = loadout;
  return { ok: true, assignments: next, slot };
}

export function unequipInventorySlot(
  assignments: EquipmentAssignments,
  ownerId: string,
  slot: EquipmentSlot,
): EquipmentAssignments {
  const loadout = assignments[ownerId];
  if (!loadout?.[slot]) return assignments;
  const next = mutableAssignments(assignments);
  const nextLoadout = { ...next[ownerId] };
  delete nextLoadout[slot];
  if (Object.keys(nextLoadout).length) next[ownerId] = nextLoadout;
  else delete next[ownerId];
  return next;
}

export function equippedOwnerId(
  assignments: EquipmentAssignments,
  instanceId: string,
): string | null {
  for (const [ownerId, loadout] of Object.entries(assignments)) {
    if (Object.values(loadout).includes(instanceId)) return ownerId;
  }
  return null;
}

/** Returns one owner's equipped inventory records in stable character-slot order. */
export function equipmentItemsForOwner(
  assignments: EquipmentAssignments,
  inventory: readonly InventoryItem[],
  ownerId: string,
): InventoryItem[] {
  const loadout = assignments[ownerId];
  if (!loadout) return [];
  const itemById = new Map(inventory.map((item) => [item.instanceId, item]));
  return EQUIPMENT_SLOTS.flatMap((slot) => {
    const instanceId = loadout[slot];
    const item = instanceId ? itemById.get(instanceId) : null;
    return item ? [item] : [];
  });
}

export function normalizeEquipment(
  value: unknown,
  inventory: readonly InventoryItem[],
): EquipmentAssignments {
  if (!value || typeof value !== "object" || Array.isArray(value)) return {};
  const itemById = new Map(inventory.map((item) => [item.instanceId, item]));
  const assigned = new Set<string>();
  const normalized: Record<string, EquipmentLoadout> = {};

  for (const [ownerId, rawLoadout] of Object.entries(value as Record<string, unknown>)) {
    if (!ownerId || !rawLoadout || typeof rawLoadout !== "object" || Array.isArray(rawLoadout)) continue;
    const loadout: EquipmentLoadout = {};
    for (const [rawSlot, rawInstanceId] of Object.entries(rawLoadout as Record<string, unknown>)) {
      if (!equipmentSlotSet.has(rawSlot) || typeof rawInstanceId !== "string" || assigned.has(rawInstanceId)) continue;
      const item = itemById.get(rawInstanceId);
      if (!item || equipmentSlotForItem(item) !== rawSlot) continue;
      loadout[rawSlot as EquipmentSlot] = rawInstanceId;
      assigned.add(rawInstanceId);
    }
    const mainHand = loadout["main-hand"]
      ? itemById.get(loadout["main-hand"]!)
      : null;
    if (mainHand?.inventorySlot === "two-hand") delete loadout["off-hand"];
    if (Object.keys(loadout).length) normalized[ownerId] = loadout;
  }
  return normalized;
}

export function equipmentItemLevel(
  assignments: EquipmentAssignments,
  inventory: readonly InventoryItem[],
  ownerId: string,
): number {
  const itemById = new Map(inventory.map((item) => [item.instanceId, item]));
  return Object.values(assignments[ownerId] ?? {}).reduce(
    (total, instanceId) => total + (instanceId ? itemById.get(instanceId)?.itemLevel ?? 0 : 0),
    0,
  );
}

/** Adds the attributes from every item equipped by one character. */
export function equipmentStats(
  assignments: EquipmentAssignments,
  inventory: readonly InventoryItem[],
  ownerId: string,
): ItemStats {
  const loadout = assignments[ownerId];
  if (!loadout) return EMPTY_ITEM_STATS;
  const itemById = new Map(inventory.map((item) => [item.instanceId, item]));
  const numeric = Object.fromEntries(ITEM_STAT_KEYS.map((key) => [key, 0])) as Record<NumericItemStatKey, number>;
  let meleeWeapon: WeaponStats | null = null;
  let rangedWeapon: WeaponStats | null = null;
  for (const instanceId of Object.values(loadout)) {
    const stats = instanceId ? itemById.get(instanceId)?.stats : null;
    if (!stats) continue;
    for (const key of ITEM_STAT_KEYS) numeric[key] += stats[key];
    if (stats.meleeWeapon) meleeWeapon = stats.meleeWeapon;
    if (stats.rangedWeapon) rangedWeapon = stats.rangedWeapon;
  }
  return Object.freeze({ ...numeric, meleeWeapon, rangedWeapon });
}

/** Keeps incompatible items owned and visibly assigned while excluding their stats in the active class orientation. */
export function activeEquipmentStatsForClass(
  assignments: EquipmentAssignments,
  inventory: readonly InventoryItem[],
  ownerId: string,
  classId: ClassId,
): ItemStats {
  const loadout = assignments[ownerId];
  if (!loadout) return EMPTY_ITEM_STATS;
  const itemById = new Map(inventory.map((item) => [item.instanceId, item]));
  const activeAssignments: EquipmentAssignments = {
    [ownerId]: Object.fromEntries(Object.entries(loadout).filter(([, instanceId]) => {
      const item = instanceId ? itemById.get(instanceId) : null;
      return Boolean(item && classCanEquipItem(classId, item));
    })),
  };
  return equipmentStats(activeAssignments, inventory, ownerId);
}