import referenceData from "./generated/azerothCoreReference.json";
import { enemyAutoEquippedOffhandContract } from "./enemyAutomaticOffhand";

export interface EnemyEquipmentItemReference {
  readonly itemClass: number;
  readonly inventoryType: number;
}

export interface EnemyEquipmentTemplateReference {
  /** Raw SQL item IDs, before ObjectMgr's Item.dbc hand-slot validation. */
  readonly sourceItems: readonly [number, number, number];
  /** Virtual item IDs after the pinned core loader's Item.dbc validation. */
  readonly items: readonly [number, number, number];
}

export interface EnemyEquipmentSpawnAssignment {
  readonly entry: number;
  readonly alternateEntries: readonly number[];
  /** creature.equipment_id selector: 0, a positive equipment ID, or -1. */
  readonly selector: number;
}

export interface EnemyEquipmentSourceReference {
  readonly equipmentAssignmentsBySpawnGuid: Readonly<Record<string, EnemyEquipmentSpawnAssignment>>;
  readonly equipmentTemplatesByEntry: Readonly<
    Record<string, Readonly<Record<string, EnemyEquipmentTemplateReference>>>
  >;
  readonly equipmentItemsById: Readonly<
    Record<string, EnemyEquipmentItemReference | null>
  >;
}

export interface EnemySpawnEquipmentContract {
  readonly entry: number;
  readonly sourceCreatureGuid: number;
  /** Original creature.equipment_id selector from the pinned spawn row. */
  readonly selector: number;
  /** Concrete equipment ID looked up by the source loader after -1 selection. */
  readonly equipmentId: number;
  /** Item.dbc-sanitized UNIT_VIRTUAL_ITEM_SLOT_ID..+2 values. */
  readonly virtualItemIds: readonly [number, number, number];
  readonly offhandItemId: number;
  readonly offhandItemClass: number | null;
  readonly autoOffhand?: ReturnType<typeof enemyAutoEquippedOffhandContract>;
}

interface AzerothCoreEquipmentReferenceShape {
  readonly creature: EnemyEquipmentSourceReference;
}

const REFERENCE = referenceData as unknown as AzerothCoreEquipmentReferenceShape;
const EMPTY_ITEMS = Object.freeze([0, 0, 0]) as readonly [number, number, number];

/**
 * Resolves the source spawn's equipment selector. AzerothCore uses an exact
 * equipment ID for positive selectors, no items for zero, and for -1 chooses
 * a random ordered map row but rewrites the resulting key to ordinal + 1.
 * This deliberately returns no contract when that source-style follow-up
 * lookup fails (including sparse equipment IDs).
 */
export function enemySpawnEquipmentContract(
  entry: number,
  sourceCreatureGuid: number,
  randomUnit?: number,
  source: EnemyEquipmentSourceReference = REFERENCE.creature,
): EnemySpawnEquipmentContract | undefined {
  if (!Number.isSafeInteger(entry) || entry <= 0
    || !Number.isSafeInteger(sourceCreatureGuid) || sourceCreatureGuid <= 0
    || !source
    || !source.equipmentAssignmentsBySpawnGuid
    || !source.equipmentTemplatesByEntry
    || !source.equipmentItemsById) return undefined;

  const assignment = source.equipmentAssignmentsBySpawnGuid[String(sourceCreatureGuid)];
  if (!assignment || !Array.isArray(assignment.alternateEntries)
    || ![assignment.entry, ...assignment.alternateEntries].includes(entry)) return undefined;

  const requestedTemplates = source.equipmentTemplatesByEntry[String(entry)];
  const sourceVariantEntries = [...new Set([assignment.entry, ...assignment.alternateEntries])];
  let equipmentId = assignment.selector;
  let equipment: EnemyEquipmentTemplateReference | undefined;
  if (assignment.selector === 0) {
    equipmentId = 0;
  } else if (assignment.selector === -1) {
    const sourceEntryTemplates = source.equipmentTemplatesByEntry[String(assignment.entry)];
    if (!sourceEntryTemplates) return undefined;
    const availableIds = Object.keys(sourceEntryTemplates)
      .map(Number)
      .filter((id) => Number.isSafeInteger(id) && id > 0)
      .sort((left, right) => left - right);
    if (!availableIds.length || randomUnit === undefined
      || !Number.isFinite(randomUnit) || randomUnit < 0 || randomUnit >= 1) return undefined;

    // ObjectMgr::GetEquipmentInfo sets the mutable ID to distance(begin, row)+1,
    // not the selected map key. Creature::LoadEquipment then looks up that ID.
    equipmentId = Math.floor(randomUnit * availableIds.length) + 1;
    if (assignment.alternateEntries.some((variantEntry) => (
      !source.equipmentTemplatesByEntry[String(variantEntry)]?.[String(equipmentId)]
    ))) return undefined;
    equipment = requestedTemplates?.[String(equipmentId)];
    if (!equipment) return undefined;
  } else if (Number.isSafeInteger(assignment.selector) && assignment.selector > 0) {
    equipmentId = assignment.selector;
    if (sourceVariantEntries.some((variantEntry) => (
      !source.equipmentTemplatesByEntry[String(variantEntry)]?.[String(equipmentId)]
    ))) return undefined;
    equipment = requestedTemplates?.[String(equipmentId)];
    if (!equipment) return undefined;
  } else {
    return undefined;
  }

  const virtualItemIds = equipment?.items ?? EMPTY_ITEMS;
  if (virtualItemIds.length !== 3
    || virtualItemIds.some((itemId) => !Number.isSafeInteger(itemId) || itemId < 0)) return undefined;
  const offhandItemId = virtualItemIds[1];
  const offhandItemClass = offhandItemId > 0
    ? source.equipmentItemsById[String(offhandItemId)]?.itemClass ?? null
    : null;
  const autoOffhand = enemyAutoEquippedOffhandContract({
    entry,
    offhandItemId,
    offhandItemClass,
  });

  return Object.freeze({
    entry,
    sourceCreatureGuid,
    selector: assignment.selector,
    equipmentId,
    virtualItemIds: Object.freeze([...virtualItemIds]) as readonly [number, number, number],
    offhandItemId,
    offhandItemClass,
    ...(autoOffhand ? { autoOffhand } : {}),
  });
}