/**
 * Resource Interaction System — Phase 4.3
 *
 * Handles player collecting elements from world resources
 * (mineral veins, geysers). Press E near a resource to collect.
 */

import { query } from 'bitecs';
import type { World } from '../ecs/world';
import { Position, Resource, PlayerTag } from '../ecs/components';
import { removeGameEntity } from '../ecs/factory';
import type { Inventory } from './inventory';

/** Metadata for a resource entity (string data that can't go in bitECS arrays) */
export interface ResourceInfo {
  itemId: string;   // element symbol or compound id
  tileX: number;
  tileY: number;
}

/** Result of an interaction attempt */
export interface InteractionResult {
  type: 'collected' | 'depleted' | 'inventory_full' | 'nothing_nearby';
  itemId?: string;
  remaining?: number;
}

/** Elements that mineral veins can yield */
export const MINERAL_ELEMENTS = ['Fe', 'Cu', 'Zn', 'Au', 'Sn'] as const;

/** Elements that geysers can yield */
export const GEYSER_ELEMENTS = ['S', 'H'] as const;

/**
 * Deterministic element picker based on tile position and seed.
 * Same (x, y, seed) always gives the same element.
 */
export function pickResourceElement(
  tileX: number,
  tileY: number,
  seed: number,
  options: readonly string[],
): string {
  // Multiplicative hash for spatial distribution
  const hash = ((tileX * 73856093) ^ (tileY * 19349663) ^ (seed * 83492791)) >>> 0;
  return options[hash % options.length];
}

/**
 * Interaction system — handles E-key resource collection.
 *
 * Finds closest resource in range, adds to inventory, decrements quantity.
 * Returns null if E not pressed, or InteractionResult describing what happened.
 */
export function interactionSystem(
  world: World,
  justPressedInteract: boolean,
  inventory: Inventory,
  resourceData: Map<number, ResourceInfo>,
): InteractionResult | null {
  if (!justPressedInteract) return null;

  // Find player position
  const players = query(world, [Position, PlayerTag]);
  if (players.length === 0) return null;
  const playerEid = players[0];
  const px = Position.x[playerEid];
  const py = Position.y[playerEid];

  // Find closest resource in range
  let closestEid: number | null = null;
  let closestDist = Infinity;

  for (const eid of query(world, [Position, Resource])) {
    const dx = Position.x[eid] - px;
    const dy = Position.y[eid] - py;
    const dist = Math.sqrt(dx * dx + dy * dy);
    const range = Resource.interactRange[eid];

    if (dist <= range && dist < closestDist) {
      closestEid = eid;
      closestDist = dist;
    }
  }

  if (closestEid === null) {
    return { type: 'nothing_nearby' };
  }

  const info = resourceData.get(closestEid);
  if (!info) return { type: 'nothing_nearby' };

  // Try to add to inventory
  const added = inventory.addItem(info.itemId, 1);
  if (added === 0) {
    return { type: 'inventory_full', itemId: info.itemId };
  }

  // Decrement resource quantity
  Resource.quantity[closestEid] -= 1;

  if (Resource.quantity[closestEid] <= 0) {
    // Resource depleted — remove entity
    removeGameEntity(world, closestEid);
    resourceData.delete(closestEid);
    return { type: 'depleted', itemId: info.itemId };
  }

  return {
    type: 'collected',
    itemId: info.itemId,
    remaining: Resource.quantity[closestEid],
  };
}