import { Injectable } from '@nestjs/common';
import { DataSource } from 'typeorm';
import { CharacterEquipment } from '../equipment/entities/character-equipment.entity';
import { EquipmentSlot } from '../items/equipment-slot.enum';
import { HP_REGEN_PER_SECOND } from './character-vitals.constants';
import { CharacterVitalsService } from './character-vitals.service';
import { Character } from './entities/character.entity';

export interface EffectiveCharacterStats {
  maxHp: number;
  currentHp: number;
  attack: number;
  weaponDamage: number;
  armor: number;
  combatPower: number;
  hpRegenPerSecond: number;
  hpRegenSince: Date | null;
}

type RepositoryScope = Pick<DataSource, 'getRepository'>;

/**
 * Single authoritative source of effective character stats (spec §18).
 * Replaces the Slice 0.3 `CharacterCombatStatsService` shortcut.
 */
@Injectable()
export class CharacterStatsService {
  constructor(
    private readonly dataSource: DataSource,
    private readonly characterVitals: CharacterVitalsService,
  ) {}

  async calculate(
    character: Character,
    scope?: RepositoryScope,
  ): Promise<EffectiveCharacterStats> {
    const db = scope ?? this.dataSource;
    const equipped = await db.getRepository(CharacterEquipment).find({
      where: { characterId: character.id },
      relations: { characterItem: { itemDefinition: true } },
    });

    let weaponDamage = 0;
    let bonusHp = 0;
    let bonusAttack = 0;
    let bonusArmor = 0;

    for (const slot of equipped) {
      const definition = slot.characterItem.itemDefinition;
      if (slot.slot === EquipmentSlot.WEAPON) {
        weaponDamage = definition.weaponDamage;
      }
      bonusHp += definition.bonusHp;
      bonusAttack += definition.bonusAttack;
      bonusArmor += definition.bonusArmor;
    }

    const maxHp = character.baseHp + bonusHp;
    const attack = character.baseAttack + bonusAttack;
    const armor = bonusArmor;

    return {
      maxHp,
      currentHp: this.characterVitals.effectiveHp(character, maxHp),
      attack,
      weaponDamage,
      armor,
      combatPower: maxHp / 10 + attack * 2 + weaponDamage * 2 + armor * 1.5,
      hpRegenPerSecond: HP_REGEN_PER_SECOND,
      hpRegenSince: character.hpRegenSince,
    };
  }
}