import { Injectable } from "@nestjs/common";
import { StorageService } from "../storage/storage.service";
import { CreateTaxReturnDto } from "./dto/create-return.dto";
import { UpdateTaxReturnDto } from "./dto/update-return.dto";

@Injectable()
export class TaxService {
  constructor(private readonly storage: StorageService) {}

  async listReturns(userId?: string) {
    const snapshot = await this.storage.load();
    return userId
      ? snapshot.taxReturns.filter((ret) => ret.userId === userId)
      : [];
  }

  async createReturn(payload: CreateTaxReturnDto) {
    const snapshot = await this.storage.load();
    const now = this.storage.now();
    const next = {
      id: this.storage.createId(),
      userId: payload.userId,
      taxYear: payload.taxYear,
      filingType: payload.filingType,
      jurisdictions: payload.jurisdictions,
      status: "draft" as const,
      createdAt: now,
      updatedAt: now,
      summary: {}
    };
    snapshot.taxReturns.push(next);
    await this.storage.save(snapshot);
    return next;
  }

  async updateReturn(id: string, payload: UpdateTaxReturnDto) {
    const snapshot = await this.storage.load();
    const index = snapshot.taxReturns.findIndex((ret) => ret.id === id);
    if (index === -1) {
      return null;
    }
    const existing = snapshot.taxReturns[index];
    const next = {
      ...existing,
      status: payload.status ?? existing.status,
      summary: payload.summary ?? existing.summary,
      updatedAt: this.storage.now()
    };
    snapshot.taxReturns[index] = next;
    await this.storage.save(snapshot);
    return next;
  }

  async addDocument(returnId: string, docType: string, metadata: Record<string, unknown>) {
    const snapshot = await this.storage.load();
    const doc = {
      id: this.storage.createId(),
      taxReturnId: returnId,
      docType,
      metadata,
      createdAt: this.storage.now()
    };
    snapshot.taxDocuments.push(doc);
    await this.storage.save(snapshot);
    return doc;
  }

  async exportReturn(id: string) {
    const snapshot = await this.storage.load();
    const taxReturn = snapshot.taxReturns.find((ret) => ret.id === id);
    if (!taxReturn) {
      return null;
    }
    const docs = snapshot.taxDocuments.filter((doc) => doc.taxReturnId === id);
    const payload = {
      return: taxReturn,
      documents: docs
    };
    taxReturn.status = "exported";
    taxReturn.updatedAt = this.storage.now();
    await this.storage.save(snapshot);
    return payload;
  }
}