/**
 * Copyright since 2025 Mifos Initiative
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

/** Angular Imports */
import { Injectable, inject } from '@angular/core';
import { HttpClient, HttpParams } from '@angular/common/http';
import { Observable, map } from 'rxjs';

/** Custom Helpers */
import { toIsoDate } from '../core/utils/api-date';
import { Declaration, formKindFor } from '../letter-mgmt/certificates/form-15gh/tds-15gh.compute';
import { TdsChallan, TdsDeductedMonth, TdsDeductee } from './tds-reports-data';

/** A declaration as recorded on the platform. */
export interface TdsDeclarationRecord {
  id: number;
  clientId: number;
  clientName?: string;
  fy: string;
  formType: '15G' | '15H' | '121';
  uin: string | null;
  acceptedOn: string;
  estimatedIncome: number | null;
  revoked: boolean;
  revokedOn: string | null;
  revokeReason: string | null;
}

export interface NewTdsDeclaration {
  clientId: number;
  fy: string;
  formType: string;
  acceptedOn: string;
  uin?: string;
  estimatedIncome?: number | null;
}

export interface NewTdsChallan {
  fy: string;
  month: string;
  amount: number;
  challanNo: string;
  bsrCode: string;
  depositedOn: string;
  paidFromGlAccountId: number;
  remarks?: string;
}

/**
 * Deposit interest, declarations and challans for the TDS screens.
 *
 * On an FD or RD the platform returns the interest that reached the customer's savings account and
 * the TDS debited there for it — TDS is tracked and taken where the interest is received. A deposit
 * is the customer's own money arriving and a fee is a charge, so neither is income and neither is
 * sent. Working the figure out here from a balance and a rate would produce a number the passbook
 * does not show.
 */
@Injectable({ providedIn: 'root' })
export class TdsReportsService {
  private http = inject(HttpClient);

  /**
   * @param financialYear the opening calendar year — 2026 means 1 Apr 2026 to 31 Mar 2027.
   *        Omit to let the platform use the year the business date falls in.
   */
  getDepositInterest(financialYear?: number, clientId?: number): Observable<TdsDeductee[]> {
    let params = new HttpParams();
    if (financialYear) {
      params = params.set('financialYear', String(financialYear));
    }
    if (clientId) {
      params = params.set('clientId', String(clientId));
    }
    return this.http
      .get<any[]>('/tds/deposit-interest', { params })
      .pipe(map((rows) => (rows || []).map((r) => this.toDeductee(r))));
  }

  getDeclarations(clientId: number): Observable<TdsDeclarationRecord[]> {
    return this.http.get<TdsDeclarationRecord[]>('/tds/declarations', {
      params: new HttpParams().set('clientId', String(clientId))
    });
  }

  createDeclaration(declaration: NewTdsDeclaration): Observable<TdsDeclarationRecord[]> {
    return this.http.post<TdsDeclarationRecord[]>('/tds/declarations', declaration);
  }

  revokeDeclaration(id: number, reason: string): Observable<TdsDeclarationRecord[]> {
    return this.http.post<TdsDeclarationRecord[]>(`/tds/declarations/${id}/revoke`, { reason });
  }

  /** Tax actually withheld per month, and the business date the books are on. */
  getDeducted(fy: string): Observable<{ asAt: string; months: TdsDeductedMonth[] }> {
    return this.http.get<any>('/tds/deducted', { params: new HttpParams().set('fy', fy) }).pipe(
      map((res) => ({
        asAt: res?.asAt ?? '',
        months: (res?.months || []).map((m: any) => ({
          month: m.month,
          amount: Number(m.amount) || 0,
          postings: Number(m.postings) || 0
        }))
      }))
    );
  }

  getChallans(fy: string): Observable<TdsChallan[]> {
    return this.http
      .get<any[]>('/tds/challans', { params: new HttpParams().set('fy', fy) })
      .pipe(map((rows) => (rows || []).map((r) => this.toChallan(r))));
  }

  getChallanTemplate(): Observable<{ paidFromOptions: { id: number; glCode: string; name: string }[] }> {
    return this.http.get<any>('/tds/challans/template');
  }

  createChallan(challan: NewTdsChallan): Observable<TdsChallan[]> {
    return this.http
      .post<any[]>('/tds/challans', challan)
      .pipe(map((rows) => (rows || []).map((r) => this.toChallan(r))));
  }

  reverseChallan(id: number): Observable<TdsChallan[]> {
    return this.http
      .post<any[]>(`/tds/challans/${id}/reverse`, {})
      .pipe(map((rows) => (rows || []).map((r) => this.toChallan(r))));
  }

  private toChallan(r: any): TdsChallan {
    return {
      id: r.id,
      fy: r.fy,
      month: r.month,
      amount: Number(r.amount) || 0,
      challanNo: r.challanNo,
      bsrCode: r.bsrCode,
      depositedOn: (r.depositedOn || '').slice(0, 10),
      paidFrom: r.paidFrom || '',
      remarks: r.remarks ?? null,
      reversed: !!r.reversed
    };
  }

  /**
   * Shapes one platform row into what the TDS computation expects.
   *
   * Dates arrive as [y, M, d] arrays and are flattened to ISO here, because the computation
   * compares them as strings when deciding which financial year a credit falls in. The platform
   * has already grouped a minor's deposit under the guardian and a joint deposit under its primary
   * holder, so every account here belongs to the deductee it is listed under.
   */
  private toDeductee(row: any): TdsDeductee {
    const dob = toIsoDate(row.dateOfBirth);
    const credit = (a: any) => (c: any) => ({
      date: toIsoDate(c.date),
      amount: Number(c.amount) || 0,
      accountNo: c.accountNo || a.accountNo || ''
    });
    return {
      clientId: row.clientId,
      customerId: row.customerId || '',
      name: row.name || '',
      pan: row.pan || '',
      dob,
      branchCode: row.branchName || '',
      declarations: this.declarationsOf(row.declarations || [], dob),
      accounts: (row.accounts || []).map((a: any) => ({
        id: a.id,
        accountNo: a.accountNo || '',
        depositTypeCode: a.depositTypeCode || '',
        // The deductee, not the holder: the grouping above already resolved whose PAN it is.
        clientId: a.clientId ?? row.clientId,
        holderClientId: a.holderClientId ?? undefined,
        holderName: a.holderName ?? undefined,
        credits: (a.credits || []).map(credit(a)),
        deductions: (a.deductions || []).map(credit(a))
      }))
    };
  }

  /**
   * Declarations keyed by year, the form the computation looks them up by ('2026-27'). A Form 121
   * carries no G/H split, so the band follows the customer's age in that year.
   */
  private declarationsOf(rows: any[], dob: string): Record<string, Declaration> {
    const out: Record<string, Declaration> = {};
    for (const d of rows) {
      const fy = d.fy;
      const kind = d.formType === '15H' ? '15H' : d.formType === '15G' ? '15G' : formKindFor(dob, fy);
      out[fy] = { kind, acceptedOn: toIsoDate(d.acceptedOn), fy, uin: d.uin || undefined };
    }
    return out;
  }
}