import { BadRequestException, Injectable } from "@nestjs/common";
import { DataSource } from "typeorm";

import type { ActorContext } from "../../common/current-actor.util";
import { LEDGER_CURRENCY, roundMoney } from "../../common/money";

/**
 * Module 4.6 — financial reports.
 *
 * Read-only, raw SQL, exactly the approach HR's 3.7 reports settled on: these
 * are cross-table aggregates over posted entries, and expressing them through
 * an ORM would obscure arithmetic that has to be readable to be trusted.
 *
 * Two rules hold throughout:
 *
 *  1. **Only POSTED entries count.** A draft has not happened. Every query
 *     filters `status <> 'DRAFT'`, and REVERSED entries ARE included — a
 *     reversal is a real transaction, and its own mirrored entry is what
 *     cancels it out. Excluding reversed entries would leave the reversal
 *     unmatched and unbalance the books.
 *
 *  2. **Sign by normal balance.** A debit-balance account reports
 *     debits − credits; a credit-balance account the reverse. Reporting raw
 *     debits − credits everywhere would show all revenue as negative.
 */
const num = (v: unknown): number => Number(v ?? 0);

/** Posted, non-deleted, in this organization — the base every report shares. */
const POSTED = `e.status <> 'DRAFT' AND e.deleted_at IS NULL AND e.organization_id = $1`;

export type TrialBalanceRow = {
  accountCode: string;
  accountName: { am: string; en: string };
  accountType: string;
  normalBalance: string;
  debit: number;
  credit: number;
};

@Injectable()
export class ReportsService {
  constructor(private readonly dataSource: DataSource) {}

  /**
   * Trial balance — every account's net movement, in the column its balance
   * naturally falls in.
   *
   * The totals MUST match. If they do not, something has bypassed the journal
   * service (a hand-written UPDATE, a restore from a bad backup), and the
   * report says so rather than presenting two different numbers side by side
   * and leaving the reader to notice.
   */
  async trialBalance(
    actor: ActorContext,
    dateFrom: string,
    dateTo: string,
  ): Promise<{
    rows: TrialBalanceRow[];
    totalDebit: number;
    totalCredit: number;
    balanced: boolean;
    difference: number;
  }> {
    const organizationId = this.requireOrganization(actor);

    const rows = await this.dataSource.query<Record<string, unknown>[]>(
      `SELECT a.code                       AS "accountCode",
              a.name                       AS "accountName",
              a.account_type               AS "accountType",
              a.normal_balance             AS "normalBalance",
              ROUND(COALESCE(SUM(l.debit), 0), 2)  AS "debitTotal",
              ROUND(COALESCE(SUM(l.credit), 0), 2) AS "creditTotal"
         FROM finance.accounts a
         JOIN finance.journal_lines l   ON l.account_id = a.id
         JOIN finance.journal_entries e ON e.id = l.journal_entry_id
        WHERE ${POSTED}
          AND e.entry_date >= $2::date
          AND e.entry_date <= $3::date
          AND a.deleted_at IS NULL
        GROUP BY a.id, a.code, a.name, a.account_type, a.normal_balance
       HAVING COALESCE(SUM(l.debit), 0) <> 0 OR COALESCE(SUM(l.credit), 0) <> 0
        ORDER BY a.code ASC`,
      [organizationId, dateFrom, dateTo],
    );

    const mapped: TrialBalanceRow[] = rows.map((row) => {
      const debitTotal = num(row.debitTotal);
      const creditTotal = num(row.creditTotal);
      const net = roundMoney(debitTotal - creditTotal);
      // Each account reports ONE side — its net, in the column it belongs in.
      // Showing gross debits and credits for every account would inflate both
      // totals and hide whether the account is actually in an odd position.
      return {
        accountCode: String(row.accountCode),
        accountName: row.accountName as { am: string; en: string },
        accountType: String(row.accountType),
        normalBalance: String(row.normalBalance),
        debit: net > 0 ? net : 0,
        credit: net < 0 ? roundMoney(-net) : 0,
      };
    });

    const totalDebit = roundMoney(mapped.reduce((s, r) => s + r.debit, 0));
    const totalCredit = roundMoney(mapped.reduce((s, r) => s + r.credit, 0));
    const difference = roundMoney(totalDebit - totalCredit);

    return {
      rows: mapped,
      totalDebit,
      totalCredit,
      balanced: Math.abs(difference) < 0.005,
      difference,
    };
  }

  /**
   * Profit and loss for a date range.
   *
   * `is_contra` is deliberately NOT applied as a sign flip here. Signing by the
   * account's normal balance already produces the right answer: a contra
   * revenue account (sales returns) accrues on the debit side, so
   * `credit − debit` comes out negative and reduces revenue on its own.
   * Flipping again would turn a deduction into an addition. The flag is
   * presentational — it tells the UI to indent the line, not the arithmetic to
   * invert it.
   */
  async profitAndLoss(actor: ActorContext, dateFrom: string, dateTo: string) {
    const organizationId = this.requireOrganization(actor);

    const rows = await this.dataSource.query<Record<string, unknown>[]>(
      `SELECT a.code           AS "accountCode",
              a.name           AS "accountName",
              a.account_type   AS "accountType",
              a.is_contra      AS "isContra",
              ROUND(COALESCE(SUM(
                CASE WHEN a.normal_balance = 'CREDIT'
                     THEN l.credit - l.debit
                     ELSE l.debit - l.credit END), 0), 2) AS amount
         FROM finance.accounts a
         JOIN finance.journal_lines l   ON l.account_id = a.id
         JOIN finance.journal_entries e ON e.id = l.journal_entry_id
        WHERE ${POSTED}
          AND e.entry_date >= $2::date
          AND e.entry_date <= $3::date
          AND a.account_type IN ('REVENUE','EXPENSE')
          AND a.deleted_at IS NULL
        GROUP BY a.id, a.code, a.name, a.account_type, a.is_contra
       HAVING COALESCE(SUM(l.debit), 0) <> 0 OR COALESCE(SUM(l.credit), 0) <> 0
        ORDER BY a.code ASC`,
      [organizationId, dateFrom, dateTo],
    );

    const signed = rows.map((row) => ({
      accountCode: String(row.accountCode),
      accountName: row.accountName as { am: string; en: string },
      accountType: String(row.accountType),
      isContra: Boolean(row.isContra),
      amount: num(row.amount),
    }));

    const revenue = signed.filter((r) => r.accountType === "REVENUE");
    const expenses = signed.filter((r) => r.accountType === "EXPENSE");
    const totalRevenue = roundMoney(revenue.reduce((s, r) => s + r.amount, 0));
    const totalExpenses = roundMoney(expenses.reduce((s, r) => s + r.amount, 0));

    return {
      dateFrom,
      dateTo,
      currency: LEDGER_CURRENCY,
      revenue,
      expenses,
      totalRevenue,
      totalExpenses,
      netResult: roundMoney(totalRevenue - totalExpenses),
    };
  }

  /**
   * Balance sheet as at a date.
   *
   * Everything up to `asOf`, not a range — a balance sheet is a position, not a
   * movement. The accounting equation is checked and reported: assets must
   * equal liabilities plus equity plus the result earned so far, and that last
   * term is why the P&L has to be folded in rather than shown separately.
   *
   * As in the P&L, `is_contra` is NOT applied as a sign flip. Accumulated
   * depreciation is an ASSET-type account that carries a credit balance, so
   * signing by type already yields a negative figure that reduces total assets.
   * Flipping it as well made it positive and ADDED the depreciation to the
   * asset side — which is precisely how the equation came out wrong by twice
   * the accumulated depreciation.
   */
  async balanceSheet(actor: ActorContext, asOf: string) {
    const organizationId = this.requireOrganization(actor);

    const rows = await this.dataSource.query<Record<string, unknown>[]>(
      `SELECT a.code         AS "accountCode",
              a.name         AS "accountName",
              a.account_type AS "accountType",
              a.is_contra    AS "isContra",
              ROUND(COALESCE(SUM(
                CASE WHEN a.normal_balance = 'DEBIT'
                     THEN l.debit - l.credit
                     ELSE l.credit - l.debit END), 0), 2) AS balance
         FROM finance.accounts a
         JOIN finance.journal_lines l   ON l.account_id = a.id
         JOIN finance.journal_entries e ON e.id = l.journal_entry_id
        WHERE ${POSTED}
          AND e.entry_date <= $2::date
          AND a.account_type IN ('ASSET','LIABILITY','EQUITY')
          AND a.deleted_at IS NULL
        GROUP BY a.id, a.code, a.name, a.account_type, a.is_contra
       HAVING COALESCE(SUM(l.debit), 0) <> 0 OR COALESCE(SUM(l.credit), 0) <> 0
        ORDER BY a.code ASC`,
      [organizationId, asOf],
    );

    const signed = rows.map((row) => ({
      accountCode: String(row.accountCode),
      accountName: row.accountName as { am: string; en: string },
      accountType: String(row.accountType),
      isContra: Boolean(row.isContra),
      balance: num(row.balance),
    }));

    const assets = signed.filter((r) => r.accountType === "ASSET");
    const liabilities = signed.filter((r) => r.accountType === "LIABILITY");
    const equity = signed.filter((r) => r.accountType === "EQUITY");

    const totalAssets = roundMoney(assets.reduce((s, r) => s + r.balance, 0));
    const totalLiabilities = roundMoney(
      liabilities.reduce((s, r) => s + r.balance, 0),
    );
    const totalEquity = roundMoney(equity.reduce((s, r) => s + r.balance, 0));

    // Revenue less expenses to date is part of equity but has not been closed
    // into it. Omitting it is why a balance sheet "does not balance".
    const [result] = await this.dataSource.query<Record<string, unknown>[]>(
      // Revenue counts positively, expenses negatively. No contra flip, for the
      // same reason as above — the natural side of the account already carries
      // the sign.
      `SELECT ROUND(COALESCE(SUM(
                CASE WHEN a.account_type = 'REVENUE'
                     THEN l.credit - l.debit
                     ELSE -(l.debit - l.credit) END), 0), 2) AS "netResult"
         FROM finance.accounts a
         JOIN finance.journal_lines l   ON l.account_id = a.id
         JOIN finance.journal_entries e ON e.id = l.journal_entry_id
        WHERE ${POSTED}
          AND e.entry_date <= $2::date
          AND a.account_type IN ('REVENUE','EXPENSE')
          AND a.deleted_at IS NULL`,
      [organizationId, asOf],
    );
    const retainedResult = num(result?.netResult);
    const equityWithResult = roundMoney(totalEquity + retainedResult);
    const difference = roundMoney(
      totalAssets - (totalLiabilities + equityWithResult),
    );

    return {
      asOf,
      currency: LEDGER_CURRENCY,
      assets,
      liabilities,
      equity,
      totalAssets,
      totalLiabilities,
      totalEquity,
      /** Revenue less expenses to date — part of equity, not yet closed into it. */
      retainedResult,
      equityWithResult,
      balanced: Math.abs(difference) < 0.005,
      difference,
    };
  }

  /**
   * Cash movement over a range, by cash/bank account.
   *
   * A direct cash view rather than an indirect cash-flow statement: the
   * indirect method needs opening/closing working-capital positions that only
   * mean something once a full year has been posted, and presenting a
   * half-derived one would be worse than presenting the movements plainly.
   */
  async cashMovement(actor: ActorContext, dateFrom: string, dateTo: string) {
    const organizationId = this.requireOrganization(actor);

    const rows = await this.dataSource.query<Record<string, unknown>[]>(
      `SELECT a.code AS "accountCode",
              a.name AS "accountName",
              ROUND(COALESCE(SUM(
                CASE WHEN e.entry_date < $2::date THEN l.debit - l.credit ELSE 0 END), 0), 2) AS "opening",
              ROUND(COALESCE(SUM(
                CASE WHEN e.entry_date BETWEEN $2::date AND $3::date THEN l.debit ELSE 0 END), 0), 2) AS "cashIn",
              ROUND(COALESCE(SUM(
                CASE WHEN e.entry_date BETWEEN $2::date AND $3::date THEN l.credit ELSE 0 END), 0), 2) AS "cashOut",
              ROUND(COALESCE(SUM(
                CASE WHEN e.entry_date <= $3::date THEN l.debit - l.credit ELSE 0 END), 0), 2) AS "closing"
         FROM finance.accounts a
         JOIN finance.journal_lines l   ON l.account_id = a.id
         JOIN finance.journal_entries e ON e.id = l.journal_entry_id
        WHERE ${POSTED}
          AND a.account_type = 'ASSET'
          AND a.code LIKE '111%'
          AND a.deleted_at IS NULL
        GROUP BY a.id, a.code, a.name
        ORDER BY a.code ASC`,
      [organizationId, dateFrom, dateTo],
    );

    const accounts = rows.map((row) => ({
      accountCode: String(row.accountCode),
      accountName: row.accountName as { am: string; en: string },
      opening: num(row.opening),
      cashIn: num(row.cashIn),
      cashOut: num(row.cashOut),
      closing: num(row.closing),
    }));

    return {
      dateFrom,
      dateTo,
      currency: LEDGER_CURRENCY,
      accounts,
      totalOpening: roundMoney(accounts.reduce((s, a) => s + a.opening, 0)),
      totalIn: roundMoney(accounts.reduce((s, a) => s + a.cashIn, 0)),
      totalOut: roundMoney(accounts.reduce((s, a) => s + a.cashOut, 0)),
      totalClosing: roundMoney(accounts.reduce((s, a) => s + a.closing, 0)),
    };
  }

  /**
   * The general ledger for one account — every line, with a running balance.
   *
   * The running balance is computed in SQL with a window function rather than
   * in JavaScript, so a paged view still shows the correct balance at each row
   * instead of one that restarts at the top of every page.
   */
  async generalLedger(
    actor: ActorContext,
    accountId: string,
    dateFrom: string,
    dateTo: string,
  ) {
    const organizationId = this.requireOrganization(actor);

    const [opening] = await this.dataSource.query<Record<string, unknown>[]>(
      `SELECT ROUND(COALESCE(SUM(
                CASE WHEN a.normal_balance = 'DEBIT'
                     THEN l.debit - l.credit
                     ELSE l.credit - l.debit END), 0), 2) AS "openingBalance"
         FROM finance.journal_lines l
         JOIN finance.journal_entries e ON e.id = l.journal_entry_id
         JOIN finance.accounts a        ON a.id = l.account_id
        WHERE ${POSTED} AND l.account_id = $2 AND e.entry_date < $3::date`,
      [organizationId, accountId, dateFrom],
    );

    const lines = await this.dataSource.query<Record<string, unknown>[]>(
      `SELECT e.entry_date::text AS "entryDate",
              e.entry_number     AS "entryNumber",
              e.memo,
              e.journal_type     AS "journalType",
              l.description,
              l.debit,
              l.credit,
              cc.code            AS "costCenterCode",
              SUM(CASE WHEN a.normal_balance = 'DEBIT'
                       THEN l.debit - l.credit
                       ELSE l.credit - l.debit END)
                OVER (ORDER BY e.entry_date, e.entry_number, l.line_number
                      ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS "movementToDate"
         FROM finance.journal_lines l
         JOIN finance.journal_entries e ON e.id = l.journal_entry_id
         JOIN finance.accounts a        ON a.id = l.account_id
         LEFT JOIN finance.cost_centers cc ON cc.id = l.cost_center_id
        WHERE ${POSTED}
          AND l.account_id = $2
          AND e.entry_date >= $3::date
          AND e.entry_date <= $4::date
        ORDER BY e.entry_date ASC, e.entry_number ASC, l.line_number ASC`,
      [organizationId, accountId, dateFrom, dateTo],
    );

    const openingBalance = num(opening?.openingBalance);
    return {
      openingBalance,
      lines: lines.map((row) => ({
        entryDate: String(row.entryDate),
        entryNumber: String(row.entryNumber),
        memo: String(row.memo ?? ""),
        journalType: String(row.journalType),
        description: row.description ? String(row.description) : null,
        costCenterCode: row.costCenterCode ? String(row.costCenterCode) : null,
        debit: num(row.debit),
        credit: num(row.credit),
        balance: roundMoney(openingBalance + num(row.movementToDate)),
      })),
      closingBalance: roundMoney(
        openingBalance + num(lines[lines.length - 1]?.movementToDate),
      ),
    };
  }

  /**
   * Revenue by mapped category — what the revenue mappings are for.
   *
   * Grouped on the mapping's `revenue_category` rather than the account, so
   * several accounts rolling up to one commercial category report as one line.
   */
  async revenueByCategory(actor: ActorContext, dateFrom: string, dateTo: string) {
    const organizationId = this.requireOrganization(actor);

    const rows = await this.dataSource.query<Record<string, unknown>[]>(
      `SELECT COALESCE(m.revenue_category, 'UNMAPPED') AS category,
              a.code AS "accountCode",
              a.name AS "accountName",
              ROUND(COALESCE(SUM(l.credit - l.debit), 0), 2) AS amount
         FROM finance.accounts a
         JOIN finance.journal_lines l   ON l.account_id = a.id
         JOIN finance.journal_entries e ON e.id = l.journal_entry_id
         LEFT JOIN LATERAL (
           SELECT rm.revenue_category
             FROM finance.revenue_mappings rm
            WHERE rm.account_id = a.id
              AND rm.organization_id = $1
              AND rm.deleted_at IS NULL
            LIMIT 1
         ) m ON TRUE
        WHERE ${POSTED}
          AND e.entry_date >= $2::date
          AND e.entry_date <= $3::date
          AND a.account_type = 'REVENUE'
          AND a.deleted_at IS NULL
        GROUP BY m.revenue_category, a.id, a.code, a.name
       HAVING COALESCE(SUM(l.credit - l.debit), 0) <> 0
        ORDER BY 1 ASC, 2 ASC`,
      [organizationId, dateFrom, dateTo],
    );

    return rows.map((row) => ({
      category: String(row.category),
      accountCode: String(row.accountCode),
      accountName: row.accountName as { am: string; en: string },
      amount: num(row.amount),
    }));
  }

  private requireOrganization(actor: ActorContext): string {
    if (!actor.organizationId) {
      throw new BadRequestException(
        "This account has no organization context, so it cannot read finance reports",
      );
    }
    return actor.organizationId;
  }
}