import { Injectable, NotFoundException, BadRequestException } from '@nestjs/common';
import { TenantService } from '../../database/tenant.service';
import { FiscalPeriodsService } from '../fiscal-periods/fiscal-periods.service';
import { CreateJournalEntryDto } from './dto/create-journal-entry.dto';

@Injectable()
export class JournalEntriesService {
  constructor(
    private tenant: TenantService,
    private fiscalPeriodsService: FiscalPeriodsService,
  ) {}

  async findAll(filters: { from?: string; to?: string; accountId?: string; type?: string }) {
    let sql = `
      SELECT je.*,
        json_agg(json_build_object(
          'id', jel.id, 'account_id', jel.account_id,
          'debit', jel.debit, 'credit', jel.credit, 'memo', jel.memo,
          'account_name', a.name, 'account_number', a.account_number
        )) as lines
      FROM journal_entries je
      LEFT JOIN journal_entry_lines jel ON jel.journal_entry_id = je.id
      LEFT JOIN accounts a ON a.id = jel.account_id
      WHERE 1=1
    `;
    const params: any[] = [];
    let idx = 1;

    if (filters.from) {
      sql += ` AND je.entry_date >= $${idx++}`;
      params.push(filters.from);
    }
    if (filters.to) {
      sql += ` AND je.entry_date <= $${idx++}`;
      params.push(filters.to);
    }
    if (filters.accountId) {
      sql += ` AND je.id IN (SELECT journal_entry_id FROM journal_entry_lines WHERE account_id = $${idx++})`;
      params.push(filters.accountId);
    }
    if (filters.type) {
      sql += ` AND je.entry_type = $${idx++}`;
      params.push(filters.type);
    }

    sql += ' GROUP BY je.id ORDER BY je.entry_date DESC, je.created_at DESC';
    return this.tenant.query(sql, params);
  }

  async findOne(id: string) {
    const rows = await this.tenant.query(
      `SELECT je.*,
        json_agg(json_build_object(
          'id', jel.id, 'account_id', jel.account_id,
          'debit', jel.debit, 'credit', jel.credit, 'memo', jel.memo,
          'account_name', a.name, 'account_number', a.account_number
        )) as lines
      FROM journal_entries je
      LEFT JOIN journal_entry_lines jel ON jel.journal_entry_id = je.id
      LEFT JOIN accounts a ON a.id = jel.account_id
      WHERE je.id = $1
      GROUP BY je.id`,
      [id],
    );
    if (!rows.length) throw new NotFoundException('Journal entry not found');
    return rows[0];
  }

  async create(dto: CreateJournalEntryDto, userId: string) {
    // Validate debits = credits
    const totalDebits = dto.lines.reduce((sum, l) => sum + (l.debit || 0), 0);
    const totalCredits = dto.lines.reduce((sum, l) => sum + (l.credit || 0), 0);

    if (Math.abs(totalDebits - totalCredits) > 0.001) {
      throw new BadRequestException(
        `Debits ($${totalDebits.toFixed(2)}) must equal credits ($${totalCredits.toFixed(2)})`,
      );
    }

    if (dto.lines.length < 2) {
      throw new BadRequestException('Journal entry must have at least 2 lines');
    }

    // Find or create fiscal period
    const entryDate = new Date(dto.entryDate);
    const fp = await this.fiscalPeriodsService.findOrCreate(
      entryDate.getFullYear(),
      entryDate.getMonth() + 1,
    );
    if (fp.status === 'locked') {
      throw new BadRequestException('Cannot post to a locked fiscal period');
    }
    if (fp.status === 'closed') {
      throw new BadRequestException('Cannot post to a closed fiscal period');
    }

    // Create journal entry
    const jeRows = await this.tenant.query(
      `INSERT INTO journal_entries (entry_date, description, reference_number, entry_type, fiscal_period_id, source_type, source_id, created_by)
       VALUES ($1, $2, $3, $4, $5, $6, $7, $8) RETURNING *`,
      [
        dto.entryDate,
        dto.description,
        dto.referenceNumber || null,
        dto.entryType || 'manual',
        fp.id,
        dto.sourceType || null,
        dto.sourceId || null,
        userId,
      ],
    );
    const je = jeRows[0];

    // Create lines
    for (const line of dto.lines) {
      await this.tenant.query(
        `INSERT INTO journal_entry_lines (journal_entry_id, account_id, debit, credit, memo)
         VALUES ($1, $2, $3, $4, $5)`,
        [je.id, line.accountId, line.debit || 0, line.credit || 0, line.memo || null],
      );
    }

    return this.findOne(je.id);
  }

  async post(id: string, userId: string) {
    const je = await this.findOne(id);
    if (je.is_posted) throw new BadRequestException('Already posted');
    if (je.is_void) throw new BadRequestException('Cannot post a voided entry');

    // Update account balances
    for (const line of je.lines) {
      const debit = parseFloat(line.debit) || 0;
      const credit = parseFloat(line.credit) || 0;
      const netAmount = debit - credit;

      await this.tenant.query(
        `UPDATE accounts SET balance = balance + $1, updated_at = NOW() WHERE id = $2`,
        [netAmount, line.account_id],
      );
    }

    await this.tenant.query(
      `UPDATE journal_entries SET is_posted = true, posted_by = $1, posted_at = NOW() WHERE id = $2`,
      [userId, id],
    );
    return this.findOne(id);
  }

  async void(id: string, userId: string, reason: string) {
    const je = await this.findOne(id);
    if (!je.is_posted) throw new BadRequestException('Cannot void an unposted entry');
    if (je.is_void) throw new BadRequestException('Already voided');

    // Reverse account balances
    for (const line of je.lines) {
      const debit = parseFloat(line.debit) || 0;
      const credit = parseFloat(line.credit) || 0;
      const reverseAmount = credit - debit;

      await this.tenant.query(
        `UPDATE accounts SET balance = balance + $1, updated_at = NOW() WHERE id = $2`,
        [reverseAmount, line.account_id],
      );
    }

    await this.tenant.query(
      `UPDATE journal_entries SET is_void = true, voided_by = $1, voided_at = NOW(), void_reason = $2 WHERE id = $3`,
      [userId, reason, id],
    );

    // Create reversing entry
    const reverseDto: CreateJournalEntryDto = {
      entryDate: new Date().toISOString().split('T')[0],
      description: `VOID: ${je.description}`,
      referenceNumber: `VOID-${je.reference_number || je.id.slice(0, 8)}`,
      entryType: 'adjustment',
      lines: je.lines.map((l: any) => ({
        accountId: l.account_id,
        debit: parseFloat(l.credit) || 0,
        credit: parseFloat(l.debit) || 0,
        memo: `Reversal of voided entry`,
      })),
    };

    const reversing = await this.create(reverseDto, userId);
    await this.post(reversing.id, userId);

    return this.findOne(id);
  }
}