package com.kaidi.oa.web;

import com.kaidi.oa.common.ApiException;
import com.kaidi.oa.common.ApiResp;
import com.kaidi.oa.common.Money;
import com.kaidi.oa.common.NotFoundException;
import com.kaidi.oa.domain.Invoice;
import com.kaidi.oa.repository.ContractRepository;
import com.kaidi.oa.repository.InvoiceRepository;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.math.BigDecimal;
import java.util.List;

/**
 * Invoice master data. type is one of 进项 / 销项;
 * status is one of 已开 / 已认证 / 作废.
 */
@RestController
@RequestMapping("/api/oa/invoices")
public class InvoiceController {

    /** Invoice statuses that count as issued, i.e. eligible to write back to the contract. */
    private static final java.util.Set<String> ISSUED_STATUSES = java.util.Set.of("已开", "已开票", "已开具", "已认证");

    private final InvoiceRepository invoiceRepo;
    private final ContractRepository contractRepo;

    public InvoiceController(InvoiceRepository invoiceRepo, ContractRepository contractRepo) {
        this.invoiceRepo = invoiceRepo;
        this.contractRepo = contractRepo;
    }

    /**
     * Only 销项 (output/sales) invoices write back to the contract's invoicedAmount
     * (receivable side). 进项 (input/purchase) invoices are payables and must NOT
     * inflate the contract's invoiced amount (H12: 应付被当应收混入资金池).
     * Unspecified type defaults to output for backward compatibility.
     */
    private static boolean isOutput(String type) {
        return !"进项".equals(type);
    }

    /** Amount that writes back to the contract: pre-tax amount, falling back to total. */
    private static BigDecimal writeBackAmount(BigDecimal amount, BigDecimal total) {
        return Money.nz(amount).signum() != 0 ? Money.nz(amount) : Money.nz(total);
    }

    /**
     * Apply a signed delta to the contract's invoicedAmount only when the invoice
     * is output (销项) and issued (counts toward the receivable). sign=+1 books the
     * amount, sign=-1 reverses it. No-op when contractId is null or the invoice does
     * not qualify. Shared by create (book new), update (reverse old + book new) and
     * delete (reverse old) so the contract's invoicedAmount never drifts.
     */
    private void applyContractDelta(Long contractId, String type, String status,
                                    BigDecimal amount, BigDecimal total, int sign) {
        if (contractId == null || !isOutput(type) || !ISSUED_STATUSES.contains(status)) {
            return;
        }
        BigDecimal base = writeBackAmount(amount, total);
        BigDecimal delta = sign < 0 ? base.negate() : base;
        if (delta.signum() == 0) {
            return;
        }
        contractRepo.findById(contractId).ifPresent(contract -> {
            contract.setInvoicedAmount(Money.add(contract.getInvoicedAmount(), delta));
            contractRepo.save(contract);
        });
    }

    @GetMapping
    public ApiResp<List<Invoice>> list(@RequestParam(required = false) Long projectId) {
        List<Invoice> list = (projectId == null)
                ? invoiceRepo.findAll()
                : invoiceRepo.findByProjectId(projectId);
        return ApiResp.ok(list);
    }

    @GetMapping("/{id}")
    public ApiResp<Invoice> get(@PathVariable Long id) {
        return ApiResp.ok(invoiceRepo.findById(id)
                .orElseThrow(() -> new NotFoundException("invoice not found: " + id)));
    }

    // total (price-and-tax sum) is derived server-side as amount + taxAmount;
    // the front-end no longer passes total raw.
    public record CreateInvoiceRequest(
            String code, String number, String type, Double amount, Double taxAmount,
            String partyName, Long projectId, Long contractId, String status,
            String issueDate) {
    }

    @Transactional
    @PostMapping
    public ApiResp<Invoice> create(@RequestBody CreateInvoiceRequest req) {
        if (req.number() == null || req.number().isBlank()) {
            throw new ApiException(400, "发票号码不能为空");
        }
        Invoice v = new Invoice();
        v.setCode(req.code());
        v.setNumber(req.number());
        v.setType(req.type());
        BigDecimal amount = Money.of(req.amount());
        BigDecimal taxAmount = Money.of(req.taxAmount());
        v.setAmount(amount);
        v.setTaxAmount(taxAmount);
        v.setTotal(Money.add(amount, taxAmount)); // -> price-and-tax total = pre-tax amount + tax
        v.setPartyName(req.partyName());
        v.setProjectId(req.projectId());
        v.setContractId(req.contractId());
        // 建单一律以"待开"起始，不接受客户端直接置"已开"——否则建单即把金额回写进合同应收(invoicedAmount)、
        // 绕过开具这一受控动作。开票回写只在后续显式 update(待开→已开) 时发生，使写回有据可查。
        v.setStatus("待开");
        v.setIssueDate(req.issueDate());
        Invoice saved = invoiceRepo.save(v);
        // 新建恒为"待开"，applyContractDelta 对未开具发票为 no-op；此调用保留以兼容（实际不回写）。
        applyContractDelta(saved.getContractId(), saved.getType(), saved.getStatus(),
                saved.getAmount(), saved.getTotal(), +1);
        return ApiResp.ok(saved);
    }

    // total is derived server-side as amount + taxAmount; not accepted from the client.
    public record UpdateInvoiceRequest(
            String code, String number, String type, Double amount, Double taxAmount,
            String partyName, Long projectId, Long contractId, String status,
            String issueDate) {
    }

    /** PUT /{id} -> update an invoice; recomputes price-and-tax total from amount + taxAmount. */
    @Transactional
    @PutMapping("/{id}")
    public ApiResp<Invoice> update(@PathVariable Long id, @RequestBody UpdateInvoiceRequest req) {
        Invoice v = invoiceRepo.findById(id)
                .orElseThrow(() -> new NotFoundException("invoice not found: " + id));
        // Snapshot the pre-update contract booking so we can reverse exactly what was
        // booked before applying the new values (handles 改额/作废/换合同/转进项).
        Long oldContractId = v.getContractId();
        String oldType = v.getType();
        String oldStatus = v.getStatus();
        BigDecimal oldAmount = v.getAmount();
        BigDecimal oldTotal = v.getTotal();
        if (req.number() != null) {
            if (req.number().isBlank()) {
                throw new ApiException(400, "发票号码不能为空");
            }
            v.setNumber(req.number());
        }
        if (req.code() != null) v.setCode(req.code());
        if (req.type() != null) v.setType(req.type());
        if (req.partyName() != null) v.setPartyName(req.partyName());
        if (req.projectId() != null) v.setProjectId(req.projectId());
        if (req.contractId() != null) v.setContractId(req.contractId());
        if (req.status() != null) v.setStatus(req.status());
        if (req.issueDate() != null) v.setIssueDate(req.issueDate());
        // When either money field is supplied, take the new value (else keep current),
        // then re-derive total = amount + taxAmount so total never drifts from its parts.
        if (req.amount() != null || req.taxAmount() != null) {
            BigDecimal amount = req.amount() == null ? v.getAmount() : Money.of(req.amount());
            BigDecimal taxAmount = req.taxAmount() == null ? v.getTaxAmount() : Money.of(req.taxAmount());
            v.setAmount(amount);
            v.setTaxAmount(taxAmount);
            v.setTotal(Money.add(amount, taxAmount)); // -> price-and-tax total = pre-tax amount + tax
        }
        Invoice saved = invoiceRepo.save(v);
        // Reverse the old booking, then book the new one. Either side is a no-op when
        // it does not qualify, so 作废(已开->作废) reverses only, and 待开->已开 books only.
        applyContractDelta(oldContractId, oldType, oldStatus, oldAmount, oldTotal, -1);
        applyContractDelta(saved.getContractId(), saved.getType(), saved.getStatus(),
                saved.getAmount(), saved.getTotal(), +1);
        return ApiResp.ok(saved);
    }

    /** DELETE /{id} -> remove an invoice and reverse its contract booking. */
    @Transactional
    @DeleteMapping("/{id}")
    public ApiResp<Void> delete(@PathVariable Long id) {
        Invoice v = invoiceRepo.findById(id)
                .orElseThrow(() -> new NotFoundException("invoice not found: " + id));
        // Reverse whatever this invoice booked onto the contract before removing it.
        applyContractDelta(v.getContractId(), v.getType(), v.getStatus(),
                v.getAmount(), v.getTotal(), -1);
        invoiceRepo.deleteById(id);
        return ApiResp.ok(null);
    }
}