package com.lincfusion.udyamlinc.apex;

import com.lincfusion.udyamlinc.common.ResourceNotFoundException;
import com.lincfusion.udyamlinc.enterprise.Enterprise;
import com.lincfusion.udyamlinc.enterprise.EnterpriseRepository;
import com.lincfusion.udyamlinc.institution.*;
import com.lincfusion.udyamlinc.master.District;
import com.lincfusion.udyamlinc.master.DistrictRepository;
import com.lincfusion.udyamlinc.security.TenantContext;
import lombok.RequiredArgsConstructor;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;

import java.math.BigDecimal;
import java.util.*;

/**
 * The supervisory tier between head office and a partner bank.
 *
 * <p>Every rollup here resolves through {@code branch → district → state →
 * office} rather than through anything stored on the bank. Six of the eight
 * partner banks are RRBs and state-bound, so a bank-level office column would
 * look right today and be wrong the moment the SFB opens a branch in a second
 * state.
 *
 * <p>Nothing on this surface returns a borrower. An office is NABARD, and the
 * reason the apex tier can be trusted with a national portfolio view at all is
 * that it can never reach a customer — extending that view to a Regional Office
 * must not quietly extend the entitlement with it.
 */
@Service
@RequiredArgsConstructor
public class RegionalOfficeService {

    private final RegionalOfficeRepository officeRepository;
    private final RegionalOfficeStateRepository officeStateRepository;
    private final InstitutionRepository institutionRepository;
    private final BranchRepository branchRepository;
    private final DistrictRepository districtRepository;
    private final EnterpriseRepository enterpriseRepository;

    @Value("${udyam.apex.min-cell-size:5}")
    private int minCellSize;

    @Value("${udyam.apex.min-cell-size.regional-office:5}")
    private int minCellSizeRegional;

    /** The threshold that applies to this caller — see the note in the properties file. */
    private int minCellFor(TenantContext tenant) {
        return tenant != null && tenant.isRegionalOffice() ? minCellSizeRegional : minCellSize;
    }

    /**
     * Offices visible to this caller: all of them for head office, exactly one
     * for a Regional Office user.
     *
     * @param populatedOnly hide offices with no portfolio. Nineteen of the
     *                      twenty-five are empty in the pilot, which is truthful
     *                      but makes a screen look broken, so the console can ask
     *                      for either.
     */
    public List<Map<String, Object>> offices(TenantContext tenant, boolean populatedOnly) {
        Long scoped = tenant.regionalOfficeFilter();
        Context ctx = load();

        List<Map<String, Object>> out = new ArrayList<>();
        for (RegionalOffice office : ctx.offices) {
            if (scoped != null && !office.getId().equals(scoped)) continue;
            Map<String, Object> row = summarise(office, ctx, tenant);
            if (populatedOnly && (int) row.get("enterprises") == 0) continue;
            out.add(row);
        }
        out.sort((a, b) -> Integer.compare((int) b.get("enterprises"), (int) a.get("enterprises")));
        return out;
    }

    /**
     * The banks one office supervises, with the response-rate column an apex
     * supervisor actually acts on.
     *
     * <p>An office the caller is not entitled to returns <b>404</b>, identical to
     * a code that does not exist. A 403 would confirm the office is real and
     * simply not theirs, which is the same reasoning that governs cross-tenant
     * borrower reads.
     */
    public List<Map<String, Object>> banks(TenantContext tenant, String officeCode) {
        Context ctx = load();
        RegionalOffice office = ctx.offices.stream()
                .filter(o -> o.getCode().equalsIgnoreCase(officeCode))
                .findFirst()
                .orElseThrow(() -> new ResourceNotFoundException("No such regional office"));

        Long scoped = tenant.regionalOfficeFilter();
        if (scoped != null && !office.getId().equals(scoped)) {
            throw new ResourceNotFoundException("No such regional office");
        }

        Set<Long> districts = districtIdsOf(office, ctx);
        Map<Long, List<Enterprise>> byInstitution = new LinkedHashMap<>();

        for (Branch branch : ctx.branches) {
            if (!districts.contains(branch.getDistrictId())) continue;
            byInstitution.computeIfAbsent(branch.getInstitutionId(), k -> new ArrayList<>())
                    .addAll(ctx.enterprisesByBranch.getOrDefault(branch.getId(), List.of()));
        }

        List<Map<String, Object>> out = new ArrayList<>();
        byInstitution.forEach((institutionId, enterprises) -> {
            Institution institution = ctx.institutionsById.get(institutionId);
            if (institution == null) return;
            Map<String, Object> row = new LinkedHashMap<>();
            row.put("institutionCode", institution.getCode());
            row.put("institutionName", institution.getName());
            row.put("type", institution.getType());
            row.putAll(bandCounts(enterprises, tenant));
            out.add(row);
        });
        out.sort((a, b) -> Integer.compare((int) b.get("enterprises"), (int) a.get("enterprises")));
        return out;
    }

    // ── internals ───────────────────────────────────────────

    private Map<String, Object> summarise(RegionalOffice office, Context ctx, TenantContext tenant) {
        Set<Long> districts = districtIdsOf(office, ctx);
        List<Enterprise> enterprises = new ArrayList<>();
        Set<Long> institutions = new LinkedHashSet<>();
        int branches = 0;

        for (Branch branch : ctx.branches) {
            if (!districts.contains(branch.getDistrictId())) continue;
            branches++;
            institutions.add(branch.getInstitutionId());
            enterprises.addAll(ctx.enterprisesByBranch.getOrDefault(branch.getId(), List.of()));
        }

        Map<String, Object> row = new LinkedHashMap<>();
        row.put("code", office.getCode());
        row.put("name", office.getName());
        row.put("nameHi", office.getNameHi());
        row.put("city", office.getCity());
        row.put("officeType", office.getOfficeType());
        row.put("states", ctx.statesByOffice.getOrDefault(office.getId(), List.of()));
        row.put("banks", institutions.size());
        row.put("branches", branches);
        row.putAll(bandCounts(enterprises, tenant));
        return row;
    }

    /**
     * Band split and portfolio value, suppressed below the minimum cell size.
     *
     * <p>Suppression bites harder here than at national level and that is not a
     * defect: an office supervising one bank of twenty borrowers has genuinely
     * small cells, and publishing them is how an aggregate stops protecting the
     * borrower underneath it.
     */
    private Map<String, Object> bandCounts(List<Enterprise> enterprises, TenantContext tenant) {
        Map<String, Object> row = new LinkedHashMap<>();
        int total = enterprises.size();
        row.put("enterprises", total);

        if (total > 0 && total < minCellFor(tenant)) {
            row.put("suppressed", true);
            row.put("red", null);
            row.put("watch", null);
            row.put("standard", null);
            row.put("stressRatePct", null);
            row.put("outstanding", null);
            return row;
        }

        // The stored band, not a band recomputed from the score.
        //
        // They are not the same number and must not be: a fired trip-wire
        // escalates the band without rewriting the score, so Madhya Pradesh reads
        // 35 RED by band and 5 RED by threshold. ApexService publishes the stored
        // band, so recomputing here would make RED drop from 35 to 5 as a
        // supervisor drilled from the national view into the office covering the
        // very same state — the one place an inconsistency is guaranteed to be
        // noticed, and the one place it destroys trust in both screens.
        int red = 0, watch = 0, standard = 0;
        BigDecimal outstanding = BigDecimal.ZERO;
        for (Enterprise e : enterprises) {
            String band = e.getBand() == null ? "STANDARD" : e.getBand();
            switch (band) {
                case "RED" -> red++;
                case "WATCH" -> watch++;
                default -> standard++;
            }
            if (e.getLoanOutstanding() != null) outstanding = outstanding.add(e.getLoanOutstanding());
        }

        row.put("suppressed", false);
        row.put("red", red);
        row.put("watch", watch);
        row.put("standard", standard);
        row.put("stressRatePct", total == 0 ? 0.0
                : Math.round((red * 1000.0) / total) / 10.0);
        row.put("outstanding", outstanding);
        return row;
    }

    private Set<Long> districtIdsOf(RegionalOffice office, Context ctx) {
        List<String> states = ctx.statesByOffice.getOrDefault(office.getId(), List.of());
        Set<Long> ids = new HashSet<>();
        for (District d : ctx.districts) {
            if (states.contains(d.getState())) ids.add(d.getId());
        }
        return ids;
    }

    /** One pass over the masters. The whole book is 263 rows; this is not worth a query per office. */
    private Context load() {
        Context ctx = new Context();
        ctx.offices = officeRepository.findByActiveTrueOrderByNameAsc();
        ctx.districts = districtRepository.findAll();
        ctx.branches = branchRepository.findAll();
        institutionRepository.findAll().forEach(i -> ctx.institutionsById.put(i.getId(), i));
        officeStateRepository.findAll().forEach(s -> ctx.statesByOffice
                .computeIfAbsent(s.getRegionalOfficeId(), k -> new ArrayList<>()).add(s.getState()));
        enterpriseRepository.findAll().forEach(e -> {
            if (e.getBranchId() == null) return;
            ctx.enterprisesByBranch.computeIfAbsent(e.getBranchId(), k -> new ArrayList<>()).add(e);
        });
        return ctx;
    }

    private static final class Context {
        List<RegionalOffice> offices = List.of();
        List<District> districts = List.of();
        List<Branch> branches = List.of();
        final Map<Long, Institution> institutionsById = new HashMap<>();
        final Map<Long, List<String>> statesByOffice = new HashMap<>();
        final Map<Long, List<Enterprise>> enterprisesByBranch = new HashMap<>();
    }
}