package com.imprimelibros.erp.datatables;

import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.data.domain.*;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;

import jakarta.persistence.criteria.*;
import java.util.*;
import java.util.function.BiConsumer;
import java.util.function.Function;

public class DataTable<T> {

    /* ===== Tipos funcionales ===== */
    public interface FilterHook<T> extends BiConsumer<SpecBuilder<T>, DataTablesRequest> {
    }

    public interface SpecBuilder<T> {
        void add(Specification<T> extra);
    }

    /**
     * Filtro custom por campo virtual: te doy (root, query, cb, value) y me
     * devuelves un Predicate
     */
    @FunctionalInterface
    public interface FieldFilter<T> {
        Predicate apply(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb, String value);
    }

    /**
     * Orden custom por campo virtual: te doy (root, query, cb) y me devuelves la
     * Expression<?> para orderBy
     */
    @FunctionalInterface
    public interface FieldOrder<T> {
        Expression<?> apply(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb);
    }

    /* ===== Estado ===== */
    private final JpaSpecificationExecutor<T> repo;
    private final Class<T> entityClass;
    private final DataTablesRequest dt;
    private final List<String> searchable;

    private final List<Function<T, Map<String, Object>>> adders = new ArrayList<>();
    private final List<Function<Map<String, Object>, Map<String, Object>>> editors = new ArrayList<>();
    private final List<FilterHook<T>> filters = new ArrayList<>();
    private Specification<T> baseSpec = (root, q, cb) -> cb.conjunction();

    private final ObjectMapper om = new ObjectMapper()
            .registerModule(new JavaTimeModule())
            .disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);

    /** whitelist de campos ordenables “simples” (por nombre) */
    private List<String> orderable = null;

    /** mapas de comportamiento custom por campo */
    private final Map<String, FieldOrder<T>> orderCustom = new HashMap<>();
    private final Map<String, FieldFilter<T>> filterCustom = new HashMap<>();

    private boolean onlyAdded = false;

    /* ===== Ctor / factory ===== */
    private DataTable(JpaSpecificationExecutor<T> repo, Class<T> entityClass, DataTablesRequest dt,
            List<String> searchable) {
        this.repo = repo;
        this.entityClass = entityClass;
        this.dt = dt;
        this.searchable = searchable != null ? searchable : List.of();
    }

    public static <T> DataTable<T> of(JpaSpecificationExecutor<T> repo, Class<T> entityClass, DataTablesRequest dt,
            List<String> searchable) {
        return new DataTable<>(repo, entityClass, dt, searchable);
    }

    /* ===== Fluent API ===== */
    public DataTable<T> onlyAddedColumns() {
        this.onlyAdded = true;
        return this;
    }

    /** WHERE base reusable */
    public DataTable<T> where(Specification<T> spec) {
        this.baseSpec = this.baseSpec.and(spec);
        return this;
    }

    /** Campos renderizados */
    public DataTable<T> add(String field, Function<T, Object> fn) {
        adders.add(entity -> {
            Map<String, Object> m = new HashMap<>();
            m.put(field, fn.apply(entity));
            return m;
        });
        return this;
    }

    public DataTable<T> addIf(boolean condition, String field, Function<T, Object> fn) {
        if (condition)
            return add(field, fn);
        return this;
    }

    public DataTable<T> add(Function<T, Map<String, Object>> fn) {
        adders.add(fn);
        return this;
    }

    /** Edita/inyecta valor usando la entidad original (guardada como __entity) */
    @SuppressWarnings("unchecked")
    public DataTable<T> edit(String field, Function<T, Object> fn) {
        editors.add(row -> {
            row.put(field, fn.apply((T) row.get("__entity")));
            return row;
        });
        return this;
    }

    /** Whitelist de campos simples ordenables (por nombre) */
    public DataTable<T> orderable(List<String> fields) {
        this.orderable = fields;
        return this;
    }

    /** Orden custom por campo virtual (expresiones) */
    public DataTable<T> orderable(String field, FieldOrder<T> orderFn) {
        this.orderCustom.put(field, orderFn);
        return this;
    }

    /** Filtro custom por campo virtual (LIKE, rangos, etc.) */
    public DataTable<T> filter(String field, FieldFilter<T> filterFn) {
        this.filterCustom.put(field, filterFn);
        return this;
    }

    /** Hook para añadir Specifications extra programáticamente */
    public DataTable<T> filter(FilterHook<T> hook) {
        filters.add(hook);
        return this;
    }

    /* ===== Helpers ===== */
    private List<String> getOrderable() {
        return (orderable == null || orderable.isEmpty()) ? this.searchable : this.orderable;
    }

    /* ===== Core ===== */
    public DataTablesResponse<Map<String, Object>> toJson(long totalCount) {
        // 1) Spec base + búsqueda (global/columnas) + hooks programáticos
        Specification<T> spec = baseSpec.and(DataTablesSpecification.build(dt, searchable));
        final Specification<T>[] holder = new Specification[] { spec };

        // Hooks externos
        filters.forEach(h -> h.accept(extra -> holder[0] = holder[0].and(extra), dt));

        // 2) Filtros por columna “custom” (virtuales)
        for (var col : dt.columns) {
            if (col == null || !col.searchable)
                continue;
            if (col.name == null || col.name.isBlank())
                continue;
            if (!filterCustom.containsKey(col.name))
                continue;
            if (col.search == null || col.search.value == null || col.search.value.isBlank())
                continue;

            var value = col.search.value;
            var filterFn = filterCustom.get(col.name);
            holder[0] = holder[0].and((root, query, cb) -> {
                Predicate p = filterFn.apply(root, query, cb, value);
                return p != null ? p : cb.conjunction();
            });
        }

        // 3) Orden:
        // - Para campos “simples” (no custom): con Sort (Spring)
        // - Para campos “custom” (virtuales/expresiones): query.orderBy(...) dentro de
        // una spec
        Sort sort = Sort.unsorted();
        List<Sort.Order> simpleOrders = new ArrayList<>();
        boolean customApplied = false;

        if (!dt.order.isEmpty() && !dt.columns.isEmpty()) {
            for (var o : dt.order) {
                var col = dt.columns.get(o.column);
                if (col == null)
                    continue;

                String field = col.name;
                if (field == null || field.isBlank())
                    continue;
                if (!col.orderable)
                    continue;
                if (!getOrderable().contains(field))
                    continue;

                if (orderCustom.containsKey(field)) {
                    final boolean asc = !"desc".equalsIgnoreCase(o.dir);
                    final FieldOrder<T> orderFn = orderCustom.get(field);

                    // aplica el ORDER BY custom dentro de la Specification (con Criteria)
                    holder[0] = holder[0].and((root, query, cb) -> {
                        Expression<?> expr = orderFn.apply(root, query, cb);
                        if (expr != null) {
                            query.orderBy(asc ? cb.asc(expr) : cb.desc(expr));
                        }
                        return cb.conjunction();
                    });
                    customApplied = true;
                } else {
                    // orden simple por nombre de propiedad real
                    simpleOrders.add(new Sort.Order(
                            "desc".equalsIgnoreCase(o.dir) ? Sort.Direction.DESC : Sort.Direction.ASC,
                            field));
                }
            }
        }

        if (!simpleOrders.isEmpty()) {
            sort = Sort.by(simpleOrders);
        }

        // 4) Paginación (Sort para simples; custom order ya va dentro de la spec)
        int page = dt.length > 0 ? dt.start / dt.length : 0;
        Pageable pageable = dt.length > 0 ? PageRequest.of(page, dt.length, sort) : Pageable.unpaged();

        var p = repo.findAll(holder[0], pageable);
        long filtered = p.getTotalElements();

        // 5) Mapeo a Map + add/edit
        List<Map<String, Object>> data = new ArrayList<>();
        for (T e : p.getContent()) {
            Map<String, Object> row;
            if (onlyAdded) {
                row = new HashMap<>();
            } else {
                try {
                    row = om.convertValue(e, Map.class);
                } catch (IllegalArgumentException ex) {
                    row = new HashMap<>();
                }
            }
            row.put("__entity", e);
            for (var ad : adders)
                row.putAll(ad.apply(e));
            for (var ed : editors)
                ed.apply(row);
            row.remove("__entity");
            data.add(row);
        }

        return new DataTablesResponse<>(dt.draw, totalCount, filtered, data);
    }

    private Predicate nullSafePredicate(CriteriaBuilder cb) {
        // Devuelve conjunción para no interferir con los demás predicados
        return cb.conjunction();
    }
}