using PayRollDAL.DTO.SAP;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;

namespace PayRollBLL.SAP.Builders
{
    /// <summary>
    /// SAP Infotype 584 — House Property.
    ///
    /// SAP confirmed two sub-types, each posted to a separate OData service:
    ///
    ///   Sub-type 1 — Housing Loan  (ZPY_ITDEC_HOUSING_LOAN_SRV / ITDecHL_HeaderSet)
    ///     Source: DeclarationDetailType 3 (Rental Income) → Particulars1 block
    ///             DeclarationDetailType 0 (Home Loan)     → Particulars2 / Lender block
    ///     Both rows merged into one SAP item per declaration.
    ///
    ///   Sub-type 2 — Other Income Sources  (endpoint TBC — see TODO comments)
    ///     Source: DeclarationDetailType 6 (Other Income)
    ///     SectionDetail keyword matching distributes amounts into the correct SAP buckets.
    ///
    /// <see cref="Build"/> returns Sub-type 1 only (used by preview/download endpoints).
    /// <see cref="BuildAll"/> returns both sub-types (used by the SAP push flow).
    /// </summary>
    public class SAP584Builder : ISapInfotypeBuilder
    {
        private const byte RentalIncomeType = 3;
        private const byte LoanType         = 0;
        private const byte OtherIncomeType  = 6;

        // ── Sub-type 1: Housing Loan ──────────────────────────────────────────────────────
        public int    Infotype       => 584;
        public string DisplayName    => "House Property";
        public string EndpointPath   => "/sap/opu/odata/sap/ZPY_ITDEC_HOUSING_LOAN_SRV/ITDecHL_HeaderSet";
        public string MsgNavProperty => "Nav2IT_Dec_HL_Msg";

        // ── Sub-type 2: Other Income Sources ─────────────────────────────────────────────
        // TODO: Replace with confirmed SAP service and entity-set name.
        private const string OtherIncomeEndpoint    = "/sap/opu/odata/sap/ZPY_ITDEC_OTHERINCOME_SRV/ITDecOtherIncomeHeaderSet";
        // TODO: Replace with confirmed navigation property name from the SAP OData response.
        private const string OtherIncomeMsgNavProp  = "NAV2OTHERINCOME_MSG";

        // ─────────────────────────────────────────────────────────────────────────────────
        // ISapInfotypeBuilder.BuildAll — overrides default to yield BOTH sub-types
        // ─────────────────────────────────────────────────────────────────────────────────

        public IEnumerable<SapSubtypePayload> BuildAll(
            IEnumerable<ITDeclarationSapDTO> rows, string date, string remarks)
        {
            // Use a list so the data can be iterated twice (Housing Loan + Other Income)
            var rowList = rows is IList<ITDeclarationSapDTO> l ? l : rows.ToList();

            // Sub-type 1 — Housing Loan
            string housingLoanJson = Build(rowList, date, remarks);
            if (!string.IsNullOrEmpty(housingLoanJson))
                yield return new SapSubtypePayload(
                    Infotype, "Housing Loan", EndpointPath, MsgNavProperty, housingLoanJson);

            // Sub-type 2 — Other Income Sources
            string otherIncomeJson = BuildOtherIncome(rowList, date, remarks);
            if (!string.IsNullOrEmpty(otherIncomeJson))
                yield return new SapSubtypePayload(
                    Infotype, "Other Income Sources", OtherIncomeEndpoint, OtherIncomeMsgNavProp, otherIncomeJson);
        }

        // ─────────────────────────────────────────────────────────────────────────────────
        // Sub-type 1 — Housing Loan  (primary Build, also used by preview endpoints)
        // ─────────────────────────────────────────────────────────────────────────────────

        public string Build(IEnumerable<ITDeclarationSapDTO> rows, string date, string remarks)
        {
            var relevant = rows
                .Where(r => r.DeclarationDetailId.HasValue &&
                            (r.DeclarationDetailType == RentalIncomeType ||
                             r.DeclarationDetailType == LoanType))
                .GroupBy(r => r.DeclarationId)
                .ToList();

            if (relevant.Count == 0) return string.Empty;

            var items = relevant.Select(g =>
            {
                var header = g.First();
                var rental = g.FirstOrDefault(r => r.DeclarationDetailType == RentalIncomeType);
                var loan   = g.FirstOrDefault(r => r.DeclarationDetailType == LoanType);

                string propertyType = (rental != null, loan != null) switch
                {
                    (true,  true)  => "Partly Rented",
                    (true,  false) => "Let Out",
                    (false, true)  => "Self Occupied",
                    _              => string.Empty
                };

                double rentalIncome      = rental?.RentReceived ?? 0;
                double localTax          = rental?.LocalTax ?? 0;
                double netAnnualValue    = rentalIncome - localTax;
                double standardDeduction = rental?.StandardDeduction ?? 0;
                double interestOnBorrow  = rental?.Interest ?? loan?.Interest ?? 0;
                double totalDeduction    = standardDeduction + interestOnBorrow;
                double netIncome         = rental?.NetIncome ?? (netAnnualValue - totalDeduction);

                return new Sap584Item
                {
                    EmployeeID         = header.EmployeeCode,
                    FiscalYear         = header.FiscalYear,
                    Type               = propertyType,

                    Particulars1       = rental?.Particulars ?? string.Empty,
                    AnnualRentalIncome = SapFmt.Amount(rentalIncome),
                    LocalTaxPaid       = SapFmt.Amount(localTax),
                    NetAnnualValue     = SapFmt.Amount(netAnnualValue),
                    StandardDeduction  = SapFmt.Amount(standardDeduction),
                    InterestOnBorrowal = SapFmt.Amount(interestOnBorrow),
                    TotalDeduction     = SapFmt.Amount(totalDeduction),
                    NetIncome          = SapFmt.Amount(netIncome),
                    EligibleFor80EEA   = "No",
                    PossesionObtained  = "Yes",
                    Remarks1           = rental?.DetailRemarks ?? string.Empty,

                    Particulars2       = loan?.Particulars ?? string.Empty,
                    PrinciplePaid      = SapFmt.Amount(loan?.Principle ?? 0),
                    InterestPaid       = SapFmt.Amount(loan?.Interest ?? 0),
                    Remarks2           = loan?.DetailRemarks ?? string.Empty,
                    LenderName         = loan?.ContactName ?? string.Empty,
                    LenderPAN          = loan?.ContactPAN ?? string.Empty,
                    LenderTAN          = loan?.ContactTAN ?? string.Empty,
                    LenderAddressLine1 = loan?.ContactAddress1 ?? string.Empty,
                    LenderAddressLine2 = loan?.ContactAddress2 ?? string.Empty,
                    LenderAddressLine3 = loan?.ContactAddress3 ?? string.Empty,
                    LenderAddressLine4 = loan?.ContactAddress4 ?? string.Empty,
                    LenderAddressLine5 = loan?.ContactAddress5 ?? string.Empty,
                };
            }).ToList();

            var payload = new Sap584Payload
            {
                Date               = date,
                Remarks            = remarks,
                Nav2IT_Dec_HL_Item = items,
            };

            return JsonSerializer.Serialize(payload, SapJsonOptions.Plain);
        }

        // ─────────────────────────────────────────────────────────────────────────────────
        // Sub-type 2 — Other Income Sources
        //
        // Each declaration can have multiple Type-6 detail rows, one per income section.
        // SectionDetail keyword matching distributes amounts into the SAP income buckets.
        // Unrecognised sections fall into OtherIncome.
        //
        // TODO: Verify keyword mappings against the actual SectionDetail values in MTDSSECTIONDETAIL.
        // TODO: Verify SAP field names once the SAP team provides the confirmed service spec.
        // ─────────────────────────────────────────────────────────────────────────────────

        private string BuildOtherIncome(IEnumerable<ITDeclarationSapDTO> rows, string date, string remarks)
        {
            var relevant = rows
                .Where(r => r.DeclarationDetailId.HasValue &&
                            r.DeclarationDetailType == OtherIncomeType)
                .GroupBy(r => r.DeclarationId)
                .ToList();

            if (relevant.Count == 0) return string.Empty;

            var items = relevant.Select(g =>
            {
                var header = g.First();

                double businessProfit  = 0;
                double ltcgNormal      = 0;
                double ltcgSpecial     = 0;
                double stCapitalGains  = 0;
                double dividends       = 0;
                double interest        = 0;
                double digitalIncome   = 0;
                double otherIncome     = 0;

                foreach (var row in g)
                {
                    string section = (row.SectionDetail ?? string.Empty).ToLowerInvariant();
                    double amount  = row.DeclaredAmount;

                    if (section.Contains("business") || section.Contains("profit"))
                        businessProfit += amount;
                    else if (section.Contains("long term") && (section.Contains("special") || section.Contains("equity") || section.Contains("share") || section.Contains("fund")))
                        ltcgSpecial += amount;
                    else if (section.Contains("long term"))
                        ltcgNormal += amount;
                    else if (section.Contains("short term"))
                        stCapitalGains += amount;
                    else if (section.Contains("dividend"))
                        dividends += amount;
                    else if (section.Contains("interest") || section.Contains("saving") || section.Contains("fixed deposit") || section.Contains("fd "))
                        interest += amount;
                    else if (section.Contains("digital") || section.Contains("online") || section.Contains("winning") || section.Contains("lottery") || section.Contains("game"))
                        digitalIncome += amount;
                    else
                        otherIncome += amount;
                }

                return new Sap584OtherIncomeItem
                {
                    EmployeeID      = header.EmployeeCode,
                    FiscalYear      = header.FiscalYear,
                    BusinessProfit  = SapFmt.Amount(businessProfit),
                    LTCGNormal      = SapFmt.Amount(ltcgNormal),
                    LTCGSpecial     = SapFmt.Amount(ltcgSpecial),
                    STCapitalGains  = SapFmt.Amount(stCapitalGains),
                    Dividends       = SapFmt.Amount(dividends),
                    Interest        = SapFmt.Amount(interest),
                    DigitalIncome   = SapFmt.Amount(digitalIncome),
                    OtherIncome     = SapFmt.Amount(otherIncome),
                };
            }).ToList();

            var payload = new Sap584OtherIncomePayload
            {
                Date                  = date,
                Remarks               = remarks,
                NAV2OTHERINCOME_ITEM  = items,
            };

            return JsonSerializer.Serialize(payload, SapJsonOptions.Plain);
        }

    }
}