using System.Globalization;
using System.Text.Json;

namespace Infrastructure.StockData;

/// <summary>
/// KRX OpenAPI(data-dbg.krx.co.kr) ESG 지수(esg/esg_index_info) 응답 파서 — 순수 C# (System.Text.Json).
/// 응답 골격: { "OutBlock_1": [ { BAS_DD, IDX_NM, CLSPRC_IDX, PRV_DD_CMPR, UPDN_RATE, TRD_ISU_CNT, ACC_TRDVOL, ACC_TRDVAL }, ... ] }.
/// 모든 값은 문자열이며 천단위 콤마 포함 가능. 시장/파생 지수와 달리 OHLC·시가총액이 없고 구성종목수(TRD_ISU_CNT)를 제공한다.
/// 등락률(UPDN_RATE, %)은 basis point(%×100, 반올림)로 저장한다 (IndexDailyPrice.FlucRateBp 와 동일 규약, "-.39"/".16" 형태도 흡수).
/// </summary>
public static class KrxEsgIndexParser
{
    /// <summary>ESG 지수 1행 (등락률은 Bp = %×100)</summary>
    public sealed record EsgIndexRow(
        string IndexName,
        DateOnly TradeDate,
        decimal Close,
        decimal ChangeVal,
        int FlucRateBp,
        int ConstituentCount,
        long Volume,
        long Value
    );

    public static IReadOnlyList<EsgIndexRow> ParseDaily(string json)
    {
        using var doc = JsonDocument.Parse(json);
        var rows = new List<EsgIndexRow>();

        if (!doc.RootElement.TryGetProperty("OutBlock_1", out var block) || block.ValueKind != JsonValueKind.Array)
        {
            return rows;
        }

        foreach (var item in block.EnumerateArray())
        {
            var name = GetString(item, "IDX_NM");
            var tradeDate = ParseDate(GetString(item, "BAS_DD"));

            if (name.Length == 0 || tradeDate is null)
            {
                continue;
            }

            rows.Add(new EsgIndexRow(
                name,
                tradeDate.Value,
                ParseDecimal(GetString(item, "CLSPRC_IDX")),
                ParseDecimal(GetString(item, "PRV_DD_CMPR")),
                ParseRateToBp(GetString(item, "UPDN_RATE")),
                ParseInt(GetString(item, "TRD_ISU_CNT")),
                ParseLong(GetString(item, "ACC_TRDVOL")),
                ParseLong(GetString(item, "ACC_TRDVAL"))
            ));
        }

        return rows;
    }

    private static string GetString(JsonElement element, string name)
    {
        if (!element.TryGetProperty(name, out var value))
        {
            return string.Empty;
        }

        return value.ValueKind switch
        {
            JsonValueKind.String => value.GetString()?.Trim() ?? string.Empty,
            JsonValueKind.Number => value.GetRawText(),
            _ => string.Empty
        };
    }

    private static DateOnly? ParseDate(string raw)
    {
        return DateOnly.TryParseExact(raw, "yyyyMMdd", CultureInfo.InvariantCulture, DateTimeStyles.None, out var date) ? date : null;
    }

    /// <summary>등락률(%) 문자열 → basis point (×100, 반올림). "-" 나 파싱 실패는 0.</summary>
    private static int ParseRateToBp(string raw)
    {
        return decimal.TryParse(raw, NumberStyles.Float | NumberStyles.AllowThousands, CultureInfo.InvariantCulture, out var pct)
            ? (int)Math.Round(pct * 100m, MidpointRounding.AwayFromZero)
            : 0;
    }

    private static int ParseInt(string raw)
    {
        return int.TryParse(raw, NumberStyles.Integer | NumberStyles.AllowThousands, CultureInfo.InvariantCulture, out var value) ? value : 0;
    }

    private static long ParseLong(string raw)
    {
        return long.TryParse(raw, NumberStyles.Integer | NumberStyles.AllowThousands, CultureInfo.InvariantCulture, out var value) ? value : 0L;
    }

    private static decimal ParseDecimal(string raw)
    {
        return decimal.TryParse(raw, NumberStyles.Float | NumberStyles.AllowThousands, CultureInfo.InvariantCulture, out var value) ? value : 0m;
    }
}