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

namespace Infrastructure.StockData;

/// <summary>
/// 공공데이터포털(금융위) 표준 JSON 응답 파서 — 순수 C# (System.Text.Json).
/// 응답 골격: response.header(resultCode/resultMsg) + response.body(totalCount, items.item[]).
/// item 이 단건이면 객체, 0건이면 items 가 빈 문자열로 오는 케이스까지 흡수한다.
/// </summary>
public static class DataGoKrStockParser
{
    /// <summary>KRX 상장종목정보 (GetKrxListedInfoService/getItemInfo) 1행</summary>
    public sealed record ListedItem(string Code, string? Isin, string Name, string MarketName, DateOnly BaseDate);

    /// <summary>주식시세정보 (GetStockSecuritiesInfoService/getStockPriceInfo) 1행</summary>
    public sealed record DailyPriceItem(
        string Code,
        DateOnly TradingDate,
        int Open,
        int High,
        int Low,
        int Close,
        long Volume,
        long TradingValue,
        int ChangeAmount,
        decimal ChangeRate,
        long? MarketCap,
        long? ListedShares
    );

    public static (IReadOnlyList<ListedItem> Items, int TotalCount) ParseListedItems(string json)
    {
        using var doc = JsonDocument.Parse(json);
        var body = GetBody(doc);
        var items = new List<ListedItem>();

        foreach (var item in EnumerateItems(body))
        {
            var code = NormalizeCode(GetString(item, "srtnCd"));
            var name = GetString(item, "itmsNm");
            var market = GetString(item, "mrktCtg");
            var baseDate = ParseDate(GetString(item, "basDt"));

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

            var isin = GetString(item, "isinCd");
            items.Add(new ListedItem(code, isin.Length == 12 ? isin : null, name, market, baseDate.Value));
        }

        return (items, GetTotalCount(body));
    }

    public static (IReadOnlyList<DailyPriceItem> Items, int TotalCount) ParseDailyPrices(string json)
    {
        using var doc = JsonDocument.Parse(json);
        var body = GetBody(doc);
        var items = new List<DailyPriceItem>();

        foreach (var item in EnumerateItems(body))
        {
            var code = NormalizeCode(GetString(item, "srtnCd"));
            var tradingDate = ParseDate(GetString(item, "basDt"));

            if (code is null || tradingDate is null)
            {
                continue;
            }

            items.Add(new DailyPriceItem(
                code,
                tradingDate.Value,
                ParseInt(GetString(item, "mkp")),
                ParseInt(GetString(item, "hipr")),
                ParseInt(GetString(item, "lopr")),
                ParseInt(GetString(item, "clpr")),
                ParseLong(GetString(item, "trqu")),
                ParseLong(GetString(item, "trPrc")),
                ParseInt(GetString(item, "vs")),
                ParseDecimal(GetString(item, "fltRt")),
                ParseNullableLong(GetString(item, "mrktTotAmt")),
                ParseNullableLong(GetString(item, "lstgStCnt"))
            ));
        }

        return (items, GetTotalCount(body));
    }

    private static JsonElement GetBody(JsonDocument doc)
    {
        if (!doc.RootElement.TryGetProperty("response", out var response))
        {
            throw new InvalidOperationException("data.go.kr 응답 형식 오류 — response 노드 없음");
        }

        if (response.TryGetProperty("header", out var header))
        {
            var resultCode = header.TryGetProperty("resultCode", out var rc) ? rc.GetString() : null;
            if (resultCode is not null && resultCode != "00")
            {
                var resultMsg = header.TryGetProperty("resultMsg", out var rm) ? rm.GetString() : null;
                throw new InvalidOperationException($"data.go.kr 오류 응답 — resultCode={resultCode}, resultMsg={resultMsg}");
            }
        }

        if (!response.TryGetProperty("body", out var body))
        {
            throw new InvalidOperationException("data.go.kr 응답 형식 오류 — body 노드 없음");
        }

        return body;
    }

    private static IEnumerable<JsonElement> EnumerateItems(JsonElement body)
    {
        // 0건이면 items 가 "" (빈 문자열) 로 온다
        if (!body.TryGetProperty("items", out var items) || items.ValueKind != JsonValueKind.Object)
        {
            yield break;
        }

        if (!items.TryGetProperty("item", out var item))
        {
            yield break;
        }

        if (item.ValueKind == JsonValueKind.Array)
        {
            foreach (var element in item.EnumerateArray())
            {
                yield return element;
            }
        }
        else if (item.ValueKind == JsonValueKind.Object)
        {
            // 단건이면 배열이 아닌 객체로 온다
            yield return item;
        }
    }

    private static int GetTotalCount(JsonElement body)
    {
        if (!body.TryGetProperty("totalCount", out var total))
        {
            return 0;
        }

        return total.ValueKind switch
        {
            JsonValueKind.Number => total.GetInt32(),
            JsonValueKind.String => ParseInt(total.GetString() ?? ""),
            _ => 0
        };
    }

    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
        };
    }

    /// <summary>단축코드 정규화 — 'A' 프리픽스 등 6자리 초과분은 뒤 6자리만 취하고, 6자리 숫자만 유효</summary>
    private static string? NormalizeCode(string raw)
    {
        if (raw.Length > 6)
        {
            raw = raw[^6..];
        }

        if (raw is not { Length: 6 } || raw.Any(c => !char.IsAsciiDigit(c)))
        {
            return null;
        }

        return raw;
    }

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

    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 long? ParseNullableLong(string raw)
    {
        return long.TryParse(raw, NumberStyles.Integer | NumberStyles.AllowThousands, CultureInfo.InvariantCulture, out var value) ? value : null;
    }

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