using System.Data;
using System.Data.Common;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Options;

namespace Admin.NET.Plugin.HwPortal;

public sealed class HwSearchQueryService : ITransient
{
    private readonly HwPortalSearchDbContext _db;
    private readonly HwPortalSearchOptions _options;
    private readonly IHwSearchSchemaService _schemaService;

    public HwSearchQueryService(HwPortalSearchDbContext db, IOptions<HwPortalSearchOptions> options, IHwSearchSchemaService schemaService)
    {
        _db = db;
        _options = options.Value;
        _schemaService = schemaService;
    }

    public async Task<List<SearchRawRecord>> SearchAsync(string keyword, int take, CancellationToken cancellationToken = default)
    {
        await _schemaService.EnsureCreatedAsync(cancellationToken);

        int normalizedTake = Math.Clamp(take, 1, _options.TakeLimit);
        List<SearchRawRecord> fullTextResult = await SearchWithFullTextAsync(keyword, normalizedTake, cancellationToken);
        if (fullTextResult.Count > 0)
        {
            return fullTextResult;
        }

        return await SearchWithLikeAsync(keyword, normalizedTake, cancellationToken);
    }

    public async Task<bool> HasIndexedDocumentAsync(CancellationToken cancellationToken = default)
    {
        await _schemaService.EnsureCreatedAsync(cancellationToken);
        return await _db.SearchDocs.AsNoTracking().AnyAsync(x => x.IsDelete == "0", cancellationToken);
    }

    private async Task<List<SearchRawRecord>> SearchWithFullTextAsync(string keyword, int take, CancellationToken cancellationToken)
    {
        DbConnection connection = _db.Database.GetDbConnection();
        bool shouldClose = connection.State != ConnectionState.Open;
        if (shouldClose)
        {
            await connection.OpenAsync(cancellationToken);
        }

        try
        {
            await using DbCommand command = connection.CreateCommand();
            command.CommandText =
                """
                SELECT
                    s.source_type AS SourceType,
                    s.biz_id AS BizId,
                    s.title AS Title,
                    s.content AS Content,
                    s.web_code AS WebCode,
                    s.type_id AS TypeId,
                    s.device_id AS DeviceId,
                    s.menu_id AS MenuId,
                    s.document_id AS DocumentId,
                    s.base_score AS Score,
                    s.updated_at AS UpdatedAt,
                    s.route AS Route,
                    s.route_query_json AS RouteQueryJson,
                    s.edit_route AS EditRoute
                FROM hw_portal_search_doc s
                WHERE s.is_delete = '0'
                  AND MATCH(s.title, s.content) AGAINST (@keyword IN NATURAL LANGUAGE MODE)
                ORDER BY
                    MATCH(s.title, s.content) AGAINST (@keyword IN NATURAL LANGUAGE MODE) DESC,
                    CASE WHEN s.title IS NOT NULL AND s.title LIKE CONCAT('%', @likeKeyword, '%') THEN 1 ELSE 0 END DESC,
                    CASE WHEN s.content IS NOT NULL AND s.content LIKE CONCAT('%', @likeKeyword, '%') THEN 1 ELSE 0 END DESC,
                    s.base_score DESC,
                    s.updated_at DESC
                LIMIT @take;
                """;
            AddParameter(command, "@keyword", keyword);
            AddParameter(command, "@likeKeyword", keyword);
            AddParameter(command, "@take", take);

            List<SearchRawRecord> rows = new();
            await using DbDataReader reader = await command.ExecuteReaderAsync(cancellationToken);
            while (await reader.ReadAsync(cancellationToken))
            {
                rows.Add(new SearchRawRecord
                {
                    SourceType = GetString(reader, "SourceType"),
                    BizId = GetString(reader, "BizId"),
                    Title = GetString(reader, "Title"),
                    Content = GetString(reader, "Content"),
                    WebCode = GetString(reader, "WebCode"),
                    TypeId = GetString(reader, "TypeId"),
                    DeviceId = GetString(reader, "DeviceId"),
                    MenuId = GetString(reader, "MenuId"),
                    DocumentId = GetString(reader, "DocumentId"),
                    Score = GetNullableInt(reader, "Score"),
                    UpdatedAt = GetNullableDateTime(reader, "UpdatedAt"),
                    Route = GetString(reader, "Route"),
                    RouteQueryJson = GetString(reader, "RouteQueryJson"),
                    EditRoute = GetString(reader, "EditRoute")
                });
            }

            return rows;
        }
        finally
        {
            if (shouldClose)
            {
                await connection.CloseAsync();
            }
        }
    }

    private async Task<List<SearchRawRecord>> SearchWithLikeAsync(string keyword, int take, CancellationToken cancellationToken)
    {
        string likeKeyword = $"%{keyword}%";

        // Why：
        // FULLTEXT 对中文和短词的命中并不稳定，因此这里保留 EF LINQ 版兜底，
        // 即使全文索引未命中，也能保证门户搜索功能可用。
        List<HwPortalSearchDoc> docs = await _db.SearchDocs
            .AsNoTracking()
            .Where(x => x.IsDelete == "0")
            .Where(x =>
                (x.Title != null && EF.Functions.Like(x.Title, likeKeyword)) ||
                (x.Content != null && EF.Functions.Like(x.Content, likeKeyword)))
            .OrderByDescending(x => x.Title != null && EF.Functions.Like(x.Title, likeKeyword))
            .ThenByDescending(x => x.Content != null && EF.Functions.Like(x.Content, likeKeyword))
            .ThenByDescending(x => x.BaseScore)
            .ThenByDescending(x => x.UpdatedAt)
            .Take(take)
            .ToListAsync(cancellationToken);

        return docs.Select(ToRawRecord).ToList();
    }

    private static SearchRawRecord ToRawRecord(HwPortalSearchDoc doc)
    {
        return new SearchRawRecord
        {
            SourceType = doc.SourceType,
            BizId = doc.BizId,
            Title = doc.Title,
            Content = doc.Content,
            WebCode = doc.WebCode,
            TypeId = doc.TypeId,
            DeviceId = doc.DeviceId,
            MenuId = doc.MenuId,
            DocumentId = doc.DocumentId,
            Score = doc.BaseScore,
            UpdatedAt = doc.UpdatedAt,
            Route = doc.Route,
            RouteQueryJson = doc.RouteQueryJson,
            EditRoute = doc.EditRoute
        };
    }

    private static void AddParameter(DbCommand command, string name, object value)
    {
        DbParameter parameter = command.CreateParameter();
        parameter.ParameterName = name;
        parameter.Value = value ?? DBNull.Value;
        command.Parameters.Add(parameter);
    }

    private static string GetString(DbDataReader reader, string name)
    {
        object value = reader[name];
        return value == DBNull.Value ? null : Convert.ToString(value);
    }

    private static int? GetNullableInt(DbDataReader reader, string name)
    {
        object value = reader[name];
        return value == DBNull.Value ? null : Convert.ToInt32(value);
    }

    private static DateTime? GetNullableDateTime(DbDataReader reader, string name)
    {
        object value = reader[name];
        return value == DBNull.Value ? null : Convert.ToDateTime(value);
    }
}