using System.Collections.Generic;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using GB5Shared.GOP.GBQueryExecutor;
using GB5Shared.DTO.Framework.Login;
using GB5Shared.DTO.Qualifier;
using Microsoft.Extensions.Logging;

namespace GB5Shared.GOP.Qualifier.Executors
{
    // ============================================================
    // DataSourceExecutor — ExecutionMode 2 (GBQueryExecutor)
    //
    // Executes a configured SQL query via IGBQueryExecutor and
    // writes the returned row's columns into the FactBag as
    // document-level facts.
    //
    // The query is identified by SnapshotMethod.QueryCode.
    // Parameters are bound from two sources, matching NCalcEvaluator's
    // precedence: ctx.Document's root properties (the caller-supplied
    // input payload, e.g. QUALIFY step's InputKeys) first, then FactBag
    // document facts on top (so downstream queries can override with
    // outputs already produced by earlier qualifiers in the same run).
    //
    // No row returned = no facts written (not an error unless a
    // rule condition checks for the fact's presence).
    // ============================================================
    public class DataSourceExecutor : IQualifierMethodExecutor
    {
        private readonly IGBQueryExecutor        _GBQueryExecutor;
        private readonly ILogger<DataSourceExecutor> _Logger;

        public DataSourceExecutor(
            IGBQueryExecutor             gbQueryExecutor,
            ILogger<DataSourceExecutor>  logger)
        {
            _GBQueryExecutor = gbQueryExecutor;
            _Logger          = logger;
        }

        public string ExecutionModeKey => "DataSource";

        public async Task<IReadOnlyList<QualifierFinding>> ExecuteAsync(
            SnapshotMethod            method,
            QualifierExecutionContext ctx,
            LoginDTO                  loginDTO,
            CancellationToken         ct)
        {
            if (string.IsNullOrWhiteSpace(method.QueryCode))
                return [];

            var parameters = new Dictionary<string, object?>();

            // Bind the caller-supplied input document first (e.g. QUALIFY step's
            // InputKeys payload) — same source NCalcEvaluator reads.
            if (ctx.Document is not null)
            {
                try
                {
                    foreach (var prop in ctx.Document.RootElement.EnumerateObject())
                        parameters[prop.Name] = ExtractJsonValue(prop.Value);
                }
                catch
                {
                    // Non-object root — no document params to bind.
                }
            }

            // FactBag document facts take precedence — outputs already produced
            // by earlier qualifiers in this run override the caller's input.
            var exported = ctx.Facts.ExportAll();
            if (exported.TryGetValue("Document", out var docSection) &&
                docSection is IReadOnlyDictionary<string, object?> docFacts)
            {
                foreach (var (k, v) in docFacts)
                    parameters[k] = v;
            }

            // Also pass EntityId so queries can filter by the specific entity.
            parameters["EntityId"] = ctx.EntityId;

            var result = await _GBQueryExecutor.ExecuteRowAsync(
                method.QueryCode, parameters, loginDTO,
                callerModule: "QualifierEngine/DataSourceExecutor",
                ct: ct);

            if (result.Found)
            {
                // Write returned columns as document-level facts.
                foreach (var (col, val) in result.Row)
                    ctx.Facts.SetDocumentFact(col, val);

                _Logger.LogDebug(
                    "DataSourceExecutor: query '{QueryCode}' returned {ColCount} columns for entity {EntityId}",
                    method.QueryCode, result.Row.Count, ctx.EntityId);
            }
            else
            {
                _Logger.LogDebug(
                    "DataSourceExecutor: query '{QueryCode}' returned no row for entity {EntityId}",
                    method.QueryCode, ctx.EntityId);
            }

            // DataSource methods populate facts; findings come from rule conditions.
            return [];
        }

        private static object? ExtractJsonValue(JsonElement element) =>
            element.ValueKind switch
            {
                JsonValueKind.String  => element.GetString(),
                JsonValueKind.Number  => element.TryGetInt64(out var l) ? (object)l : element.GetDouble(),
                JsonValueKind.True    => true,
                JsonValueKind.False   => false,
                JsonValueKind.Null    => null,
                _                     => element.GetRawText()
            };
    }
}