using com.sun.xml.@internal.rngom.ast.builder;
using InABox.Core;
using InABox.Scripting;
using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text;

namespace PRSDesktop
{
    public class CreateTableArgs
    {
        public Stream Stream { get; set; }

        public CreateTableArgs(Stream stream)
        {
            Stream = stream;
        }
    }

    public class LoadDataArgs
    {
        public Stream Stream { get; set; }

        public CoreTable Table { get; set; }

        public LoadDataArgs(Stream stream, CoreTable table)
        {
            Stream = stream;
            Table = table;
        }
    }

    public class CustomImporterSettings : BaseObject
    {
        [ScriptEditor]
        public string Script { get; set; }

        public CustomImporterSettings()
        {
            Script = "";
        }

        public string DefaultScript()
        {
            return
@"using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime;
using System.Windows;
using System.Windows.Media;
using InABox.Core;
using InABox.Scripting;
using Comal.Classes;
using PRSDesktop;

public class Module
{
    // Initialise a table with the necessary columns.
    public CoreTable? CreateTable(CreateTableArgs args)
    {
        var table = new CoreTable();
        table.Columns.Add(new CoreColumn { ColumnName = ..., DataType = typeof(string) });
        return table;
    }

    public void LoadData(LoadDataArgs args)
    {
        // Read data from args.Stream;
    
        // Add it to the results with:
        //
        //   var row = args.Table.NewRow();
        //   args.Table.Rows.Add(row);
        //
    }
}";
        }
    }

    public class CustomImporter<T> : SettingsImporter<T, CustomImporterSettings>
        where T : Entity, IRemotable, IPersistent, new()
    {

        #region Script

        private ScriptDocument? _script;

        private ScriptDocument? Script
        {
            get
            {
                EnsureScript();
                return _script;
            }
        }

        private object? _scriptObject;
        private object ScriptObject
        {
            get
            {
                EnsureScript();
                return _scriptObject;
            }
        }

        [MemberNotNull(nameof(_scriptObject), nameof(_createTableMethod), nameof(_loadDataMethod))]
        private void EnsureScript()
        {
            if(_script is null)
            {
                if (!Settings.Script.IsNullOrWhiteSpace())
                {
                    _script = new ScriptDocument(Settings.Script);
                    if (!_script.Compile())
                    {
                        throw new Exception("Script in Custom Importer failed to compile!");
                    }
                    _scriptObject = _script.GetObject()
                        ?? throw new Exception("Error in Custom Importer script.");
                    _createTableMethod = _script.GetMethod(methodName: "CreateTable")
                        ?? throw new Exception("CreateTable() not provided");
                    _loadDataMethod = _script.GetMethod(methodName: "LoadData")
                        ?? throw new Exception("LoadData(LoadDataArgs args) not provided");
                }
                else
                {
                    throw new Exception("No script provided for custom importer.");
                }
            }
        }

        private MethodInfo? _createTableMethod;
        private MethodInfo? _loadDataMethod;

        private MethodInfo CreateTableMethod
        {
            get
            {
                EnsureScript();
                return _createTableMethod;
            }
        }
        private MethodInfo LoadDataMethod
        {
            get
            {
                EnsureScript();
                return _loadDataMethod;
            }
        }

        #endregion

        private CoreTable? _table;
        private bool _loaded;
        private Stream? _stream;
        private int rowIdx;

        public override void Close()
        {
            _table = null;
            _loaded = false;
            _stream = null;
        }

        public override bool MoveNext()
        {
            EnsureData();
            ++rowIdx;
            return rowIdx < _table.Rows.Count;
        }

        public override bool Open(Stream stream)
        {
            _stream = stream;
            return true;
        }

        [MemberNotNullWhen(true, nameof(_table))]
        public override bool ReadHeader()
        {
            if (_stream is null)
            {
                throw new Exception("Cannot read header before Open() is called.");
            }
            var args = new CreateTableArgs(_stream);
            _table = CreateTableMethod.Invoke(ScriptObject, new object[] { args }) as CoreTable;
            if(_table is not null)
            {
                Fields = _table.Columns.Select(x => x.ColumnName).ToArray();
                return true;
            }
            else
            {
                return false;
            }
        }

        [MemberNotNull(nameof(_table))]
        private void EnsureData()
        {
            if (_table is null)
            {
                if (!ReadHeader())
                {
                    throw new Exception("Failed to read header.");
                }
            }
            if (!_loaded)
            {
                if (_stream is null)
                {
                    throw new Exception("Cannot import before Open() is called.");
                }
                LoadDataMethod.Invoke(ScriptObject, new object?[] { new LoadDataArgs(_stream, _table) });
                _loaded = true;
                rowIdx = -1;
            }
        }

        public override Dictionary<string, string> ReadLine()
        {
            EnsureData();
            var row = _table.Rows[rowIdx];
            return _table.Columns.ToDictionary(
                x => x.ColumnName,
                x => row[x.ColumnName]?.ToString() ?? "");
        }
    }
}