using System;
using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;

namespace FastExcel
{
    partial class FastExcel
    {
        /// <summary>
        /// Dictionary of defined names
        /// </summary>
        internal IReadOnlyDictionary<string, DefinedName> DefinedNames
        {
            get
            {
                if (_definedNames == null)
                {
                    LoadDefinedNames();
                }

                return _definedNames;
            }
        }
        private Dictionary<string, DefinedName> _definedNames;

        private void LoadDefinedNames()
        {
            XDocument document;
            try
            {
                document = XDocument.Load(Archive.GetEntry("xl/workbook.xml").Open());
            }
            catch (Exception exception)
            {
                throw new DefinedNameLoadException("Unable to open stream to read internal workbook.xml file", exception);
            }
            if (document == null)
            {
                throw new DefinedNameLoadException("Unable to load workbook.xml from open stream. Probable corrupt file.");
            }

            _definedNames = new Dictionary<string, DefinedName>();

            foreach (var e in (from d2 in document.Descendants().Where(dx => dx.Name.LocalName == "definedNames").Descendants()
                               select d2))
            {
                var currentDefinedName = new DefinedName(e);
                _definedNames.Add(currentDefinedName.Key, currentDefinedName);
            }

        }

        /// <summary>
        /// Retrieves ranges of cells by their defined name
        /// </summary>
        /// <param name="definedName">Defined Name</param>
        /// <param name="worksheetIndex">If scoped to a sheet, the worksheetIndex</param>
        /// <returns>List of cells encapsulated in another list representing seperate ranges</returns>
        public IEnumerable<IEnumerable<Cell>> GetCellRangesByDefinedName(string definedName, int? worksheetIndex = null)
        {
            var result = new List<List<Cell>>();

            string key = !worksheetIndex.HasValue ? definedName : definedName + ":" + worksheetIndex;

            if (!DefinedNames.ContainsKey(key))
            {
                return result;
            }

            string[] references = DefinedNames[key].Reference.Split(',');

            foreach (string reference in references)
            {
                CellRange cellRange;
                try
                {
                    cellRange = new CellRange(reference);
                }
                catch (ArgumentException)
                {
                    // reference is invalid or not supported
                    continue;
                }

                Worksheet worksheet = Read(cellRange.SheetName);

                result.Add(worksheet.GetCellsInRange(cellRange).ToList());
            }

            return result;
        }

        /// <summary>
        /// Gets all cells by defined name
        /// Like GetCellRangesByCellName, but just retreives all cells in a single list
        /// </summary>
        /// <param name="definedName"></param>
        /// <param name="worksheetIndex"></param>
        /// <returns></returns>
        public IEnumerable<Cell> GetCellsByDefinedName(string definedName, int? worksheetIndex = null)
        {
            var cells = new List<Cell>();
            var cellRanges = GetCellRangesByDefinedName(definedName) as List<List<Cell>>;

            foreach (var cellRange in cellRanges)
            {
                cells.InsertRange(cells.Count, cellRange);
            }

            return cells;
        }

        /// <summary>
        /// Returns cell by defined name
        /// If theres more than one, this is the first one.
        /// </summary>
        public Cell GetCellByDefinedName(string definedName, int? worksheetIndex = null)
        {
            return GetCellsByDefinedName(definedName, worksheetIndex).FirstOrDefault();
        }
        
        /// <summary>
        /// Returns all cells in a column by name, within optional row range
        /// </summary>
        /// <param name="columnName"></param>
        /// <param name="rowStart"></param>
        /// <param name="rowEnd"></param>
        /// <returns></returns>
        public IEnumerable<Cell> GetCellsByColumnName(string columnName, int rowStart = 1, int? rowEnd = null)
        {
            var columnCells = GetCellsByDefinedName(columnName) as List<Cell>;
            if (!rowEnd.HasValue)
            {
                rowEnd = columnCells.Last().RowNumber;
            }

            return columnCells.Where(cell => cell.RowNumber >= rowStart && cell.RowNumber <= rowEnd).ToList();
        }
    }
}