using System;
using System.Collections;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Text;
using System.Threading;
using System.Collections.Concurrent;
using System.Threading.Tasks;

namespace Tango.CSV
{
    /// <summary>
    /// Represents a component for reading and writing CSV files.
    /// </summary>
    /// <seealso cref="System.IDisposable" />
    public class CsvFile : IDisposable
    {
        protected bool _is_disposed;

        internal protected Stream BaseStream;
        protected static DateTime DateTimeZero = new DateTime();

        /// <summary>
        /// Initializes the <see cref="CsvFile"/> class.
        /// </summary>
        static CsvFile()
        {
            DefaultCsvDefinition = new CsvDefinition
            {
                EndOfLine = "\r\n",
                FieldSeparator = ',',
                TextQualifier = '"'
            };
            UseLambdas = true;
            UseTasks = false;
            FastIndexOfAny = true;
        }

        /// <summary>
        /// Gets or sets the default CSV definition.
        /// </summary>
        public static CsvDefinition DefaultCsvDefinition { get; set; }

        /// <summary>
        /// Gets or sets a value indicating whether [use lambdas].
        /// </summary>
        public static bool UseLambdas { get; set; }

        /// <summary>
        /// Gets or sets a value indicating whether [use tasks].
        /// </summary>
        public static bool UseTasks { get; set; }

        /// <summary>
        /// Gets or sets a value indicating whether [fast index of any].
        /// </summary>
        public static bool FastIndexOfAny { get; set; }

        /// <summary>
        /// Reads the specified CSV source.
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="csvSource">The CSV source.</param>
        /// <returns></returns>
        public static IEnumerable<T> Read<T>(CsvSource csvSource) where T : new()
        {
            var csvFileReader = new CsvFileReader<T>(csvSource);
            return (IEnumerable<T>)csvFileReader;
        }

        /// <summary>
        /// Gets the columns.
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="csvSource">The CSV source.</param>
        /// <returns></returns>
        public static IEnumerable<string> GetColumns<T>(CsvSource csvSource) where T : new()
        {
            var csvFileReader = new CsvFileReader<T>(csvSource);
            return csvFileReader.Columns;
        }

        /// <summary>
        /// Gets the field separator.
        /// </summary>
        /// <value>
        /// The field separator.
        /// </value>
        public char FieldSeparator { get; private set; }

        /// <summary>
        /// Gets the text qualifier.
        /// </summary>
        /// <value>
        /// The text qualifier.
        /// </value>
        public char TextQualifier { get; private set; }

        /// <summary>
        /// Gets the columns.
        /// </summary>
        /// <value>
        /// The columns.
        /// </value>
        public IEnumerable<String> Columns { get; protected set; }

        /// <summary>
        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
        }

        /// <summary>
        /// Releases unmanaged and - optionally - managed resources.
        /// </summary>
        /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
        protected virtual void Dispose(bool disposing)
        {
            // overriden in derived classes
        }
    }

    /// <summary>
    /// Represents a component for reading and writing CSV files from and to a collection of objects.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <seealso cref="System.IDisposable" />
    public class CsvFile<T> : CsvFile
    {
        private readonly char fieldSeparator;
        private readonly string fieldSeparatorAsString;
        private readonly char[] invalidCharsInFields;
        private readonly StreamWriter streamWriter;
        private readonly char textQualifier;
        private readonly String[] columns;
        private Func<T, object>[] getters;
        readonly bool[] isInvalidCharInFields;
        private int linesToWrite;
        private readonly BlockingCollection<string> csvLinesToWrite = new BlockingCollection<string>(5000);
        private readonly Thread writeCsvLinesTask;
        private Task addAsyncTask;

        /// <summary>
        /// Initializes a new instance of the <see cref="CsvFile{T}"/> class.
        /// </summary>
        /// <param name="csvDestination">The CSV destination.</param>
        public CsvFile(CsvDestination csvDestination)
            : this(csvDestination, null)
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="CsvFile{T}"/> class.
        /// </summary>
        public CsvFile()
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="CsvFile{T}"/> class.
        /// </summary>
        /// <param name="csvDestination">The CSV destination.</param>
        /// <param name="csvDefinition">The CSV definition.</param>
        public CsvFile(CsvDestination csvDestination, CsvDefinition csvDefinition)
        {
            if (csvDefinition == null)
                csvDefinition = DefaultCsvDefinition;
            this.columns = (csvDefinition.Columns ?? InferColumns(typeof(T))).ToArray();
            this.fieldSeparator = csvDefinition.FieldSeparator;
            this.fieldSeparatorAsString = this.fieldSeparator.ToString(CultureInfo.InvariantCulture);
            this.textQualifier = csvDefinition.TextQualifier;
            this.streamWriter = csvDestination.StreamWriter;

            this.invalidCharsInFields = new[] { '\r', '\n', this.textQualifier, this.fieldSeparator };
            this.isInvalidCharInFields = new bool[256];

            foreach (var c in this.invalidCharsInFields)
            {
                this.isInvalidCharInFields[c] = true;
            }
            this.WriteHeader();

            this.CreateGetters();
            if (CsvFile.UseTasks)
            {
                writeCsvLinesTask = new Thread((o) => this.WriteCsvLines());
                writeCsvLinesTask.Start();
            }
            this.addAsyncTask = Task.Factory.StartNew(() => { });

        }

        /// <summary>
        /// Releases unmanaged and - optionally - managed resources.
        /// </summary>
        /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                _is_disposed = true;
                // free managed resources
                addAsyncTask.Wait();
                if (csvLinesToWrite != null)
                {
                    csvLinesToWrite.CompleteAdding();
                }
                if (writeCsvLinesTask != null)
                    writeCsvLinesTask.Join();
                this.streamWriter.Close();
            }
        }

        /// <summary>
        /// Infers the columns.
        /// </summary>
        /// <param name="recordType">Type of the record.</param>
        /// <returns></returns>
        protected static IEnumerable<string> InferColumns(Type recordType)
        {
            var columns = recordType
                .GetProperties(BindingFlags.Public | BindingFlags.Instance)
                .Where(pi => pi.GetIndexParameters().Length == 0
                    && pi.GetSetMethod() != null
                    && !Attribute.IsDefined(pi, typeof(CsvIgnoreAttribute)))
                .Select(pi => pi.Name)
                .Concat(recordType
                    .GetFields(BindingFlags.Public | BindingFlags.Instance)
                    .Where(fi => !Attribute.IsDefined(fi, typeof(CsvIgnoreAttribute)))
                    .Select(fi => fi.Name))
                .ToList();
            return columns;
        }

        /// <summary>
        /// Writes the CSV lines.
        /// </summary>
        private void WriteCsvLines()
        {
            int written = 0;
            foreach (var csvLine in csvLinesToWrite.GetConsumingEnumerable())
            {
                this.streamWriter.WriteLine(csvLine);
                written++;
            }
            Interlocked.Add(ref this.linesToWrite, -written);
        }

        /// <summary>
        /// Appends the specified record.
        /// </summary>
        /// <param name="record">The record.</param>
        public void Append(T record)
        {
            if (_is_disposed)
            {
                return;
            }

            if (CsvFile.UseTasks)
            {

                var linesWaiting = Interlocked.Increment(ref this.linesToWrite);
                Action<Task> addRecord = (t) =>
                {
                    if (!_is_disposed)
                    {
                        var csvLine = this.ToCsv(record);
                        this.csvLinesToWrite.Add(csvLine);
                    }
                };

                if (linesWaiting < 10000)
                    this.addAsyncTask = this.addAsyncTask.ContinueWith(addRecord);
                else
                    addRecord(null);
            }
            else
            {
                var csvLine = this.ToCsv(record);
                this.streamWriter.WriteLine(csvLine);
            }
        }

        /// <summary>
        /// Finds the getter.
        /// </summary>
        /// <param name="c">The c.</param>
        /// <param name="staticMember">if set to <c>true</c> [static member].</param>
        /// <returns></returns>
        private static Func<T, object> FindGetter(string c, int index, bool staticMember)
        {
            var flags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.IgnoreCase | (staticMember ? BindingFlags.Static : BindingFlags.Instance);
            Func<T, object> func = null;

            PropertyInfo pi = null;
            pi = typeof(T).GetProperty(c);

            if (pi == null) //Then try get by column index,
            {
                pi = typeof(T).GetProperties()[index];
                pi = typeof(T).GetProperties()[index]; //Workaround for some weired problem that makes the program not take the value.
            }

            if (CsvFile.UseLambdas)
            {
                Expression expr = null;
                ParameterExpression parameter = Expression.Parameter(typeof(T), "r");
                Type type = null;

                if (pi != null)
                {
                    type = pi.PropertyType;
                    expr = Expression.Property(parameter, pi.Name);
                }
                if (expr != null)
                {
                    Expression<Func<T, object>> lambda;
                    if (type.IsValueType)
                    {
                        lambda = Expression.Lambda<Func<T, object>>(Expression.TypeAs(expr, typeof(object)), parameter);
                    }
                    else
                    {
                        lambda = Expression.Lambda<Func<T, object>>(expr, parameter);
                    }
                    func = lambda.Compile();
                }
            }
            else
            {
                if (pi != null)
                    func = o => pi.GetValue(o, null);
            }
            return func;
        }

        /// <summary>
        /// Creates the getters.
        /// </summary>
        private void CreateGetters()
        {
            var list = new List<Func<T, object>>();

            for (int i = 0; i < columns.Length; i++)
            {
                Func<T, Object> func = null;
                var propertyName = (columns[i].IndexOf(' ') < 0 ? columns[i] : columns[i].Replace(" ", ""));
                func = FindGetter(columns[i], i, false) ?? FindGetter(columns[i], i, true);

                list.Add(func);
            }
            this.getters = list.ToArray();
        }

        /// <summary>
        /// To the CSV.
        /// </summary>
        /// <param name="record">The record.</param>
        /// <returns></returns>
        /// <exception cref="System.ArgumentException">Cannot be null;record</exception>
        private string ToCsv(T record)
        {
            if (record == null)
                throw new ArgumentException("Cannot be null", "record");

            string[] csvStrings = new string[getters.Length];

            for (int i = 0; i < getters.Length; i++)
            {
                var getter = getters[i];
                object fieldValue = getter == null ? null : getter(record);
                csvStrings[i] = this.ToCsvString(fieldValue);
            }
            return string.Join(this.fieldSeparatorAsString, csvStrings);

        }

        /// <summary>
        /// To the CSV string.
        /// </summary>
        /// <param name="o">The o.</param>
        /// <returns></returns>
        private string ToCsvString(object o)
        {
            if (o != null)
            {
                string valueString = o as string ?? Convert.ToString(o, CultureInfo.CurrentUICulture);
                if (RequireQuotes(valueString))
                {
                    var csvLine = new StringBuilder();
                    csvLine.Append(this.textQualifier);
                    foreach (char c in valueString)
                    {
                        if (c == this.textQualifier)
                            csvLine.Append(c); // double the double quotes
                        csvLine.Append(c);
                    }
                    csvLine.Append(this.textQualifier);
                    return csvLine.ToString();
                }
                else
                    return valueString;
            }
            return string.Empty;
        }

        /// <summary>
        /// Requires the quotes.
        /// </summary>
        /// <param name="valueString">The value string.</param>
        /// <returns></returns>
        private bool RequireQuotes(string valueString)
        {
            if (CsvFile.FastIndexOfAny)
            {
                var len = valueString.Length;
                for (int i = 0; i < len; i++)
                {
                    char c = valueString[i];
                    if (c <= 255 && this.isInvalidCharInFields[c])
                        return true;
                }
                return false;
            }
            else
            {
                return valueString.IndexOfAny(this.invalidCharsInFields) >= 0;
            }
        }

        /// <summary>
        /// Writes the header.
        /// </summary>
        private void WriteHeader()
        {
            var csvLine = new StringBuilder();
            for (int i = 0; i < this.columns.Length; i++)
            {
                if (i > 0)
                    csvLine.Append(this.fieldSeparator);
                csvLine.Append(this.ToCsvString(this.columns[i]));
            }
            this.streamWriter.WriteLine(csvLine.ToString());
        }
    }
}