CSV.cs

using System;
using System.Text;
using Waher.Runtime.Collections;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Model;
using Waher.Script.Objects.Matrices;
 
namespace Waher.Content
{
    public delegate string ToString(IElement Element);
 
    public static class CSV
    {
        #region Encoding/Decoding
 
        public static string[][] Parse(string Csv)
        {
            int Pos = 0;
            int Len = Csv.Length;
            string[][] Result = Parse(Csv, ref Pos, Len);
            char ch;
 
            while (Pos < Len && ((ch = Csv[Pos]) <= ' ' || ch == 160))
                Pos++;
 
            if (Pos < Len)
                throw new Exception("Unexpected content at end of string.");
 
            return Result;
        }
 
        private static string[][] Parse(string Csv, ref int Pos, int Len)
        {
            ChunkedList<string[]> Records = new ChunkedList<string[]>();
            ChunkedList<string> Fields = new ChunkedList<string>();
            StringBuilder sb = new StringBuilder();
            int State = 0;
            int i = 0;
            char ch;
            bool sbEmpty = true;
 
            while (Pos < Len)
            {
                ch = Csv[Pos++];
                switch (State)
                {
                    case 0:
                        if (ch == '"')
                            State += 2;
                        else if (ch == ',')
                            Fields.Add(string.Empty);
                        else if (ch == '\r' || ch == '\n')
                        {
                            if (Fields.Count > 0)
                            {
                                Records.Add(Fields.ToArray());
                                Fields.Clear();
                            }
                        }
                        else
                        {
                            sb.Append(ch);
                            sbEmpty = false;
                            State++;
                        }
                        break;
 
                    case 1: // Undelimited string
                        if (ch == ',')
                        {
                            Fields.Add(sb.ToString());
                            sb.Clear();
                            sbEmpty = true;
                            State = 0;
                        }
                        else if (ch == '\r' || ch == '\n')
                        {
                            Fields.Add(sb.ToString());
                            sb.Clear();
                            sbEmpty = true;
                            State = 0;
 
                            Records.Add(Fields.ToArray());
                            Fields.Clear();
                        }
                        else
                        {
                            sb.Append(ch);
                            sbEmpty = false;
                        }
                        break;
 
                    case 2: // String.
                        if (ch == '\\')
                            State++;
                        else if (ch == '"')
                            State--;
                        else
                        {
                            sb.Append(ch);
                            sbEmpty = false;
                        }
                        break;
 
                    case 3: // String, escaped character.
                        switch (ch)
                        {
                            case 'a':
                                sb.Append('\a');
                                break;
 
                            case 'b':
                                sb.Append('\b');
                                break;
 
                            case 'f':
                                sb.Append('\f');
                                break;
 
                            case 'n':
                                sb.Append('\n');
                                break;
 
                            case 'r':
                                sb.Append('\r');
                                break;
 
                            case 't':
                                sb.Append('\t');
                                break;
 
                            case 'v':
                                sb.Append('\v');
                                break;
 
                            case 'x':
                                i = 0;
                                State += 4;
                                break;
 
                            case 'u':
                                i = 0;
                                State += 2;
                                break;
 
                            default:
                                sb.Append(ch);
                                break;
                        }
 
                        sbEmpty = false;
                        State--;
                        break;
 
                    case 4: // hex digit 1(4)
                        i = JSON.HexDigit(ch);
                        State++;
                        break;
 
                    case 5: // hex digit 2(4)
                        i <<= 4;
                        i |= JSON.HexDigit(ch);
                        State++;
                        break;
 
                    case 6: // hex digit 3(4)
                        i <<= 4;
                        i |= JSON.HexDigit(ch);
                        State++;
                        break;
 
                    case 7: // hex digit 4(4)
                        i <<= 4;
                        i |= JSON.HexDigit(ch);
                        sb.Append((char)i);
                        sbEmpty = false;
                        State -= 5;
                        break;
                }
            }
 
            if (!sbEmpty)
                Fields.Add(sb.ToString());
 
            if (Fields.Count > 0)
                Records.Add(Fields.ToArray());
 
            return Records.ToArray();
        }
 
        public static string Encode(string[][] Records)
        {
            StringBuilder sb = new StringBuilder();
            bool First;
 
            foreach (string[] Record in Records)
            {
                First = true;
 
                foreach (string Field in Record)
                {
                    bool Comma = false;
                    bool Control = false;
                    bool Quote = false;
 
                    if (First)
                        First = false;
                    else
                        sb.Append(',');
 
                    if (Field is null)
                        continue;
 
                    foreach (char ch in Field)
                    {
                        if (ch == ',')
                            Comma = true;
                        else if (ch == '"')
                            Quote = true;
                        else if (ch < ' ')
                            Control = true;
                    }
 
                    if (Comma || Quote || Control)
                    {
                        string Escaped = Field;
 
                        if (Quote)
                            Escaped = Escaped.Replace("\"", "\\\"");
 
                        if (Control)
                        {
                            Escaped = Escaped.
                                Replace("\a", "\\a").
                                Replace("\b", "\\b").
                                Replace("\f", "\\f").
                                Replace("\n", "\\n").
                                Replace("\r", "\\r").
                                Replace("\t", "\\t").
                                Replace("\v", "\\v");
                        }
 
                        sb.Append('"');
                        sb.Append(Escaped);
                        sb.Append('"');
                    }
                    else
                        sb.Append(Field);
                }
 
                sb.AppendLine();
            }
 
            return sb.ToString();
        }
 
        public static string Encode(IMatrix Matrix)
        {
            return Encode(Matrix, (E) =>
            {
                if (E.AssociatedObjectValue is string s)
                    return s;
                else if (E.AssociatedObjectValue is double d)
                    return CommonTypes.Encode(d);
                else
                    return ScriptNode.ToString(E);
            });
        }
 
        public static string Encode(IMatrix Matrix, ToString ElementToString)
        {
            if (ElementToString is null)
                throw new ArgumentNullException(nameof(ElementToString));
 
            ChunkedList<string[]> Records = new ChunkedList<string[]>();
            ChunkedList<string> Fields = new ChunkedList<string>();
 
            if (Matrix is ObjectMatrix M)
            {
                if (!(M.ColumnNames is null))
                    Records.Add(M.ColumnNames);
            }
 
            int Row, NrRows = Matrix.Rows;
            int Column, NrColumns = Matrix.Columns;
 
            for (Row = 0; Row < NrRows; Row++)
            {
                for (Column = 0; Column < NrColumns; Column++)
                    Fields.Add(ElementToString(Matrix.GetElement(Column, Row)));
 
                Records.Add(Fields.ToArray());
                Fields.Clear();
            }
 
            return Encode(Records.ToArray());
        }
 
        #endregion
    }
}