using System;
using System.Collections.Generic;
using System.Configuration;
using System.IO;
using System.Security.Policy;

namespace Bandersnatch
{
    public class Parser
    {
        private static bool GetInt(string line, ref int pos, out int integer)
        {
            int length = line.Length;
            string strInt = "";

            for (int i = 0; i < length; i++)
            {
                if (line[i] == ':')
                {
                    pos = i + 1;
                    break;
                }
                strInt = strInt + line[i];
            }
            return Int32.TryParse(strInt, out integer);
        }

        private static bool GetMessage(string line, ref int pos, out string message)
        {
            int length = line.Length;
            message = "";
            bool isNeighbours = false;

            for (int i = pos; i < length; i++)
            {
                if (line[i] == ':')
                {
                    isNeighbours = true;
                    pos = i + 1;
                    break;
                }
                message = message + line[i];
            }
            return isNeighbours;
        }

        private static bool GetNeighbours(string line, ref int pos, ref Dictionary<int, string> options)
        {
            int length = line.Length;
            int id = -1;
            string message = "";
            bool error = false;

            while (pos < length)
            {
                if (GetInt(line, ref pos, out id))
                    error = true;
                GetMessage(line, ref pos, out message);
                options.Add(id, message);
            }
            return error;
        }

        private static bool ParseLine(string line, out int id, out int type, out string message, ref Dictionary<int, string> options)
        {
            int pos = 0;
            id = -1;
            type = -1;
            message = "";
            bool error = false;

            if (GetInt(line, ref pos, out id))
                error = true;
            else if (GetInt(line, ref pos, out type))
                error = true;
            else if (GetMessage(line, ref pos, out message))
                GetNeighbours(line, ref pos, ref options);
            return error;
        }

        public static Graph CreateGraph(string filename)
        {
            if (!File.Exists(filename))
                return null;

            Graph g = new Graph();
            var lines = File.ReadAllLines(filename);
            bool error = false;

            foreach (string line in lines)
            {
                int id, type;
                string message;
                Dictionary<int, string> options = new Dictionary<int, string>();
                error = ParseLine(line, out id, out type, out message, ref options);
                if (error)
                    break;
                Node n = new Node(message, (NodeType)type);
                g.AddNode(id, n);
                g.GetNode(id).neighbours = options;
            }
            return error ? null : g;
        }
    }
}