using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Serialization;
using TransportGame.Primitives;

namespace TransportGame.Model.Road
{
    /// <summary>
    /// Represents a road segment
    /// </summary>
    [XmlRoot("segment")]
    public class RoadSegment
    {
        /// <summary>
        /// Gets or sets the id
        /// </summary>
        [XmlAttribute("id")]
        public int Id { get; set; }

        /// <summary>
        /// Gets or sets the parent network
        /// </summary>
        [XmlIgnore]
        public RoadNetwork ParentNetwork { get; set; }

        /// <summary>
        /// Gets or sets the id of the first terminal
        /// </summary>
        [XmlAttribute("term1")]
        public int Terminal1Id { get; set; }

        /// <summary>
        /// Gets or sets the id of the second terminal
        /// </summary>
        [XmlAttribute("term2")]
        public int Terminal2Id { get; set; }

        /// <summary>
        /// Gets or sets the first terminal
        /// </summary>
        [XmlIgnore]
        public RoadNode Terminal1
        {
            get
            {
                return (Terminal1Id == -1) ? null : ParentNetwork.Nodes[Terminal1Id];
            }
            set
            {
                Terminal1Id = (value == null) ? -1 : value.Id;
            }
        }
        
        /// <summary>
        /// Gets or sets the second terminal
        /// </summary>
        [XmlIgnore]
        public RoadNode Terminal2
        {
            get
            {
                return (Terminal2Id == -1) ? null : ParentNetwork.Nodes[Terminal2Id];
            }
            set
            {
                Terminal2Id = (value == null) ? -1 : value.Id;
            }
        }

        /// <summary>
        /// Gets or sets the number of lanes going from terminal 1 to terminal 2
        /// </summary>
        [XmlAttribute("lanesTo2")]
        public int LanesTo2 { get; set; }

        /// <summary>
        /// Gets or sets the number of lanes going form terminal 2 to terminal 1
        /// </summary>
        [XmlAttribute("lanesTo1")]
        public int LanesTo1 { get; set; }
        
        /// <summary>
        /// Gets the direction vector of this road segment
        /// </summary>
        [XmlIgnore]
        public Vector2 Direction
        {
            get
            {
                if (Terminal1Id == -1 || Terminal2Id == -1 || ParentNetwork == null)
                    return Vector2.Zero;

                return (Terminal2.Position - Terminal1.Position).Normalized;
            }
        }

        /// <summary>
        /// Gets the road segment as a line segment
        /// </summary>
        /// <returns></returns>
        public LineSegment AsLineSegment()
        {
            if (Terminal1Id == -1 || Terminal2Id == -1 || ParentNetwork == null)
                throw new InvalidOperationException("Terminals are not initialized.");

            return new LineSegment(Terminal1.Position, Terminal2.Position);
        }

        /// <summary>
        /// Initializes road segment
        /// </summary>
        public RoadSegment()
        {
            LanesTo1 = 1;
            LanesTo2 = 1;
            Terminal1Id = -1;
            Terminal2Id = -1;
        }

        public override string ToString()
        {
            return string.Format("(segment id={0}, {1}->{2})", Id, Terminal1, Terminal2);
        }
    }
}