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// Copyright by Barry G. Becker, 2016-2017. Licensed under MIT License: http://www.opensource.org/licenses/MIT
package com.barrybecker4.simulation.snake

import com.barrybecker4.simulation.snake.data.SnakeData
import com.barrybecker4.simulation.snake.geometry.HeadSegment
import com.barrybecker4.simulation.snake.geometry.Segment
import javax.vecmath.Point2d
import javax.vecmath.Vector2d


/**
  * Data structure and methods for representing a single dynamic snake
  * The geometry of the snake is defined by SnakeData
  * General Improvements:
  *    - auto optimize with hill-climbing (let the snake learn how to move faster on its own)
  *    - add texture for snake skin
  *    - collision detection, walls, multiple snakes
  *    - goal directed path search
  *
  * Performance Improvements:
  *    - profile (where is the time spent? rendering or computation)
  *    - only draw every nth frame
  *    - run OptimizeIt
  * 3/2011 (java version) frames per second for basic snake = 64.5. Speed = 0.32
  * 3/2017 (ported to scala) frames per second for basic snake = 185.5. Speed = 0.36
  *
  * Use a hardcoded static data interface to initialize so it can be easily run in an applet without using resources.
  * @param snakeData defines the snake geometry
  * @author Barry Becker
  */
class Snake(var snakeData: SnakeData) {

  /** the array of segments which make up the snake */
  private var segment: Array[Segment] = _
  setData(snakeData)

  /** @param snakeData the data defining the snakes geometrical shape. */
  def setData(snakeData: SnakeData): Unit = {
    this.snakeData = snakeData
    initFromData()
  }

  def reset(): Unit = { resetFromData() }
  def getNumSegments: Int = snakeData.numSegments
  def getSegment(i: Int): Segment = segment(i)

  /** use this if you need to avoid reading from a file */
  private def initFromData(): Unit = {
    segment = Array.ofDim[Segment](snakeData.numSegments)
    resetFromData()
  }

  private def resetFromData(): Unit = {
    var width1 = snakeData.widths(0)
    var width2 = snakeData.widths(1)
    val numSegments = snakeData.numSegments
    val segmentLength = snakeData.segmentLength
    val length = 80 + numSegments * segmentLength
    var segment: Segment = new HeadSegment(width1, width2, segmentLength, new Point2d(length, 320.0), this)
    this.segment(0) = segment
    var segmentInFront = segment
    width1 = width2
    for (i <- 1 until numSegments - 1) {
      width2 = snakeData.widths(i)
      segment = new Segment(width1, width2, segmentLength, segmentInFront, i, this)
      this.segment(i) = segment
      segmentInFront = segment
      width1 = width2
    }
    this.segment(numSegments - 1) = new Segment(width1, width2, segmentLength, segmentInFront, numSegments - 1, this)
  }

  /** @return the center point of the snake */
  def getCenter: Point2d = {
    val center = new Point2d(0.0, 0.0)
    var ct = 0
    for (i <- 0 until snakeData.numSegments by 2) {
      ct += 1
      center.add(segment(i).getCenterParticle)
    }
    center.scale(1.0 / ct.toDouble)
    center
  }

  /** shift/translate the whole snake by the specified vector */
  def translate(vec: Vector2d): Unit =
    for (i <- 0 until snakeData.numSegments) segment(i).translate(vec)

  /**
    * the snake is not considered stable if the angle between any edge segments exceeds Snake.MIN_EDGE_ANGLE
    * @return true if the snake has not gotten twisted too badly
    */
  def isStable: Boolean = {
    for (i <- 2 until snakeData.numSegments) {
      if (!segment(i).isStable) return false
    }
    true
  }
}