using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public struct Pos {
    public int X;
    public int Y;

    public Pos(int x, int y) {
        X = x;
        Y = y;
    }

    public static Pos operator -(Pos pos1, Pos pos2) {
        return new Pos(pos1.X - pos2.X, pos1.Y - pos2.Y);
    }

    public static Pos operator +(Pos pos1, Pos pos2) {
        return new Pos(pos1.X + pos2.X, pos1.Y + pos2.Y);
    }

    public static Pos operator *(Pos pos1, int koef) {
        return new Pos(pos1.X * koef, pos1.Y * koef);
    }

    public static Pos operator *(int koef, Pos pos1) {
        return new Pos(pos1.X * koef, pos1.Y * koef);
    }
}

public class Snake : MonoBehaviour {

    public Field field;
    public BlocksManager blocksManager;

    public List<Pos> Positions;
    public int Height = 20;
    public int Width = 10;
    public GameObject SnakePrefab;
    public List<SpriteRenderer> Segments;
    public int MaxSnakeSegments = 8;
    public int CurSnakeSegments;
    public int CurHeadDownIndex;

    void Start() {
        CreateSnakeSegments();
    }

    public void CreateSnakeSegments() {
        Segments = new List<SpriteRenderer>();
        for (int i = 0; i < MaxSnakeSegments; i++) {
            Segments.Add(Instantiate(SnakePrefab, transform).GetComponent<SpriteRenderer>());
        }
    }

    private int GetBodyIndex(int ind) {
        Pos last = Positions[ind - 1];
        Pos cur = Positions[ind];
        Pos next = Positions[ind + 1];

        Pos curLast = last - cur;
        Pos curNext = next - cur;

        if (curLast.Y == -1) {
            if (curNext.X == -1) {
                return (int)SnakeBlocks.PartOfBody.DownLeft;
            }
            else if (curNext.Y == 1) {
                return (int)SnakeBlocks.PartOfBody.DownUp;
            }
            else {//X==1
                return (int)SnakeBlocks.PartOfBody.DownRight;
            }
        }
        else if (curLast.X == -1) {
            if (curNext.Y == 1) {
                return (int)SnakeBlocks.PartOfBody.LeftUp;
            }
            else if (curNext.X == 1) {
                return (int)SnakeBlocks.PartOfBody.LeftRight;
            }
            else {//Y==-1
                return (int)SnakeBlocks.PartOfBody.DownLeft;
            }
        }
        else if (curLast.Y == 1) {
            if (curNext.X == 1) {
                return (int)SnakeBlocks.PartOfBody.UpRight;
            }
            else if (curNext.Y == -1) {
                return (int)SnakeBlocks.PartOfBody.DownUp;
            }
            else {//X==-1
                return (int)SnakeBlocks.PartOfBody.LeftUp;
            }
        }
        else {//X==1
            if (curNext.Y == -1) {
                return (int)SnakeBlocks.PartOfBody.DownRight;
            }
            else if (curNext.X == -1) {
                return (int)SnakeBlocks.PartOfBody.LeftRight;
            }
            else {//Y==1
                return (int)SnakeBlocks.PartOfBody.UpRight;
            }
        }
    }

    private int GetHeadIndex() {
        Pos cur = Positions[0];
        Pos next = Positions[1];

        Pos curNext = next - cur;

        if (curNext.Y == -1) {
            return (int)SnakeBlocks.PartOfBody.HeadUp;
        }
        else if (curNext.X == -1) {
            return (int)SnakeBlocks.PartOfBody.HeadRight;
        }
        else if (curNext.Y == 1) {
            return (int)SnakeBlocks.PartOfBody.HeadDown;
        }
        else {//X==1
            return (int)SnakeBlocks.PartOfBody.HeadLeft;
        }
    }

    private int GetTailIndex() {
        Pos cur = Positions[CurSnakeSegments - 1];
        Pos last = Positions[CurSnakeSegments - 2];

        Pos curLast = last - cur;

        if (curLast.Y == -1) {
            return (int)SnakeBlocks.PartOfBody.TailUp;
        }
        else if (curLast.X == -1) {
            return (int)SnakeBlocks.PartOfBody.TailRight;
        }
        else if (curLast.Y == 1) {
            return (int)SnakeBlocks.PartOfBody.TailDown;
        }
        else {//X==1
            return (int)SnakeBlocks.PartOfBody.TailLeft;
        }
    }

    private
    private bool CooldownFinished() {
        Time.
    }

    public IEnumerator SnakeMoving() {
        yield return null;
        int visible = 1;
        while (true) {
            Debug.Log(Time.deltaTime);

            yield return new WaitForSeconds(1f);

            Pos head = Positions[0];
            Positions[0] += Positions[0] - Positions[1];
            Segments[0].transform.position = new Vector2(Positions[0].X, Positions[0].Y);
            for (int i = CurSnakeSegments - 1; i > 1; i--) {
                Positions[i] = Positions[i - 1];
                Segments[i].transform.position = new Vector2(Positions[i].X, Positions[i].Y);
            }
            Positions[1] = head;
            Segments[1].transform.position = new Vector2(Positions[1].X, Positions[1].Y);

            Segments[0].sprite = blocksManager.Blocks[CurHeadDownIndex + GetHeadIndex()];
            if (visible < CurSnakeSegments) {
                for (int i = 1; i < visible; i++) {
                    Segments[i].sprite = blocksManager.Blocks[CurHeadDownIndex + GetBodyIndex(i)];
                }
            }
            else {
                for (int i = 1; i < CurSnakeSegments - 1; i++) {
                    Segments[i].sprite = blocksManager.Blocks[CurHeadDownIndex + GetBodyIndex(i)];
                }
                Segments[CurSnakeSegments - 1].sprite = blocksManager.Blocks[CurHeadDownIndex + GetTailIndex()];
            }
            visible++;
        }
    }

    public void NewSnake(int segments/*, int headDownIndex*/) {
        for (int i = segments; i < CurSnakeSegments; i++) {
            Segments[i].sprite = null;
        }
        CurSnakeSegments = segments;
        Positions = new List<Pos>(segments);
        Positions.Add(new Pos(Random.Range(0, Width), Height));
        for (int i = 1; i < segments; i++) {
            Positions.Add(new Pos(Positions[i - 1].X, Positions[i - 1].Y+1));
        }
        CurHeadDownIndex = 1;
        StartCoroutine(SnakeMoving());
    }
}