using System.Collections.Generic;
using StereoKit;

namespace snake;

static class Mono
{
    public static double game_time = 0.0;
    public static double step_step = 60.0 / 80; // 80|100|120 bpm
    public static double step_time = 0.0;
    public static double step_t = 0.0;

    public static double intro_skip = 0.0;
    public static bool intro = true; // press to move until x condition or hold to skip
    public static bool menu = true;

    public static Pose box_pose = new(0, -3 * U.cm, -10 * U.cm);
    public static float box_scale = 1.333f * U.cm;
    public const int SD_X = 3, SD_Y = 2, SD_Z = 3;
    public static SpatialArray<int>
        box_space = new(SD_X - 1, SD_Y - 1, SD_Z - 1, -1),
        s_array = new(SD_X, SD_Y, SD_Z, -1),
        tail_fill = new(SD_X, SD_Y, SD_Z, -1);

    static void update_s_array()
    {
        s_array.Clear(-1);
        for (int i = 0; i < snake_len; i++)
        {
            s_array[snake[i]] = i;
        }
    }

    public static XYZi[] snake = new XYZi[
        Maths.u_length(SD_X) * Maths.u_length(SD_Y) * Maths.u_length(SD_Z)
    ];
    public static int snake_len = 1;
    public static int grow_buffer = 3;
    public static XYZi snake_dir = new(0, 0, 1);
    public static DeltaBool in_box = new(true);
    public static Dictionary<XYZi, XYZi> holes = new();
    public static XYZi food = new(0, 0, 0); // [!] start random to keep new game fresh?
    public static int eaten = 0;
    public static DeltaBool eaten_latch = new(false);
    public static double eat_timestamp = 0.0;

    public enum BoxMode
    {
        Float = -1,
        Hold = 0,
        Mount = 1,
    }
    // start mounted & in_cone
    public static BoxMode box_mode = BoxMode.Mount;
    public static DeltaBool in_cone = new(true);
    public static DeltaBool in_dist = new(false);

    public static void Init()
    {
        for (int i = 0; i < snake.Length; i++)
        {
            snake[i] = new XYZi(0, 0, 0);
        }
        update_s_array();
    }

    public static void Frame()
    {
        if (Rig.btn_back.delta == +1)
        {
            menu = !menu;
            SFX.click.PlayBox(new XYZi(0, 0, Mono.SD_Z + 1));
        }

        if (menu)
        {
            // just one btn(resume) in menu rn
            if (Rig.btn_select.delta == +1)
            {
                Rig.btn_select.delta = 0; // [!] hacky capture
                menu = false;
                SFX.click.PlayBox(new XYZi(0, 0, Mono.SD_Z + 1));
            }
        }

        // flatscreen dev controls
        if (Device.Name == "Simulator")
        {
            if (Input.Key(Key.MouseCenter).IsActive())
            {
                float sx = Input.Mouse.posChange.x;
                Renderer.CameraRoot *= Matrix.R(
                    Quat.FromAngles(0, -sx * 180.0f * Time.Stepf, 0)
                );
                // orbital_view
                box_pose.position = Input.Head.position + Input.Head.orientation * V.XYZ(0, -0 * U.cm, -10 * U.cm);
            }
        }
        else
        {
            in_dist.Step(Vec3.Distance(Rig.r_con_stick.position, box_pose.position) < 6 * U.cm);
            bool pickup = in_dist.state && Rig.btn_grip.delta == +1;
            in_cone.Step(Vec3.AngleBetween(
                Rig.head.orientation * Vec3.Forward,
                Vec3.Direction(box_pose.position, Rig.head.position)
            ) < 15.0f);
            switch (box_mode)
            {
                case BoxMode.Float:
                    if (pickup) { box_mode = BoxMode.Hold; }
                    break;
                case BoxMode.Hold:
                    box_pose.position = Rig.r_con_stick.position;
                    if (Rig.btn_grip.delta == -1) { box_mode = in_cone.state ? BoxMode.Mount : BoxMode.Float; }
                    break;
                case BoxMode.Mount:
                    // orbital_view
                    box_pose.position = Rig.head.position + Rig.head.orientation * V.XYZ(0, -(SD_Y + 0.5f) * box_scale, -32 * U.cm);
                    if (pickup) { box_mode = BoxMode.Hold; }
                    break;
            }
        }

        XYZi next_pos = snake[0] + Rig.new_dir;
        bool neck_break = next_pos == snake[1];
        if (!neck_break)
        {
            snake_dir = Rig.new_dir;
        }
    }

    public static void Step()
    {
        // eat tail
        if (snake[0] + snake_dir == snake[snake_len - 1])
        {
            snake_len--;
            grow_buffer = 0;
        }
        else if (s_array[snake[0] + snake_dir] > -1)
        {
            // lose condition
            bool stuck = true;
            for (int i = 0; i < directions.Length; i++)
            {
                if (s_array[snake[0] + directions[i]] == -1)
                {
                    stuck = false;
                }
            }
            if (stuck)
            {
                Log.Info("your stuck");
            }
            return;
        }

        bool in_or_around_box = s_array.InRange(snake[0] + snake_dir);
        if (!in_or_around_box)
        {
            return;
        }

        if (snake_len == snake.Length)
        {
            // win condition
            Log.Info("full snake");
            return;
        }
        else
        {
            if (grow_buffer > 0)
            {
                snake_len++;
                grow_buffer--;
            }
        }

        // slither
        for (int i = snake.Length - 1; i > 0; i--)
        {
            snake[i] = snake[i - 1];
        }
        snake[0] += snake_dir;

        in_box.Step(box_space.InRange(snake[0]));
        if (in_box.delta != 0) // 1 just in -1 just out
        {
            holes.Add(snake[0], snake_dir);
            SFX.punch_through.PlayBox(snake[0]);
            Arts.box_shake += snake_dir.ToVec3;
        }
        if (holes.ContainsKey(snake[snake_len - 1]))
        {
            holes.Remove(snake[snake_len - 1]);
        }

        update_s_array();

        // eat
        if (!eaten_latch.state)
        {
            eaten_latch.Step(food == snake[0]);
            if (eaten_latch.delta == +1)
            {
                eat_timestamp = Time.Total;
                grow_buffer += 3;
                eaten++;

                VFX.Play(snake[0]);
                SFX.crisp_nom.PlayBox(snake[0]);
            }
        }
        else
        {
            (bool viable, XYZi cell) = Feed();
            eaten_latch.Step(!viable);
            if (eaten_latch.delta == -1)
            {
                food = cell;
            }
        }
    }

    static (bool, XYZi) Feed()
    {
        // [!] handle out of the box exception on tail
        // by making the spatial arrays encapsulate the layer outside of the box
        tail_fill.Clear(-1);
        Gas(tail_fill, snake[snake_len - 1]);

        // step from head using directions towards the tail
        // and stop at either 1 cell away from the tail or 5 spaces away from the head
        bool viable = false;
        bool viable_step = false;
        XYZi cell = snake[0];
        for (int step = 0; step < 5; step++)
        {
            viable_step = false;
            int min_dist = 100;
            XYZi min_cell = new();
            int[] dir_indices = GetShuffledIndices(directions);
            for (int i = 0; i < directions.Length; i++)
            {
                XYZi dir = directions[dir_indices[i]];
                XYZi dir_cell = cell + dir;
                int tail_dist = tail_fill[dir_cell];
                if (tail_dist > 1 && tail_dist < min_dist && box_space.InRange(dir_cell))
                {
                    min_dist = tail_dist;
                    min_cell = dir_cell;
                    viable = true;
                    viable_step = true;
                }
            }
            if (viable_step)
            {
                tail_fill[min_cell] = -1; // prevent backtracking
                cell = min_cell;
            }
            // if (min_dist <= 1)
            // {
            //     break;
            // }
        }

        return (viable, cell);
    }

    // space fill algorithm
    static void Gas(SpatialArray<int> fill_array, XYZi sv)
    {
        Queue<XYZi> queue = new Queue<XYZi>();
        queue.Enqueue(sv);
        fill_array[sv] = 0;

        while (queue.Count > 0)
        {
            XYZi _sv = queue.Dequeue();
            int currentDistance = fill_array[_sv];

            // check all 6 directions
            foreach (XYZi dir in directions)
            {
                XYZi newV = _sv + dir;

                if (fill_array.InRange(newV) && fill_array[newV] == -1 && s_array[newV] == -1)
                {
                    fill_array[newV] = currentDistance + 1;
                    queue.Enqueue(newV);
                }
            }
        }
    }

    static int[] GetShuffledIndices<T>(T[] array)
    {
        int[] indices = new int[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            indices[i] = i;
        }
        for (int i = indices.Length - 1; i > 0; i--)
        {
            int j = System.Random.Shared.Next(i + 1);
            (indices[j], indices[i]) = (indices[i], indices[j]);
        }
        return indices;
    }

    // directions for moving in the grid
    static readonly XYZi[] directions = new XYZi[]
    {
        new(-1, 0, 0), // lft
        new(+1, 0, 0), // rht
        new(0, -1, 0), // dwn
        new(0, +1, 0), // up
        new(0, 0, -1), // fwd
        new(0, 0, +1), // back
    };
    static readonly XYZi[] corners = new XYZi[]
    {
        new(-1, -1, -1),
        new(-1, -1, +1),
        new(-1, +1, -1),
        new(-1, +1, +1),
        new(+1, -1, -1),
        new(+1, -1, +1),
        new(+1, +1, -1),
        new(+1, +1, +1)
    };

    static XYZi InsetCell(XYZi cell)
    {
        // [!] don't inset past 0
        return new(
            cell.x - Maths.sign(cell.x),
            cell.y - Maths.sign(cell.y),
            cell.z - Maths.sign(cell.z)
        );
    }
}