using BruTile;
using BruTile.MbTiles;
using SQLite;
using System.Collections.Generic;
using System.IO;
using System.Linq.Expressions;
using System.Net;
using UnityEngine;
using UnityEngine.UI;

// Overlay tiles received from mbtiles 
public class OverlayManager : MonoBehaviour
{
    private OnlineMaps map;

    [Tooltip("Tiles has to be placed in StreamingAssets Folder")]
    public List<Overlay> OverlayTilesName;

    private int resolution = 256;

    private void Start()
    {
        map = OnlineMaps.instance;
        

        if (OnlineMapsCache.instance != null)
        {
            // Subscribe to the cache events.
            OnlineMapsCache.instance.OnLoadedFromCache += LoadTileFromMB;
        }

        // Subscribe to the tile download event.
        OnlineMapsTileManager.OnStartDownloadTile += OnStartDownloadTile;
    }

    public void ToggleOverlay(string overlayName)
    {
        ChangeEnableState(overlayName);
    }

    // This function updates information about the textures we want to overlay and should overlay a new update texture on the tiles
    private void ChangeEnableState(string overlayName)
    {
        overlayName = overlayName.ToLower();

        foreach (Overlay overlay in OverlayTilesName)
        {
            if (overlay.Name.ToLower().Equals(overlayName))
            {
                overlay.Enabled = !overlay.Enabled;
            }
        }

        // How to redraw/reload new texture onto the current tiles? 
        OnlineMapsCache.instance.ClearAllCaches();
        map.RedrawImmediately();
        OnlineMaps.instance.tileManager.StartDownloading();
    }

    // Create a texture from mbtiles sources and apply them as an overlay texture
    private void LoadTileFromMB(OnlineMapsTile tile)
    {
        List<Texture2D> layers = new List<Texture2D>();

        // Add all texture layers to the TextureArray
        for (int i = 0; i < OverlayTilesName.Count; i++)
        {
            Texture2D tileTexture = new Texture2D(resolution, resolution);
            string path = $"{Application.streamingAssetsPath}/{OverlayTilesName[i].Path}.mbtiles";

            // Check if path exist
            if (!File.Exists(path))
            {                                                              
                Debug.LogError($"The {OverlayTilesName[i]} mbtile file does not exist");
            }
            else if (!OverlayTilesName[i].Enabled)
            {
                continue;
            }
            else
            {
                MbTilesTileSource mbTileSource = new MbTilesTileSource(new SQLiteConnectionString(path, false));

                // flip y because MBTiles is TMS schemed format, we need it in xyz
                int flippedY = (1 << tile.zoom) - 1 - tile.y;
                byte[] mbTilesTile = mbTileSource.GetTile(new TileInfo { Index = new TileIndex(tile.x, flippedY, tile.zoom) });

                if (mbTilesTile != null)
                {
                    tileTexture.LoadImage(mbTilesTile);
                    layers.Add(tileTexture);
                }
            }
        }

        // If there's no new layers, just return
        if (layers.Count == 0)
            return;

        Texture2D finalTexture = MakeTexture(layers);
        finalTexture.wrapMode = TextureWrapMode.Clamp;
        tile.overlayBackTexture = Instantiate(finalTexture);

        // Destroy because it is no longer needed
        OnlineMapsUtils.Destroy(finalTexture);
    }

    // Make a texture from the given layers. Assumption is that all layers given are non empty.
    private Texture2D MakeTexture(List<Texture2D> layers) 
    {
        Texture2D finalTexture = new Texture2D(resolution, resolution);
        Color[] finalColorArray = new Color[resolution * resolution];

        Color[][] sourceColorArray = new Color[layers.Count][];

        // Assign texture's color to SrcArray
        for(int i = 0; i < layers.Count; i++)
        {
            sourceColorArray[i] = layers[i].GetPixels();
        }

        // Loop through final color array 
        for(int x = 0; x < finalTexture.height; x++) // loop through row
        {
            for(int y = 0; y < finalTexture.width; y++) // loop through column
            {
                int pixelIndex = y + x * finalTexture.width; // current index on a 1d array
                for(int i = 0; i < layers.Count; i++)
                {
                    Color srcPixel = sourceColorArray[i][pixelIndex];
                    if (srcPixel.a > 0) // only add pixels to final color array if the pixel is not transparent
                        finalColorArray[pixelIndex] = srcPixel;
                }
            }
        }

        finalTexture.SetPixels(finalColorArray);
        finalTexture.Apply();
        return finalTexture;
    }

    private void OnStartDownloadTile(OnlineMapsTile tile)
    {
        LoadTileFromMB(tile);

        Debug.Log("On start called");

        OnlineMapsTileManager.StartDownloadTile(tile);

        // Redraw map (using best redraw type)
        map.Redraw();
    }
}