More work on automatic map creation

frontend/server/package.json

@@ -23,9 +23,10 @@
     "regedit": "^5.1.2",
     "save": "^2.9.0",
     "sha256": "^0.2.0",
+    "sharp": "^0.33.2",
     "srtm-elevation": "^2.1.2",
     "tcp-ping-port": "^1.0.1",
     "uuid": "^9.0.1",
     "yargs": "^17.7.2"
   }
-}
+}

frontend/server/routes/resources.js

@@ -1,4 +1,7 @@
 const express = require('express');
+const sharp = require('sharp')
+const fs = require('fs');
+const pfs = require('fs/promises')
 const router = express.Router();
 
 router.get('/theme/*', function (req, res, next) {
@@ -15,4 +18,126 @@ router.put('/theme/:newTheme', function (req, res, next) {
     res.end("Ok");
 });
 
+router.get('/maps/:map/:z/:x/:y.png', async function (req, res, next) {
+    let map = req.params.map;
+    let x = req.params.x;
+    let y = req.params.y;
+    let z = req.params.z;
+
+    if (fs.existsSync(`.\\public\\maps\\${map}`)) {
+        if (!await renderImage(map, z, x, y, res)) {
+            /* No image was found */
+            res.sendStatus(404);
+        }
+    } else {
+        /* The requested map does not exist */
+        res.sendStatus(404);
+    }    
+});
+
+async function renderImage(map, z, x, y, res, recursionDepth = 0) {
+    if (recursionDepth == 20) {
+        console.log("Render image, maximum recursion depth reached")
+        /* We have reached limit recusion depth, something went wrong */
+        return false;
+    }
+    /* If the requested image exists, send it straight away */
+    if (fs.existsSync(`.\\public\\maps\\${map}\\${z}\\${x}\\${y}.png`)) {
+        res.sendFile(`${process.cwd()}\\public\\maps\\${map}\\${z}\\${x}\\${y}.png`);
+        return true;
+    } else {
+        /* If the requested image doesn't exist check if there is a "source" tile at a lower zoom level we can split up */
+        let sourceZoom = z - 1;
+        let sourceX = Math.floor(x / 2);
+        let sourceY = Math.floor(y / 2);
+
+        /* Keep decreasing the zoom level until we either find an image or reach maximum zoom out and must return false */
+        while (sourceZoom >= 0) {
+            /* We have found a possible source image */
+            if (fs.existsSync(`.\\public\\maps\\${map}\\${sourceZoom}\\${sourceX}\\${sourceY}.png`)) {
+                /* Split the image into four. We can retry up to 10 times to clear any race condition on the files */
+                let retries = 10;
+                while (!await splitTile(map, sourceZoom, sourceX, sourceY) && retries > 0) {
+                    await new Promise(r => setTimeout(r, 1000));
+                    retries--;
+                }
+                /* Check if we exited because we reached the maximum retry value */
+                if (retries != 0) {
+                    /* Recursively recall the function now that we have a new "source" image */
+                    return await renderImage(map, z, x, y, res, recursionDepth + 1);
+                } else {
+                    return false;
+                }
+            } else {
+                /* Keep searching at a higher level */
+                sourceZoom = sourceZoom - 1;
+                sourceX = Math.floor(sourceX / 2);
+                sourceY = Math.floor(sourceY / 2);
+            }
+        }
+        return false;
+    }
+}
+
+async function splitTile(map, z, x, y) {
+    try {
+        /* Load the source image */
+        let img = sharp(`${process.cwd()}\\public\\maps\\${map}\\${z}\\${x}\\${y}.png`);
+
+        /* Create the necessary folders */
+        await pfs.mkdir(`${process.cwd()}\\public\\maps\\${map}\\${z + 1}\\${2*x}`, { recursive: true })
+        await pfs.mkdir(`${process.cwd()}\\public\\maps\\${map}\\${z + 1}\\${2*x + 1}`, { recursive: true })
+
+        /* Split the image into four parts */
+        await resizePromise(img, 0,     0,      map, z + 1, 2 * x,      2 * y);
+        img = sharp(`${process.cwd()}\\public\\maps\\${map}\\${z}\\${x}\\${y}.png`);
+        await resizePromise(img, 128,   0,      map, z + 1, 2 * x + 1,  2 * y);
+        img = sharp(`${process.cwd()}\\public\\maps\\${map}\\${z}\\${x}\\${y}.png`);
+        await resizePromise(img, 0,     128,    map, z + 1, 2 * x,      2 * y + 1);
+        img = sharp(`${process.cwd()}\\public\\maps\\${map}\\${z}\\${x}\\${y}.png`);
+        await resizePromise(img, 128,   128,    map, z + 1, 2 * x + 1,  2 * y + 1);
+        return true;
+    } catch (err) {
+        if (err.code !== 'EBUSY') {
+            console.error(err);
+        }
+        return false;
+    }
+}
+
+/* Returns a promise, extracts a 128x128 pixel chunk from an image, resizes it to 256x256, and saves it to file */
+function resizePromise(img, left, top, map, z, x, y) {
+    return new Promise((res, rej) => {
+        if (fs.existsSync(`${process.cwd()}\\public\\maps\\${map}\\${z}\\${x}\\${y}.png`)) {
+            res(true);
+        } 
+        img.extract({ left: left, top: top, width: 128, height: 128 }).resize(256, 256).toFile(`${process.cwd()}\\public\\maps\\${map}\\${z}\\${x}\\${y}.temp.png`, function (err) {
+            if (err) {
+                rej(err);
+            } else {
+                try {
+                    fs.renameSync(`${process.cwd()}\\public\\maps\\${map}\\${z}\\${x}\\${y}.temp.png`, `${process.cwd()}\\public\\maps\\${map}\\${z}\\${x}\\${y}.png`);
+                } catch (err) {
+                    if (err.code === 'EBUSY') {
+                        /* The resource is busy, someone else is writing or renaming it. Reject the promise so we can try again */
+                        rej(err);
+                    } else if (err.code === 'ENOENT') {
+                        /* Someone else renamed the file already so this is not a real error */
+                        if (fs.existsSync(`${process.cwd()}\\public\\maps\\${map}\\${z}\\${x}\\${y}.png`)) {
+                            res(true);
+                        }
+                        /* Something odd happened, reject and try again */
+                        else {
+                            rej(err);
+                        }
+                    } else {
+                        rej(err);
+                    }
+                }
+                res(true)
+            }
+        });
+    })    
+}
+
 module.exports = router;