Cutt maps for tiles. Clean project architecture

gnss/services/tiles.py

@@ -0,0 +1,79 @@
+import base64
+import shutil
+import subprocess
+from pathlib import Path
+from typing import Iterable, Optional
+
+from fastapi.responses import FileResponse, Response
+
+
+DEFAULT_PLACEHOLDER_PNG = base64.b64decode(
+    "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mP8/x8AAwMB/6Xq3lYAAAAASUVORK5CYII="
+)
+
+
+class TileCutError(RuntimeError):
+    pass
+
+
+class TileService:
+    def __init__(self, tiles_dir: Path, placeholder: Path):
+        self.tiles_dir = Path(tiles_dir)
+        self.placeholder = Path(placeholder)
+
+    def ensure_tiles_dir(self) -> None:
+        self.tiles_dir.mkdir(parents=True, exist_ok=True)
+
+    def _find_gdal2tiles(self) -> str:
+        for name in ("gdal2tiles.py", "gdal2tiles"):
+            found = shutil.which(name)
+            if found:
+                return found
+        raise TileCutError("gdal2tiles not found in PATH. Install GDAL (e.g., apt install gdal-bin).")
+
+    def slice_to_tiles(
+        self,
+        source: Path,
+        destination: Path,
+        min_zoom: int,
+        max_zoom: int,
+        resampling: str = "bilinear",
+        tile_format: str = "png",
+        web_mercator: bool = True,
+        extra_args: Optional[Iterable[str]] = None,
+    ) -> Path:
+        if not source.exists():
+            raise TileCutError(f"source does not exist: {source}")
+        if min_zoom < 0 or max_zoom < min_zoom:
+            raise TileCutError(f"invalid zoom range: {min_zoom}-{max_zoom}")
+
+        destination.mkdir(parents=True, exist_ok=True)
+
+        gdal2tiles = self._find_gdal2tiles()
+        cmd = [
+            gdal2tiles,
+            "-z",
+            f"{min_zoom}-{max_zoom}",
+            "-r",
+            resampling,
+            "-f",
+            tile_format.lower(),
+        ]
+        if web_mercator:
+            cmd += ["-p", "mercator"]
+        if extra_args:
+            cmd += list(extra_args)
+        cmd += [str(source), str(destination)]
+
+        result = subprocess.run(cmd, capture_output=True, text=True)
+        if result.returncode != 0:
+            raise TileCutError(f"gdal2tiles failed: {result.stderr or result.stdout}")
+        return destination
+
+    def get_tile_response(self, zoom: int, x: int, y: int):
+        tile_path = self.tiles_dir / str(zoom) / str(x) / f"{y}.png"
+        if tile_path.is_file():
+            return FileResponse(tile_path, media_type="image/png")
+        if self.placeholder.is_file():
+            return FileResponse(self.placeholder, media_type="image/png")
+        return Response(content=DEFAULT_PLACEHOLDER_PNG, media_type="image/png")