feat: Add example data to the frontend

Author: Linked-Liszt

docker/ui.Dockerfile

@@ -25,6 +25,7 @@ COPY src/ui/requirements.txt ./
 RUN pip install --no-cache-dir -r requirements.txt
 
 COPY src/ui/app/ ./app/
+COPY src/ui/example_data/ ./example_data/
 
 COPY --from=frontend-builder /app/frontend/dist ./frontend/dist
 

src/ui/app/main.py

@@ -2,12 +2,13 @@
 FastAPI main application for XRD Analysis Tool.
 Serves both the API endpoints and the static React frontend.
 """
-from fastapi import FastAPI, UploadFile, File
+from fastapi import FastAPI, UploadFile, File, HTTPException
 from fastapi.staticfiles import StaticFiles
-from fastapi.responses import FileResponse, JSONResponse
+from fastapi.responses import FileResponse, JSONResponse, PlainTextResponse
 from fastapi.middleware.cors import CORSMiddleware
 from pathlib import Path
 from typing import Dict, List
+import re
 import torch
 import numpy as np
 
@@ -110,7 +111,82 @@ async def predict(data: dict):
         )
 
 
+# ---------------------------------------------------------------------------
+# Example data endpoints
+# ---------------------------------------------------------------------------
+EXAMPLE_DATA_DIR = Path(__file__).parent.parent / "example_data"
+
+# Map of crystal system number -> human-readable name
+CRYSTAL_SYSTEM_NAMES = {
+    "1": "Triclinic",
+    "2": "Monoclinic",
+    "3": "Orthorhombic",
+    "4": "Tetragonal",
+    "5": "Trigonal",
+    "6": "Hexagonal",
+    "7": "Cubic",
+}
+
+
+def _parse_example_metadata(filepath: Path) -> dict:
+    """Extract metadata from the header lines of a .dif file."""
+    meta = {
+        "filename": filepath.name,
+        "material_id": None,
+        "crystal_system": None,
+        "crystal_system_name": None,
+        "space_group": None,
+        "wavelength": None,
+    }
+    with open(filepath, "r") as f:
+        for line in f:
+            line = line.strip()
+            # Stop reading once we hit the data section
+            if line and not line.startswith("#") and not line.startswith("CELL") and not line.startswith("SPACE") and not line.lower().startswith("wavelength"):
+                break
+
+            if m := re.search(r"Material ID:\s*(\S+)", line):
+                meta["material_id"] = m.group(1)
+            if m := re.search(r"Crystal System:\s*(\d+)", line):
+                num = m.group(1)
+                meta["crystal_system"] = num
+                meta["crystal_system_name"] = CRYSTAL_SYSTEM_NAMES.get(num, f"Unknown ({num})")
+            if m := re.search(r"SPACE GROUP:\s*(\d+)", line):
+                meta["space_group"] = m.group(1)
+            if m := re.search(r"wavelength:\s*([\d.]+)", line, re.IGNORECASE):
+                meta["wavelength"] = m.group(1)
+    return meta
+
+
+@app.get("/api/examples")
+async def list_examples():
+    """List available example data files with metadata."""
+    if not EXAMPLE_DATA_DIR.exists():
+        return []
+
+    examples = []
+    for fp in sorted(EXAMPLE_DATA_DIR.glob("*.dif")):
+        examples.append(_parse_example_metadata(fp))
+    return examples
+
+
+@app.get("/api/examples/{filename}")
+async def get_example(filename: str):
+    """Return the raw text content of an example data file."""
+    # Sanitise: only allow filenames, no path traversal
+    if "/" in filename or "\\" in filename or ".." in filename:
+        raise HTTPException(status_code=400, detail="Invalid filename")
+
+    filepath = EXAMPLE_DATA_DIR / filename
+    if not filepath.exists() or not filepath.is_file():
+        raise HTTPException(status_code=404, detail="Example file not found")
+
+    return PlainTextResponse(filepath.read_text())
+
+
+# ---------------------------------------------------------------------------
 # Static files and SPA support
+# ---------------------------------------------------------------------------
 frontend_dist = Path(__file__).parent.parent / "frontend" / "dist"
 
 if frontend_dist.exists():