Fix Silvertown Tunnel, UK WASM data requests

Author: JoostGevaert

examples/uk_silvertown_tunnel_ags4/uk_silvertown_tunnel_ags4_to_brgi_geodb.py

@@ -25,13 +25,13 @@ def _():
 
     import geopandas as gpd
     import marimo as mo
-    import requests
     from python_ags4 import AGS4
 
-    print(platform.system())
+    platform_system = platform.system()
+    print(platform_system)
     print(sys.version)
     # print(sys.executable)
-    return AGS4, gpd, io, mo, requests
+    return AGS4, gpd, io, mo, platform_system
 
 
 @app.cell(hide_code=True)
@@ -46,7 +46,8 @@ def _(mo):
 
     The GI data for the Silvertown tunnel can be found on the British Geological Survey's ([BGS](https://www.bgs.ac.uk/)) [Deposited data search page](https://webapps.bgs.ac.uk/services/ngdc/accessions/index.html):  
     [**Title**: Preliminary GI for Silvertown Tunnel  
-    **Description**: 	77 exploratory holes carried out for the design of the Silvertown Tunnel, London](https://webapps.bgs.ac.uk/services/ngdc/accessions/index.html?simpleText=silvertown#item162465)
+    **Description**: 	77 exploratory holes carried out for the design of the Silvertown Tunnel, London](https://webapps.bgs.ac.uk/services/ngdc/accessions/index.html?simpleText=silvertown#item162465)  
+    For convenience, the AGS 4 file has also been uploaded to GitHub such that you can have a quick look what this AGS 4 data [looks like 🔎](https://raw.githubusercontent.com/bedrock-engineer/bedrock-ge/refs/heads/main/examples/uk_silvertown_tunnel_ags4/20110770-2021-02-16_1308-Final-6.ags). 
 
     The ground model has been published as an [AGSi Ground Model](https://www.ags.org.uk/data-format/agsi-ground-model/) by the Association of Geotechnical & Geoenvironmental Specialists ([AGS](https://www.ags.org.uk/)):  
     [AGSi Guidance / Example files](https://ags-data-format-wg.gitlab.io/agsi/AGSi_Documentation/Example_Silvertown)
@@ -56,20 +57,22 @@ def _(mo):
 
 
 @app.cell
-def _(requests):
-    # raw_githubusercontent_url = "https://raw.githubusercontent.com/bedrock-engineer/bedrock-ge/refs/heads/main/examples/uk_silvertown_tunnel_ags4/20110770-2021-02-16_1308-Final-6.ags"
-    # ags_bytes = requests.get(raw_githubusercontent_url).content
-
-    # Preferribly, the data can be directly used from the BGS webservice, but maybe this will not be possible in the marimo playground?
+async def _(io, platform_system):
     bgs_url = "https://webservices.bgs.ac.uk/accessions/download/162465?fileName=20110770%20-%202021-02-16%201308%20-%20Final%20-%206.ags"
-    ags_bytes = requests.get(bgs_url).content
-    ags_bytes
-    return (ags_bytes,)
+    # When running this marimo notebook in WebAssembly (WASM, a.k.a. Emscripten), use pyodide to request the data
+    if platform_system == "Emscripten":
+        from pyodide.http import pyfetch
+        response = await pyfetch(bgs_url)
+        ags = io.BytesIO(await response.bytes())
+    else:
+        import requests
+        ags = io.BytesIO(requests.get(bgs_url).content)
+    return (ags,)
 
 
 @app.cell
-def _(AGS4, ags_bytes, io):
-    ags_tables, headings = AGS4.AGS4_to_dataframe(io.BytesIO(ags_bytes))
+def _(AGS4, ags):
+    ags_tables, headings = AGS4.AGS4_to_dataframe(ags)
     for group, data in ags_tables.items():
         ags_tables[group] = (
             AGS4.convert_to_numeric(data).drop(columns=["HEADING"])