Update README

Author: dbrgn

README.md

@@ -1,30 +1,27 @@
-# EVMap OSM Data Updater (PoC)
+# EVMap OSM Loader
 
-This is a proof-of-concept for a charging station data fetcher for
-OpenStreetMap. The script fetches all charging stations worldwide through the
-Overpass API, preprocesses the data and writes it to a gzip-compressed JSON
-file.
-
-## Requirements
-
-- [curl](https://curl.se/)
-- [jq](https://stedolan.github.io/jq/)
-- [gzip](https://www.gnu.org/software/gzip/)
+A Rust implementation of the Overpass API data loader for charging stations.
+This tool downloads worldwide charging station data from OpenStreetMap via the
+Overpass API, preprocesses it, and saves the result as a compressed JSON file
+(for consumption by EVMap).
 
 ## Data Format
 
 The resulting gzipped JSON file contains data in the following format:
 
 ```json5
 {
-  "timestamp": 1633282807.294814, // UNIX timestamp in seconds
+  "timestamp": 1633282807, // UNIX timestamp in seconds
+  "count": 4376, // Number of elements below
   "elements": [
     {
       // Unique numeric ID
       "id": 9079237567,
       // Latitude, longitude (WGS84 coordinates, I assume)
       "lat": 47.0701573,
       "lon": 7.5664432,
+      // Type of element (node, way, relation)
+      "type": "node",
       // Timestamp of last update
       "timestamp": "2021-09-10T11:47:56Z",
       // Numeric, monotonically increasing version number
@@ -34,29 +31,108 @@ The resulting gzipped JSON file contains data in the following format:
       // Raw key-value OSM tags
       "tags": {
         "amenity": "charging_station",
-        ...
+        ... // More OSM tags
       }
     },
-    ...
+    ... // More elements
   ]
 }
 ```
 
 For the tagging schema, see <https://wiki.openstreetmap.org/wiki/DE:Tag:amenity%3Dcharging_station>
 
+## Building
+
+Make sure you have Rust and Cargo installed.
+
+Build the project:
+
+    cargo build --release
+
+The binary will be available at `target/release/evmap-osm-loader`.
+
 ## Usage
 
-Simply invoke the script:
+### Basic Usage
+
+Download charging station data with default settings:
 
-    ./load-overpass.sh
+    evmap-osm-loader
 
-Note: The API query may take multiple minutes. The default timeout is set to 15
-minutes, but depending on the load on the API endpoint, this may not be
+**Note 1:** The API query may take multiple minutes. The default timeout is set
+to 15 minutes, but depending on the load on the API endpoint, this may not be
 sufficient.
 
-The script can be adjusted by editing the configuration variables. Possible
-configuration variables include the Overpass API endpoint or the download
-timeout.
+**Note 2:** By default, the script uses the Overpass API interpreter at
+<https://overpass.osm.ch/api/interpreter>, which returns only data within
+Switzerland. This is great for testing with a reduced data set. For a worldwide
+result set, you can specify the URL `https://overpass-api.de/api/interpreter`
+using the `--overpass-url` option.
+
+Show usage:
+
+    evmap-osm-loader --help
+
+### Command-Line Options
+
+```
+evmap-osm-loader [OPTIONS]
+
+Options:
+      --keep-intermediate <BOOL>
+          Keep intermediate raw response file
+          [default: false]
+
+      --overpass-url <OVERPASS_URL>
+          Overpass API interpreter URL
+          [default: https://overpass.osm.ch/api/interpreter]
+
+      --timeout-seconds <TIMEOUT_SECONDS>
+          Timeout in seconds for the Overpass query
+          [default: 900]
+
+      --outfile-raw <OUTFILE_RAW>
+          Output file for raw response (only written if --keep-intermediate=true)
+          [default: overpass-result.json]
+
+      --outfile-compressed <OUTFILE_COMPRESSED>
+          Output file for compressed result
+          [default: charging-stations-osm.json.gz]
+
+  -h, --help
+          Print help
+
+  -V, --version
+          Print version
+```
+
+## Query Details
+
+The tool executes the following Overpass QL query:
+
+```
+[out:json][timeout:900];
+(
+  node[amenity=charging_station];
+  area[amenity=charging_station];
+  relation[amenity=charging_station];
+);
+out meta qt;
+```
+
+This query retrieves:
+
+- All nodes tagged as charging stations
+- All areas (ways) tagged as charging stations
+- All relations tagged as charging stations
+
+## Future Enhancements
+
+The async architecture allows for future parallelization opportunities, such as:
+
+- Parallel processing of large datasets
+- Concurrent API requests for different regions
+- Streamed parsing and processing of HTTP response
 
 ## License