From 4c8a73029b63c4dd43ed9229c420aec3af74fdfe Mon Sep 17 00:00:00 2001
From: Austen Adler <agadler@austenadler.com>
Date: Sat, 11 Mar 2023 15:18:01 -0500
Subject: [PATCH] Compute the max difference between actual and expected
 distances

---
 Cargo.lock          |  7 +++++++
 Cargo.toml          |  1 +
 tests/algorithm.rs  | 49 ++++++++++++++++-----------------------------
 tests/common/mod.rs | 12 ++++++++---
 4 files changed, 34 insertions(+), 35 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 7b057f6..b257d33 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -444,6 +444,12 @@ dependencies = [
  "version_check",
 ]
 
+[[package]]
+name = "geoutils"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "36d244a08113319b5ebcabad2b8b7925732d15eec46d7e7ac3c11734f3b7a6ad"
+
 [[package]]
 name = "getrandom"
 version = "0.2.8"
@@ -1813,6 +1819,7 @@ name = "xpin"
 version = "0.1.0"
 dependencies = [
  "csv",
+ "geoutils",
  "s2",
  "serde",
  "thiserror",
diff --git a/Cargo.toml b/Cargo.toml
index 42143c9..30f45c4 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,4 +22,5 @@ words = {path="./words"}
 
 [dev-dependencies]
 csv = "1.1"
+geoutils = "0.5.1"
 serde={version="1", features=["derive"]}
diff --git a/tests/algorithm.rs b/tests/algorithm.rs
index 926089d..e664f09 100644
--- a/tests/algorithm.rs
+++ b/tests/algorithm.rs
@@ -23,51 +23,36 @@ fn test_invalid_lat_lon() {
 
 #[test]
 fn test_decoding_lat_lon() {
-    let mut max = f64::MIN;
-    let mut min = f64::MAX;
+    let mut max_error_m = f64::MIN;
+    let mut min_error_m = f64::MAX;
     for (idx, entry) in test_events().iter().enumerate() {
         eprintln!("Testing row {idx}");
 
         let addr = Address::from_lat_lon(entry.lat, entry.lon).unwrap();
         let addr_latlon = addr.as_lat_lon();
 
-        let (lat_diff, lon_diff) = (
-            (entry.lat - addr_latlon.0).abs(),
-            (entry.lon - addr_latlon.1).abs(),
-        );
+        // The difference between the input lat/lon and the encoded-then-decoded lat/lon
+        // This distance is essentially the error
+        // If you pick a point on the map, this is how far off the encoded point actually represents
+        let difference_m = approx_geodetic_difference_m(addr_latlon, (entry.lat, entry.lon));
 
-        min = if lat_diff < min {
-            lat_diff
-        } else if lon_diff < min {
-            lon_diff
-        } else {
-            min
-        };
-
-        max = if lat_diff > max && lat_diff < 1_f64 {
-            lat_diff
-        } else if lon_diff > max && lon_diff < 1_f64 {
-            lon_diff
-        } else {
-            max
-        };
-
-        if lat_diff > 0.01_f64 || lon_diff > 0.01_f64 {
-            eprintln!(
-                "Uh oh: {lat_diff}, {lon_diff}, ({}, {}) => ({:?}) => ({:?})",
-                entry.lat, entry.lon, addr, addr_latlon
-            );
+        // Compute the max and min differences for fun
+        if difference_m > max_error_m {
+            eprintln!("Setting max to {difference_m}");
+            max_error_m = difference_m;
+        }
+        if difference_m < min_error_m {
+            min_error_m = difference_m;
         }
 
+        eprintln!("Distance in meters: {:?}", difference_m);
+
         // Ensure the distance is not more than the allowed distance
-        // assert!(
-        //     approx_geodetic_difference_m(addr_latlon, (entry.lat, entry.lon))
-        //         < ALLOWED_DISTANCE_ERROR_M
-        // );
+        assert!(difference_m <= ALLOWED_DISTANCE_ERROR_M);
 
         // assert_eq!((entry.lat, entry.lon), (latlon.0, latlon.1));
     }
-    eprintln!("Got max: {max} and min: {min}");
+    eprintln!("Got max: {max_error_m} and min: {min_error_m}");
 }
 
 #[test]
diff --git a/tests/common/mod.rs b/tests/common/mod.rs
index 1a3436a..03b2b0a 100644
--- a/tests/common/mod.rs
+++ b/tests/common/mod.rs
@@ -1,4 +1,5 @@
 #![allow(dead_code)]
+use geoutils::Location;
 use std::fs::File;
 
 use csv::ReaderBuilder;
@@ -7,7 +8,9 @@ use serde::{Deserialize, Serialize};
 /// The allowed error for encoding and decoding points, in meters
 ///
 /// Due to the selected S2 level being 23, our error is expected to be under 2 meters
-pub const ALLOWED_DISTANCE_ERROR_M: f64 = 0.0_f64;
+///
+/// With the encoding I selected, the max difference of my sample data actually fits in under 1 meter!
+pub const ALLOWED_DISTANCE_ERROR_M: f64 = 1.0_f64;
 // The earth's approximate latitude circumfrence
 pub const EARTH_CIRCUMFERENCE_LAT: f64 = 0.0_f64;
 // The earth's approximate longitude circumfrence
@@ -62,7 +65,10 @@ pub struct TestEntry {
     pub cellid: u64,
 }
 
-/// Gets the approximate geodetic difference in meters between two latlons
+/// Gets the approximate geodetic difference in meters between two latlons in meters
 pub fn approx_geodetic_difference_m((lat1, lon1): (f64, f64), (lat2, lon2): (f64, f64)) -> f64 {
-    1000.0_f64
+    Location::new(lat1, lon1)
+        .distance_to(&Location::new(lat2, lon2))
+        .unwrap()
+        .meters()
 }