From 7a810a97509a4cdee4f7958bd5bb310f7e54f4b0 Mon Sep 17 00:00:00 2001
From: Michael Kirk <michael.code@endoftheworl.de>
Date: Wed, 15 Jan 2025 13:35:54 -0800
Subject: [PATCH] Add processor to compute geometry bounds

---
 geozero/CHANGELOG.md  |   1 +
 geozero/src/bounds.rs | 123 ++++++++++++++++++++++++++++++++++++++++++
 geozero/src/lib.rs    |   3 ++
 3 files changed, 127 insertions(+)
 create mode 100644 geozero/src/bounds.rs

diff --git a/geozero/CHANGELOG.md b/geozero/CHANGELOG.md
index 394b8bb..9748a11 100644
--- a/geozero/CHANGELOG.md
+++ b/geozero/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## UNRELEASED
 
+* Add `BoundsProcessor` to compute bounds of geometry
 * Update Deps:
   * BREAKING: `flatgeobuf` to 4.5.0
   * BREAKING: `dbase` to 0.5.0
diff --git a/geozero/src/bounds.rs b/geozero/src/bounds.rs
new file mode 100644
index 0000000..10b9e28
--- /dev/null
+++ b/geozero/src/bounds.rs
@@ -0,0 +1,123 @@
+use crate::{FeatureProcessor, GeomProcessor, PropertyProcessor};
+
+#[derive(Default, Debug, Clone, PartialEq)]
+pub struct Bounds {
+    min_x: f64,
+    min_y: f64,
+    max_x: f64,
+    max_y: f64,
+}
+
+impl Bounds {
+    pub fn extend(&mut self, x: f64, y: f64) {
+        if x < self.min_x {
+            self.min_x = x;
+        }
+        if x > self.max_x {
+            self.max_x = x;
+        }
+        if y < self.min_y {
+            self.min_y = y;
+        }
+        if y > self.max_y {
+            self.max_y = y;
+        }
+    }
+
+    pub fn min_x(&self) -> f64 {
+        self.min_x
+    }
+
+    pub fn min_y(&self) -> f64 {
+        self.min_y
+    }
+
+    pub fn max_x(&self) -> f64 {
+        self.max_x
+    }
+
+    pub fn max_y(&self) -> f64 {
+        self.max_y
+    }
+}
+
+/// Computes the bounds of a Geomtry
+#[derive(Default, Debug)]
+pub struct BoundsProcessor {
+    bounds: Option<Bounds>,
+}
+
+impl BoundsProcessor {
+    pub fn new() -> Self {
+        Self::default()
+    }
+    pub fn bounds(&self) -> Option<Bounds> {
+        self.bounds.clone()
+    }
+}
+
+impl GeomProcessor for BoundsProcessor {
+    fn xy(&mut self, x: f64, y: f64, _idx: usize) -> crate::error::Result<()> {
+        let Some(bounds) = self.bounds.as_mut() else {
+            self.bounds = Some(Bounds {
+                min_x: x,
+                min_y: y,
+                max_x: x,
+                max_y: y,
+            });
+            return Ok(());
+        };
+        bounds.extend(x, y);
+        Ok(())
+    }
+
+    fn coordinate(
+        &mut self,
+        x: f64,
+        y: f64,
+        _z: Option<f64>,
+        _m: Option<f64>,
+        _t: Option<f64>,
+        _tm: Option<u64>,
+        idx: usize,
+    ) -> crate::error::Result<()> {
+        self.xy(x, y, idx)
+    }
+}
+
+impl PropertyProcessor for BoundsProcessor {}
+impl FeatureProcessor for BoundsProcessor {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::GeozeroGeometry;
+
+    #[test]
+    fn test_bounds() {
+        let wkt = crate::wkt::Wkt("LINESTRING(1 2,3 4,5 6)");
+        let mut bounds_processor = BoundsProcessor::new();
+
+        wkt.process_geom(&mut bounds_processor).unwrap();
+
+        assert_eq!(
+            bounds_processor.bounds,
+            Some(Bounds {
+                min_x: 1.0,
+                min_y: 2.0,
+                max_x: 5.0,
+                max_y: 6.0,
+            })
+        )
+    }
+
+    #[test]
+    fn test_empty() {
+        let wkt = crate::wkt::Wkt("LINESTRING EMPTY");
+        let mut bounds_processor = BoundsProcessor::new();
+
+        wkt.process_geom(&mut bounds_processor).unwrap();
+
+        assert_eq!(bounds_processor.bounds, None);
+    }
+}
diff --git a/geozero/src/lib.rs b/geozero/src/lib.rs
index 9e3547f..7bb8851 100644
--- a/geozero/src/lib.rs
+++ b/geozero/src/lib.rs
@@ -124,6 +124,9 @@ pub use crate::wkt::conversion::*;
 
 #[cfg(feature = "with-mvt")]
 pub mod mvt;
+
+pub mod bounds;
+
 #[cfg(feature = "with-mvt")]
 pub use crate::mvt::conversion::*;