refactors mapgen into chained builders

src/map_builders/area_starting_points.rs

@@ -0,0 +1,73 @@
+use super::{BuilderMap, MetaMapBuilder, Position, TileType};
+use rltk::RandomNumberGenerator;
+
+#[allow(dead_code)]
+pub enum XStart {
+    LEFT,
+    CENTRE,
+    RIGHT,
+}
+
+#[allow(dead_code)]
+pub enum YStart {
+    TOP,
+    CENTRE,
+    BOTTOM,
+}
+
+pub struct AreaStartingPosition {
+    x: XStart,
+    y: YStart,
+}
+
+impl MetaMapBuilder for AreaStartingPosition {
+    fn build_map(&mut self, rng: &mut rltk::RandomNumberGenerator, build_data: &mut BuilderMap) {
+        self.build(rng, build_data);
+    }
+}
+
+impl AreaStartingPosition {
+    #[allow(dead_code)]
+    pub fn new(x: XStart, y: YStart) -> Box<AreaStartingPosition> {
+        Box::new(AreaStartingPosition { x, y })
+    }
+
+    fn build(&mut self, _rng: &mut RandomNumberGenerator, build_data: &mut BuilderMap) {
+        let seed_x;
+        let seed_y;
+
+        match self.x {
+            XStart::LEFT => seed_x = 1,
+            XStart::CENTRE => seed_x = build_data.map.width / 2,
+            XStart::RIGHT => seed_x = build_data.map.width - 2,
+        }
+        match self.y {
+            YStart::TOP => seed_y = 1,
+            YStart::CENTRE => seed_y = build_data.map.height / 2,
+            YStart::BOTTOM => seed_y = build_data.map.height - 2,
+        }
+
+        let mut available_floors: Vec<(usize, f32)> = Vec::new();
+        for (idx, tiletype) in build_data.map.tiles.iter().enumerate() {
+            if *tiletype == TileType::Floor {
+                available_floors.push((
+                    idx,
+                    rltk::DistanceAlg::PythagorasSquared.distance2d(
+                        rltk::Point::new(idx as i32 % build_data.map.width, idx as i32 / build_data.map.width),
+                        rltk::Point::new(seed_x, seed_y),
+                    ),
+                ));
+            }
+        }
+        if available_floors.is_empty() {
+            panic!("No valid floors to start on");
+        }
+
+        available_floors.sort_by(|a, b| a.1.partial_cmp(&b.1).unwrap());
+
+        let start_x = available_floors[0].0 as i32 % build_data.map.width;
+        let start_y = available_floors[0].0 as i32 / build_data.map.width;
+
+        build_data.starting_position = Some(Position { x: start_x, y: start_y });
+    }
+}