1 files changed, 93 insertions, 0 deletions
diff --git a/frontend/src/actions/map.js b/frontend/src/actions/map.js
new file mode 100644
index 00000000..82546c00
--- /dev/null
+++ b/frontend/src/actions/map.js
@@ -0,0 +1,93 @@
+import {
+  MAP_MAX_SCALE,
+  MAP_MIN_SCALE,
+  MAP_SCALE_PER_EVENT,
+  MAP_SIZE_IN_PIXELS
+} from "../components/app/map/MapConstants";
+
+export const SET_MAP_POSITION = "SET_MAP_POSITION";
+export const SET_MAP_DIMENSIONS = "SET_MAP_DIMENSIONS";
+export const SET_MAP_SCALE = "SET_MAP_SCALE";
+
+export function setMapPosition(x, y) {
+  return {
+    type: SET_MAP_POSITION,
+    x,
+    y
+  };
+}
+
+export function setMapDimensions(width, height) {
+  return {
+    type: SET_MAP_DIMENSIONS,
+    width,
+    height
+  };
+}
+
+export function setMapScale(scale) {
+  return {
+    type: SET_MAP_SCALE,
+    scale
+  };
+}
+
+export function zoomInOnCenter(zoomIn) {
+  return (dispatch, getState) => {
+    const state = getState();
+
+    dispatch(
+      zoomInOnPosition(
+        zoomIn,
+        state.map.dimensions.width / 2,
+        state.map.dimensions.height / 2
+      )
+    );
+  };
+}
+
+export function zoomInOnPosition(zoomIn, x, y) {
+  return (dispatch, getState) => {
+    const state = getState();
+
+    const centerPoint = {
+      x: x / state.map.scale - state.map.position.x / state.map.scale,
+      y: y / state.map.scale - state.map.position.y / state.map.scale
+    };
+    const newScale = zoomIn
+      ? state.map.scale * MAP_SCALE_PER_EVENT
+      : state.map.scale / MAP_SCALE_PER_EVENT;
+    const boundedScale = Math.min(
+      Math.max(MAP_MIN_SCALE, newScale),
+      MAP_MAX_SCALE
+    );
+
+    const newX = -(centerPoint.x - x / boundedScale) * boundedScale;
+    const newY = -(centerPoint.y - y / boundedScale) * boundedScale;
+
+    dispatch(setMapPositionWithBoundsCheck(newX, newY));
+    dispatch(setMapScale(boundedScale));
+  };
+}
+
+export function setMapPositionWithBoundsCheck(x, y) {
+  return (dispatch, getState) => {
+    const state = getState();
+
+    const scaledMapSize = MAP_SIZE_IN_PIXELS * state.map.scale;
+    const updatedX =
+      x > 0
+        ? 0
+        : x < -scaledMapSize + state.map.dimensions.width
+          ? -scaledMapSize + state.map.dimensions.width
+          : x;
+    const updatedY =
+      y > 0
+        ? 0
+        : y < -scaledMapSize + state.map.dimensions.height
+          ? -scaledMapSize + state.map.dimensions.height
+          : y;
+
+    dispatch(setMapPosition(updatedX, updatedY));
+  };
+}