build environment and basic folder structure

1 files changed, 21 insertions, 0 deletions

diff --git a/src_js/hatter/lenses.js b/src_js/hatter/lenses.js
new file mode 100644
index 0000000..39da314
--- /dev/null
+++ b/src_js/hatter/lenses.js
@@ -0,0 +1,21 @@
+import R from 'ramda';
+
+
+export const index = R.lensIndex;
+
+export const prop = R.lensProp;
+
+export function path(...xs) {
+    return R.reduce((acc, i) => R.compose(acc, pathParamToLens(i)),
+                    R.identity, xs);
+}
+
+function pathParamToLens(x) {
+    switch (typeof(x)) {
+        case 'function': return x;
+        case 'number': return index(x);
+        case 'string': return prop(x);
+        case 'object': if (Array.isArray(x)) return R.apply(path, x);
+    }
+    throw 'Invalid path parameter';
+}