From 9a858417a857b36f62ed6eb110b914c1330845ba Mon Sep 17 00:00:00 2001
From: Sam Saccone <samccone@gmail.com>
Date: Sat, 1 Jun 2019 13:46:49 -0700
Subject: [PATCH] Implement prefix trimming logic for resolve flow.

---
 explorer/app/src/resolve/trim.test.ts | 28 ++++++++++++++
 explorer/app/src/resolve/trim.ts      | 56 +++++++++++++++++++++++++++
 2 files changed, 84 insertions(+)
 create mode 100644 explorer/app/src/resolve/trim.test.ts
 create mode 100644 explorer/app/src/resolve/trim.ts

diff --git a/explorer/app/src/resolve/trim.test.ts b/explorer/app/src/resolve/trim.test.ts
new file mode 100644
index 0000000..556f374
--- /dev/null
+++ b/explorer/app/src/resolve/trim.test.ts
@@ -0,0 +1,28 @@
+import { findTrims } from "./trim";
+
+it("finds no trims when no /", () => {
+  expect(findTrims(["wow"], ["wo"])).toEqual({});
+});
+
+it("finds no trims", () => {
+  expect(findTrims(["wo/ok"], ["../ok"])).toEqual({});
+});
+
+it("finds trims", () => {
+  expect(findTrims(["a/b/ok"], ["b/ok"])).toEqual({
+    "a/": 1
+  });
+
+  expect(findTrims(["b/ok"], ["a/b/ok"])).toEqual({
+    "a/": 1
+  });
+});
+
+it("finds multi trims", () => {
+  expect(
+    findTrims(["a/b/ok", "nothing", "../a/b.js"], ["b/ok", "a/b.js"])
+  ).toEqual({
+    "a/": 1,
+    "../": 1
+  });
+});
diff --git a/explorer/app/src/resolve/trim.ts b/explorer/app/src/resolve/trim.ts
new file mode 100644
index 0000000..8ceb845
--- /dev/null
+++ b/explorer/app/src/resolve/trim.ts
@@ -0,0 +1,56 @@
+function generatePrefixList(items: string[]) {
+  const kk: { [prefix: string]: number } = {};
+
+  for (const i of items) {
+    const components = i.split("/");
+    let prev = components[0] + "/";
+    for (const c of components.slice(1)) {
+      kk[prev + c] = kk[prev + c] || 0;
+      kk[prev + c]++;
+      prev = prev + c + "/";
+    }
+  }
+
+  let prefixItems = [];
+  for (const k of Object.keys(kk)) {
+    prefixItems.push({ prefix: k, count: kk[k] });
+  }
+
+  return prefixItems.sort((a, b) => b.count - a.count);
+}
+
+/**
+ * Given two lists of strings find common prefixes that when removed would
+ * align the two lists of strings.
+ * @param items 
+ * @param items2 
+ */
+export function findTrims(items: string[], items2: string[]) {
+  const prefixList1 = generatePrefixList(items);
+  const prefixList2 = generatePrefixList(items2);
+  const recommendedTrims: { [prefix: string]: number } = {};
+  for (let i = 0; i < prefixList1.length; i++) {
+    for (let j = 0; j < prefixList2.length; j++) {
+      if (prefixList1[i].prefix.length > prefixList2[j].prefix.length) {
+        const idx = prefixList1[i].prefix.indexOf(prefixList2[j].prefix);
+        if (idx > -1) {
+          const str = prefixList1[i].prefix.slice(0, idx);
+          if (str !== "") {
+            recommendedTrims[str] = recommendedTrims[str] || 0;
+            recommendedTrims[str]++;
+          }
+        }
+      } else {
+        const idx = prefixList2[j].prefix.indexOf(prefixList1[i].prefix);
+        if (idx > -1) {
+          const str = prefixList2[j].prefix.slice(0, idx);
+          if (str !== "") {
+            recommendedTrims[str] = recommendedTrims[str] || 0;
+            recommendedTrims[str]++;
+          }
+        }
+      }
+    }
+  }
+  return recommendedTrims;
+}