From 90329e5453b5c0e93964c9ab6ada815f7977f441 Mon Sep 17 00:00:00 2001
From: Fangrui Song <i@maskray.me>
Date: Mon, 19 Mar 2018 00:39:22 -0700
Subject: [PATCH] Simplify ComputeGuessScore

---
 src/fuzzy_match.cc |  1 +
 src/project.cc     | 36 +++++++-----------------------------
 2 files changed, 8 insertions(+), 29 deletions(-)

diff --git a/src/fuzzy_match.cc b/src/fuzzy_match.cc
index c37f24cb..f91655ed 100644
--- a/src/fuzzy_match.cc
+++ b/src/fuzzy_match.cc
@@ -152,6 +152,7 @@ TEST_SUITE("fuzzy_match") {
     Ranks("ab", {"ab", "aoo_boo", "acb"});
     Ranks("CC", {"CamelCase", "camelCase", "camelcase"});
     Ranks("cC", {"camelCase", "CamelCase", "camelcase"});
+    Ranks("c c", {"camel case", "camelCase", "CamelCase", "camelcase", "camel ace"});
     Ranks("Da.Te", {"Data.Text", "Data.Text.Lazy", "Data.Aeson.Encoding.text"});
     // prefix
     Ranks("is", {"isIEEE", "inSuf"});
diff --git a/src/project.cc b/src/project.cc
index f8c21ccb..6411d1ae 100644
--- a/src/project.cc
+++ b/src/project.cc
@@ -496,37 +496,15 @@ std::vector<Project::Entry> LoadCompilationEntriesFromDirectory(
 // Computes a score based on how well |a| and |b| match. This is used for
 // argument guessing.
 int ComputeGuessScore(const std::string& a, const std::string& b) {
-  const int kMatchPrefixWeight = 100;
-  const int kMismatchDirectoryWeight = 100;
-  const int kMatchPostfixWeight = 1;
-
-  int score = 0;
-  size_t i = 0;
-
-  // Increase score based on matching prefix.
-  for (i = 0; i < a.size() && i < b.size(); ++i) {
-    if (a[i] != b[i])
-      break;
-    score += kMatchPrefixWeight;
-  }
+  // Increase score based on common prefix and suffix. Prefixes are prioritized.
+  size_t i = std::mismatch(a.begin(), a.end(), b.begin()).first - a.begin();
+  size_t j = std::mismatch(a.rbegin(), a.rend(), b.rbegin()).first - a.rbegin();
+  int score = 10 * i + j;
 
   // Reduce score based on mismatched directory distance.
-  for (size_t j = i; j < a.size(); ++j) {
-    if (a[j] == '/')
-      score -= kMismatchDirectoryWeight;
-  }
-  for (size_t j = i; j < b.size(); ++j) {
-    if (b[j] == '/')
-      score -= kMismatchDirectoryWeight;
-  }
-
-  // Increase score based on common ending. Don't increase as much as matching
-  // prefix or directory distance.
-  for (size_t offset = 1; offset <= a.size() && offset <= b.size(); ++offset) {
-    if (a[a.size() - offset] != b[b.size() - offset])
-      break;
-    score += kMatchPostfixWeight;
-  }
+  if (i + j < std::min(a.size(), b.size()))
+    score -= 100 * (std::count(a.begin() + i, a.end() - j, '/') +
+                    std::count(b.begin() + i, b.end() - j, '/'));
 
   return score;
 }