From b6d5c2760e90739ea845a774e2c34a0d8a0d2694 Mon Sep 17 00:00:00 2001
From: Vladislav Nepogodin <nepogodin.vlad@gmail.com>
Date: Wed, 3 Jul 2024 23:50:15 +0400
Subject: [PATCH] =?UTF-8?q?=F0=9F=91=B7=20gucc:=20rewrite=20pacmanconf=20t?=
 =?UTF-8?q?o=20reuse=20file=20content?=
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don't make extra memory allocations:
- don't allocate vector of strings to find locations
- don't convert that vector of strings into new string

previously:
```
heaptrack stats:
	allocations:          	69
	leaked allocations:   	0
	temporary allocations:	4
```

after:
```
heaptrack stats:
	allocations:          	32
	leaked allocations:   	0
	temporary allocations:	5
```
---
 gucc/src/pacmanconf_repo.cpp   | 36 ++++++++++++++++++++--------------
 gucc/tests/unit-pacmanconf.cpp |  4 ++--
 2 files changed, 23 insertions(+), 17 deletions(-)

diff --git a/gucc/src/pacmanconf_repo.cpp b/gucc/src/pacmanconf_repo.cpp
index 22943d4..1e55c97 100644
--- a/gucc/src/pacmanconf_repo.cpp
+++ b/gucc/src/pacmanconf_repo.cpp
@@ -1,5 +1,6 @@
 #include "gucc/pacmanconf_repo.hpp"
 #include "gucc/file_utils.hpp"
+#include "gucc/string_utils.hpp"
 
 #include <fstream>  // for ofstream
 #include <string>   // for string
@@ -17,9 +18,9 @@
 #pragma GCC diagnostic ignored "-Wold-style-cast"
 #endif
 
+#include <range/v3/algorithm/find_if.hpp>
 #include <range/v3/range/conversion.hpp>
 #include <range/v3/view/filter.hpp>
-#include <range/v3/view/join.hpp>
 #include <range/v3/view/split.hpp>
 
 #if defined(__clang__)
@@ -31,33 +32,38 @@
 namespace gucc::detail::pacmanconf {
 
 bool push_repos_front(std::string_view file_path, std::string_view value) noexcept {
-    using StringVec     = std::vector<std::string>;
     auto&& file_content = file_utils::read_whole_file(file_path);
     if (file_content.empty()) {
         spdlog::error("[PACMANCONFREPO] '{}' error occurred!", file_path);
         return false;
     }
-    auto&& content_lines = file_content | ranges::views::split('\n') | ranges::to<std::vector<std::string>>();
-    for (std::size_t i = 1; i < content_lines.size(); ++i) {
-        const std::string_view current_line{content_lines[i - 1]};
-        if (current_line.empty() || current_line.starts_with('#') || !current_line.starts_with('[') || current_line.starts_with("[options]")) {
-            continue;
-        }
 
-        auto&& to_be_inserted = value | ranges::views::split('\n') | ranges::to<std::vector<std::string>>();
-        to_be_inserted.emplace_back("\n");
-        content_lines.insert(content_lines.begin() + static_cast<StringVec::iterator::difference_type>(i - 1),
-            std::move_iterator(to_be_inserted.begin()), std::move_iterator(to_be_inserted.end()));
-        break;
+    auto file_split_view = utils::make_split_view(file_content);
+    // Find the insertion point (using ranges for iteration)
+    auto insertion_point_it = ranges::find_if(
+        file_split_view,
+        [](auto&& rng) {
+            auto&& line = std::string_view(&*rng.begin(), static_cast<size_t>(ranges::distance(rng)));
+            return !line.empty() && !line.starts_with('#') && line.starts_with('[') && !line.starts_with("[options]");
+        });
+
+    // Handle case where insertion point is not found
+    if (insertion_point_it == ranges::end(file_split_view)) {
+        // No suitable insertion point found
+        spdlog::error("[PACMANCONFREPO] Could not find a suitable insertion point in {}", file_path);
+        return false;
     }
 
+    auto line = *insertion_point_it;
+    auto pos  = file_content.find(line);
+    file_content.insert(pos - 1, std::string{'\n'} + std::string{value} + std::string{'\n'});
+
     std::ofstream pacmanconf_file{file_path.data()};
     if (!pacmanconf_file.is_open()) {
         spdlog::error("[PACMANCONFREPO] '{}' open failed: {}", file_path, std::strerror(errno));
         return false;
     }
-    std::string&& result = content_lines | ranges::views::join('\n') | ranges::to<std::string>();
-    pacmanconf_file << result;
+    pacmanconf_file << file_content;
     return true;
 }
 
diff --git a/gucc/tests/unit-pacmanconf.cpp b/gucc/tests/unit-pacmanconf.cpp
index ca7fb13..bc20d39 100644
--- a/gucc/tests/unit-pacmanconf.cpp
+++ b/gucc/tests/unit-pacmanconf.cpp
@@ -98,7 +98,6 @@ ParallelDownloads = 10
 [cachyos]
 Include = /etc/pacman.d/cachyos-mirrorlist
 
-
 [core]
 Include = /etc/pacman.d/mirrorlist
 
@@ -115,7 +114,8 @@ Include = /etc/pacman.d/mirrorlist
 #Include = /etc/pacman.d/mirrorlist
 
 [multilib]
-Include = /etc/pacman.d/mirrorlist)";
+Include = /etc/pacman.d/mirrorlist
+)";
 
 int main() {
     using namespace gucc;