From b4d6df902253637f24647d3db2bc3781d69eec1c Mon Sep 17 00:00:00 2001
From: Joel Klinghed <the_jk@spawned.biz>
Date: Thu, 20 Feb 2025 22:54:56 +0100
Subject: Initial commit

---
 src/args.cc | 293 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 293 insertions(+)
 create mode 100644 src/args.cc

(limited to 'src/args.cc')

diff --git a/src/args.cc b/src/args.cc
new file mode 100644
index 0000000..a89c418
--- /dev/null
+++ b/src/args.cc
@@ -0,0 +1,293 @@
+#include "args.hh"
+
+#include <cassert>
+#include <iostream>
+#include <unordered_map>
+#include <vector>
+
+namespace {
+
+class OptionImpl : public OptionWithArg {
+public:
+  OptionImpl(char short_name, std::string long_name, std::string description,
+             bool require_arg, std::string arg_description)
+    : short_name_(short_name),
+      long_name_(std::move(long_name)),
+      description_(std::move(description)),
+      require_arg_(require_arg),
+      arg_description_(std::move(arg_description)) {
+  }
+
+  bool is_set() const override { return set_; }
+
+  std::string const& arg() const override { return arg_; }
+
+  char short_name() const { return short_name_; }
+
+  std::string const& long_name() const { return long_name_; }
+
+  std::string const& description() const { return description_; }
+
+  bool require_arg() const { return require_arg_; }
+
+  std::string const& arg_description() const { return arg_description_; }
+
+  void reset() {
+    set_ = false;
+    arg_.clear();
+  }
+
+  void set() {
+    set_ = true;
+  }
+
+  void set_arg(std::string arg) {
+    arg_ = std::move(arg);
+  }
+
+private:
+  char const short_name_;
+  std::string const long_name_;
+  std::string const description_;
+  bool const require_arg_;
+  std::string const arg_description_;
+  bool set_ = false;
+  std::string arg_;
+};
+
+class ArgsImpl : public Args {
+public:
+  ArgsImpl() = default;
+
+  std::shared_ptr<Option const> add_option(char short_name,
+                                           std::string long_name,
+                                           std::string description) override {
+    prepare_option(short_name, long_name);
+    options_.push_back(std::make_shared<OptionImpl>(short_name,
+                                                    std::move(long_name),
+                                                    std::move(description),
+                                                    false, std::string()));
+    return options_.back();
+  }
+
+  std::shared_ptr<OptionWithArg const> add_option_with_arg(
+      char short_name,
+      std::string long_name,
+      std::string description,
+      std::string arg_description) override {
+    prepare_option(short_name, long_name);
+    options_.push_back(std::make_shared<OptionImpl>(short_name,
+                                                    std::move(long_name),
+                                                    std::move(description),
+                                                    true, arg_description));
+    return options_.back();
+  }
+
+  bool run(int argc, char** argv, std::string_view prgname, std::ostream& err,
+           std::vector<std::string>& out) override {
+    for (int a = 1; a < argc; ++a) {
+      if (argv[a][0] == '-') {
+        if (argv[a][1] == '-') {
+          if (argv[a][2] != '\0') {
+            // A long name with optional "=" argument
+            size_t len = 2;
+            while (argv[a][len] != '=' && argv[a][len])
+              ++len;
+            std::string name(argv[a] + 2, len - 2);
+            auto it = long_names_.find(name);
+            if (it == long_names_.end()) {
+              err << prgname << ": unrecognized option '--"
+                  << name << "'" << std::endl;
+              return false;
+            }
+            auto* opt = options_[it->second].get();
+            opt->set();
+            if (argv[a][len]) {
+              if (opt->require_arg()) {
+                opt->set_arg(std::string(argv[a] + len + 1));
+              } else {
+                err << prgname << ": option '--"
+                    << name << "' doesn't allow an argument" << std::endl;
+                return false;
+              }
+            } else {
+              if (opt->require_arg()) {
+                if (a + 1 >= argc) {
+                  err << prgname << ": option '--"
+                      << name << "' requires an argument" << std::endl;
+                  return false;
+                } else {
+                  opt->set_arg(argv[++a]);
+                }
+              }
+            }
+            continue;
+          } else {
+            // "--", all following values are arguments
+            for (++a; a < argc; ++a)
+              out.push_back(argv[a]);
+            break;
+          }
+        } else if (argv[a][1] != '\0') {
+          // One or more short names
+          for (auto* name = argv[a] + 1; *name; ++name) {
+            auto it = short_names_.find(*name);
+            if (it == short_names_.end()) {
+              err << prgname << ": invalid option -- '"
+                  << *name << "'" << std::endl;
+              return false;
+            }
+            auto* opt = options_[it->second].get();
+            opt->set();
+            if (opt->require_arg()) {
+              if (a + 1 >= argc) {
+                err << prgname << ": option requires an argument"
+                    << " -- '" << *name << "'" << std::endl;
+                return false;
+              } else {
+                opt->set_arg(argv[++a]);
+              }
+            }
+          }
+          continue;
+        } else {
+          // single "-", treat as argument
+        }
+      }
+
+      out.push_back(argv[a]);
+    }
+    return true;
+  }
+
+  void print_descriptions(std::ostream& out,
+                          uint32_t column_width) const override {
+    uint32_t max_left = 0;
+    for (auto const& option : options_) {
+      uint32_t left = 0;
+      if (option->short_name() != '\0') {
+        if (!option->long_name().empty()) {
+          left = 6 + option->long_name().size();  // -S, --long
+        } else {
+          left = 2;                               // -S
+        }
+      } else if (!option->long_name().empty()) {
+        left = 2 + option->long_name().size();  // --long
+      }
+      if (option->require_arg())
+        left += 1 + option->arg_description().size();  // (=| )ARG
+      if (left > 0)
+        left += 2;  // Need at least two spaces between option and desc
+      // Prefix with two spaces (either infront of option or desc)
+      left += 2;
+
+      if (left > max_left)
+        max_left = left;
+    }
+
+    uint32_t const avail_right =
+      max_left > column_width ? 0 : column_width - max_left;
+
+    if (avail_right < 20) {
+      // Fallback mode, description on its own row.
+      for (auto const& option : options_) {
+        print_option(out, *option);
+        out << '\n' << option->description() << '\n';
+      }
+      return;
+    }
+
+    // Check if all descriptions fit, justify to the right on a 80 col width
+    bool all_desc_fit = true;
+    uint32_t max_right = 0;
+    for (auto const& option : options_) {
+      uint32_t right = option->description().size();
+      if (right > avail_right) {
+        all_desc_fit = false;
+        break;
+      }
+      if (right > max_right)
+        max_right = right;
+    }
+
+    if (all_desc_fit)
+      max_left = std::max(80u, column_width) - max_right;
+
+    for (auto const& option : options_) {
+      out << "  ";
+      uint32_t left = 2 + print_option(out, *option);
+      std::fill_n(std::ostreambuf_iterator<char>(out), max_left - left, ' ');
+
+      if (option->description().size() <= avail_right) {
+        out << option->description() << '\n';
+        continue;
+      }
+
+      // Wrap description
+      size_t last = 0;
+      bool first = true;
+      while (true) {
+        if (first) {
+          first = false;
+        } else {
+          std::fill_n(std::ostreambuf_iterator<char>(out), max_left, ' ');
+        }
+
+        size_t end = last + avail_right;
+        if (end >= option->description().size()) {
+          out << option->description().substr(last) << '\n';
+          break;
+        }
+        size_t space = option->description().rfind(' ', end);
+        if (space == std::string::npos || space < last) {
+          space = end;
+        }
+        out << option->description().substr(last, space - last) << '\n';
+        last = space < end ? space + 1 : end;
+      }
+    }
+  }
+
+private:
+  void prepare_option(char short_name, std::string const& long_name) {
+    if (short_name != '\0')
+      short_names_.emplace(short_name, options_.size());
+    if (!long_name.empty()) {
+      assert(long_name.find('=') == std::string::npos);
+      long_names_.emplace(long_name, options_.size());
+    }
+  }
+
+  size_t print_option(std::ostream& out, const OptionImpl& option) const {
+    bool only_short = false;
+    size_t ret = 0;
+    if (option.short_name() != '\0') {
+      out << '-' << option.short_name();
+      if (!option.long_name().empty()) {
+        out << ", --" << option.long_name();
+        ret = 6 + option.long_name().size();
+      } else {
+        ret = 2;
+        only_short = true;
+      }
+    } else if (!option.long_name().empty()) {
+      out << "--" << option.long_name();
+      ret = 2 + option.long_name().size();
+    }
+    if (option.require_arg()) {
+      out << (only_short ? ' ' : '=') << option.arg_description();
+      ret += 1 + option.arg_description().size();
+    }
+    return ret;
+  }
+
+  std::vector<std::shared_ptr<OptionImpl>> options_;
+  std::unordered_map<char, size_t> short_names_;
+  std::unordered_map<std::string, size_t> long_names_;
+};
+
+}  // namespace
+
+std::unique_ptr<Args> Args::create() {
+  return std::make_unique<ArgsImpl>();
+}
-- 
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