Improve description searching and add a cache.

Closes Homebrew/homebrew#42281.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

10 files changed, 226 insertions, 8 deletions

diff --git a/Library/Contributions/brew_bash_completion.sh b/Library/Contributions/brew_bash_completion.sh
index 5c2992126..83087ea54 100644
--- a/Library/Contributions/brew_bash_completion.sh
+++ b/Library/Contributions/brew_bash_completion.sh
@@ -195,6 +195,18 @@ _brew_deps ()
     __brew_complete_formulae
 }
 
+_brew_desc ()
+{
+    local cur="${COMP_WORDS[COMP_CWORD]}"
+    case "$cur" in
+    --*)
+        __brewcomp "--search --name --description"
+        return
+        ;;
+    esac
+    __brew_complete_formulae
+}
+
 _brew_doctor () {
     local cur="${COMP_WORDS[COMP_CWORD]}"
     __brewcomp "$(brew doctor --list-checks)"
@@ -599,6 +611,7 @@ _brew ()
     cleanup)                    _brew_cleanup ;;
     create)                     _brew_create ;;
     deps)                       _brew_deps ;;
+    desc)                       _brew_desc ;;
     doctor|dr)                  _brew_doctor ;;
     diy|configure)              _brew_diy ;;
     fetch)                      _brew_fetch ;;
diff --git a/Library/Contributions/brew_zsh_completion.zsh b/Library/Contributions/brew_zsh_completion.zsh
index dec63b84d..27faa339a 100644
--- a/Library/Contributions/brew_zsh_completion.zsh
+++ b/Library/Contributions/brew_zsh_completion.zsh
@@ -40,6 +40,7 @@ _1st_arguments=(
   'config:show homebrew and system configuration'
   'create:create a new formula'
   'deps:list dependencies and dependants of a formula'
+  'desc:display a description of a formula'
   'doctor:audits your installation for common issues'
   'edit:edit a formula'
   'fetch:download formula resources to the cache'
@@ -95,7 +96,7 @@ if (( CURRENT == 1 )); then
 fi
 
 case "$words[1]" in
-  install|reinstall|audit|home|homepage|log|info|abv|uses|cat|deps|edit|options|switch)
+  install|reinstall|audit|home|homepage|log|info|abv|uses|cat|deps|desc|edit|options|switch)
     _brew_all_formulae
     _wanted formulae expl 'all formulae' compadd -a formulae ;;
   list|ls)
diff --git a/Library/Homebrew/cmd/desc.rb b/Library/Homebrew/cmd/desc.rb
new file mode 100644
index 000000000..77078e8f5
--- /dev/null
+++ b/Library/Homebrew/cmd/desc.rb
@@ -0,0 +1,40 @@
+require "descriptions"
+require "cmd/search"
+
+module Homebrew
+  def desc
+    if ARGV.options_only.empty?
+      if ARGV.named.empty?
+        raise FormulaUnspecifiedError
+        exit
+      end
+      results = Descriptions.named(ARGV.formulae.map(&:full_name))
+    else
+      if ARGV.options_only.count != 1
+        odie "Pick one, and only one, of -s/--search, -n/--name, or -d/--description."
+      end
+
+      search_arg = ARGV.options_only.first
+
+      search_type = case search_arg
+        when '-s', '--search'
+          :either
+        when '-n', '--name'
+          :name
+        when '-d', '--description'
+          :desc
+        else
+          odie "Unrecognized option '#{search_arg}'."
+        end
+
+      if arg = ARGV.named.first
+        regex = Homebrew::query_regexp(arg)
+        results = Descriptions.search(regex, search_type)
+      else
+        odie "You must provide a search term."
+      end
+    end
+
+    results.print unless results.nil?
+  end
+end
diff --git a/Library/Homebrew/cmd/search.rb b/Library/Homebrew/cmd/search.rb
index 10e0a8269..9e5f28815 100644
--- a/Library/Homebrew/cmd/search.rb
+++ b/Library/Homebrew/cmd/search.rb
@@ -3,6 +3,7 @@ require "blacklist"
 require "utils"
 require "thread"
 require "official_taps"
+require 'descriptions'
 
 module Homebrew
   SEARCH_ERROR_QUEUE = Queue.new
@@ -23,11 +24,7 @@ module Homebrew
     elsif ARGV.include? "--desc"
       query = ARGV.next
       rx = query_regexp(query)
-      Formula.each do |formula|
-        if formula.desc =~ rx
-          puts "#{Tty.white}#{formula.full_name}:#{Tty.reset} #{formula.desc}"
-        end
-      end
+      Descriptions.search(rx, :desc).print
     elsif ARGV.empty?
       puts_columns Formula.full_names
     elsif ARGV.first =~ HOMEBREW_TAP_FORMULA_REGEX
diff --git a/Library/Homebrew/cmd/tap.rb b/Library/Homebrew/cmd/tap.rb
index 0c8960cbd..291407aff 100644
--- a/Library/Homebrew/cmd/tap.rb
+++ b/Library/Homebrew/cmd/tap.rb
@@ -1,4 +1,5 @@
 require "tap"
+require "descriptions"
 
 module Homebrew
   def tap
@@ -41,6 +42,7 @@ module Homebrew
 
     formula_count = tap.formula_files.size
     puts "Tapped #{formula_count} formula#{plural(formula_count, "e")} (#{tap.path.abv})"
+    Descriptions.cache_formulae(tap.formula_names)
 
     if !clone_target && tap.private?
       puts <<-EOS.undent
diff --git a/Library/Homebrew/cmd/untap.rb b/Library/Homebrew/cmd/untap.rb
index 1e8bfdcab..22dab7383 100644
--- a/Library/Homebrew/cmd/untap.rb
+++ b/Library/Homebrew/cmd/untap.rb
@@ -1,4 +1,5 @@
 require "cmd/tap" # for tap_args
+require "descriptions"
 
 module Homebrew
   def untap
@@ -13,6 +14,7 @@ module Homebrew
       tap.unpin if tap.pinned?
 
       formula_count = tap.formula_files.size
+      Descriptions.uncache_formulae(tap.formula_names)
       tap.path.rmtree
       tap.path.dirname.rmdir_if_possible
       puts "Untapped #{formula_count} formula#{plural(formula_count, "e")}"
diff --git a/Library/Homebrew/cmd/update.rb b/Library/Homebrew/cmd/update.rb
index 1d4eb5928..4be763b6a 100644
--- a/Library/Homebrew/cmd/update.rb
+++ b/Library/Homebrew/cmd/update.rb
@@ -2,6 +2,7 @@ require "cmd/tap"
 require "formula_versions"
 require "migrator"
 require "formulary"
+require "descriptions"
 
 module Homebrew
   def update
@@ -100,6 +101,7 @@ module Homebrew
       puts "Updated Homebrew from #{master_updater.initial_revision[0, 8]} to #{master_updater.current_revision[0, 8]}."
       report.dump
     end
+    Descriptions.update_cache(report)
   end
 
   private
diff --git a/Library/Homebrew/descriptions.rb b/Library/Homebrew/descriptions.rb
new file mode 100644
index 000000000..428f42a5e
--- /dev/null
+++ b/Library/Homebrew/descriptions.rb
@@ -0,0 +1,151 @@
+require "formula"
+require "csv"
+
+class Descriptions
+  CACHE_FILE = HOMEBREW_CACHE + "desc_cache"
+
+  def self.cache
+    @cache || self.load_cache
+  end
+
+  # If the cache file exists, load it into, and return, a hash; otherwise,
+  # return nil.
+  def self.load_cache
+    if CACHE_FILE.exist?
+      @cache = {}
+      CSV.foreach(CACHE_FILE) { |name, desc| @cache[name] = desc }
+      @cache
+    end
+  end
+
+  # Write the cache to disk after ensuring the existence of the containing
+  # directory.
+  def self.save_cache
+    HOMEBREW_CACHE.mkpath
+    CSV.open(CACHE_FILE, 'w') do |csv|
+      @cache.each do |name, desc|
+        csv << [name, desc]
+      end
+    end
+  end
+
+  # Create a hash mapping all formulae to their descriptions;
+  # save it for future use.
+  def self.generate_cache
+    @cache = {}
+    Formula.map do |f|
+      @cache[f.full_name] = f.desc
+    end
+    self.save_cache
+  end
+
+  # Return true if the cache exists, and neither Homebrew nor any of the Taps
+  # repos were updated more recently than it was.
+  def self.cache_fresh?
+    if CACHE_FILE.exist?
+      cache_date = File.mtime(CACHE_FILE)
+
+      ref_master = ".git/refs/heads/master"
+      master = HOMEBREW_REPOSITORY/ref_master
+
+      last_update = (master.exist? ? File.mtime(master) : Time.at(0))
+
+      Dir.glob(HOMEBREW_LIBRARY/"Taps/**"/ref_master).each do |repo|
+        repo_mtime = File.mtime(repo)
+        last_update = repo_mtime if repo_mtime > last_update
+      end
+      last_update <= cache_date
+    end
+  end
+
+  # Create the cache if it doesn't already exist.
+  def self.ensure_cache
+    self.generate_cache unless self.cache_fresh? && self.cache
+  end
+
+  # Take a {Report}, as generated by cmd/update.rb.
+  # Unless the cache file exists, do nothing.
+  # If it does exist, but the Report is empty, just touch the cache file.
+  # Otherwise, use the report to update the cache.
+  def self.update_cache(report)
+    if CACHE_FILE.exist?
+      if report.empty?
+        FileUtils.touch CACHE_FILE
+      else
+        renamings = report.select_formula(:R)
+        alterations = report.select_formula(:A) + report.select_formula(:M) +
+                      renamings.map(&:last)
+        self.cache_formulae(alterations, :save => false)
+        self.uncache_formulae(report.select_formula(:D) +
+                              renamings.map(&:first))
+      end
+    end
+  end
+
+  # Given an array of formula names, add them and their descriptions to the
+  # cache. Save the updated cache to disk, unless explicitly told not to.
+  def self.cache_formulae(formula_names, options = { :save => true })
+    if self.cache
+      formula_names.each { |name| @cache[name] = Formula[name].desc }
+      self.save_cache if options[:save]
+    end
+  end
+
+  # Given an array of formula names, remove them and their descriptions from
+  # the cache. Save the updated cache to disk, unless explicitly told not to.
+  def self.uncache_formulae(formula_names, options = { :save => true })
+    if self.cache
+      formula_names.each { |name| @cache.delete(name) }
+      self.save_cache if options[:save]
+    end
+  end
+
+  # Given an array of formula names, return a {Descriptions} object mapping
+  # those names to their descriptions.
+  def self.named(names)
+    self.ensure_cache
+
+    results = {}
+    unless names.empty?
+      results = names.inject({}) do |accum, name|
+        accum[name] = @cache[name]
+        accum
+      end
+    end
+
+    new(results)
+  end
+
+  # Given a regex, find all formulae whose specified fields contain a match.
+  def self.search(regex, field = :either)
+    self.ensure_cache
+
+    results = case field
+    when :name
+      @cache.select { |name, _| name =~ regex }
+    when :desc
+      @cache.select { |_, desc| desc =~ regex }
+    when :either
+      @cache.select { |name, desc| (name =~ regex) || (desc =~ regex) }
+    end
+
+    results = Hash[results] if RUBY_VERSION <= "1.8.7"
+
+    new(results)
+  end
+
+  # Create an actual instance.
+  def initialize(descriptions)
+    @descriptions = descriptions
+  end
+
+  # Take search results -- a hash mapping formula names to descriptions -- and
+  # print them.
+  def print
+    blank = "#{Tty.yellow}[no description]#{Tty.reset}"
+    @descriptions.keys.sort.each do |name|
+      description = @descriptions[name] || blank
+      puts "#{Tty.white}#{name}:#{Tty.reset} #{description}"
+    end
+  end
+end
diff --git a/Library/Homebrew/manpages/brew.1.md b/Library/Homebrew/manpages/brew.1.md
index 5adcb2180..06df14196 100644
--- a/Library/Homebrew/manpages/brew.1.md
+++ b/Library/Homebrew/manpages/brew.1.md
@@ -126,6 +126,16 @@ Note that these flags should only appear after a command.
     type dependencies, pass `--skip-build`. Similarly, pass `--skip-optional`
     to skip `:optional` dependencies.
 
+  * `desc` <formula>:
+    Display <formula>'s name and one-line description.
+
+  * `desc [-s|-n|-d] <pattern>`:
+    Search both name and description (`-s`), just the names (`-n`), or just  the
+    descriptions (`-d`) for `<pattern>`. `<pattern>` is by default interpreted
+    as a literal string; if flanked by slashes, it is instead interpreted as a
+    regular expression. Formula descriptions are cached; the cache is created on
+    the first search, making that search slower than subsequent ones.
+
   * `diy [--name=<name>] [--version=<version>]`:
     Automatically determine the installation prefix for non-Homebrew software.
 
diff --git a/Library/Homebrew/utils.rb b/Library/Homebrew/utils.rb
index 2b496565c..bec8861da 100644
--- a/Library/Homebrew/utils.rb
+++ b/Library/Homebrew/utils.rb
@@ -255,8 +255,8 @@ def puts_columns(items, star_items = [])
     # determine the best width to display for different console sizes
     console_width = `/bin/stty size`.chomp.split(" ").last.to_i
     console_width = 80 if console_width <= 0
-    longest = items.sort_by(&:length).last
-    optimal_col_width = (console_width.to_f / (longest.length + 2).to_f).floor
+    max_len = items.reduce(0) { |max, item| l = item.length ; l > max ? l : max }
+    optimal_col_width = (console_width.to_f / (max_len + 2).to_f).floor
     cols = optimal_col_width > 1 ? optimal_col_width : 1
 
     IO.popen("/usr/bin/pr -#{cols} -t -w#{console_width}", "w") { |io| io.puts(items) }