require "keg"
require "formula"
require "linkage_cache_store"

class LinkageChecker
  attr_reader :undeclared_deps

  def initialize(keg, formula = nil, cache_db:, rebuild_cache: false)
    @keg = keg
    @formula = formula || resolve_formula(keg)
    @store = LinkageCacheStore.new(keg.to_s, cache_db)

    @system_dylibs    = Set.new
    @broken_dylibs    = Set.new
    @variable_dylibs  = Set.new
    @brewed_dylibs    = Hash.new { |h, k| h[k] = Set.new }
    @reverse_links    = Hash.new { |h, k| h[k] = Set.new }
    @broken_deps      = Hash.new { |h, k| h[k] = [] }
    @indirect_deps    = []
    @undeclared_deps  = []
    @unnecessary_deps = []
    @unwanted_system_dylibs = []
    @version_conflict_deps = []

    check_dylibs(rebuild_cache: rebuild_cache)
  end

  def display_normal_output
    display_items "System libraries", @system_dylibs
    display_items "Homebrew libraries", @brewed_dylibs
    display_items "Indirect dependencies with linkage", @indirect_deps
    display_items "Variable-referenced libraries", @variable_dylibs
    display_items "Missing libraries", @broken_dylibs
    display_items "Broken dependencies", @broken_deps
    display_items "Undeclared dependencies with linkage", @undeclared_deps
    display_items "Dependencies with no linkage", @unnecessary_deps
    display_items "Unwanted system libraries", @unwanted_system_dylibs
  end

  def display_reverse_output
    return if @reverse_links.empty?
    sorted = @reverse_links.sort
    sorted.each do |dylib, files|
      puts dylib
      files.each do |f|
        unprefixed = f.to_s.strip_prefix "#{keg}/"
        puts "  #{unprefixed}"
      end
      puts if dylib != sorted.last.first
    end
  end

  def display_test_output(puts_output: true)
    display_items "Missing libraries", @broken_dylibs, puts_output: puts_output
    display_items "Broken dependencies", @broken_deps, puts_output: puts_output
    display_items "Unwanted system libraries", @unwanted_system_dylibs, puts_output: puts_output
    display_items "Conflicting libraries", @version_conflict_deps, puts_output: puts_output
    puts "No broken library linkage" unless broken_library_linkage?
  end

  def broken_library_linkage?
    !@broken_dylibs.empty? ||
      !@broken_deps.empty? ||
      !@unwanted_system_dylibs.empty? ||
      !@version_conflict_deps.empty?
  end

  private

  attr_reader :keg, :formula, :store

  def dylib_to_dep(dylib)
    dylib =~ %r{#{Regexp.escape(HOMEBREW_PREFIX)}/(opt|Cellar)/([\w+-.@]+)/}
    Regexp.last_match(2)
  end

  def check_dylibs(rebuild_cache:)
    keg_files_dylibs = nil

    if rebuild_cache
      store&.flush_cache!
    else
      keg_files_dylibs = store&.fetch_type(:keg_files_dylibs)
    end

    keg_files_dylibs_was_empty = false
    keg_files_dylibs ||= {}
    if keg_files_dylibs.empty?
      keg_files_dylibs_was_empty = true
      @keg.find do |file|
        next if file.symlink? || file.directory?
        next if !file.dylib? && !file.binary_executable? && !file.mach_o_bundle?
        # weakly loaded dylibs may not actually exist on disk, so skip them
        # when checking for broken linkage
        keg_files_dylibs[file] =
          file.dynamically_linked_libraries(except: :LC_LOAD_WEAK_DYLIB)
      end
    end

    checked_dylibs = Set.new

    keg_files_dylibs.each do |file, dylibs|
      dylibs.each do |dylib|
        @reverse_links[dylib] << file

        next if checked_dylibs.include? dylib
        checked_dylibs << dylib

        if dylib.start_with? "@"
          @variable_dylibs << dylib
          next
        end

        begin
          owner = Keg.for Pathname.new(dylib)
        rescue NotAKegError
          @system_dylibs << dylib
        rescue Errno::ENOENT
          next if harmless_broken_link?(dylib)
          if (dep = dylib_to_dep(dylib))
            @broken_deps[dep] |= [dylib]
          else
            @broken_dylibs << dylib
          end
        else
          tap = Tab.for_keg(owner).tap
          f = if tap.nil? || tap.core_tap?
            owner.name
          else
            "#{tap}/#{owner.name}"
          end
          @brewed_dylibs[f] << dylib
        end
      end
    end

    if formula
      @indirect_deps, @undeclared_deps, @unnecessary_deps,
        @version_conflict_deps = check_formula_deps
    end

    return unless keg_files_dylibs_was_empty

    store&.update!(keg_files_dylibs: keg_files_dylibs)
  end
  alias generic_check_dylibs check_dylibs

  def check_formula_deps
    filter_out = proc do |dep|
      next true if dep.build?
      next false unless dep.optional? || dep.recommended?
      formula.build.without?(dep)
    end

    declared_deps_full_names = formula.deps
                                      .reject { |dep| filter_out.call(dep) }
                                      .map(&:name)
    declared_deps_names = declared_deps_full_names.map do |dep|
      dep.split("/").last
    end
    recursive_deps = formula.runtime_formula_dependencies(undeclared: false)
                            .map(&:name)

    indirect_deps = []
    undeclared_deps = []
    @brewed_dylibs.each_key do |full_name|
      name = full_name.split("/").last
      next if name == formula.name
      if recursive_deps.include?(name)
        indirect_deps << full_name unless declared_deps_names.include?(name)
      else
        undeclared_deps << full_name
      end
    end

    sort_by_formula_full_name!(indirect_deps)
    sort_by_formula_full_name!(undeclared_deps)

    unnecessary_deps = declared_deps_full_names.reject do |full_name|
      next true if Formula[full_name].bin.directory?
      name = full_name.split("/").last
      @brewed_dylibs.keys.map { |l| l.split("/").last }.include?(name)
    end

    missing_deps = @broken_deps.values.flatten.map { |d| dylib_to_dep(d) }
    unnecessary_deps -= missing_deps

    version_hash = {}
    version_conflict_deps = Set.new
    @brewed_dylibs.keys.each do |l|
      name = l.split("/").last
      unversioned_name, = name.split("@")
      version_hash[unversioned_name] ||= Set.new
      version_hash[unversioned_name] << name
      next if version_hash[unversioned_name].length < 2
      version_conflict_deps += version_hash[unversioned_name]
    end

    [indirect_deps, undeclared_deps,
     unnecessary_deps, version_conflict_deps.to_a]
  end

  def sort_by_formula_full_name!(arr)
    arr.sort! do |a, b|
      if a.include?("/") && !b.include?("/")
        1
      elsif !a.include?("/") && b.include?("/")
        -1
      else
        a <=> b
      end
    end
  end

  # Whether or not dylib is a harmless broken link, meaning that it's
  # okay to skip (and not report) as broken.
  def harmless_broken_link?(dylib)
    # libgcc_s_* is referenced by programs that use the Java Service Wrapper,
    # and is harmless on x86(_64) machines
    [
      "/usr/lib/libgcc_s_ppc64.1.dylib",
      "/opt/local/lib/libgcc/libgcc_s.1.dylib",
    ].include?(dylib)
  end

  # Display a list of things.
  # Things may either be an array, or a hash of (label -> array)
  def display_items(label, things, puts_output: true)
    return if things.empty?
    output = "#{label}:"
    if things.is_a? Hash
      things.keys.sort.each do |list_label|
        things[list_label].sort.each do |item|
          output += "\n  #{item} (#{list_label})"
        end
      end
    else
      things.sort.each do |item|
        output += "\n  #{item}"
      end
    end
    puts output if puts_output
    output
  end

  def resolve_formula(keg)
    Formulary.from_keg(keg)
  rescue FormulaUnavailableError
    opoo "Formula unavailable: #{keg.name}"
  end
end

require "extend/os/linkage_checker"
