class Bundler::Resolver

def all_versions_for(package)
  name = package.name
  results = (@base[name] + filter_prereleases(@all_specs[name], package)).uniq {|spec| [spec.version.hash, spec.platform] }
  locked_requirement = base_requirements[name]
  results = filter_matching_specs(results, locked_requirement) if locked_requirement
  versions = results.group_by(&:version).reduce([]) do |groups, (version, specs)|
    platform_specs = package.platforms.flat_map {|platform| select_best_platform_match(specs, platform) }
    next groups if platform_specs.empty?
    ruby_specs = select_best_platform_match(specs, Gem::Platform::RUBY)
    groups << Resolver::Candidate.new(version, :specs => ruby_specs) if ruby_specs.any?
    next groups if platform_specs == ruby_specs || package.force_ruby_platform?
    groups << Resolver::Candidate.new(version, :specs => platform_specs)
    groups
  end
  sort_versions(package, versions)
end

def base_requirements
  @base.base_requirements
end

def bundler_not_found_message(conflict_dependencies)
  candidate_specs = filter_matching_specs(source_for(:default_bundler).specs.search("bundler"), conflict_dependencies)
  if candidate_specs.any?
    target_version = candidate_specs.last.version
    new_command = [File.basename($PROGRAM_NAME), "_#{target_version}_", *ARGV].join(" ")
    "Your bundle requires a different version of Bundler than the one you're running.\n" \
    "Install the necessary version with `gem install bundler:#{target_version}` and rerun bundler using `#{new_command}`\n"
  else
    "Your bundle requires a different version of Bundler than the one you're running, and that version could not be found.\n"
  end
end

def debug?
  ENV["BUNDLER_DEBUG_RESOLVER"] ||
    ENV["BUNDLER_DEBUG_RESOLVER_TREE"] ||
    ENV["DEBUG_RESOLVER"] ||
    ENV["DEBUG_RESOLVER_TREE"] ||
    false
end

def filter_matching_specs(specs, requirements)
  Array(requirements).flat_map do |requirement|
    specs.select {| spec| requirement_satisfied_by?(requirement, spec) }
  end
end

def filter_prereleases(specs, package)
  return specs unless package.ignores_prereleases? && specs.size > 1
  specs.reject {|s| s.version.prerelease? }
end

def find_names_to_relax(incompatibility)
  names_to_unlock = []
  names_to_allow_prereleases_for = []
  extended_explanation = nil
  while incompatibility.conflict?
    cause = incompatibility.cause
    incompatibility = cause.incompatibility
    incompatibility.terms.each do |term|
      package = term.package
      name = package.name
      if base_requirements[name]
        names_to_unlock << name
      elsif package.ignores_prereleases?
        names_to_allow_prereleases_for << name
      end
      no_versions_incompat = [cause.incompatibility, cause.satisfier].find {|incompat| incompat.cause.is_a?(PubGrub::Incompatibility::NoVersions) }
      next unless no_versions_incompat
      extended_explanation = no_versions_incompat.extended_explanation
    end
  end
  [names_to_unlock.uniq, names_to_allow_prereleases_for.uniq, extended_explanation]
end

def incompatibilities_for(package, version)
  package_deps = @cached_dependencies[package]
  sorted_versions = @sorted_versions[package]
  package_deps[version].map do |dep_package, dep_constraint|
    low = high = sorted_versions.index(version)
    # find version low such that all >= low share the same dep
    while low > 0 && package_deps[sorted_versions[low - 1]][dep_package] == dep_constraint
      low -= 1
    end
    low =
      if low == 0
        nil
      else
        sorted_versions[low]
      end
    # find version high such that all < high share the same dep
    while high < sorted_versions.length && package_deps[sorted_versions[high]][dep_package] == dep_constraint
      high += 1
    end
    high =
      if high == sorted_versions.length
        nil
      else
        sorted_versions[high]
      end
    range = PubGrub::VersionRange.new(:min => low, :max => high, :include_min => true)
    self_constraint = PubGrub::VersionConstraint.new(package, :range => range)
    dep_term = PubGrub::Term.new(dep_constraint, false)
    self_term = PubGrub::Term.new(self_constraint, true)
    custom_explanation = if dep_package.meta? && package.root?
      "current #{dep_package} version is #{dep_constraint.constraint_string}"
    end
    PubGrub::Incompatibility.new([self_term, dep_term], :cause => :dependency, :custom_explanation => custom_explanation)
  end
end

def initialize(base, gem_version_promoter)
  @source_requirements = base.source_requirements
  @base = base
  @gem_version_promoter = gem_version_promoter
end

def name_for_explicit_dependency_source
  Bundler.default_gemfile.basename.to_s
rescue StandardError
  "Gemfile"
end

def no_versions_incompatibility_for(package, unsatisfied_term)
  cause = PubGrub::Incompatibility::NoVersions.new(unsatisfied_term)
  name = package.name
  constraint = unsatisfied_term.constraint
  constraint_string = constraint.constraint_string
  requirements = constraint_string.split(" OR ").map {|req| Gem::Requirement.new(req.split(",")) }
  if name == "bundler"
    custom_explanation = "the current Bundler version (#{Bundler::VERSION}) does not satisfy #{constraint}"
    extended_explanation = bundler_not_found_message(requirements)
  else
    specs_matching_other_platforms = filter_matching_specs(@all_specs[name], requirements)
    platforms_explanation = specs_matching_other_platforms.any? ? " for any resolution platforms (#{package.platforms.join(", ")})" : ""
    custom_explanation = "#{constraint} could not be found in #{repository_for(package)}#{platforms_explanation}"
    label = "#{name} (#{constraint_string})"
    extended_explanation = other_specs_matching_message(specs_matching_other_platforms, label) if specs_matching_other_platforms.any?
  end
  Incompatibility.new([unsatisfied_term], :cause => cause, :custom_explanation => custom_explanation, :extended_explanation => extended_explanation)
end

def other_specs_matching_message(specs, requirement)
  message = String.new("The source contains the following gems matching '#{requirement}':\n")
  message << specs.map {|s| "  * #{s.full_name}" }.join("\n")
  message
end

def parse_dependency(package, dependency)
  range = if repository_for(package).is_a?(Source::Gemspec)
    PubGrub::VersionRange.any
  else
    requirement_to_range(dependency)
  end
  PubGrub::VersionConstraint.new(package, :range => range)
end

def prepare_dependencies(requirements, packages)
  to_dependency_hash(requirements, packages).map do |dep_package, dep_constraint|
    name = dep_package.name
    next [dep_package, dep_constraint] if name == "bundler"
    versions = versions_for(dep_package, dep_constraint.range)
    if versions.empty? && dep_package.ignores_prereleases?
      @sorted_versions.delete(dep_package)
      dep_package.consider_prereleases!
      versions = versions_for(dep_package, dep_constraint.range)
    end
    next [dep_package, dep_constraint] unless versions.empty?
    next unless dep_package.current_platform?
    raise_not_found!(dep_package)
  end.compact.to_h
end

def raise_not_found!(package)
  name = package.name
  source = source_for(name)
  specs = @all_specs[name]
  matching_part = name
  requirement_label = SharedHelpers.pretty_dependency(package.dependency)
  cache_message = begin
                      " or in gems cached in #{Bundler.settings.app_cache_path}" if Bundler.app_cache.exist?
                    rescue GemfileNotFound
                      nil
                    end
  specs_matching_requirement = filter_matching_specs(specs, package.dependency.requirement)
  if specs_matching_requirement.any?
    specs = specs_matching_requirement
    matching_part = requirement_label
    platforms = package.platforms
    platform_label = platforms.size == 1 ? "platform '#{platforms.first}" : "platforms '#{platforms.join("', '")}"
    requirement_label = "#{requirement_label}' with #{platform_label}"
  end
  message = String.new("Could not find gem '#{requirement_label}' in #{source}#{cache_message}.\n")
  if specs.any?
    message << "\n#{other_specs_matching_message(specs, matching_part)}"
  end
  raise GemNotFound, message
end

def repository_for(package)
  source_for(package.name)
end

def requirement_satisfied_by?(requirement, spec)
  requirement.satisfied_by?(spec.version) || spec.source.is_a?(Source::Gemspec)
end

def requirement_to_range(requirement)
  ranges = requirement.requirements.map do |(op, version)|
    ver = Resolver::Candidate.new(version).generic!
    platform_ver = Resolver::Candidate.new(version).platform_specific!
    case op
    when "~>"
      name = "~> #{ver}"
      bump = Resolver::Candidate.new(version.bump.to_s + ".A")
      PubGrub::VersionRange.new(:name => name, :min => ver, :max => bump, :include_min => true)
    when ">"
      PubGrub::VersionRange.new(:min => platform_ver)
    when ">="
      PubGrub::VersionRange.new(:min => ver, :include_min => true)
    when "<"
      PubGrub::VersionRange.new(:max => ver)
    when "<="
      PubGrub::VersionRange.new(:max => platform_ver, :include_max => true)
    when "="
      PubGrub::VersionRange.new(:min => ver, :max => platform_ver, :include_min => true, :include_max => true)
    when "!="
      PubGrub::VersionRange.new(:min => ver, :max => platform_ver, :include_min => true, :include_max => true).invert
    else
      raise "bad version specifier: #{op}"
    end
  end
  ranges.inject(&:intersect)
end

def setup_solver
  root = Resolver::Root.new(name_for_explicit_dependency_source)
  root_version = Resolver::Candidate.new(0)
  @all_specs = Hash.new do |specs, name|
    specs[name] = source_for(name).specs.search(name).reject do |s|
      s.dependencies.any? {|d| d.name == name && !d.requirement.satisfied_by?(s.version) } # ignore versions that depend on themselves incorrectly
    end.sort_by {|s| [s.version, s.platform.to_s] }
  end
  @sorted_versions = Hash.new do |candidates, package|
    candidates[package] = if package.root?
      [root_version]
    else
      all_versions_for(package).sort
    end
  end
  root_dependencies = prepare_dependencies(@requirements, @packages)
  @cached_dependencies = Hash.new do |dependencies, package|
    dependencies[package] = if package.root?
      { root_version => root_dependencies }
    else
      Hash.new do |versions, version|
        versions[version] = to_dependency_hash(version.dependencies.reject {|d| d.name == package.name }, @packages)
      end
    end
  end
  logger = Bundler::UI::Shell.new
  logger.level = debug? ? "debug" : "warn"
  [root, logger]
end

def solve_versions(root:, logger:)
  solver = PubGrub::VersionSolver.new(:source => self, :root => root, :logger => logger)
  result = solver.solve
  result.map {|package, version| version.to_specs(package) }.flatten.uniq
rescue PubGrub::SolveFailure => e
  incompatibility = e.incompatibility
  names_to_unlock, names_to_allow_prereleases_for, extended_explanation = find_names_to_relax(incompatibility)
  names_to_relax = names_to_unlock + names_to_allow_prereleases_for
  if names_to_relax.any?
    if names_to_unlock.any?
      Bundler.ui.debug "Found conflicts with locked dependencies. Will retry with #{names_to_unlock.join(", ")} unlocked...", true
      @base.unlock_names(names_to_unlock)
    end
    if names_to_allow_prereleases_for.any?
      Bundler.ui.debug "Found conflicts with dependencies with prereleases. Will retrying considering prereleases for #{names_to_allow_prereleases_for.join(", ")}...", true
      @base.include_prereleases(names_to_allow_prereleases_for)
    end
    root, logger = setup_solver
    Bundler.ui.debug "Retrying resolution...", true
    retry
  end
  explanation = e.message
  if extended_explanation
    explanation << "\n\n"
    explanation << extended_explanation
  end
  raise SolveFailure.new(explanation)
end

def sort_versions(package, versions)
  if versions.size > 1
    @gem_version_promoter.sort_versions(package, versions).reverse
  else
    versions
  end
end

def source_for(name)
  @source_requirements[name] || @source_requirements[:default]
end

def start
  @requirements = @base.requirements
  @packages = @base.packages
  root, logger = setup_solver
  Bundler.ui.info "Resolving dependencies...", true
  solve_versions(:root => root, :logger => logger)
end

def to_dependency_hash(dependencies, packages)
  dependencies.inject({}) do |deps, dep|
    package = packages[dep.name]
    current_req = deps[package]
    new_req = parse_dependency(package, dep.requirement)
    deps[package] = if current_req
      current_req.intersect(new_req)
    else
      new_req
    end
    deps
  end
end

def versions_for(package, range=VersionRange.any)
  versions = range.select_versions(@sorted_versions[package])
  sort_versions(package, versions)
end