require 'yaml'
require 'erb'
require 'tmpdir'

# Multi-database test runner
# ==========================
# When database.yml contains more than one `test*` configuration, every
# standard test task (test, test:models, test:system, …) is automatically
# rewritten to run the full suite against EACH configured database in turn.
#
# Convention — any top-level key that starts with "test" and holds a Hash:
#
#   test:           ← required primary database
#     adapter: mysql2
#     database: fixinme_test
#     ...
#
#   test_sqlite:    ← optional additional databases
#     adapter: sqlite3
#     database: db/fixinme_test.sqlite3
#
#   test_pg:
#     adapter: postgresql
#     ...
#
# A single-database setup is unchanged: every task behaves exactly as before.
#
# The mechanism uses RAILS_DATABASE_YML — an env var read by
# config/application.rb(.dist) to override Rails' database config path before
# initialisation, giving each subprocess a clean, isolated database config.

module MultiDbTests
  ADAPTER_GEMS = {
    'mysql2'      => 'mysql2',
    'sqlite3'     => 'sqlite3',
    'postgresql'  => 'pg',
    'pg'          => 'pg',
  }.freeze

  ADAPTER_BUNDLE_GROUPS = {
    'mysql2'      => 'mysql',
    'sqlite3'     => 'sqlite',
    'postgresql'  => 'postgresql',
    'pg'          => 'postgresql',
  }.freeze

  # Rake task names generated by railties/lib/rails/test_unit/testing.rake
  # that use run_from_rake — these are the ones we rewrite.
  WRAPPED_TASKS = (
    ['test'] +
    Rails::TestUnit::Runner::TEST_FOLDERS.map { |f| "test:#{f}" } +
    %w[test:all test:system test:generators test:units test:functionals]
  ).freeze

  class << self
    # Returns {name => config_hash} for every key starting with "test".
    def test_configs
      @test_configs ||= begin
        db_file = Rails.root.join('config', 'database.yml')
        all     = YAML.safe_load(ERB.new(db_file.read).result, aliases: true) || {}
        all.select { |k, v| k.to_s.start_with?('test') && v.is_a?(Hash) }
      end
    end

    def non_test_configs
      @non_test_configs ||= begin
        db_file = Rails.root.join('config', 'database.yml')
        all     = YAML.safe_load(ERB.new(db_file.read).result, aliases: true) || {}
        all.reject { |k, _| k.to_s.start_with?('test') }
      end
    end

    # Run rails +task_name+ for every configured test database.
    # Called from the rewritten rake task actions.
    def run(task_name)
      cfgs    = test_configs
      results = {}

      cfgs.each do |db_name, config|
        adapter = config['adapter'].to_s
        puts "\n#{'─' * 64}"
        puts "  #{task_name}  ·  #{db_name}  (#{adapter})"
        puts '─' * 64

        unless adapter_available?(adapter)
          warn "  SKIPPED — '#{adapter}' gem not in bundle.\n" \
               "  Run: bundle config --local with \"#{current_with} #{adapter_group(adapter)}\""
          results[db_name] = :skipped
          next
        end

        Dir.mktmpdir('rails_test_') do |tmpdir|
          tmp_yml = File.join(tmpdir, 'database.yml')
          File.write(tmp_yml, non_test_configs.merge('test' => config).to_yaml)
          env = { 'RAILS_DATABASE_YML' => tmp_yml }

          if system(env, 'bundle exec rails db:test:prepare')
            results[db_name] = system(env, 'rails', task_name) ? :pass : :fail
          else
            results[db_name] = :prepare_failed
          end
        end
      end

      print_summary(cfgs, results)

      failed = results.count { |_, s| [:fail, :prepare_failed].include?(s) }
      exit(false) if failed > 0
    end

    private

    def adapter_available?(adapter)
      require ADAPTER_GEMS.fetch(adapter, adapter)
      true
    rescue LoadError
      false
    end

    def adapter_group(adapter)
      ADAPTER_BUNDLE_GROUPS.fetch(adapter, adapter)
    end

    def current_with
      (Bundler.settings[:with] || '').split(':').join(' ')
    end

    def print_summary(cfgs, results)
      return if results.size <= 1  # no summary for single-DB runs

      puts "\n#{'═' * 64}"
      puts '  SUMMARY'
      puts '═' * 64
      results.each do |db_name, status|
        adapter = cfgs.dig(db_name, 'adapter') || '?'
        icon    = status == :pass ? '✓' : (status == :skipped ? '–' : '✗')
        label   = { pass: 'PASS', fail: 'FAIL',
                    prepare_failed: 'PREPARE FAILED', skipped: 'SKIPPED' }[status]
        puts "  #{icon}  #{db_name.ljust(26)} (#{adapter.ljust(12)})  #{label}"
      end
      puts '═' * 64
    end
  end
end

# Rewrite every standard test task to run against all configured databases.
# This file loads after railties/testing.rake, so all tasks already exist.
# Single-database setups are completely unaffected.
if MultiDbTests.test_configs.size > 1
  MultiDbTests::WRAPPED_TASKS.each do |task_name|
    next unless Rake::Task.task_defined?(task_name)

    Rake::Task[task_name].clear_actions
    Rake::Task[task_name].enhance do
      MultiDbTests.run(task_name)
    end
  end
end