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

namespace :test do
  desc <<~DESC
    Run the full test suite against every test database configured in database.yml.

    Any top-level key that starts with "test" and contains a Hash is treated as a
    test database configuration:

      test:           # always required — the primary test database
        adapter: mysql2
        database: fixinme_test
        ...

      test_sqlite:    # optional additional databases
        adapter: sqlite3
        database: db/fixinme_test.sqlite3

      test_pg:
        adapter: postgresql
        database: fixinme_test
        ...

    For each database the task will:
      1. Check that the required adapter gem is available (skip with warning if not).
      2. Run `rails db:test:prepare` to create/migrate the database.
      3. Run `rails test` and record pass/fail.

    A summary is printed at the end. The task exits non-zero if any database fails.
  DESC
  task :all_databases do
    db_file    = Rails.root.join('config', 'database.yml')
    all        = YAML.safe_load(ERB.new(db_file.read).result, aliases: true) || {}
    test_cfgs  = all.select { |k, v| k.to_s.start_with?('test') && v.is_a?(Hash) }
    non_test   = all.reject { |k, _| k.to_s.start_with?('test') }

    abort "No test database configurations found in #{db_file}." if test_cfgs.empty?

    results = {}

    test_cfgs.each do |name, config|
      adapter = config['adapter'].to_s

      puts "\n#{'─' * 64}"
      puts "  #{name}  (adapter: #{adapter})"
      puts '─' * 64

      unless adapter_available?(adapter)
        puts "  SKIPPED — gem for '#{adapter}' adapter not available in bundle."
        puts "  Add it to Gemfile (e.g. `bundle config --local with #{adapter_group(adapter)}`)"
        results[name] = :skipped
        next
      end

      Dir.mktmpdir('rails_test_db_') do |tmpdir|
        tmp_yml = File.join(tmpdir, 'database.yml')
        # Write a standalone database.yml with just this config as `test:`
        # (non-test configs are preserved so boot doesn't fail on `production:` lookup)
        File.write(tmp_yml, non_test.merge('test' => config).to_yaml)

        env = { 'RAILS_DATABASE_YML' => tmp_yml }

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

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

    failed = results.count { |_, s| s == :fail || s == :prepare_failed }
    abort "\n  #{failed} database(s) failed." if failed > 0
  end
end

private

# Returns true if the gem required for this adapter is loadable.
ADAPTER_GEMS = {
  'mysql2'     => 'mysql2',
  'sqlite3'    => 'sqlite3',
  'postgresql' => 'pg',
  'pg'         => 'pg',
}.freeze

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

# Returns the Bundler group name that installs the adapter gem.
ADAPTER_GROUPS = {
  'mysql2'     => 'mysql',
  'sqlite3'    => 'sqlite',
  'postgresql' => 'postgresql',
  'pg'         => 'postgresql',
}.freeze

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