require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  gem "activerecord", "~> 6.1.3"
  gem "mysql2"
end

require "active_record"
require "minitest/autorun"
require "logger"

ActiveRecord::Base.establish_connection(
  adapter: "mysql2",
  database: 'check_constraint_schema_dump_bug',
  charset: 'utfmb4',
  encoding: 'utf8mb4',
  collation: 'utf8mb4_unicode_ci',
  username: ENV.fetch("MYSQL_USERNAME") { "rails" },
  password: ENV.fetch("MYSQL_PASSWORD") { "" },
  host: ENV.fetch("MYSQL_HOST") { "127.0.0.1" },
  port: ENV.fetch("MYSQL_PORT") { 3306 }
)
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts, force: true do |t|
    t.string :title
    t.check_constraint "(title <> 'forbidden_title')"
  end
end

class BugTest < Minitest::Test
  def test_adapter_check_constraint_quoting
    expected = %q(`title` <> _utf8mb4'forbidden_title')

    assert_equal ActiveRecord::Base.connection.check_constraints('posts').first.expression, expected
  end

  def test_schema_dumper_not_including_wrong_quotes
    dumped_schema = ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, StringIO.new).string

    wrong = %q(t.check_constraint "`title` <> _utf8mb4\\\\'forbidden_title\\\\'")
    refute_includes dumped_schema, wrong
  end

  def test_schema_dumper_including_correct_quotes
    dumped_schema = ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, StringIO.new).string

    expected = %q(t.check_constraint "`title` <> _utf8mb4'forbidden_title'")
    assert_includes dumped_schema, expected
  end
end

create_table :posts, force: true do |t|
  t.string :title
  t.check_constraint "(title <> 'forbidden_title')"
end

create_table "posts", charset: "utf8mb4", force: :cascade do |t|
  t.string "title"
  t.check_constraint "`title` <> _utf8mb4'forbidden_title'"
end

create_table "posts", charset: "utf8mb4", force: :cascade do |t|
  t.string "title"
  t.check_constraint "`title` <> _utf8mb4\\'forbidden_title\\'" # <-- Notice the slashes
end

module ActiveRecord
  module ConnectionAdapters
    class AbstractMysqlAdapter
      def check_constraints(table_name)
        if supports_check_constraints?
          scope = quoted_scope(table_name)

          chk_info = exec_query(<<~SQL, "SCHEMA")
            SELECT cc.constraint_name AS 'name',
                  cc.check_clause AS 'expression'
            FROM information_schema.check_constraints cc
            JOIN information_schema.table_constraints tc
            USING (constraint_schema, constraint_name)
            WHERE tc.table_schema = #{scope[:schema]}
              AND tc.table_name = #{scope[:name]}
              AND cc.constraint_schema = #{scope[:schema]}
          SQL

          chk_info.map do |row|
            options = {
              name: row["name"]
            }
            expression = row["expression"].gsub("\\'", "'") # <-- replace duplicate escaping
            expression = expression[1..-2] unless mariadb? # remove parentheses added by mysql
            CheckConstraintDefinition.new(table_name, expression, options)
          end
        else
          raise NotImplementedError
        end
      end
    end
  end
end