module ActiveRecord::ConnectionAdapters::SQLite3::SchemaStatements

def add_check_constraint(table_name, expression, **options)
  alter_table(table_name) do |definition|
    definition.check_constraint(expression, **options)
  end
end

def add_foreign_key(from_table, to_table, **options)
  alter_table(from_table) do |definition|
    to_table = strip_table_name_prefix_and_suffix(to_table)
    definition.foreign_key(to_table, **options)
  end
end

def check_constraints(table_name)
  table_sql = query_value(<<-SQL, "SCHEMA")
    SELECT sql
    FROM sqlite_master
    WHERE name = #{quote(table_name)} AND type = 'table'
    UNION ALL
    SELECT sql
    FROM sqlite_temp_master
    WHERE name = #{quote(table_name)} AND type = 'table'
  SQL
  table_sql.to_s.scan(/CONSTRAINT\s+(?<name>\w+)\s+CHECK\s+\((?<expression>(:?[^()]|\(\g<expression>\))+)\)/i).map do |name, expression|
    CheckConstraintDefinition.new(table_name, expression, name: name)
  end
end

def create_schema_dumper(options)
  SQLite3::SchemaDumper.create(self, options)
end

def create_table_definition(name, **options)
  SQLite3::TableDefinition.new(self, name, **options)
end

def data_source_sql(name = nil, type: nil)
  scope = quoted_scope(name, type: type)
  scope[:type] ||= "'table','view'"
  sql = +"SELECT name FROM sqlite_master WHERE name <> 'sqlite_sequence'"
  sql << " AND name = #{scope[:name]}" if scope[:name]
  sql << " AND type IN (#{scope[:type]})"
  sql
end

def indexes(table_name)
  exec_query("PRAGMA index_list(#{quote_table_name(table_name)})", "SCHEMA").filter_map do |row|
    # Indexes SQLite creates implicitly for internal use start with "sqlite_".
    # See https://www.sqlite.org/fileformat2.html#intschema
    next if row["name"].start_with?("sqlite_")
    index_sql = query_value(<<~SQL, "SCHEMA")
      SELECT sql
      FROM sqlite_master
      WHERE name = #{quote(row['name'])} AND type = 'index'
      UNION ALL
      SELECT sql
      FROM sqlite_temp_master
      WHERE name = #{quote(row['name'])} AND type = 'index'
    SQL
    /\bON\b\s*"?(\w+?)"?\s*\((?<expressions>.+?)\)(?:\s*WHERE\b\s*(?<where>.+))?(?:\s*\/\*.*\*\/)?\z/i =~ index_sql
    columns = exec_query("PRAGMA index_info(#{quote(row['name'])})", "SCHEMA").map do |col|
      col["name"]
    end
    orders = {}
    if columns.any?(&:nil?) # index created with an expression
      columns = expressions
    else
      # Add info on sort order for columns (only desc order is explicitly specified,
      # asc is the default)
      if index_sql # index_sql can be null in case of primary key indexes
        index_sql.scan(/"(\w+)" DESC/).flatten.each { |order_column|
          orders[order_column] = :desc
        }
      end
    end
    IndexDefinition.new(
      table_name,
      row["name"],
      row["unique"] != 0,
      columns,
      where: where,
      orders: orders
    )
  end
end

def new_column_from_field(table_name, field)
  default = field["dflt_value"]
  type_metadata = fetch_type_metadata(field["type"])
  default_value = extract_value_from_default(default)
  default_function = extract_default_function(default_value, default)
  Column.new(
    field["name"],
    default_value,
    type_metadata,
    field["notnull"].to_i == 0,
    default_function,
    collation: field["collation"]
  )
end

def quoted_scope(name = nil, type: nil)
  type = \
    case type
    when "BASE TABLE"
      "'table'"
    when "VIEW"
      "'view'"
    end
  scope = {}
  scope[:name] = quote(name) if name
  scope[:type] = type if type
  scope
end

def remove_check_constraint(table_name, expression = nil, **options)
  check_constraints = check_constraints(table_name)
  chk_name_to_delete = check_constraint_for!(table_name, expression: expression, **options).name
  check_constraints.delete_if { |chk| chk.name == chk_name_to_delete }
  alter_table(table_name, foreign_keys(table_name), check_constraints)
end

def remove_foreign_key(from_table, to_table = nil, **options)
  return if options.delete(:if_exists) == true && !foreign_key_exists?(from_table, to_table)
  to_table ||= options[:to_table]
  options = options.except(:name, :to_table, :validate)
  foreign_keys = foreign_keys(from_table)
  fkey = foreign_keys.detect do |fk|
    table = to_table || begin
      table = options[:column].to_s.delete_suffix("_id")
      Base.pluralize_table_names ? table.pluralize : table
    end
    table = strip_table_name_prefix_and_suffix(table)
    fk_to_table = strip_table_name_prefix_and_suffix(fk.to_table)
    fk_to_table == table && options.all? { |k, v| fk.options[k].to_s == v.to_s }
  end || raise(ArgumentError, "Table '#{from_table}' has no foreign key for #{to_table || options}")
  foreign_keys.delete(fkey)
  alter_table(from_table, foreign_keys)
end

def schema_creation
  SQLite3::SchemaCreation.new(self)
end

def validate_index_length!(table_name, new_name, internal = false)
  super unless internal
end