# frozen_string_literal: true

require "stringio"

module ActiveRecord
  # = Active Record Schema Dumper
  #
  # This class is used to dump the database schema for some connection to some
  # output format (i.e., ActiveRecord::Schema).
  class SchemaDumper # :nodoc:
    private_class_method :new

    ##
    # :singleton-method:
    # A list of tables which should not be dumped to the schema.
    # Acceptable values are strings and regexps.
    cattr_accessor :ignore_tables, default: []

    ##
    # :singleton-method:
    # Specify a custom regular expression matching foreign keys which name
    # should not be dumped to db/schema.rb.
    cattr_accessor :fk_ignore_pattern, default: /^fk_rails_[0-9a-f]{10}$/

    ##
    # :singleton-method:
    # Specify a custom regular expression matching check constraints which name
    # should not be dumped to db/schema.rb.
    cattr_accessor :chk_ignore_pattern, default: /^chk_rails_[0-9a-f]{10}$/

    ##
    # :singleton-method:
    # Specify a custom regular expression matching exclusion constraints which name
    # should not be dumped to db/schema.rb.
    cattr_accessor :excl_ignore_pattern, default: /^excl_rails_[0-9a-f]{10}$/

    ##
    # :singleton-method:
    # Specify a custom regular expression matching unique constraints which name
    # should not be dumped to db/schema.rb.
    cattr_accessor :unique_ignore_pattern, default: /^uniq_rails_[0-9a-f]{10}$/

    class << self
      def dump(pool = ActiveRecord::Base.connection_pool, stream = $stdout, config = ActiveRecord::Base)
        pool.with_connection do |connection|
          connection.create_schema_dumper(generate_options(config)).dump(stream)
        end
        stream
      end

      private
        def generate_options(config)
          {
            table_name_prefix: config.table_name_prefix,
            table_name_suffix: config.table_name_suffix
          }
        end
    end

    def dump(stream)
      header(stream)
      schemas(stream)
      extensions(stream)
      types(stream)
      tables(stream)
      virtual_tables(stream)
      trailer(stream)
      stream
    end

    private
      attr_accessor :table_name

      def initialize(connection, options = {})
        @connection = connection
        @version = connection.pool.migration_context.current_version rescue nil
        @options = options
        @ignore_tables = [
          ActiveRecord::Base.schema_migrations_table_name,
          ActiveRecord::Base.internal_metadata_table_name,
          self.class.ignore_tables
        ].flatten
      end

      # turns 20170404131909 into "2017_04_04_131909"
      def formatted_version
        stringified = @version.to_s
        return stringified unless stringified.length == 14
        stringified.insert(4, "_").insert(7, "_").insert(10, "_")
      end

      def define_params
        @version ? "version: #{formatted_version}" : ""
      end

      def header(stream)
        stream.puts <<~HEADER
          # This file is auto-generated from the current state of the database. Instead
          # of editing this file, please use the migrations feature of Active Record to
          # incrementally modify your database, and then regenerate this schema definition.
          #
          # This file is the source Rails uses to define your schema when running `bin/rails
          # db:schema:load`. When creating a new database, `bin/rails db:schema:load` tends to
          # be faster and is potentially less error prone than running all of your
          # migrations from scratch. Old migrations may fail to apply correctly if those
          # migrations use external dependencies or application code.
          #
          # It's strongly recommended that you check this file into your version control system.

          ActiveRecord::Schema[#{ActiveRecord::Migration.current_version}].define(#{define_params}) do
        HEADER
      end

      def trailer(stream)
        stream.puts "end"
      end

      # extensions are only supported by PostgreSQL
      def extensions(stream)
      end

      # (enum) types are only supported by PostgreSQL
      def types(stream)
      end

      # schemas are only supported by PostgreSQL
      def schemas(stream)
      end

      # virtual tables are only supported by SQLite
      def virtual_tables(stream)
      end

      def tables(stream)
        sorted_tables = @connection.tables.sort

        not_ignored_tables = sorted_tables.reject { |table_name| ignored?(table_name) }

        not_ignored_tables.each_with_index do |table_name, index|
          table(table_name, stream)
          stream.puts if index < not_ignored_tables.count - 1
        end

        # dump foreign keys at the end to make sure all dependent tables exist.
        if @connection.supports_foreign_keys?
          foreign_keys_stream = StringIO.new
          not_ignored_tables.each do |tbl|
            foreign_keys(tbl, foreign_keys_stream)
          end

          foreign_keys_string = foreign_keys_stream.string
          stream.puts if foreign_keys_string.length > 0

          stream.print foreign_keys_string
        end
      end

      def table(table, stream)
        columns = @connection.columns(table)
        begin
          self.table_name = table

          tbl = StringIO.new

          # first dump primary key column
          pk = @connection.primary_key(table)

          tbl.print "  create_table #{remove_prefix_and_suffix(table).inspect}"

          case pk
          when String
            tbl.print ", primary_key: #{pk.inspect}" unless pk == "id"
            pkcol = columns.detect { |c| c.name == pk }
            pkcolspec = column_spec_for_primary_key(pkcol)
            unless pkcolspec.empty?
              if pkcolspec != pkcolspec.slice(:id, :default)
                pkcolspec = { id: { type: pkcolspec.delete(:id), **pkcolspec }.compact }
              end
              tbl.print ", #{format_colspec(pkcolspec)}"
            end
          when Array
            tbl.print ", primary_key: #{pk.inspect}"
          else
            tbl.print ", id: false"
          end

          table_options = @connection.table_options(table)
          if table_options.present?
            tbl.print ", #{format_options(table_options)}"
          end

          tbl.puts ", force: :cascade do |t|"

          # then dump all non-primary key columns
          columns.each do |column|
            raise StandardError, "Unknown type '#{column.sql_type}' for column '#{column.name}'" unless @connection.valid_type?(column.type)
            next if column.name == pk

            type, colspec = column_spec(column)
            if type.is_a?(Symbol)
              tbl.print "    t.#{type} #{column.name.inspect}"
            else
              tbl.print "    t.column #{column.name.inspect}, #{type.inspect}"
            end
            tbl.print ", #{format_colspec(colspec)}" if colspec.present?
            tbl.puts
          end

          indexes_in_create(table, tbl)
          remaining = check_constraints_in_create(table, tbl) if @connection.supports_check_constraints?
          exclusion_constraints_in_create(table, tbl) if @connection.supports_exclusion_constraints?
          unique_constraints_in_create(table, tbl) if @connection.supports_unique_constraints?

          tbl.puts "  end"

          if remaining
            tbl.puts
            tbl.print remaining.string
          end

          stream.print tbl.string
        rescue => e
          stream.puts "# Could not dump table #{table.inspect} because of following #{e.class}"
          stream.puts "#   #{e.message}"
          stream.puts
        ensure
          self.table_name = nil
        end
      end

      # Keep it for indexing materialized views
      def indexes(table, stream)
        if (indexes = @connection.indexes(table)).any?
          add_index_statements = indexes.map do |index|
            table_name = remove_prefix_and_suffix(index.table).inspect
            "  add_index #{([table_name] + index_parts(index)).join(', ')}"
          end

          stream.puts add_index_statements.sort.join("\n")
          stream.puts
        end
      end

      def indexes_in_create(table, stream)
        if (indexes = @connection.indexes(table)).any?
          if @connection.supports_exclusion_constraints? && (exclusion_constraints = @connection.exclusion_constraints(table)).any?
            exclusion_constraint_names = exclusion_constraints.collect(&:name)

            indexes = indexes.reject { |index| exclusion_constraint_names.include?(index.name) }
          end

          if @connection.supports_unique_constraints? && (unique_constraints = @connection.unique_constraints(table)).any?
            unique_constraint_names = unique_constraints.collect(&:name)

            indexes = indexes.reject { |index| unique_constraint_names.include?(index.name) }
          end

          index_statements = indexes.map do |index|
            "    t.index #{index_parts(index).join(', ')}"
          end
          stream.puts index_statements.sort.join("\n")
        end
      end

      def index_parts(index)
        index_parts = [
          index.columns.inspect,
          "name: #{index.name.inspect}",
        ]
        index_parts << "unique: true" if index.unique
        index_parts << "length: #{format_index_parts(index.lengths)}" if index.lengths.present?
        index_parts << "order: #{format_index_parts(index.orders)}" if index.orders.present?
        index_parts << "opclass: #{format_index_parts(index.opclasses)}" if index.opclasses.present?
        index_parts << "where: #{index.where.inspect}" if index.where
        index_parts << "using: #{index.using.inspect}" if !@connection.default_index_type?(index)
        index_parts << "include: #{index.include.inspect}" if index.include
        index_parts << "nulls_not_distinct: #{index.nulls_not_distinct.inspect}" if index.nulls_not_distinct
        index_parts << "type: #{index.type.inspect}" if index.type
        index_parts << "comment: #{index.comment.inspect}" if index.comment
        index_parts
      end

      def check_constraints_in_create(table, stream)
        if (check_constraints = @connection.check_constraints(table)).any?
          check_valid, check_invalid = check_constraints.partition { |chk| chk.validate? }

          unless check_valid.empty?
            check_constraint_statements = check_valid.map do |check|
              "    t.check_constraint #{check_parts(check).join(', ')}"
            end

            stream.puts check_constraint_statements.sort.join("\n")
          end

          unless check_invalid.empty?
            remaining = StringIO.new
            table_name = remove_prefix_and_suffix(table).inspect

            add_check_constraint_statements = check_invalid.map do |check|
              "  add_check_constraint #{([table_name] + check_parts(check)).join(', ')}"
            end

            remaining.puts add_check_constraint_statements.sort.join("\n")
            remaining
          end
        end
      end

      def check_parts(check)
        check_parts = [ check.expression.inspect ]
        check_parts << "name: #{check.name.inspect}" if check.export_name_on_schema_dump?
        check_parts << "validate: #{check.validate?.inspect}" unless check.validate?
        check_parts
      end

      def foreign_keys(table, stream)
        if (foreign_keys = @connection.foreign_keys(table)).any?
          add_foreign_key_statements = foreign_keys.map do |foreign_key|
            parts = [
              "add_foreign_key #{remove_prefix_and_suffix(foreign_key.from_table).inspect}",
              remove_prefix_and_suffix(foreign_key.to_table).inspect,
            ]

            if foreign_key.column != @connection.foreign_key_column_for(foreign_key.to_table, "id")
              parts << "column: #{foreign_key.column.inspect}"
            end

            if foreign_key.custom_primary_key?
              parts << "primary_key: #{foreign_key.primary_key.inspect}"
            end

            if foreign_key.export_name_on_schema_dump?
              parts << "name: #{foreign_key.name.inspect}"
            end

            parts << "on_update: #{foreign_key.on_update.inspect}" if foreign_key.on_update
            parts << "on_delete: #{foreign_key.on_delete.inspect}" if foreign_key.on_delete
            parts << "deferrable: #{foreign_key.deferrable.inspect}" if foreign_key.deferrable
            parts << "validate: #{foreign_key.validate?.inspect}" unless foreign_key.validate?

            "  #{parts.join(', ')}"
          end

          stream.puts add_foreign_key_statements.sort.join("\n")
        end
      end

      def format_colspec(colspec)
        colspec.map do |key, value|
          "#{key}: #{ value.is_a?(Hash) ? "{ #{format_colspec(value)} }" : value }"
        end.join(", ")
      end

      def format_options(options)
        options.map { |key, value| "#{key}: #{value.inspect}" }.join(", ")
      end

      def format_index_parts(options)
        if options.is_a?(Hash)
          "{ #{format_options(options)} }"
        else
          options.inspect
        end
      end

      def remove_prefix_and_suffix(table)
        # This method appears at the top when profiling active_record test cases run.
        # Avoid costly calculation when there are no prefix and suffix.
        return table if @options[:table_name_prefix].blank? && @options[:table_name_suffix].blank?

        prefix = Regexp.escape(@options[:table_name_prefix].to_s)
        suffix = Regexp.escape(@options[:table_name_suffix].to_s)
        table.sub(/\A#{prefix}(.+)#{suffix}\z/, "\\1")
      end

      def ignored?(table_name)
        @ignore_tables.any? do |ignored|
          ignored === remove_prefix_and_suffix(table_name)
        end
      end
  end
end
