module PgGraph::Data

  class SqlRender
    attr_reader :database

    attr_reader :format
    def format=(format)
      constrain format, lambda { |v| [:sql, :exec, :psql] }, "Illegal value"
      @format = format
    end

    # Which data to delete:
    #   none - don't delete any data
    #   touched - delete data for tables in the fox file
    #   recursive - delete data for table in the fox file including recursively depending tables
    #   all - delete data from the whole database
    attr_reader :delete
      
    # +ids+ is a map from table UID to ID. Records with larger IDs will
    # be emitted as insert statements, records with IDs less or equal to the
    # given ID is emitted as update statements
    #
    # +delete+ control which tables are deleted. It can be :none, :touched,
    # :recursive, :all Only records with an ID greater than the corresponding
    # ID from +ids+ will be deleted
    #
    # +files+ is a list of source file names to be included in the psql SQL
    # header as documentation. It can be set explicitly when #to_a or #to_h is
    # called (FIXME: is this used?)
    def initialize(database, format, ids: {}, delete: :all, files: [])
#     puts "SqlRender#initialize"
#     puts "  format: #{format.inspect}"
#     puts "  ids: #{ids.inspect}"
#     puts "  delete: #{delete.inspect}"
#     puts "  files: #{files.inspect}"
      constrain database, Database
      constrain ids, String => Integer
      @database = database
      self.format = format
      (@ids = ids.dup).default = 0
      @delete = delete
      @files = files

      @tables = database.schemas.map(&:tables).flatten.sort
      @insert_tables = []
      @update_tables = []
      @insert_records = {}
      @update_records = []
      @tables.each { |table|
        next if table.empty?
        @insert_tables << table if table.max_id > @ids[table.uid]
        @update_tables << table if table.ids.min || 0 <= @ids[table.uid]
        inserts, updates = table.records.partition { |record| record.id > @ids[table.uid] }
        @insert_records[table] = inserts if !inserts.empty?
        @update_records += updates
      }
      @table_uids = @tables.select { |table| !table.empty? }.map(&:uid)
      @materialized_views = @tables.map(&:type).map(&:depending_materialized_views).flatten.uniq
    end

    def to_a(files = @files)
      case format
        when :sql; to_sql.flatten
        when :exec; to_exec.flatten
        when :psql; to_psql(files).flatten.compact
      end
    end

    def to_s(files = @files)
      case format
        when :sql; to_a.join("\n")
        when :exec; to_a.join("\n")
        when :psql; to_psql(files).map { |group| group.join("\n") }.join("\n\n") 
      end
    end

    def to_h
      @to_h ||= {
        disable: render_triggers(:disable),
        delete: render_deletes(delete),
        update: render_updates,
        insert: render_inserts,
        restart: render_restart_sequences,
        enable: render_triggers(:enable),
        refresh: render_refresh_materialized_views
      }
    end

  protected
    # Returns a single-element array of array of SQL statements
    def to_sql
      [to_h[:delete] + to_h[:update] + to_h[:insert]]
    end

    # Returns an array of non-empty arrays of SQL statements
    def to_exec() to_h.values.reject(&:empty?) end

    # Returns an array of arrays of SQL statements
    def to_psql(files = [])
      [render_psql_header(files), render_begin] + to_exec.select { |a| !a.empty? } + [render_commit]
    end

    def render_psql_header(files = [])
      if files.empty?
        files_text = ""
      else
        files_text = " from " + files.join(", ")
      end
      [
          "-- Auto-generated by fox(1)" + files_text,
          "",
          "\\set QUIET",
          "\\set ON_ERROR_STOP"
      ]
    end

    def render_begin() 
      [ "begin;" ]
    end

    def render_truncate()
      @tables.empty? ? [] : [ "truncate #{@tables.map(&:uid).join(", ")} restart identity cascade;" ]
    end

    # :call-seq:
    #   render_triggers(arg)
    #
    # +arg+ can be :disable or :enable
    #
    def render_triggers(arg)
      [:disable, :enable].include?(arg) or raise Error, "Illegal value"
      tables = @with_deletes ? @tables : @tables.reject(&:empty?)
      tables.map { |table| "alter table #{table.uid} #{arg} trigger all;" }
    end

    def render_deletes(kind)
      table_uids = 
          case kind
            when :none; []
            when :touched; @tables.reject(&:empty?).map(&:uid)
            when :recursive
              tables = @tables.reject(&:empty?)
              (tables.map(&:uid) + tables.map { |table| table.type.depending_tables.map(&:uid) }.flatten).uniq
            when :all; @tables.map(&:uid)
          else
            raise ArgumentError
          end
      table_uids.map { |uid|
        if !@ids.key?(uid)
          "delete from #{uid};"
        else
          "delete from #{uid} where id > #{@ids[uid]};"
        end
      }
    end

    def render_updates
      @update_records.map { |record|
        "update #{record.table.uid} set " \
            + record.value_columns
                .select { |column| !column.type.primary_key? }
                .map { |column| "#{column.name} = #{render_value(column)}" }
                .join(", ") + " " \
            + "where id = #{record.id};" 
      }
    end

    def render_inserts
      @insert_records.map { |table, records|
        "insert into #{table.uid} (#{table.type.value_columns.map(&:name).join(', ')}) values " + \
        records.sort_by(&:id).map { |record|
          "(" +
              record.type.value_columns.map { |column_type|
                record.field?(column_type.name) ? render_value(record[column_type.name]) : 'DEFAULT'
              }.join(", ") +
          ")"
        }.join(", ") + ";"
      }
    end

    def render_literal(value, element_type = nil)
      case value
        when TrueClass, FalseClass; value.to_s
        when Integer; value.to_s
        when String; "'#{PG::Connection.escape_string(value.to_s)}'"
        when NilClass; "NULL"
        when Array
          if value.empty?
            "ARRAY[]::#{element_type}[]" # FIXME: Doesn't handle multidimensional arrays
          else
            "ARRAY[" + value.map { |v| render_literal(v) }.join(",") + "]"
          end
        when Hash
          "'" + value.to_json + "'"
        when Time
          "'" + value.to_s + "'"
      else
        raise "Oops: got #{value.inspect} (#{value.class})"
      end
    end

    def render_value(column)
      type = column.value_type.type
      if type.array?
        render_literal(column.value, type.element_type)
      else
        render_literal(column.value)
      end
    end

    def render_restart_sequences()
      @tables.map { |table|
        if table.type.subtable?
          nil
        elsif table.empty? && @with_deletes || !table.empty? && table.max_id > @ids[table.uid]
          "alter table #{table.uid} alter column id restart with #{table.max_id+1};"
        else
          nil
        end
      }.compact
    end

    def render_refresh_materialized_views()
      if @materialized_views.empty?
        []
      else
        @materialized_views.map { |view| "refresh materialized view #{view.uid};" }
      end
    end

    def render_commit() 
      [ "commit;" ]
    end
  end
end