require "active_record"

require "query_helper/version"
require "query_helper/filter"
require "query_helper/column_map"
require "query_helper/associations"
require "query_helper/query_helper_concern"
require "query_helper/sql_parser"
require "query_helper/sql_manipulator"
require "query_helper/sql_filter"
require "query_helper/sql_sort"
require "query_helper/invalid_query_error"

class QueryHelper

  attr_accessor :model, :bind_variables, :sql_filter, :sql_sort, :page, :per_page, :single_record, :associations, :as_json_options, :executed_query, :api_payload, :preload
  attr_reader :query

  def initialize(
    model: nil, # the model to run the query against
    query: nil, # a sql string or an active record query
    bind_variables: {}, # a list of bind variables to be embedded into the query
    sql_filter: SqlFilter.new(), # a SqlFilter object
    sql_sort: SqlSort.new(), # a SqlSort object
    page: nil, # define the page you want returned
    per_page: nil, # define how many results you want per page
    single_record: false, # whether or not you expect the record to return a single result, if toggled, only the first result will be returned
    associations: [], # a list of activerecord associations you'd like included in the payload
    as_json_options: nil, # a list of as_json options you'd like run before returning the payload
    custom_mappings: {}, # custom keyword => sql_expression mappings
    api_payload: false, # Return the paginated payload or simply return the result array
    preload: [] # preload activerecord associations - used instead of `associations` when you don't want them included in the payload
  )
    @query = query.class < ActiveRecord::Relation ? query.to_sql : query
    @model = query.class < ActiveRecord::Relation ? query.base_class : model
    @bind_variables = bind_variables
    @sql_filter = sql_filter
    @sql_sort = sql_sort
    @page = page.to_i if page
    @per_page = per_page.to_i if per_page
    @single_record = single_record
    @associations = associations
    @as_json_options = as_json_options
    @custom_mappings = custom_mappings
    @api_payload = api_payload
    @preload = preload

    if @page && @per_page
      # Determine limit and offset
      limit = @per_page
      offset = (@page - 1) * @per_page

      # Merge limit/offset variables into bind_variables
      @bind_variables.merge!({limit: limit, offset: offset})
    end
  end

  def update(
    query: nil,
    model: nil,
    bind_variables: {},
    filters: [],
    associations: [],
    as_json_options: nil,
    single_record: nil,
    custom_mappings: nil,
    preload: []
  )
    @query = query.class < ActiveRecord::Relation ? query.to_sql : query if query
    @model = query.class < ActiveRecord::Relation ? query.base_class : model if model || query
    @bind_variables.merge!(bind_variables)
    filters.each{ |f| add_filter(**f) }
    @associations = @associations | associations
    @single_record = single_record if single_record
    @as_json_options = as_json_options if as_json_options
    @custom_mappings = custom_mappings if custom_mappings
    @preload = preload if preload
    return self
  end

  def add_filter(operator_code:, criterion:, comparate:)
    @sql_filter.filter_values["comparate"] = { operator_code => criterion }
  end

  def query=(value)
    if value.class < ActiveRecord::Relation
      @query = value.to_sql
      @model = value.base_class
    else
      @query = value
    end
    return ""
  end

  def build_query
    # Create column maps to be used by the filter and sort objects
    column_maps = create_column_maps()

    @sql_filter.column_maps = column_maps
    @sql_sort.column_maps = column_maps

    # create the filters from the column maps
    @sql_filter.create_filters()

    # merge the filter bind variables into the query bind variables
    @bind_variables.merge!(@sql_filter.bind_variables)

    # Execute Sql Query
    manipulator = SqlManipulator.new(
      sql: @query,
      where_clauses: @sql_filter.where_clauses,
      having_clauses:  @sql_filter.having_clauses,
      order_by_clauses: @sql_sort.parse_sort_string,
      include_limit_clause: @page && @per_page ? true : false,
      additional_select_clauses:  @sql_sort.select_strings
    )
    manipulator.build()
  end

  def to_json(args)
    JSON.generate(results)
  end

  def to_sql
    query = build_query()
    return query if @bind_variables.length == 0
    begin
      return @model.sanitize_sql_array([query, @bind_variables])
    rescue NoMethodError 
      # sanitize_sql_array is a protected method before Rails v5.2.3
      return @model.send(:sanitize_sql_array, [query, @bind_variables])
    end
  end

  def view_query
    to_sql
  end

  def execute_query
    query = build_query()
    @results = @model.find_by_sql([query, @bind_variables]) # Execute Sql Query
    @results = @results.first if @single_record # Return a single result if requested

    determine_count()
    preload_associations()
    load_associations()
    clean_results()
  end

  def results
    execute_query()
    return paginated_results() if @api_payload
    return @results
  end

  private

    def paginated_results
      { pagination: pagination_results(),
        data: @results }
    end

    def determine_count
      # Determine total result count (unpaginated)
      if @single_record
        @count = 1
      else
        @count = @page && @per_page && @results.length > 0 ? @results.first["_query_full_count"] : @results.length
      end
    end

    def load_associations
      @results = Associations.load_associations(
        payload: @results,
        associations: @associations,
        as_json_options: @as_json_options
      )
    end

    def preload_associations
      Associations.preload_associations(
        payload: @results,
        preload: @preload
      )
    end

    def clean_results
      @results.map!{ |r| r.except("_query_full_count") } if @page && @per_page && !@single_record
    end

    def pagination_results
      # Set pagination params if they aren't provided
      @per_page = @count unless @per_page
      @page = 1 unless @page

      total_pages = (@count/(@per_page.nonzero? || 1).to_f).ceil
      next_page = @page + 1 if @page.between?(1, total_pages - 1)
      previous_page = @page - 1 if @page.between?(2, total_pages)
      first_page = @page == 1
      last_page = @page == total_pages
      out_of_range = !@page.between?(1,total_pages)

      { count: @count,
        current_page: @page,
        next_page: next_page,
        previous_page: previous_page,
        total_pages: total_pages,
        per_page: @per_page,
        first_page: first_page,
        last_page: last_page,
        out_of_range: out_of_range }
    end

    def create_column_maps
      ColumnMap.create_column_mappings(
        query: @query,
        custom_mappings: @custom_mappings,
        model: @model
      )
    end
end