require 'ostruct'
require 'digest/md5'

module SpatialFeatures
  module Importers
    class Shapefile < Base
      class_attribute :default_proj4_projection

      def initialize(data, *args, proj4: nil, **options)
        super(data, **options)
        @proj4 = proj4
      end

      def cache_key
        @cache_key ||= Digest::MD5.file(archive).to_s
      end

      def self.create_all(data, **options)
        Download.open_each(data, unzip: [/\.shp$/], downcase: true).map do |file|
          new(file, **options)
        end
      rescue Unzip::PathNotFound
        raise ImportError, INVALID_ARCHIVE
      end

      private

      def build_features
        validate_shapefile!
        super
      end

      def each_record(&block)
        RGeo::Shapefile::Reader.open(file.path) do |records|
          records.each do |record|
            yield OpenStruct.new data_from_wkt(record.geometry.as_text, proj4_projection).merge(:metadata => record.attributes) if record.geometry.present?
          end
        end
      rescue Errno::ENOENT => e
        case e.message
        when /No such file or directory @ rb_sysopen - (.+)/
          raise IncompleteShapefileArchive, "Shapefile archive is missing a required file: #{::File.basename($1)}"
        else
          raise e
        end
      end

      def proj4_projection
        @proj4 ||= proj4_from_file || default_proj4_projection || raise(IndeterminateShapefileProjection, 'Could not determine shapefile projection. Check that `gdalsrsinfo` is installed.')
      end

      def proj4_from_file
        # Sanitize: "'+proj=utm +zone=11 +datum=NAD83 +units=m +no_defs '\n" and lately
        #           "+proj=utm +zone=11 +datum=NAD83 +units=m +no_defs \n" to
        #           "+proj=utm +zone=11 +datum=NAD83 +units=m +no_defs"
        `gdalsrsinfo "#{file.path}" -o proj4`.strip.remove(/^'|'$/).presence
      end

      def data_from_wkt(wkt, proj4)
        ActiveRecord::Base.connection.select_one <<-SQL
          SELECT ST_Transform(ST_GeomFromText('#{wkt}'), '#{proj4}', 4326) AS geog, GeometryType(ST_GeomFromText('#{wkt}')) AS feature_type
        SQL
      end

      # the individual SHP file for processing (automatically extracted from a ZIP archive if necessary)
      def file
        @file ||= Unzip.is_zip?(archive) ? possible_shp_files.first : archive
      end

      # a zip archive may contain multiple SHP files
      def possible_shp_files
        @possible_shp_files ||= begin
          Download.open_each(archive, unzip: /\.shp$/, downcase: true)
        rescue Unzip::PathNotFound
          raise ::SpatialFeatures::Importers::IncompleteShapefileArchive, "Shapefile archive is missing a SHP file"
        end
      end

      def validate_shapefile!
        Validation.validate_shapefile!(file, default_proj4_projection: default_proj4_projection)
      end

      def archive
        @archive ||= Download.open(@data)
      end
    end

    # ERRORS
    class IndeterminateShapefileProjection < SpatialFeatures::ImportError; end
    class IncompleteShapefileArchive < SpatialFeatures::ImportError; end
    class InvalidShapefileArchive < SpatialFeatures::ImportError; end
  end
end