# frozen_string_literal: true

require_relative "extensions/hash"
require_relative "smarter_csv/version"

require_relative "smarter_csv/smarter_csv" unless ENV['CI'] # does not compile/link in CI?
# require 'smarter_csv.bundle' unless ENV['CI'] # does not compile/link in CI?

module SmarterCSV
  class SmarterCSVException < StandardError; end
  class HeaderSizeMismatch < SmarterCSVException; end
  class IncorrectOption < SmarterCSVException; end
  class DuplicateHeaders < SmarterCSVException; end
  class MissingHeaders < SmarterCSVException; end
  class NoColSepDetected < SmarterCSVException; end
  class KeyMappingError < SmarterCSVException; end
  class MalformedCSVError < SmarterCSVException; end

  # first parameter: filename or input object which responds to readline method
  def SmarterCSV.process(input, options = {}, &block)
    options = default_options.merge(options)
    options[:invalid_byte_sequence] = '' if options[:invalid_byte_sequence].nil?
    puts "SmarterCSV OPTIONS: #{options.inspect}" if options[:verbose]

    headerA = []
    result = []
    @file_line_count = 0
    @csv_line_count = 0
    has_rails = !!defined?(Rails)
    begin
      fh = input.respond_to?(:readline) ? input : File.open(input, "r:#{options[:file_encoding]}")

      # auto-detect the row separator
      options[:row_sep] = guess_line_ending(fh, options) if options[:row_sep]&.to_sym == :auto
      # attempt to auto-detect column separator
      options[:col_sep] = guess_column_separator(fh, options) if options[:col_sep]&.to_sym == :auto

      if (options[:force_utf8] || options[:file_encoding] =~ /utf-8/i) && (fh.respond_to?(:external_encoding) && fh.external_encoding != Encoding.find('UTF-8') || fh.respond_to?(:encoding) && fh.encoding != Encoding.find('UTF-8'))
        puts 'WARNING: you are trying to process UTF-8 input, but did not open the input with "b:utf-8" option. See README file "NOTES about File Encodings".'
      end

      if options[:skip_lines].to_i > 0
        options[:skip_lines].to_i.times do
          readline_with_counts(fh, options)
        end
      end

      headerA, header_size = process_headers(fh, options)

      # in case we use chunking.. we'll need to set it up..
      if !options[:chunk_size].nil? && options[:chunk_size].to_i > 0
        use_chunks = true
        chunk_size = options[:chunk_size].to_i
        chunk_count = 0
        chunk = []
      else
        use_chunks = false
      end

      # now on to processing all the rest of the lines in the CSV file:
      until fh.eof? # we can't use fh.readlines() here, because this would read the whole file into memory at once, and eof => true
        line = readline_with_counts(fh, options)

        # replace invalid byte sequence in UTF-8 with question mark to avoid errors
        line = line.force_encoding('utf-8').encode('utf-8', invalid: :replace, undef: :replace, replace: options[:invalid_byte_sequence]) if options[:force_utf8] || options[:file_encoding] !~ /utf-8/i

        print "processing file line %10d, csv line %10d\r" % [@file_line_count, @csv_line_count] if options[:verbose]

        next if options[:comment_regexp] && line =~ options[:comment_regexp] # ignore all comment lines if there are any

        # cater for the quoted csv data containing the row separator carriage return character
        # in which case the row data will be split across multiple lines (see the sample content in spec/fixtures/carriage_returns_rn.csv)
        # by detecting the existence of an uneven number of quote characters

        multiline = line.count(options[:quote_char]).odd? # should handle quote_char nil
        while line.count(options[:quote_char]).odd? # should handle quote_char nil
          next_line = fh.readline(options[:row_sep])
          next_line = next_line.force_encoding('utf-8').encode('utf-8', invalid: :replace, undef: :replace, replace: options[:invalid_byte_sequence]) if options[:force_utf8] || options[:file_encoding] !~ /utf-8/i
          line += next_line
          @file_line_count += 1
        end
        print "\nline contains uneven number of quote chars so including content through file line %d\n" % @file_line_count if options[:verbose] && multiline

        line.chomp!(options[:row_sep])

        dataA, _data_size = parse(line, options, header_size)

        dataA.map!{|x| x.strip} if options[:strip_whitespace]

        # if all values are blank, then ignore this line
        next if options[:remove_empty_hashes] && (dataA.empty? || blank?(dataA))

        hash = Hash.zip(headerA, dataA) # from Facets of Ruby library

        # make sure we delete any key/value pairs from the hash, which the user wanted to delete:
        # Note: Ruby < 1.9 doesn't allow empty symbol literals!
        hash.delete(nil)
        hash.delete('')
        eval('hash.delete(:"")') if RUBY_VERSION.to_f > 1.8

        if options[:remove_empty_values] == true
          hash.delete_if{|_k, v| has_rails ? v.blank? : blank?(v)}
        end

        hash.delete_if{|_k, v| !v.nil? && v =~ /^(\d+|\d+\.\d+)$/ && v.to_f == 0} if options[:remove_zero_values] # values are typically Strings!
        hash.delete_if{|_k, v| v =~ options[:remove_values_matching]} if options[:remove_values_matching]

        if options[:convert_values_to_numeric]
          hash.each do |k, v|
            # deal with the :only / :except options to :convert_values_to_numeric
            next if only_or_except_limit_execution(options, :convert_values_to_numeric, k)

            # convert if it's a numeric value:
            case v
            when /^[+-]?\d+\.\d+$/
              hash[k] = v.to_f
            when /^[+-]?\d+$/
              hash[k] = v.to_i
            end
          end
        end

        if options[:value_converters]
          hash.each do |k, v|
            converter = options[:value_converters][k]
            next unless converter

            hash[k] = converter.convert(v)
          end
        end

        next if options[:remove_empty_hashes] && hash.empty?

        hash[:csv_line_number] = @csv_line_count if options[:with_line_numbers]

        if use_chunks
          chunk << hash # append temp result to chunk

          if chunk.size >= chunk_size || fh.eof? # if chunk if full, or EOF reached
            # do something with the chunk
            if block_given?
              yield chunk # do something with the hashes in the chunk in the block
            else
              result << chunk # not sure yet, why anybody would want to do this without a block
            end
            chunk_count += 1
            chunk = [] # initialize for next chunk of data
          else

            # the last chunk may contain partial data, which also needs to be returned (BUG / ISSUE-18)

          end

          # while a chunk is being filled up we don't need to do anything else here

        else # no chunk handling
          if block_given?
            yield [hash] # do something with the hash in the block (better to use chunking here)
          else
            result << hash
          end
        end
      end

      # print new line to retain last processing line message
      print "\n" if options[:verbose]

      # last chunk:
      if !chunk.nil? && chunk.size > 0
        # do something with the chunk
        if block_given?
          yield chunk # do something with the hashes in the chunk in the block
        else
          result << chunk # not sure yet, why anybody would want to do this without a block
        end
        chunk_count += 1
        chunk = [] # initialize for next chunk of data
      end
    ensure
      fh.close if fh.respond_to?(:close)
    end
    if block_given?
      return chunk_count # when we do processing through a block we only care how many chunks we processed
    else
      return result # returns either an Array of Hashes, or an Array of Arrays of Hashes (if in chunked mode)
    end
  end

  class << self
    def has_acceleration?
      @has_acceleration ||= !!defined?(parse_csv_line_c)
    end

    def raw_header
      @raw_header
    end

    def headers
      @headers
    end

    protected

    # NOTE: this is not called when "parse" methods are tested by themselves
    def default_options
      {
        acceleration: true,
        auto_row_sep_chars: 500,
        chunk_size: nil,
        col_sep: ',',
        comment_regexp: nil, # was: /\A#/,
        convert_values_to_numeric: true,
        downcase_header: true,
        duplicate_header_suffix: nil,
        file_encoding: 'utf-8',
        force_simple_split: false,
        force_utf8: false,
        headers_in_file: true,
        invalid_byte_sequence: '',
        keep_original_headers: false,
        key_mapping_hash: nil,
        quote_char: '"',
        remove_empty_hashes: true,
        remove_empty_values: true,
        remove_unmapped_keys: false,
        remove_values_matching: nil,
        remove_zero_values: false,
        required_headers: nil,
        row_sep: $/,
        silence_missing_keys: false,
        skip_lines: nil,
        strings_as_keys: false,
        strip_chars_from_headers: nil,
        strip_whitespace: true,
        user_provided_headers: nil,
        value_converters: nil,
        verbose: false,
        with_line_numbers: false,
      }
    end

    def readline_with_counts(filehandle, options)
      line = filehandle.readline(options[:row_sep])
      @file_line_count += 1
      @csv_line_count += 1
      line
    end

    ###
    ### Thin wrapper around C-extension
    ###
    def parse(line, options, header_size = nil)
      # puts "SmarterCSV.parse OPTIONS: #{options[:acceleration]}" if options[:verbose]

      if options[:acceleration] && has_acceleration?
        # :nocov:
        has_quotes = line =~ /#{options[:quote_char]}/
        elements = parse_csv_line_c(line, options[:col_sep], options[:quote_char], header_size)
        elements.map!{|x| cleanup_quotes(x, options[:quote_char])} if has_quotes
        return [elements, elements.size]
        # :nocov:
      else
        # puts "WARNING: SmarterCSV is using un-accelerated parsing of lines. Check options[:acceleration]"
        return parse_csv_line_ruby(line, options, header_size)
      end
    end

    # ------------------------------------------------------------------
    # Ruby equivalent of the C-extension for parse_line
    #
    # parses a single line: either a CSV header and body line
    # - quoting rules compared to RFC-4180 are somewhat relaxed
    # - we are not assuming that quotes inside a fields need to be doubled
    # - we are not assuming that all fields need to be quoted (0 is even)
    # - works with multi-char col_sep
    # - if header_size is given, only up to header_size fields are parsed
    #
    # We use header_size for parsing the body lines to make sure we always match the number of headers
    # in case there are trailing col_sep characters in line
    #
    # Our convention is that empty fields are returned as empty strings, not as nil.
    #
    #
    # the purpose of the max_size parameter is to handle a corner case where
    # CSV lines contain more fields than the header.
    # In which case the remaining fields in the line are ignored
    #
    def parse_csv_line_ruby(line, options, header_size = nil)
      return [] if line.nil?

      line_size = line.size
      col_sep = options[:col_sep]
      col_sep_size = col_sep.size
      quote = options[:quote_char]
      quote_count = 0
      elements = []
      start = 0
      i = 0

      while i < line_size
        if line[i...i+col_sep_size] == col_sep && quote_count.even?
          break if !header_size.nil? && elements.size >= header_size

          elements << cleanup_quotes(line[start...i], quote)
          i += col_sep.size
          start = i
        else
          quote_count += 1 if line[i] == quote
          i += 1
        end
      end
      elements << cleanup_quotes(line[start..-1], quote) if header_size.nil? || elements.size < header_size
      [elements, elements.size]
    end

    def cleanup_quotes(field, quote)
      return field if field.nil?

      # return if field !~ /#{quote}/ # this check can probably eliminated

      if field.start_with?(quote) && field.end_with?(quote)
        field.delete_prefix!(quote)
        field.delete_suffix!(quote)
      end
      field.gsub!("#{quote}#{quote}", quote)
      field
    end

    # SEE: https://github.com/rails/rails/blob/32015b6f369adc839c4f0955f2d9dce50c0b6123/activesupport/lib/active_support/core_ext/object/blank.rb#L121
    # and in the future we might also include UTF-8 space characters: https://www.compart.com/en/unicode/category/Zs
    BLANK_RE = /\A\s*\z/.freeze

    def blank?(value)
      case value
      when String
        value.empty? || BLANK_RE.match?(value)

      when NilClass
        true

      when Array
        value.empty? || value.inject(true){|result, x| result &&= elem_blank?(x)}

      when Hash
        value.empty? || value.values.inject(true){|result, x| result &&= elem_blank?(x)}

      else
        false
      end
    end

    def elem_blank?(value)
      case value
      when String
        value.empty? || BLANK_RE.match?(value)

      when NilClass
        true

      else
        false
      end
    end

    # acts as a road-block to limit processing when iterating over all k/v pairs of a CSV-hash:
    def only_or_except_limit_execution(options, option_name, key)
      if options[option_name].is_a?(Hash)
        if options[option_name].has_key?(:except)
          return true if Array(options[option_name][:except]).include?(key)
        elsif options[option_name].has_key?(:only)
          return true unless Array(options[option_name][:only]).include?(key)
        end
      end
      return false
    end

    # raise exception if none is found
    def guess_column_separator(filehandle, options)
      del = [',', "\t", ';', ':', '|']
      n = Hash.new(0)

      5.times do
        line = filehandle.readline(options[:row_sep])
        del.each do |d|
          n[d] += line.scan(d).count
        end
      rescue EOFError # short files
        break
      end

      filehandle.rewind
      raise SmarterCSV::NoColSepDetected if n.values.max == 0

      col_sep = n.key(n.values.max)
    end

    # limitation: this currently reads the whole file in before making a decision
    def guess_line_ending(filehandle, options)
      counts = {"\n" => 0, "\r" => 0, "\r\n" => 0}
      quoted_char = false

      # count how many of the pre-defined line-endings we find
      # ignoring those contained within quote characters
      last_char = nil
      lines = 0
      filehandle.each_char do |c|
        quoted_char = !quoted_char if c == options[:quote_char]
        next if quoted_char

        if last_char == "\r"
          if c == "\n"
            counts["\r\n"] += 1
          else
            counts["\r"] += 1 # \r are counted after they appeared
          end
        elsif c == "\n"
          counts["\n"] += 1
        end
        last_char = c
        lines += 1
        break if options[:auto_row_sep_chars] && options[:auto_row_sep_chars] > 0 && lines >= options[:auto_row_sep_chars]
      end
      filehandle.rewind

      counts["\r"] += 1 if last_char == "\r"
      # find the most frequent key/value pair:
      k, _ = counts.max_by{|_, v| v}
      return k
    end

    def process_headers(filehandle, options)
      @raw_header = nil
      @headers = nil
      if options[:headers_in_file] # extract the header line
        # process the header line in the CSV file..
        # the first line of a CSV file contains the header .. it might be commented out, so we need to read it anyhow
        header = readline_with_counts(filehandle, options)
        @raw_header = header

        header = header.force_encoding('utf-8').encode('utf-8', invalid: :replace, undef: :replace, replace: options[:invalid_byte_sequence]) if options[:force_utf8] || options[:file_encoding] !~ /utf-8/i
        header = header.sub(options[:comment_regexp], '') if options[:comment_regexp]
        header = header.chomp(options[:row_sep])

        header = header.gsub(options[:strip_chars_from_headers], '') if options[:strip_chars_from_headers]

        file_headerA, file_header_size = parse(header, options)

        file_headerA.map!{|x| x.gsub(%r/#{options[:quote_char]}/, '')}
        file_headerA.map!{|x| x.strip} if options[:strip_whitespace]
        unless options[:keep_original_headers]
          file_headerA.map!{|x| x.gsub(/\s+|-+/, '_')}
          file_headerA.map!{|x| x.downcase} if options[:downcase_header]
        end
      else
        raise SmarterCSV::IncorrectOption, "ERROR: If :headers_in_file is set to false, you have to provide :user_provided_headers" unless options[:user_provided_headers]
      end
      if options[:user_provided_headers] && options[:user_provided_headers].class == Array && !options[:user_provided_headers].empty?
        # use user-provided headers
        headerA = options[:user_provided_headers]
        if defined?(file_header_size) && !file_header_size.nil?
          if headerA.size != file_header_size
            raise SmarterCSV::HeaderSizeMismatch, "ERROR: :user_provided_headers defines #{headerA.size} headers !=  CSV-file has #{file_header_size} headers"
          else
            # we could print out the mapping of file_headerA to headerA here
          end
        end
      else
        headerA = file_headerA
      end

      # detect duplicate headers and disambiguate
      headerA = process_duplicate_headers(headerA, options) if options[:duplicate_header_suffix]
      header_size = headerA.size # used for splitting lines

      headerA.map!{|x| x.to_sym } unless options[:strings_as_keys] || options[:keep_original_headers]

      unless options[:user_provided_headers] # wouldn't make sense to re-map user provided headers
        key_mappingH = options[:key_mapping]

        # do some key mapping on the keys in the file header
        #   if you want to completely delete a key, then map it to nil or to ''
        if !key_mappingH.nil? && key_mappingH.class == Hash && key_mappingH.keys.size > 0
          unless options[:silence_missing_keys]
            # if silence_missing_keys are not set, raise error if missing header
            missing_keys = key_mappingH.keys - headerA
            puts "WARNING: missing header(s): #{missing_keys.join(",")}" unless missing_keys.empty?
          end

          headerA.map!{|x| key_mappingH.has_key?(x) ? (key_mappingH[x].nil? ? nil : key_mappingH[x]) : (options[:remove_unmapped_keys] ? nil : x)}
        end
      end

      # header_validations
      duplicate_headers = []
      headerA.compact.each do |k|
        duplicate_headers << k if headerA.select{|x| x == k}.size > 1
      end

      unless options[:user_provided_headers] || duplicate_headers.empty?
        raise SmarterCSV::DuplicateHeaders, "ERROR: duplicate headers: #{duplicate_headers.join(',')}"
      end

      if options[:required_headers] && options[:required_headers].is_a?(Array)
        missing_headers = []
        options[:required_headers].each do |k|
          missing_headers << k unless headerA.include?(k)
        end
        raise SmarterCSV::MissingHeaders, "ERROR: missing headers: #{missing_headers.join(',')}" unless missing_headers.empty?
      end

      @headers = headerA
      [headerA, header_size]
    end

    def process_duplicate_headers(headers, options)
      counts = Hash.new(0)
      result = []
      headers.each do |key|
        counts[key] += 1
        if counts[key] == 1
          result << key
        else
          result << [key, options[:duplicate_header_suffix], counts[key]].join
        end
      end
      result
    end
  end
end