# frozen_string_literal: true

# keila_csv_lib.rb — Shared library for keila2csv and csv2keila
#
# Keila stores custom contact data as a JSON object in a "data" column.
# This library converts between:
#   - Keila's format: standard columns + a "data" column with a JSON blob
#   - A flat format:  standard columns + one column per custom data key

require "csv"
require "json"

module KeilaCsv
  # Keila's built-in contact fields in their canonical capitalisation for import.
  # Used both for identifying standard fields (downcased) and for writing output headers.
  KEILA_FIELDS_CANONICAL = %w[Email First_name Last_name External_id Tags Data].freeze
  KEILA_FIELDS = KEILA_FIELDS_CANONICAL.map(&:downcase).freeze

  # Lookup from lowercase field name → canonical capitalisation
  KEILA_FIELDS_MAP = KEILA_FIELDS.zip(KEILA_FIELDS_CANONICAL).to_h.freeze

  # keila2csv: Expand Keila's "data" JSON column into individual columns.
  #
  # Each top-level key in the JSON object becomes its own column.
  # Nested objects/arrays are kept as JSON strings in their column.
  # Contacts without a "data" value simply get empty cells.
  # The output column order is: standard fields (minus "data"), then all
  # discovered custom keys (union across all rows, alphabetically sorted).
  def self.keila_to_csv(input_path, output_path)
    rows = CSV.read(input_path, headers: true, header_converters: :downcase)

    # First pass: collect all custom data keys across all rows
    data_keys = []
    rows.each do |row|
      raw = row["data"]
      next if raw.nil? || raw.strip.empty?

      parsed = JSON.parse(raw)
      data_keys |= parsed.keys.sort if parsed.is_a?(Hash)
    rescue JSON::ParserError => e
      warn "Warning: could not parse JSON for #{row['email']}: #{e.message}"
    end

    standard_headers = rows.headers.reject { |h| h == "data" }
    output_headers = standard_headers + data_keys

    # Second pass: write output
    CSV.open(output_path, "w", headers: output_headers, write_headers: true) do |csv|
      rows.each do |row|
        out = {}
        standard_headers.each { |h| out[h] = row[h] }

        raw = row["data"]
        if raw && !raw.strip.empty?
          begin
            parsed = JSON.parse(raw)
            if parsed.is_a?(Hash)
              parsed.each do |key, value|
                out[key] = value.is_a?(String) ? value : value.to_json
              end
            else
              warn "Warning: 'data' for #{row['email']} is not a JSON object — skipping."
            end
          rescue JSON::ParserError => e
            warn "Warning: could not parse JSON for #{row['email']}: #{e.message}"
          end
        end

        csv << output_headers.map { |h| out[h] }
      end
    end

    {
      contacts: rows.length,
      custom_fields: data_keys
    }
  end

  # csv2keila: Collect non-standard columns back into a Keila "data" JSON object.
  #
  # Any column not in KEILA_FIELDS is treated as custom data and packed into
  # the "data" JSON column. Empty cells are omitted from the JSON entirely
  # (so they don't overwrite existing values on re-import).
  # Values that look like JSON objects or arrays are re-parsed as structured
  # data; plain strings remain strings.
  def self.csv_to_keila(input_path, output_path)
    rows = CSV.read(input_path, headers: true, header_converters: :downcase)

    custom_headers = rows.headers - KEILA_FIELDS
    present_standard = rows.headers & (KEILA_FIELDS - ["data"])
    # Write headers in Keila's canonical capitalisation (e.g. "Email", "First_name")
    output_headers = present_standard.map { |h| KEILA_FIELDS_MAP[h] } + ["Data"]

    CSV.open(output_path, "w", headers: output_headers, write_headers: true) do |csv|
      rows.each do |row|
        out = {}
        # Row data is still keyed by lowercase; map to canonical for output
        present_standard.each { |h| out[KEILA_FIELDS_MAP[h]] = row[h] }

        data_hash = {}
        custom_headers.each do |key|
          val = row[key]
          next if val.nil? || val.strip.empty?

          # Re-parse JSON structures (objects/arrays); keep everything else as string
          data_hash[key] = begin
            parsed = JSON.parse(val)
            parsed.is_a?(Hash) || parsed.is_a?(Array) ? parsed : val
          rescue JSON::ParserError
            val
          end
        end

        out["Data"] = data_hash.empty? ? nil : data_hash.to_json
        csv << output_headers.map { |h| out[h] }
      end
    end

    {
      contacts: rows.length,
      custom_fields: custom_headers
    }
  end
end