module UnitConvert

# File lib/unit_convert.rb, line 31
def convert(amount:, from:, to:)
  from = from.to_s.downcase
  to = to.to_s.downcase
  return { error: usage_message } if from.empty? || to.empty?

if temperature?(from) && temperature?(to)
    return { value: convert_temperature(amount, from, to) }
  end

  factor = CONVERSIONS[[from, to]]
  return { error: "Cannot convert #{from} to #{to}" } unless factor

  { value: amount * factor }
end

# File lib/unit_convert.rb, line 50
def convert_temperature(amount, from, to)
  from = from.downcase
  to = to.downcase
  celsius = case from
            when "c" then amount
            when "f" then (amount - 32) * 5.0 / 9.0
            when "k" then amount - 273.15
            end

  case to
  when "c" then celsius
  when "f" then (celsius * 9.0 / 5.0) + 32
  when "k" then celsius + 273.15
  end
end

# File lib/unit_convert.rb, line 66
def format_result(amount:, from:, to:, value:)
  rounded = value.is_a?(Float) ? value.round(4) : value
  "#{amount} #{from} = #{rounded} #{to}"
end

# File lib/unit_convert.rb, line 19
def parse_command(text)
  parts = text.to_s.strip.split(/\s+/)
  return { error: usage_message } if parts.length < 3

  amount = parts[0].to_f
  return { error: usage_message } if parts[0] !~ /\A-?\d+(?:\.\d+)?\z/

  from = parts[1].downcase
  to = parts[2].downcase
  { amount: amount, from: from, to: to }
end

# File lib/unit_convert.rb, line 46
def temperature?(unit)
  %w[c f k].include?(unit.to_s.downcase)
end

# File lib/unit_convert.rb, line 15
def usage_message
  "Usage: !convert <amount> <from> <to> — e.g. !convert 100 km mi, !convert 25 c f"
end