#!/usr/bin/env ruby

require 'ballista'
require 'yaml'
require 'mercenary'
require 'cymbal'
require 'date'

def parse_config(file)
  Cymbal.symbolize(YAML.safe_load(File.read(file)))
end

def count_months(months)
  return unless months
  start_dt = Date.today + 1
  end_dt = start_dt >> months.to_i
  [start_dt, end_dt]
end

def parse_start_end(start_dt, end_dt)
  return unless start_dt || end_dt
  raise('Must specify start and end together') unless start_dt && end_dt
  [Date.parse(start_dt), Date.parse(end_dt)]
end

def parse_range(months, start_dt, end_dt)
  if months && (start_dt || end_dt)
    raise('Cannot specify months *and* start/end')
  end
  count_months(months) || parse_start_end(start_dt, end_dt) || count_months(12)
end

Mercenary.program(:ballista) do |p|
  p.version Ballista::VERSION
  p.description 'Tool for projecting future activity with Ledger'
  p.syntax 'ballista [options] CONFIG_FILE'

  p.option :output, '-o FILE', '--output FILE', 'Output file for ledger'
  p.option :months, '-m INT', '--months INT', 'How far ahead to project'
  p.option :start, '-s DATE', '--start DATE', 'When to start the projection'
  p.option :end, '-e DATE', '--end DATE', 'When to end the projection'

  p.action do |_, options|
    config_file = ARGV.shift
    puts p unless config_file
    config = parse_config(config_file)

    start_dt, end_dt = parse_range(*options.values_at(:months, :start, :end))

    projection = Ballista.new(entries: config).project(start_dt, end_dt)
    if options[:output]
      File.open(options[:output], 'w') { |fh| fh << projection.to_s }
    else
      puts projection
    end
  end
end