#!/usr/bin/env ruby -w
# frozen_string_literal: true

# Driver script executes this script like this:
# ruby /usr/src/m2/mysql/partitions/generate_partitions_list.rb "$DAYS" "$TABLE" "$START_DATE" "$SHELL_PID" > "$partitions_sql"

# Takes existing partitions from existing_partitions_dates file and
# generates SQLs to create partitions for next DAYS in the future, skipping existing ones
# SQLs go to STDOUT

# Use only stdlib, no gems, no bs
require 'date'

class Date
  # d20200101
  def partition_format
    format('d%04d%02d%02d', year, month, day)
  end

  # 20200101
  def simple_format
    format('%04d%02d%02d', year, month, day)
  end
end

def warn_and_exit(message)
  warn "#{$PROGRAM_NAME}:", message
  exit 1
end

# All errors, warnings and exceptions go to SDTDER
# SQL list goes to STDOUT, which driver script will redirect to file
# In case of detected error, script will return 1 and driver script will exit accordingly
# In casae of uncaught exception, script will return non-zero exit value and driver script will exit accordingly
############################## Argument Handling ##############################

DAYS = ARGV[0]
TABLE = ARGV[1]
START_DATE = ARGV[2]
SHELL_PID = ARGV[3]

unless DAYS =~ /^\d+$/
  warn_and_exit 'Script first argument should be a number (days to generate partitions in the future)'
end

unless TABLE == 'calls' || TABLE == 'calls_old'
  warn_and_exit 'Script 2nd argument should be either calls or calls_old'
end

today = Date.jd(DateTime.now.jd)
start_date = today

# start_day is either today or START_DATE
unless START_DATE.to_s == 'today'
  begin
    start_date = Date.parse(START_DATE)
    if (today - start_date).to_i > 200
      warn_and_exit 'START_DATE is more than 150 days in the past. Please check your START_DATE  parameter'
    end
  rescue StandardError
    warn_and_exit 'Error parsing START_DATE. Exiting.'
  end
end

############################## Main Script ##############################

existing_partitions_dates = "/tmp/partition_managment/partitions_dates#{SHELL_PID}.txt"
warn_and_exit "Partition file #{existing_partitions_dates} does not exist. Exiting" unless File.file?(existing_partitions_dates)

# Read dates from file into hash
# Validate lines in process, exit if bad value detected
dates_hash = {}
File.open(existing_partitions_dates) do |fp|
  fp.each do |line|
    partition_date = line.chomp
    unless partition_date =~ /\d{4}\d{2}\d{2}$/
      warn_and_exit "Bad partition date detected #{partition_date}"
    end
    dates_hash[partition_date] = true
  end
end

warn_and_exit "Cannot find at least one partition with correct date in #{existing_partitions_dates}. Exiting" if dates_hash.empty?

begin
  max_date = Date.parse(dates_hash.keys.max)
rescue StandardError
  warn_and_exit 'Error parsing max date from dates_hash. Exiting.'
end

if !max_date.nil? && start_date < max_date && !dates_hash.key?(start_date.simple_format)
  warn_and_exit "Cannot create partition for #{start_date}, because latest partition is already at #{max_date}"
end

# Iterate over dates from start_date to start_date + DAYS in the future
# and create partitions SQLs for missing partitions
# Abort if holes detected in date space

end_date = start_date + DAYS.to_i - 1

start_date.upto(end_date) do |day|
  next if dates_hash.key?(day.simple_format)

  if day < max_date
    warn_and_exit "Cannot create partition for #{day}, because latest partition is already at #{max_date}"
  end

  day_after = day + 1
  puts "ALTER TABLE #{TABLE} REORGANIZE PARTITION future INTO (PARTITION #{day.partition_format} VALUES LESS THAN ('#{day_after}'), PARTITION future VALUES LESS THAN MAXVALUE);"
end