#!/usr/bin/env nix-shell
#!nix-shell -p ruby -i ruby
#!nix-shell -p hydra-unstable

# This script uses hydra's `hydra-eval-jobs` to evaluate a given expression,
# defaulting to `release.nix`.

require "open3"
require "json"
require "shellwords"

module MD
  extend self

  def _title(s, level)
    "\n#{"#" * level} #{s}\n\n"
  end

  def title(s)
    "\n#{s}\n#{s.gsub(/./, "=")}\n\n"
  end

  def section(s)
    "\n#{s}\n#{s.gsub(/./, "-")}\n\n"
  end

  def list_item(s)
    "  * #{s}"
  end

  def code(s)
    "`#{s}`"
  end

  def pre(s)
    "```\n#{s}\n```"
  end

  def paragraph(s)
    "#{s.strip}\n\n"
  end

  def subtitle(s)
    _title(s, 3)
  end
end

def usage(io=$stdout)
  io.puts "Usage: bin/hydra-eval [args...]"
  io.puts ""
  io.puts "Arguments are passed-through to `hydra-eval-jobs`."
  io.puts ""
  io.puts "You are likely to want to use:"
  io.puts ""
  io.puts %q{    $ bin/hydra-eval release.nix --arg systems '[ "x86_64-linux" "aarch64-linux" ]' > out.md}
  io.puts ""
end

# No arguments, or `--help`?
if ARGV.length == 0 || ARGV.grep(/^--help/).length > 0
  usage()
  exit 0
end

# We're only keeping `NIX_PATH` from the env.
env = ENV.filter do |k, v|
  [
    "NIX_PATH",
  ].include?(k)
end

args = []

# Allow access to files in CWD
args << "-I"
args << "./"

# Run the eval
out, ret = Open3.capture2(env, "hydra-eval-jobs", *args, *ARGV)

# Read the output JSON
hydra_eval = JSON.parse(out)

errors, valid_jobs = hydra_eval.partition do |k, v|
  v.has_key?("error")
end.map(&:to_h)

out = $stdout

out.puts MD.title "Hydra-like evaluation"

out.puts MD.paragraph "Command used to generate this report:"
out.puts MD.pre " $ " + (["bin/hydra-eval"] + ARGV).shelljoin()

out.puts MD.section "#{valid_jobs.length} valid jobs"

valid_jobs.each do |attrname, job|
  out.puts MD.list_item(
    MD.code(attrname) +
    " → " +
    MD.code(job["drvPath"])
  )
end

out.puts MD.section "#{errors.length} errors"

errors.each do |attrname, obj|
  out.puts MD.subtitle(MD.code(attrname))
  out.puts MD.pre(obj["error"])
end

# vim: ft=ruby