require "crinja"

def sanitize_path(path)
	path.gsub /\/\/+/, "/"
end

module Configure
	def self.parse_options(unparsed : Array(String))
		options = ARGV.map(&.split '=')

		hash = Hash(String, String | Array(String) | Crinja::Callable::Instance | Hash(String, String)).new

		options.each do |entry|
			key, value = entry

			old_value = hash[key]?

			case old_value
			when nil
				hash[key] = value
			when String
				hash[key] = [old_value, value]
			when Array(String)
				old_value << value
			end
		end

		hash
	end
end

class Configure::Exception < Exception
end

class Configure::Context
	getter root : String

	def initialize(@root)
	end

	def generate(template, target : String, options : Hash(String, String | Array(String) | Crinja::Callable::Instance | Hash(String, String)))
		target_file = File.open target, "w"

		# FIXME: Alter default sources at build-time.
		# FIXME: We’ll want a way to alter those context-wide.
		sources = [
			"/etc/templates",
			"/usr/share/templates"
		]

		sources = sources
			.map(&.+("/#{template}.j2"))
			.map { |x| sanitize_path x }

		source = sources.find do |source|
			if File.exists? source
				puts "Generating '#{target}' from '#{source}'"

				next true
			end
		end

		unless source
			raise Exception.new "Could not find template to generate file ('#{target}')."
		end

		options["id"] = ENV["SERVICE_ID"]? || ""
		options["environment"] = ENV["ENVIRONMENT"]? || ""
		options["port"] = Crinja.function do
			service = (arguments.varargs[0]? || "").to_s.gsub /\//, ':'
			`get-port #{service}`
		end

		providers = {} of String => String
		ENV["SERVICE_TOKENS"].try &.split(':').each do |token|
			providers[token] = ENV["#{token.upcase}_PROVIDER"]? || ""
		end
		options["providers"] = providers

		template = File.read source

		target_file << Crinja.render(template, options)
		target_file.close
	end
end

template = ARGV[0]?
target = ARGV[1]?

if target.nil?
	puts "usage: configure <template-name> <target> [option1=value1 [option2=value2 […]]]"
	exit 1
end

ARGV.shift
ARGV.shift

options = Configure.parse_options ARGV

begin
	Configure::Context.new("/").generate(template, target, options)
rescue e : Configure::Exception
	STDERR.puts "Fatal error: #{e.message}"
	exit 1
end