(define-module (gnu services cloud-init)
  #:use-module (gnu packages bash)
  #:use-module (gnu packages python-web)
  #:use-module (gnu services)
  #:use-module (gnu services shepherd)
  #:use-module (guix gexp)
  #:use-module (guix records)
  #:export (cloud-init-configuration cloud-init-service
                                     cloud-init-service-type))

(define-record-type* <cloud-init-configuration> cloud-init-configuration
                     make-cloud-init-configuration
  cloud-init-configuration?

  (cloud-init cloud-init-configuration-cloud-init ;file-like
              (default python-cloud-init))
  (init-modules cloud-init-configuration-init-modules ;list of symbols
                (default '(seed_random growpart
                                       resizefs
                                       disk_setup
                                       mounts
                                       set_hostname
                                       update_hostname
                                       users_groups
                                       ssh
                                       set_passwords)))
  (config-modules cloud-init-configuration-config-modules ;list of symbols
                  (default '()))
  (final-modules cloud-init-configuration-final-modules ;list of symbols
                 (default '(ssh_authkey_fingerprints)))
  (extra-configuration-files
   cloud-init-configuration-extra-configuration-files ;list of file-likes
   (default '())))

(define %cloud-dir
  "/etc/cloud")

(define %cloud-cfg
  (string-append %cloud-dir "/cloud.cfg"))

(define %cloud-run
  (mixed-text-file "run.sh"
                   "#!"
                   (file-append bash "/bin/bash")
                   "\n\nset -euo pipefail\n\n"
                   (file-append python-cloud-init "/bin/cloud-init")
                   " init --local\n"
                   (file-append python-cloud-init "/bin/cloud-init")
                   " init\n"
                   (file-append python-cloud-init "/bin/cloud-init")
                   " modules --mode config\n"
                   (file-append python-cloud-init "/bin/cloud-init")
                   " modules --mode final\n"))

(define %cloud-cfg-d
  (string-append %cloud-dir "/cloud.cfg.d"))

(define (cloud-init-initialization init-modules config-modules final-modules
                                   extra)
  "Return the gexp to initialize the cloud-init configuration files"
  #~(begin
      (use-modules (srfi srfi-1)
                   (srfi srfi-2)
                   (guix build utils))

      (define reduce-modules
        (lambda (mods)
          (string-join (map (lambda (mod)
                              (string-append "\n  - "
                                             (symbol->string mod))) mods))))

      (mkdir-p #$%cloud-cfg-d)

      (copy-file #$%cloud-run
                 (string-append #$%cloud-dir "/run.sh"))
      (chmod (string-append #$%cloud-dir "/run.sh") #o755)

      (unless (null? '(#$@extra))
        (for-each (lambda (file)
                    (symlink (cadr file)
                             (string-append #$%cloud-cfg-d "/"
                                            (car file))))
                  '(#$@extra)))

      (call-with-output-file #$%cloud-cfg
        (lambda (p)
          (unless (null? '(#$@init-modules))
            (display (string-append "cloud_init_modules:"
                                    (reduce-modules '(#$@init-modules)) "\n\n")
                     p))
          (unless (null? '(#$@config-modules))
            (display (string-append "cloud_config_modules:"
                                    (reduce-modules '(#$@config-modules))
                                    "\n\n") p))
          (unless (null? '(#$@final-modules))
            (display (string-append "cloud_final_modules:"
                                    (reduce-modules '(#$@final-modules))
                                    "\n\n") p))))))

(define (cloud-init-activation config)
  "Return the activation gexp for CONFIG."
  #~(begin
      (use-modules (guix build utils))
      #$(cloud-init-initialization (cloud-init-configuration-init-modules
                                    config)
                                   (cloud-init-configuration-config-modules
                                    config)
                                   (cloud-init-configuration-final-modules
                                    config)
                                   (cloud-init-configuration-extra-configuration-files
                                    config))))

(define (cloud-init-service config)
  "Return a <cloud-init-service> for cloud-init with CONFIG."
  (define cloud-init
    (cloud-init-configuration-cloud-init config))

  (list (shepherd-service (documentation "cloud-init service")
                          (provision '(cloud-init))
                          (requirement '(networking))
                          (one-shot? #t)
                          (start #~(fork+exec-command (list (string-append #$%cloud-dir
                                                             "/run.sh"))
                                                      #:log-file (string-append
                                                                  "/var/log/cloud-init.log")
                                                      #:environment-variables '
                                                      ("PATH=/run/current-system/profile/bin:/run/current-system/profile/sbin:"))))))

(define cloud-init-service-type
  (service-type (name 'cloud-init)
                (default-value (cloud-init-configuration))
                (description "cloud init")
                (extensions (list (service-extension
                                   shepherd-root-service-type
                                   cloud-init-service)
                                  (service-extension activation-service-type
                                                     cloud-init-activation)))))