(define-module (tw services grafana)
  #:use-module (gnu)
  #:use-module ((gnu packages admin) #:select (shadow))
  #:use-module ((gnu packages docker) #:select (docker-cli))
  #:use-module (gnu services)
  #:use-module (gnu services configuration)
  #:use-module (gnu services databases)
  #:use-module (gnu services shepherd)
  #:use-module (guix records)
  #:use-module (tw services web)
  #:export (grafana-service-type
            grafana-configuration))

;; TODO: Mimir for long-term Prometheus metrics storage?
;; TODO: Store Grafana data in Postgres instead of SQLite?

(define %grafana-user "grafana")
(define %grafana-uid 472)  ; to match container

(define-configuration/no-serialization grafana-configuration
  ;; TODO: update to 10.2.2
  ;; https://hub.docker.com/r/grafana/grafana-oss/tags
  (container (string "docker.io/grafana/grafana-oss:9.5.2") "Container image to run.")
  (domain (string "localhost") "The external domain which will resolve to this
Grafana instance.")
  (bind-address (string "0.0.0.0") "The host IP to bind to.")
  (host-port (integer 3000) "The port to bind to on the host.")
  (data-path (string "/var/lib/grafana") "The path to store data in, on the host.")
  (metrics-credentials-file (string "/etc/grafana/metrics-credentials") "The
file name containing the user name and password to use for basic
authentication to Grafana's metrics endpoint.  These are specified as the
GF_METRICS_BASIC_AUTH_USERNAME and GF_METRICS_BASIC_AUTH_PASSWORD environment
variables."))

(define (grafana-accounts config)
  (list (user-account
         (name %grafana-user)
         (uid %grafana-uid)
         (group "nogroup")
         (comment "Grafana server user")
         (system? #t)
         (home-directory (grafana-configuration-data-path config))
         (shell (file-append shadow "/sbin/nologin")))))

(define (grafana-shepherd-service config)
  (list (shepherd-service
         (provision '(grafana))
         (requirement '(networking))
         (documentation "Run a Grafana instance using Docker.")
         (start #~(make-forkexec-constructor
                   ;; https://grafana.com/docs/grafana/latest/setup-grafana/installation/docker/
                   (list #$(file-append docker-cli "/bin/docker") "run" "--rm" "--network=host"
                         "--name" "grafana" "--user" '#$%grafana-user
                         "-v" '#$(format #f "~a:/var/lib/grafana" (grafana-configuration-data-path config))
                         "--env-file" '#$(grafana-configuration-metrics-credentials-file config)
                         ;; https://grafana.com/docs/grafana/latest/setup-grafana/configure-docker/
                         "-e" "GF_SERVER_PROTOCOL=http"  ; use Wireguard for encryption
                         "-e" '#$(format #f "GF_SERVER_HTTP_ADDR=~a" (grafana-configuration-bind-address config))
                         "-e" '#$(format #f "GF_SERVER_HTTP_PORT=~a" (grafana-configuration-host-port config))
                         "-e" "GF_SERVER_ENABLE_GZIP=true"  ; recommended by docs
                         "-e" "GF_ANALYTICS_REPORTING_ENABLED=false"
                         "-e" "GF_ANALYTICS_CHECK_FOR_UPDATES=false"
                         "-e" "GF_ANALYTICS_CHECK_FOR_PLUGIN_UPDATES=false"
                         "-e" "GF_SNAPSHOTS_ENABLED=false"  ; disable publishing dashboard snapshots to the internet
                         "-e" "GF_DATE_FORMATS_INTERVAL_HOUR=DD.MM. HH:mm"  ; use sensible date format
                         "-e" "GF_DATE_FORMATS_INTERVAL_DAY=DD.MM."         ; use sensible date format
                         ;; TODO: https://grafana.com/docs/grafana/latest/setup-grafana/configure-grafana/#smtp
                         '#$(grafana-configuration-container config))))
         (stop #~(make-kill-destructor)))))

(define (grafana-reverse-proxy config)
  (match-record config <grafana-configuration> (domain bind-address host-port)
    (if (string=? domain "localhost") (list)
        (list (https-reverse-proxy-configuration
               (domains (list domain))
               (destination-port host-port)
               (destination-ip
                (if (string=? bind-address "0.0.0.0")
                    "127.0.0.1"
                    bind-address)))))))

(define grafana-service-type
  (service-type
   (name 'grafana)
   (extensions
    (list (service-extension shepherd-root-service-type grafana-shepherd-service)
          (service-extension account-service-type grafana-accounts)
          (service-extension https-reverse-proxy-service-type grafana-reverse-proxy)))
   (default-value (grafana-configuration))
   (description "Grafana server, running under Docker.")))