From e0d9dd6602df9e27a077dcbd897d75329357c334 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rn-Michael=20Miehe?=
 <40151420+ldericher@users.noreply.github.com>
Date: Fri, 25 Feb 2022 17:24:50 +0100
Subject: [PATCH] refactoring + README

---
 Dockerfile |   4 +-
 README.md  |  40 +++++++++----
 cron-exec  | 151 ----------------------------------------------
 kiwi-cron  | 172 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 203 insertions(+), 164 deletions(-)
 delete mode 100755 cron-exec
 create mode 100755 kiwi-cron

diff --git a/Dockerfile b/Dockerfile
index b93af9c..035128a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -18,6 +18,6 @@ RUN set -ex; \
         docker-cli \
     ;
 
-COPY cron-exec /usr/local/bin/
+COPY kiwi-cron /usr/local/bin/
 
-CMD [ "cron-exec" ]
\ No newline at end of file
+CMD [ "kiwi-cron" ]
\ No newline at end of file
diff --git a/README.md b/README.md
index 443dcab..5e2f7d8 100644
--- a/README.md
+++ b/README.md
@@ -8,18 +8,36 @@ Simple cron-jobs  for [`kiwi-scp`](https://github.com/ldericher/kiwi-scp)
 
 ## Quick start
 
-kiwi-cron comes with a pre-configured cron daemon for periodic jobs. 
-Just drop your scripts into the relevant directory under `/kiwi-cron/` and that's it.
+`kiwi-cron` comes with a (slightly) opinionated `cron` daemon config for periodic jobs. 
+Just drop your scripts into the relevant directory under `/kiwi-cron`, that's it.
 
-- `/kiwi-cron/hourly` – is run every full hour
-- `/kiwi-cron/daily` – is run every day at 2 am
-- `/kiwi-cron/weekly` – is run every saturday at 3 am
-- `/kiwi-cron/monthly` – is run on the first day of every month at 5 am
-- `/kiwi-cron/yearly` and `/kiwi-cron/annually` – is run on every January 1st at 12 am
+You will likely want to automate some tasks regarding your `docker` infrastructure. 
+That's why the `kiwi-cron` images package a current `docker-cli` – you can just mount your `docker.sock` in its containers and use `docker` commands normally.
 
-## `/kiwi-cron/every` directory
+## Simple jobs
 
-You can use directories like `/kiwi-cron/every/5_minutes` to run scripts every 5 minutes. 
-`kiwi-cron` automatically picks up on that format and generates cron schedules for you.
+On startup, `kiwi-cron` checks for possible job files in the `/kiwi-cron` directory structure.
 
-You can define schedules to be run every N minutes, hours, days, or months that way.
+For each subdirectory, a random valid cron schedule is generated, so that:
+
+- `/kiwi-cron/hourly` runs once every hour (random minute)
+- `/kiwi-cron/daily` runs once every day (random nighttime value)
+- `/kiwi-cron/weekly` runs once every weekend (random nighttime value on Saturday or Sunday)
+- `/kiwi-cron/monthly` runs once every month (random nighttime value on a random day)
+- `/kiwi-cron/yearly` and `/kiwi-cron/annually` runs once a year (random nighttime value on a random day in January or February)
+
+Cron schedules are regenerated once on each startup, only for directories that have files.
+
+## Finer granularity: The `/kiwi-cron/every` directory
+
+Directories like `/kiwi-cron/every/5_minutes` will run scripts every 5 minutes. 
+`kiwi-cron` picks up on that format and generates valid `cron` schedules on startup.
+
+You can define schedules to be run every N minutes, hours, days, or months by creating the corresponding directories. 
+
+Scheduling for every N weeks (or years) doesn't work that way; jobs in those directories will instead be run every week (or every year).
+
+## Inspection
+
+Checking the generated `cron` schedules is done using the standard `crontab` command:
+`docker exec kiwi-cron-container crontab -l` will show the effective schedules.
diff --git a/cron-exec b/cron-exec
deleted file mode 100755
index b4f79ed..0000000
--- a/cron-exec
+++ /dev/null
@@ -1,151 +0,0 @@
-#!/bin/sh
-
-crontab_append () {
-  crontab="$(
-    printf '%s\n%s' \
-      "${crontab}" "${1}"
-  )"
-}
-
-print_cron_schedule() {
-    cas_min="${1}"
-    cas_hour="${2}"
-    cas_day="${3}"
-    cas_month="${4}"
-    cas_weekday="${5}"
-    cas_command="${6}"
-    
-    printf '%-8s%-8s%-8s%-8s%-8s%s\n' \
-      "${cas_min}" "${cas_hour}" "${cas_day}" "${cas_month}" "${cas_weekday}" "${cas_command}"
-}
-
-crontab='# crontab generated for kiwi-cron'
-crontab_append '# generation time: '"$(date)"
-crontab_append '#'
-crontab_append "$( 
-  print_cron_schedule \
-    "# min" "hour" "day" "month" "weekday" "command" 
-)"
-
-# check *ly dirs in root directory
-schedule_dirs="$( 
-  find "/kiwi-cron" -type d -name "*ly" -mindepth 1 -maxdepth 1
-)"
-
-for schedule_dir in ${schedule_dirs}; do
-  # count files in scheduler directory
-  schedule_filecount="$( 
-    find "${schedule_dir}" -type f -mindepth 1 -maxdepth 1 \
-    | wc -l
-  )"
-
-  # ignore if empty
-  if [ "${schedule_filecount}" -eq "0" ]; then
-    continue
-  fi
-
-  # infer cron schedule by directory name
-  units="${schedule_dir##*/}"
-
-  case "${units}" in
-    hourly)
-      crontab_append "$( 
-        print_cron_schedule \
-          "0" "*" "*" "*" "*" "run-parts '${schedule_dir}'" 
-      )"
-      ;;
-
-    daily)
-      crontab_append "$( 
-        print_cron_schedule \
-          "0" "2" "*" "*" "*" "run-parts '${schedule_dir}'" 
-      )"
-      ;;
-
-    weekly)
-      crontab_append "$( 
-        print_cron_schedule \
-          "0" "3" "*" "*" "6" "run-parts '${schedule_dir}'" 
-      )"
-      ;;
-
-    monthly)
-      crontab_append "$( 
-        print_cron_schedule \
-          "0" "5" "1" "*" "*" "run-parts '${schedule_dir}'" 
-      )"
-      ;;
-
-    yearly|annually)
-      crontab_append "$( 
-        print_cron_schedule \
-          "0" "0" "1" "1" "*" "run-parts '${schedule_dir}'" 
-      )"
-      ;;
-  esac
-done
-
-# check dirs in "every" subdirectory
-every_schedule_dirs="$( 
-  find "/kiwi-cron/every" -type d -mindepth 1 -maxdepth 1
-)"
-
-for schedule_dir in ${every_schedule_dirs}; do
-  # count files in scheduler directory
-  schedule_filecount="$( 
-    find "${schedule_dir}" -type f -mindepth 1 -maxdepth 1 \
-    | wc -l
-  )"
-
-  # ignore if empty
-  if [ "${schedule_filecount}" -eq "0" ]; then
-    continue
-  fi
-
-  # infer cron schedule by directory name
-  schedule="${schedule_dir##*/}"
-  every="$( echo "${schedule}" | awk -F_ '{print $1}' )"
-  units="$( echo "${schedule}" | awk -F_ '{print $2}' )"
-  units="${units%s}"
-
-  # generate valid random values
-  rand_min=$(( RANDOM % 60 ))
-  # rand_hour=$(( RANDOM % 24 ))
-  # generating nighttime values seems like a good idea!
-  rand_hour=$(( (RANDOM % 7 + 21) % 24 ))
-  rand_day=$(( RANDOM % 31 + 1 ))
-
-  case "${units}" in
-    minute)
-      crontab_append "$( 
-        print_cron_schedule \
-          "*/${every}" "*" "*" "*" "*" "run-parts '${schedule_dir}'" 
-      )"
-      ;;
-
-    hour)
-      crontab_append "$( 
-        print_cron_schedule \
-          "${rand_min}" "*/${every}" "*" "*" "*" "run-parts '${schedule_dir}'" 
-      )"
-      ;;
-
-    day)
-      crontab_append "$( 
-        print_cron_schedule \
-          "${rand_min}" "${rand_hour}" "*/${every}" "*" "*" "run-parts '${schedule_dir}'" 
-      )"
-      ;;
-
-    month)
-      crontab_append "$( 
-        print_cron_schedule \
-          "${rand_min}" "${rand_hour}" "${rand_day}" "*/${every}" "*" "run-parts '${schedule_dir}'" 
-      )"
-      ;;
-  esac
-done
-
-# replace crontab
-echo "${crontab}" | crontab -
-exec crond -fd 8
diff --git a/kiwi-cron b/kiwi-cron
new file mode 100755
index 0000000..4660c02
--- /dev/null
+++ b/kiwi-cron
@@ -0,0 +1,172 @@
+#!/bin/sh
+
+crontab=''
+crontab_line () {
+  if [ -z "${crontab}" ]; then
+    crontab="${1}"
+  else
+    crontab="$( 
+      printf '%s\n%s' "${crontab}" "${1}"; 
+    )"
+  fi
+}
+
+print_cron_schedule() {
+  pcs_min="${1}"
+  pcs_hour="${2}"
+  pcs_day="${3}"
+  pcs_month="${4}"
+  pcs_weekday="${5}"
+  pcs_command="${6}"
+  
+  printf '%-8s%-8s%-8s%-8s%-8s%s\n' \
+    "${pcs_min}" "${pcs_hour}" "${pcs_day}" "${pcs_month}" "${pcs_weekday}" "${pcs_command}"
+}
+
+create_schedule() {
+  cs_every="${1:-1}"
+  cs_units="${2}"
+  cs_command="${3}"
+
+  if [ "${cs_every}" -eq 1 ]; then
+    cs_every=""
+  else
+    cs_every="/${cs_every}"
+  fi
+
+  # generate valid random schedule values
+  # generally, "nighttime" and "weekend" will be preferred.
+
+  # shellcheck disable=SC3028
+  rand_min=$(( RANDOM % 60 ))
+
+  # shellcheck disable=SC3028
+  # rand_hour=$(( RANDOM % 24 ))
+  rand_hour=$(( (21 + RANDOM % 7) % 24 ))
+
+  # shellcheck disable=SC3028
+  rand_day=$(( RANDOM % 31 + 1 ))
+
+  # shellcheck disable=SC3028
+  # rand_weekday=$(( RANDOM % 7 ))
+  rand_weekday=$(( (6 + RANDOM % 2) % 7 ))
+
+  # shellcheck disable=SC3028
+  # rand_month=$(( RANDOM % 12 + 1 ))
+  rand_month=$(( RANDOM % 2 + 1 ))
+
+  case "${cs_units}" in
+  minute)
+    print_cron_schedule \
+      "*${cs_every}" "*" "*" "*" "*" "${cs_command}" 
+    ;;
+  hour)
+    print_cron_schedule \
+      "${rand_min}" "*${cs_every}" "*" "*" "*" "${cs_command}" 
+    ;;
+  day)
+    print_cron_schedule \
+      "${rand_min}" "${rand_hour}" "*${cs_every}" "*" "*" "${cs_command}" 
+    ;;
+  week)
+    print_cron_schedule \
+      "${rand_min}" "${rand_hour}" "*" "*" "${rand_weekday}" "${cs_command}" 
+    ;;
+  month)
+    print_cron_schedule \
+      "${rand_min}" "${rand_hour}" "${rand_day}" "*${cs_every}" "*" "${cs_command}" 
+    ;;
+  year)
+    print_cron_schedule \
+      "${rand_min}" "${rand_hour}" "${rand_day}" "${rand_month}" "*" "${cs_command}" 
+    ;;
+  esac
+}
+
+dir_has_no_files () {
+  dhnf_directory="${1}"
+
+  # count files in directory
+  dhnf_filecount="$( 
+    find "${dhnf_directory}" -type f -mindepth 1 -maxdepth 1 \
+    | wc -l
+  )"
+
+  # true if empty
+  test "${dhnf_filecount}" -eq "0"
+}
+
+dir_to_unit () {
+  dtu_dirname="${1}"
+
+  case "${dtu_dirname}" in
+    minute|hour|day|week|month|year)
+      echo "${dtu_dirname}" 
+      ;;
+    
+    # truncated "daily"
+    dai) 
+      echo "day"
+      ;;
+    
+    # truncated "annually"
+    annual) 
+      echo "year"
+      ;;
+  esac
+}
+
+crontab_line '# crontab generated by kiwi-cron'
+crontab_line '# generation time: '"$(date)"
+crontab_line '#'
+crontab_line "$( 
+  print_cron_schedule \
+    "# min" "hour" "day" "month" "weekday" "command" 
+)"
+
+# check *ly dirs in "/kiwi-cron" directory
+schedule_dirs="$( 
+  find "/kiwi-cron" -type d -name "*ly" -mindepth 1 -maxdepth 1
+)"
+
+for schedule_dir in ${schedule_dirs}; do
+  # ignore if no files
+  if dir_has_no_files "${schedule_dir}"; then
+    continue
+  fi
+
+  # infer units by directory name
+  dir_name="${schedule_dir##*/}"
+  units="${dir_name%ly}"
+  units="$( dir_to_unit "${units}" )"
+
+  crontab_line "$( 
+    create_schedule "1" "${units}" "run-parts '${schedule_dir}'"
+  )"
+done
+
+# check dirs in "/kiwi-cron/every" directory
+every_schedule_dirs="$( 
+  find "/kiwi-cron/every" -type d -mindepth 1 -maxdepth 1
+)"
+
+for schedule_dir in ${every_schedule_dirs}; do
+  # ignore if no files
+  if dir_has_no_files "${schedule_dir}"; then
+    continue
+  fi
+
+  # infer schedule params by directory name
+  dir_name="${schedule_dir##*/}"
+  every="$( echo "${dir_name}" | awk -F_ '{print $1}' )"
+  units="$( echo "${dir_name}" | awk -F_ '{print $2}' )"
+  units="${units%s}"
+
+  crontab_line "$( 
+    create_schedule "${every}" "${units}" "run-parts '${schedule_dir}'"
+  )"
+done
+
+# replace crontab, run crond
+echo "${crontab}" | crontab -
+exec crond -fd 8