feat(package): +migrator

package/migrator/default.nix

@@ -0,0 +1,20 @@
+{ dash, hectic }:
+let
+  shell = "${dash}/bin/dash";
+  bashOptions = [
+    "errexit"
+    "nounset"
+  ];
+
+  migrator = hectic.writeShellApplication {
+    inherit shell bashOptions;
+    name = "migrator";
+    runtimeInputs = [ ];
+
+    text = ''
+      ${builtins.readFile hectic.helpers.posix-shell.log}
+      ${builtins.readFile ./migrator.sh}
+    '';
+  };
+in
+migrator

package/migrator/migrator.sh

@@ -0,0 +1,125 @@
+#!/bin/dash
+
+if ! command -v psql >/dev/null; then
+    log error "Required tool (psql) are not installed."
+    exit 127
+fi
+
+MIGRATION_DIR="${MIGRATION_DIR:-migration}"
+
+while [ $# -gt 0 ]; do
+  case $1 in
+    migrate|create|fetch)
+      [ -n "$SUBCOMMAND" ] || (printf 'ambiguous subcommand, decide %s or %s' "$SUBCOMMAND" "$1"; exit 1)
+      SUBCOMMAND=$1
+      shift
+    ;;
+    --migration-dir|-d)
+      MIGRATION_DIR=$2
+      shift 2
+    ;;
+    --inherits)
+      INHERITS_LIST="${INHERITS_LIST:+$INHERITS_LIST }$2"
+      shift 2
+    ;;
+    --*|-*) ;; # skip all unrecognized arguments
+    *)
+      printf 'subcommand %s does not exists' "$1"
+      exit 1
+    ;;
+  esac
+done
+
+[ -z "$SUBCOMMAND" ] || (log error "no subcomand specified"; exit 1)
+
+help() {
+  # inherits: List one or more tables the migration table must inherit from
+  echo help
+}
+
+migrate() {
+  while [ $# -gt 0 ]; do
+    case $1 in
+      up|down|to)
+        [ -n "$MIGRATE_SUBCOMMAND" ] || (printf 'ambiguous migrate subcommand, decide %s or %s' "$MIGRATE_SUBCOMMAND" "$1"; exit 1)
+	MIGRATE_SUBCOMMAND="$1"
+      ;;
+      --db-url|-u)
+        DB_URL="$2"
+        shift 2
+      ;;
+      --force|-f)
+        FORCE=1
+        shift
+      ;;
+      --set|-v)
+	VARIABLE_LIST="${VARIABLE_LIST:+$VARIABLE_LIST }$2"
+        shift 2
+      ;;
+      --*|-*)
+        printf 'argument %s does not exists' "$1"
+        exit 1
+      ;;
+      *)
+        printf 'migrate subcommand %s does not exists' "$1"
+        exit 1
+      ;;
+    esac
+  done
+
+  # Get the list of new migrations from disk
+  fs_migrations=$(
+    find "$MIGRATION_DIR" -maxdepth 1 -type f -name '*.sql' \
+      | sort \
+      | xargs -n1 basename
+  )
+
+  # Get the list of already applied migrations from DB
+  db_migrations=$(
+    psql -Atqc "SELECT name FROM hectic.migration ORDER BY name ASC" \
+      | awk NF
+  )
+
+  # Check if the DB migrations form a proper prefix of disk migrations
+  # (meaning all DB-applied migration filenames should appear in the same order at the start).
+  i=0
+  for db_migration in $db_migrations; do
+    fs_migration=$(echo "$fs_migrations" | sed -n "$((i+1))p")
+    if [ -z "$fs_migration" ] || [ "$fs_migration" != "$db_migration" ]; then
+      if [ -z "$FORCE" ]; then
+        echo "Unrelated migration tree detected. Use --force to proceed." >&2
+        exit 2
+      else
+        echo "Unrelated migration tree forced. Proceeding..." >&2
+        break
+      fi
+    fi
+    i=$((i+1))
+  done
+}
+
+create() {
+  while [ $# -gt 0 ]; do
+    case $1 in
+      --name|-n)
+	# shellcheck disable=SC2034
+        NAME=$2
+        shift 2
+      ;;
+    esac
+  done
+}
+
+fetch() {
+  while [ $# -gt 0 ]; do
+    case $1 in
+      --db-url|-u)
+	# shellcheck disable=SC2034
+        DB_URL=$2
+        shift 2
+      ;;
+    esac
+  done
+}
+
+"$SUBCOMMAND"