#!/usr/bin/env bash
set -euo pipefail

ROOT_DIR="$(cd "$(dirname "$0")/.." && pwd)"
STATE_DIR="${TDC114_WSL_MAINTENANCE_STATE_DIR:-$ROOT_DIR/.tmp}"
STATE_FILE="${TDC114_WSL_MAINTENANCE_STATE_FILE:-$STATE_DIR/wsl-maintenance-last-check.txt}"
ANCHOR_DATE="${TDC114_WSL_MAINTENANCE_ANCHOR_DATE:-2026-07-16}"
INTERVAL_DAYS="${TDC114_WSL_MAINTENANCE_INTERVAL_DAYS:-14}"
MODE="${1:-status}"
TODAY="${TDC114_WSL_MAINTENANCE_TODAY:-$(date +%F)}"

usage() {
  cat <<EOF
Usage: $0 [status|record|reset]

status : print whether the recurring WSL maintenance check is due
record : mark today's date as the completed maintenance date
reset  : remove the stored completion date
EOF
}

require_date() {
  local value="$1"
  if ! date -d "$value" +%F >/dev/null 2>&1; then
    echo "Invalid date: $value" >&2
    exit 2
  fi
}

require_non_negative_integer() {
  local value="$1"
  case "$value" in
    ''|*[!0-9]*)
      echo "Interval must be a non-negative integer: $value" >&2
      exit 2
      ;;
  esac
}

days_since() {
  local from_date="$1"
  local to_date="$2"
  local from_epoch
  local to_epoch

  from_epoch="$(date -d "$from_date" +%s)"
  to_epoch="$(date -d "$to_date" +%s)"
  echo $(((to_epoch - from_epoch) / 86400))
}

print_due_message() {
  local base_date="$1"
  local elapsed_days="$2"
  local next_due_date

  next_due_date="$(date -d "$base_date + $INTERVAL_DAYS days" +%F)"

  cat <<EOF
WSL maintenance reminder: DUE
Base date: $base_date
Days elapsed: $elapsed_days
Due date: $next_due_date

General PowerShell:
1. Close VS Code, WSL terminals, Docker Desktop, and any \\\\wsl$ Explorer windows.
2. Run: wsl --shutdown

Administrator PowerShell:
1. Run: diskpart
2. Then run:
   select vdisk file="%LOCALAPPDATA%\\Packages\\CanonicalGroupLimited.Ubuntu_79rhkp1fndgsc\\LocalState\\ext4.vhdx"
   attach vdisk readonly
   compact vdisk
   detach vdisk
   exit

After maintenance is complete, record it with:
  ./scripts/check-wsl-maintenance.sh record
EOF
}

print_not_due_message() {
  local base_date="$1"
  local elapsed_days="$2"
  local remaining_days
  local next_due_date

  remaining_days=$((INTERVAL_DAYS - elapsed_days))
  next_due_date="$(date -d "$base_date + $INTERVAL_DAYS days" +%F)"

  cat <<EOF
WSL maintenance reminder: OK
Base date: $base_date
Days elapsed: $elapsed_days
Next due date: $next_due_date
Days remaining: $remaining_days
EOF
}

require_date "$ANCHOR_DATE"
require_date "$TODAY"
require_non_negative_integer "$INTERVAL_DAYS"
mkdir -p "$STATE_DIR"

case "$MODE" in
  status)
    base_date="$ANCHOR_DATE"
    if [ -f "$STATE_FILE" ] && [ -s "$STATE_FILE" ]; then
      base_date="$(tr -d '[:space:]' < "$STATE_FILE")"
      require_date "$base_date"
    fi

    elapsed_days="$(days_since "$base_date" "$TODAY")"
    if [ "$elapsed_days" -lt 0 ]; then
      echo "Stored date is in the future: $base_date" >&2
      exit 2
    fi

    if [ "$elapsed_days" -ge "$INTERVAL_DAYS" ]; then
      print_due_message "$base_date" "$elapsed_days"
    else
      print_not_due_message "$base_date" "$elapsed_days"
    fi
    ;;
  record)
    printf '%s\n' "$TODAY" > "$STATE_FILE"
    echo "Recorded WSL maintenance date: $TODAY"
    ;;
  reset)
    rm -f "$STATE_FILE"
    echo "Removed recorded WSL maintenance date: $STATE_FILE"
    ;;
  --help|-h|help)
    usage
    ;;
  *)
    echo "Unknown mode: $MODE" >&2
    usage >&2
    exit 2
    ;;
esac