#!/usr/bin/env bash
# WTM File Watcher - Monitor other sessions' changes and notify
# Runs as a background process per session

source "${HOME}/.wtm/lib/common.sh"

if [[ $# -lt 1 ]]; then
  echo "Usage: wtm-watch <session-id>"
  exit 1
fi

SESSION_ID="$1"
LOG_FILE="${WTM_LOGS}/watch-${SESSION_ID//[:\/]/_}.log"

# Get this session's worktree
SESSION_DATA=$(get_session "${SESSION_ID}") || {
  log_error "Session '${SESSION_ID}' not found"
  exit 1
}

MY_WORKTREE=$(echo "${SESSION_DATA}" | python3 -c "import json,sys; print(json.loads(sys.stdin.read()).get('worktree',''))")
MY_PROJECT=$(echo "${SESSION_DATA}" | python3 -c "import json,sys; print(json.loads(sys.stdin.read()).get('project',''))")

# Find all OTHER session worktrees for the same project
get_other_worktrees() {
  python3 -c "
import json
with open('${WTM_SESSIONS}') as f:
    data = json.load(f)
for sid, s in data.get('sessions', {}).items():
    if sid != '${SESSION_ID}' and s.get('project') == '${MY_PROJECT}':
        print(f\"{sid}|{s.get('worktree', '')}\")
"
}

# Write change notification
notify_change() {
  local other_session="$1"
  local changed_file="$2"
  local timestamp
  timestamp=$(now_iso)

  # Write to this session's change log
  echo "${timestamp}|${other_session}|${changed_file}" >> "${LOG_FILE}"

  # Write to a notification file that Claude Code hooks can read
  local notify_dir="${MY_WORKTREE}/.wtm-notifications"
  mkdir -p "${notify_dir}"
  echo "${timestamp}|${other_session}|${changed_file}" >> "${notify_dir}/pending.log"

  # Keep only last 100 notifications
  if [[ -f "${notify_dir}/pending.log" ]]; then
    tail -100 "${notify_dir}/pending.log" > "${notify_dir}/pending.log.tmp"
    mv "${notify_dir}/pending.log.tmp" "${notify_dir}/pending.log"
  fi
}

# Check if fswatch is available
if ! command -v fswatch &>/dev/null; then
  log_warn "fswatch not installed. Using polling fallback (30s interval)."

  # Polling fallback
  while true; do
    while IFS='|' read -r other_sid other_worktree; do
      if [[ -d "${other_worktree}" ]]; then
        # Check for recent changes via git
        changes=$(cd "${other_worktree}" && git diff --name-only 2>/dev/null)
        if [[ -n "${changes}" ]]; then
          while IFS= read -r file; do
            notify_change "${other_sid}" "${file}"
          done <<< "${changes}"
        fi
      fi
    done < <(get_other_worktrees)

    sleep 30
  done
else
  # fswatch-based real-time monitoring
  log_info "Starting fswatch for session ${SESSION_ID}..."

  # Build list of worktrees to watch
  WATCH_DIRS=()
  while IFS='|' read -r other_sid other_worktree; do
    if [[ -d "${other_worktree}" ]]; then
      WATCH_DIRS+=("${other_worktree}")
      log_info "Watching: ${other_sid} -> ${other_worktree}"
    fi
  done < <(get_other_worktrees)

  if [[ ${#WATCH_DIRS[@]} -eq 0 ]]; then
    log_info "No other sessions to watch. Waiting for new sessions..."
    # Re-check every 60s for new sessions
    while true; do
      sleep 60
      NEW_DIRS=()
      while IFS='|' read -r other_sid other_worktree; do
        if [[ -d "${other_worktree}" ]]; then
          NEW_DIRS+=("${other_worktree}")
        fi
      done < <(get_other_worktrees)

      if [[ ${#NEW_DIRS[@]} -gt 0 ]]; then
        # Restart with new targets
        exec bash "${HOME}/.wtm/bin/wtm-watch" "${SESSION_ID}"
      fi
    done
  fi

  # Watch with fswatch
  fswatch -r \
    --exclude '\.git' \
    --exclude 'node_modules' \
    --exclude '\.next' \
    --exclude '\.psm-' \
    --exclude '__pycache__' \
    "${WATCH_DIRS[@]}" | while read -r changed_path; do

    # Determine which session owns this change
    for other_entry in $(get_other_worktrees); do
      IFS='|' read -r other_sid other_worktree <<< "${other_entry}"
      if [[ "${changed_path}" == "${other_worktree}"* ]]; then
        rel_path="${changed_path#${other_worktree}/}"
        notify_change "${other_sid}" "${rel_path}"
        break
      fi
    done
  done
fi