#!/usr/bin/env bash
# gstack-settings-hook — add/remove SessionStart hooks in Claude Code settings.json
#
# Usage:
#   gstack-settings-hook add <hook-command>     # add SessionStart hook
#   gstack-settings-hook remove <hook-command>  # remove SessionStart hook
#
# Requires: bun (already a gstack hard dependency)
# Writes atomically: .tmp + rename to prevent corruption on crash/disk-full.

set -euo pipefail

ACTION="${1:-}"
HOOK_CMD="${2:-}"
SETTINGS_FILE="${GSTACK_SETTINGS_FILE:-$HOME/.claude/settings.json}"

if [ -z "$ACTION" ] || [ -z "$HOOK_CMD" ]; then
  echo "Usage: gstack-settings-hook {add|remove} <hook-command>" >&2
  exit 1
fi

if ! command -v bun >/dev/null 2>&1; then
  echo "Error: bun is required but not installed." >&2
  exit 1
fi

case "$ACTION" in
  add)
    bun -e "
      const fs = require('fs');
      const settingsPath = '$SETTINGS_FILE';
      const hookCmd = $(printf '%s' "$HOOK_CMD" | bun -e "process.stdout.write(JSON.stringify(require('fs').readFileSync('/dev/stdin','utf8')))");

      let settings = {};
      try { settings = JSON.parse(fs.readFileSync(settingsPath, 'utf8')); } catch {}

      if (!settings.hooks) settings.hooks = {};
      if (!settings.hooks.SessionStart) settings.hooks.SessionStart = [];

      // Dedup: check if hook command already registered
      const exists = settings.hooks.SessionStart.some(entry =>
        entry.hooks && entry.hooks.some(h => h.command && h.command.includes('gstack-session-update'))
      );

      if (!exists) {
        settings.hooks.SessionStart.push({
          hooks: [{ type: 'command', command: hookCmd }]
        });
      }

      const tmp = settingsPath + '.tmp';
      fs.writeFileSync(tmp, JSON.stringify(settings, null, 2) + '\n');
      fs.renameSync(tmp, settingsPath);
    " 2>/dev/null
    ;;
  remove)
    [ -f "$SETTINGS_FILE" ] || exit 0
    bun -e "
      const fs = require('fs');
      const settingsPath = '$SETTINGS_FILE';

      let settings = {};
      try { settings = JSON.parse(fs.readFileSync(settingsPath, 'utf8')); } catch { process.exit(0); }

      if (settings.hooks && settings.hooks.SessionStart) {
        settings.hooks.SessionStart = settings.hooks.SessionStart.filter(entry =>
          !(entry.hooks && entry.hooks.some(h => h.command && h.command.includes('gstack-session-update')))
        );
        if (settings.hooks.SessionStart.length === 0) delete settings.hooks.SessionStart;
        if (Object.keys(settings.hooks).length === 0) delete settings.hooks;
      }

      const tmp = settingsPath + '.tmp';
      fs.writeFileSync(tmp, JSON.stringify(settings, null, 2) + '\n');
      fs.renameSync(tmp, settingsPath);
    " 2>/dev/null
    ;;
  *)
    echo "Unknown action: $ACTION (expected add or remove)" >&2
    exit 1
    ;;
esac
