#!/bin/bash
# PostToolUse hook: Log cost events and enforce budget.
# Bash 3.2 compatible. Uses python3 for JSON parsing.
#
# Follows Paperclip's post-hoc enforcement pattern:
# 1. Log cost event after each tool call
# 2. Check cumulative cost against budget policy
# 3. Warn at soft threshold, pause at hard threshold
#
# Placeholders:
#   {{WORKING_DIR}} - absolute path to project directory

WORKING_DIR="{{WORKING_DIR}}"
BUDGET_DIR="$WORKING_DIR/budget"
COST_LOG="$BUDGET_DIR/cost-events.jsonl"
BUDGET_FILE="$WORKING_DIR/BUDGET.md"
PAUSED_FLAG="$BUDGET_DIR/PAUSED"

mkdir -p "$BUDGET_DIR"

# Read hook input
INPUT=$(cat)
TOOL_NAME=$(echo "$INPUT" | python3 -c "import sys,json; print(json.load(sys.stdin).get('tool_name',''))" 2>/dev/null)

# Log cost event
python3 -c "
import json, sys, time, os

try:
    data = json.loads('''$INPUT''')
except:
    sys.exit(0)

tool_name = data.get('tool_name', '')
event = {
    'timestamp': time.strftime('%Y-%m-%dT%H:%M:%SZ', time.gmtime()),
    'tool_name': tool_name,
    'agent': os.environ.get('AGENT_NAME', 'unknown'),
    'estimated_tokens': 0
}

cost_log = '$COST_LOG'
with open(cost_log, 'a') as f:
    f.write(json.dumps(event) + '\n')
" 2>/dev/null

# Check budget if BUDGET.md exists
if [ -f "$BUDGET_FILE" ] && [ -f "$COST_LOG" ]; then
  BUDGET_RESULT=$(BUDGET_FILE="$BUDGET_FILE" COST_LOG="$COST_LOG" PAUSED_FLAG="$PAUSED_FLAG" python3 -c "
import re, json, os
budget_file = os.environ.get('BUDGET_FILE', '')
cost_log = os.environ.get('COST_LOG', '')
paused_flag = os.environ.get('PAUSED_FLAG', '')
try:
    content = open(budget_file).read()
    limit_m = re.search(r'limit:\s*(\d+)\s*cents', content)
    if not limit_m: print('ok'); exit(0)
    limit = int(limit_m.group(1))
    warn_m = re.search(r'warn_percent:\s*(\d+)', content)
    warn_pct = int(warn_m.group(1)) if warn_m else 80
    hard_m = re.search(r'hard_stop:\s*(\w+)', content)
    hard_stop = hard_m.group(1).lower() == 'true' if hard_m else True
    event_count = sum(1 for _ in open(cost_log))
    estimated_cents = event_count
    pct = (estimated_cents / limit * 100) if limit > 0 else 0
    if pct >= 100 and hard_stop:
        open(paused_flag, 'w').write('Budget exceeded: ' + str(estimated_cents) + '/' + str(limit) + ' cents')
        print('hard_stop')
    elif pct >= warn_pct:
        print('warn')
    else:
        print('ok')
except Exception as e:
    print('ok')
" 2>/dev/null)

  if [ "$BUDGET_RESULT" = "hard_stop" ]; then
    echo "BUDGET EXCEEDED — agent paused. Check $PAUSED_FLAG" >&2
  elif [ "$BUDGET_RESULT" = "warn" ]; then
    echo "BUDGET WARNING — approaching limit" >&2
  fi
fi

# Check if agent is paused
if [ -f "$PAUSED_FLAG" ]; then
  echo '{"decision": "block", "reason": "Agent paused: budget exceeded. Remove '"$PAUSED_FLAG"' to resume."}'
  exit 2
fi

exit 0