#!/bin/bash
# `~/.claude/hooks/cache-timestamp.sh`
# Stop hook: stamps the cache expiry time so the statusline can render a live countdown.
# Reads the transcript JSONL, finds the last assistant turn that touched the cache
# (read OR creation > 0), and writes (that turn's timestamp + TTL) as epoch seconds to
# /tmp/cache_expiry_<session_id>.
#   - Creation matters because the first turn of a session only *writes* the cache
#     (cache_read is still 0) yet the cache is warm for the full TTL.
#   - Anchoring to the turn's own timestamp (when the cache was actually touched) rather
#     than "now" keeps the countdown honest on long turns, where Stop can fire minutes
#     after the API response that (re)set the TTL.

# Change to 300 for the default 5 minute prompt cache TTL.
CACHE_TTL_SECONDS=3600

INPUT=$(cat)

SESSION_ID=$(printf '%s' "$INPUT" | jq -r '.session_id // "default"')
TRANSCRIPT=$(printf '%s' "$INPUT" | jq -r '.transcript_path // ""')

[ -z "$TRANSCRIPT" ] || [ ! -f "$TRANSCRIPT" ] && exit 0

# Epoch (seconds) of the last assistant turn that touched the cache, or empty if none.
LAST_TOUCH=$(python3 -c "
import json, datetime
ts = ''
with open('$TRANSCRIPT') as f:
    for line in f:
        try:
            d = json.loads(line)
            if d.get('type') == 'assistant':
                u = d.get('message', {}).get('usage', {})
                if u.get('cache_read_input_tokens', 0) + u.get('cache_creation_input_tokens', 0) > 0:
                    ts = d.get('timestamp') or ts
        except:
            pass
if ts:
    try:
        print(int(datetime.datetime.fromisoformat(ts.replace('Z', '+00:00')).timestamp()))
    except Exception:
        pass
" 2>/dev/null)

if [ -n "$LAST_TOUCH" ] 2>/dev/null; then
  echo $(( LAST_TOUCH + CACHE_TTL_SECONDS )) > "/tmp/cache_expiry_${SESSION_ID}"
fi

##################################################
# and then this goes in your statusline-command.sh
##################################################

# Cache warmth countdown (1h TTL). Expiry is stamped by hooks/cache-timestamp.sh.
# green: first 5min  yellow: middle  red: last 5min  ❄: expired  dim: idle
cache_part=" \033[90mcache idle\033[0m"
exp_file="/tmp/cache_expiry_${session}"
if [ -f "$exp_file" ]; then
  exp=$(cat "$exp_file" 2>/dev/null)
  remain=$((${exp:-0} - $(date +%s)))
  if [ "$remain" -gt 0 ]; then
    ts=$(printf '%d:%02d' "$((remain / 60))" "$((remain % 60))")
    if [ "$remain" -gt 3300 ]; then
      c='\033[32m'
    elif [ "$remain" -gt 300 ]; then
      c='\033[33m'
    else
      c='\033[31m'
    fi
    cache_part=" ${c}cache ${ts}\033[0m"
  else
    cache_part=" ❄"
  fi
fi