#!/usr/bin/env bash
# Pre-compact hook: save a copy of the session transcript before compaction.
# Claude Code pipes JSON to stdin with session_id, transcript_path, cwd, etc.

set -euo pipefail

# Parse stdin JSON for transcript path and session ID
INPUT="$(cat)"
TRANSCRIPT_PATH="$(echo "$INPUT" | python3 -c "import sys,json; print(json.load(sys.stdin).get('transcript_path',''))" 2>/dev/null)"
SESSION_ID="$(echo "$INPUT" | python3 -c "import sys,json; print(json.load(sys.stdin).get('session_id',''))" 2>/dev/null)"
TRIGGER="$(echo "$INPUT" | python3 -c "import sys,json; print(json.load(sys.stdin).get('trigger','unknown'))" 2>/dev/null)"

if [ -z "$TRANSCRIPT_PATH" ] || [ ! -f "$TRANSCRIPT_PATH" ]; then
    echo "pre-compact-backup: no transcript found, skipping" >&2
    exit 0
fi

# Save to ~/.claude/transcript-backups/ with timestamp
BACKUP_DIR="$HOME/.claude/transcript-backups"
mkdir -p "$BACKUP_DIR"

TIMESTAMP="$(date +%Y%m%d-%H%M%S)"
BACKUP_FILE="${BACKUP_DIR}/${TIMESTAMP}-${SESSION_ID:0:8}-${TRIGGER}.jsonl"

cp "$TRANSCRIPT_PATH" "$BACKUP_FILE"

# Prune backups older than 30 days
find "$BACKUP_DIR" -name "*.jsonl" -mtime +30 -delete 2>/dev/null || true

echo "pre-compact-backup: saved $(wc -l < "$BACKUP_FILE") lines to ${BACKUP_FILE##*/}" >&2