#!/usr/bin/env bash
# Pre-compact hook: save a copy of the session transcript before compaction.
# Claude Code pipes JSON with session_id, cwd, hook_event_name (no transcript_path).
# Derives the transcript location from session_id + cwd.
# After saving, registers the backup in ~/.claude/transcript-backups/tracking.json.

set -euo pipefail

# Parse stdin JSON
INPUT="$(cat)"
SESSION_ID="$(echo "$INPUT" | python3 -c "import sys,json; print(json.load(sys.stdin).get('session_id',''))" 2>/dev/null)"
CWD="$(echo "$INPUT" | python3 -c "import sys,json; print(json.load(sys.stdin).get('cwd',''))" 2>/dev/null)"
PROVIDED_PATH="$(echo "$INPUT" | python3 -c "import sys,json; print(json.load(sys.stdin).get('transcript_path',''))" 2>/dev/null)"

if [ -z "$SESSION_ID" ]; then
    echo "pre-compact-backup: missing session_id in hook input, skipping" >&2
    exit 0
fi

# Try provided path first (older Claude Code versions), then derive from session_id + cwd
if [ -n "$PROVIDED_PATH" ] && [ -f "$PROVIDED_PATH" ]; then
    TRANSCRIPT_PATH="$PROVIDED_PATH"
elif [ -n "$CWD" ]; then
    # Derive transcript path: /home/paul/dev/claude -> -home-paul-dev-claude
    PROJECT_DIR="$(echo "$CWD" | tr '/' '-')"
    TRANSCRIPT_PATH="$HOME/.claude/projects/${PROJECT_DIR}/${SESSION_ID}.jsonl"
else
    echo "pre-compact-backup: cannot locate transcript (no cwd or transcript_path), skipping" >&2
    exit 0
fi

if [ ! -f "$TRANSCRIPT_PATH" ]; then
    echo "pre-compact-backup: transcript not found at ${TRANSCRIPT_PATH}, skipping" >&2
    exit 0
fi

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

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

cp "$TRANSCRIPT_PATH" "$BACKUP_FILE"

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

# Register backup in tracking.json using the register helper
python3 "$HOME/.claude/scripts/extract-transcripts.py" \
    --register "$BACKUP_NAME" \
    --session-id "$SESSION_ID" \
    --cwd "$CWD" \
    2>/dev/null \
    && TRACKED=" [tracked]" \
    || TRACKED=" [tracking failed]"

echo "pre-compact-backup: saved $(wc -l < "$BACKUP_FILE") lines to ${BACKUP_NAME} [project: ${CWD}]${TRACKED}" >&2