#!/usr/bin/env python3
"""SessionEnd hook: append one metadata + token-usage line to ~/.claude/log.md."""
import json, sys, pathlib
from datetime import datetime

try:
    data = json.load(sys.stdin)
except Exception:
    data = {}

ts = datetime.now().strftime("%Y-%m-%dT%H:%M:%S")
cwd = data.get("cwd", "?")
reason = data.get("reason", "?")
sid = data.get("session_id") or "?"
sid_short = sid[:8]


def find_transcript():
    tp = data.get("transcript_path")
    if tp and pathlib.Path(tp).exists():
        return pathlib.Path(tp)
    if cwd == "?" or sid == "?":
        return None
    slug = cwd.replace("/", "-")
    candidate = pathlib.Path.home() / ".claude" / "projects" / slug / f"{sid}.jsonl"
    return candidate if candidate.exists() else None


def sum_tokens(path):
    totals = {"input": 0, "output": 0, "cache_read": 0, "cache_write": 0}
    try:
        with path.open() as f:
            for line in f:
                try:
                    rec = json.loads(line)
                except Exception:
                    continue
                if rec.get("type") != "assistant":
                    continue
                u = rec.get("message", {}).get("usage") or {}
                totals["input"] += u.get("input_tokens", 0)
                totals["output"] += u.get("output_tokens", 0)
                totals["cache_read"] += u.get("cache_read_input_tokens", 0)
                totals["cache_write"] += u.get("cache_creation_input_tokens", 0)
    except Exception:
        pass
    return totals


def fmt(n):
    if n >= 1_000_000:
        return f"{n/1_000_000:.1f}M"
    if n >= 1_000:
        return f"{n/1_000:.1f}k"
    return str(n)


tpath = find_transcript()
if tpath:
    t = sum_tokens(tpath)
    total = sum(t.values())
    tok_str = (
        f"tokens=total:{fmt(total)} "
        f"in:{fmt(t['input'])} out:{fmt(t['output'])} "
        f"cache_r:{fmt(t['cache_read'])} cache_w:{fmt(t['cache_write'])}"
    )
else:
    tok_str = "tokens=unavailable"

line = f"- {ts} | session={sid_short} | cwd={cwd} | reason={reason} | {tok_str}\n"
log = pathlib.Path.home() / ".claude" / "log.md"
if not log.exists():
    log.write_text("# Session Log\n\n")
with log.open("a") as f:
    f.write(line)