#!/usr/bin/env bash
set -uo pipefail

# CASAN H6 cost-spike detector (WP-C).
# Answers the H6 key question: "if a step suddenly costs 3x the tokens, does
# anyone know?". Reads real per-step usage from provider-usage.jsonl, computes
# the median total_tokens across steps, and flags any step exceeding
# MULTIPLIER x median. Exits non-zero if a spike is found (so a pipeline/CI gate
# goes red).
#
# Usage: cost-spike-detect.sh [provider-usage.jsonl] [multiplier]
# Exit: 0 no spike, 2 spike detected, 64 usage, 3 not enough data.

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
PROJECT_ROOT="$(cd "$SCRIPT_DIR/../../.." && pwd)"
LOG="${1:-$PROJECT_ROOT/.specify/logs/level5/provider-usage.jsonl}"
MULT="${2:-3.0}"

[[ -f "$LOG" ]] || { echo "COST_SPIKE_NO_DATA file=$LOG" >&2; exit 3; }

python3 - "$LOG" "$MULT" <<'PY'
import json, sys, statistics
path, mult = sys.argv[1], float(sys.argv[2])
rows = []
for line in open(path, encoding="utf-8"):
    line = line.strip()
    if not line:
        continue
    try:
        r = json.loads(line)
    except ValueError:
        continue
    if "total_tokens" in r:
        rows.append((r.get("step", "?"), int(r["total_tokens"])))
if len(rows) < 3:
    sys.stderr.write(f"COST_SPIKE_NO_DATA records={len(rows)} (need >=3)\n")
    raise SystemExit(3)
tokens = [t for _, t in rows]
median = statistics.median(tokens)
threshold = median * mult
spikes = [(s, t) for s, t in rows if t > threshold]
print(f"records={len(rows)} median_tokens={median} threshold={threshold:.0f} (x{mult})")
for s, t in spikes:
    print(f"SPIKE step={s} tokens={t} (> {threshold:.0f})")
if spikes:
    sys.stderr.write(f"COST_SPIKE_DETECTED count={len(spikes)}\n")
    raise SystemExit(2)
print("COST_SPIKE_NONE")
PY