#!/usr/bin/env python3
"""M-D2-CST: USD cost of agentic work, attributed to workplan tasks.

Normative spec: specs/CostAccounting.md. Decision: decisions/ADR-0003.

Reads Claude Code session transcripts, deduplicates by requestId, prices
each response at its own model's rate and its own cache TTL, and attributes
it to the task named by the next commit at or after it within the same
session.

Positive control (InnerLoop v1.0 §Step 5, CostAccounting CA-02/CA-14):
this tool asserts it did the work it reports. `--self-test` exercises four
assertions against fixtures with known answers; every reporting run checks
the dedup invariant and reconciles attributed + unattributed + open +
unpriced against the raw total, aborting rather than printing a number that
does not add up.

Usage:
  python3 tools/cb-cost.py                      # whole repo, no pin
  python3 tools/cb-cost.py --pin fc76445        # pinned at a commit
  python3 tools/cb-cost.py --by-task            # per-task attribution
  python3 tools/cb-cost.py --composition        # cost split by component
  python3 tools/cb-cost.py --self-test          # positive control
  python3 tools/cb-cost.py --json
"""

import argparse
import collections
import datetime
import glob
import json
import os
import re
import subprocess
import sys

try:
    import tomllib
except ModuleNotFoundError:  # pragma: no cover - py<3.11
    print("ERROR: needs Python 3.11+ for tomllib", file=sys.stderr)
    sys.exit(1)

REPO = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
PRICES = os.path.join(REPO, "benchmarks", "baselines", "model-prices.toml")
COMPONENTS = ("input", "output", "cache_read", "write_5m", "write_1h")
TASK_RE = re.compile(r"\bT\d\d\b")
UNATTRIBUTED = "UNATTRIBUTED"
OPEN_REMAINDER = "OPEN (uncommitted)"


class Abort(Exception):
    """A positive-control failure. Never degrades to a printed number."""


# ---------------------------------------------------------------- pricing


def load_prices(path=PRICES):
    with open(path, "rb") as fh:
        return tomllib.load(fh)


def components(usage):
    """Token counts per billable component (CA-04: writes split by TTL)."""
    cc = usage.get("cache_creation") or {}
    return {
        "input": usage.get("input_tokens", 0),
        "output": usage.get("output_tokens", 0),
        "cache_read": usage.get("cache_read_input_tokens", 0),
        "write_5m": cc.get("ephemeral_5m_input_tokens", 0),
        "write_1h": cc.get("ephemeral_1h_input_tokens", 0),
    }


def price_of(prices, model, toks):
    """USD for one response. Returns None when the model is unpriced (CA-05)."""
    pr = prices.get(model)
    if not pr:
        return None
    cache = prices["cache"]
    unit = pr["input"] / 1e6
    return (
        toks["input"] * unit
        + toks["output"] * pr["output"] / 1e6
        + toks["cache_read"] * unit * cache["read"]
        + toks["write_5m"] * unit * cache["write_5m"]
        + toks["write_1h"] * unit * cache["write_1h"]
    )


# ------------------------------------------------------------- transcripts


def transcript_paths(slug):
    """Every transcript for the repo, including the subagent tree (CA-06)."""
    base = os.path.expanduser(f"~/.claude/projects/{slug}")
    return sorted(glob.glob(f"{base}/*.jsonl")) + sorted(
        glob.glob(f"{base}/*/subagents/agent-*.jsonl")
    )


def read_responses(path, pin=None):
    """Deduplicate one transcript by requestId, asserting CA-02."""
    groups = collections.defaultdict(list)
    for line in open(path):
        try:
            d = json.loads(line)
        except json.JSONDecodeError:
            continue
        if d.get("type") != "assistant":
            continue
        usage = (d.get("message") or {}).get("usage")
        if usage is None:
            continue
        ts = d.get("timestamp") or ""
        if pin and ts > pin:
            continue
        groups[d.get("requestId")].append(d)

    out = []
    for rid, rows in groups.items():
        # CA-02 positive control. Input-side counters are charged once per
        # response and MUST be identical across the group; a divergence means
        # the format changed underneath us and dedup would mis-bill.
        #
        # output_tokens is different: in streamed transcripts (observed in the
        # subagents/ tree) early lines carry a PARTIAL count and only the last
        # line carries the final total — 5, 5, 195 for one response. Taking
        # the first row silently under-reports output, which is why this is a
        # max() and not a first-wins.
        seen_model = {r["message"].get("model") for r in rows}
        if len(seen_model) != 1:
            raise Abort(
                f"{os.path.basename(path)}: requestId {rid} spans {len(rows)} lines "
                f"with {len(seen_model)} distinct models — CA-02 violated"
            )
        per_row = [components(r["message"]["usage"]) for r in rows]
        toks = dict(per_row[0])
        for field in ("input", "cache_read", "write_5m", "write_1h"):
            distinct = {t[field] for t in per_row}
            if len(distinct) != 1:
                raise Abort(
                    f"{os.path.basename(path)}: requestId {rid} has {len(distinct)} "
                    f"distinct values for {field} across {len(rows)} lines "
                    f"({sorted(distinct)}) — CA-02 violated; input-side counters "
                    f"are charged once per response and must not vary"
                )
        toks["output"] = max(t["output"] for t in per_row)
        head = rows[0]
        out.append(
            {
                "request_id": rid,
                "model": head["message"].get("model"),
                "timestamp": head.get("timestamp") or "",
                "session": head.get("sessionId") or os.path.basename(path),
                "toks": toks,
                "subagent": "/subagents/" in path,
            }
        )
    return out


# ------------------------------------------------------------- attribution


def commit_index(pin=None):
    """(utc_time, subject) for each commit, oldest first (CA-09)."""
    fmt = subprocess.run(
        ["git", "-C", REPO, "log", "--format=%cI|%s", "--reverse"],
        capture_output=True,
        text=True,
        check=True,
    ).stdout.splitlines()
    rows = []
    for line in fmt:
        iso, _, subject = line.partition("|")
        # CA-09: convert, never subtract a fixed offset — this repo has two.
        utc = (
            datetime.datetime.fromisoformat(iso)
            .astimezone(datetime.timezone.utc)
            .isoformat()
            .replace("+00:00", "Z")
        )
        rows.append((utc, subject))
    if pin:
        rows = [r for r in rows if r[0] <= pin]
    return rows


def resolve_pin(ref):
    """A commit-ish pin becomes the UTC instant of that commit."""
    if not ref:
        return None
    if ref.endswith("Z"):
        return ref
    iso = subprocess.run(
        ["git", "-C", REPO, "log", "-1", "--format=%cI", ref],
        capture_output=True,
        text=True,
        check=True,
    ).stdout.strip()
    return (
        datetime.datetime.fromisoformat(iso)
        .astimezone(datetime.timezone.utc)
        .isoformat()
        .replace("+00:00", "Z")
    )


def attribute(responses, commits):
    """Assign each response a bucket per CA-08/CA-10/CA-11.

    Intervals are ending-at-commit: (prev_commit, this_commit]. Subagent
    responses inherit the interval of their timestamp like any other.
    """
    label_for = []
    prev = ""
    for ts, subject in commits:
        m = TASK_RE.search(subject)
        label_for.append((prev, ts, m.group(0) if m else UNATTRIBUTED))
        prev = ts
    last = commits[-1][0] if commits else ""

    for r in responses:
        ts = r["timestamp"]
        if last and ts > last:
            r["task"] = OPEN_REMAINDER  # CA-11
            continue
        r["task"] = UNATTRIBUTED
        for lo, hi, label in label_for:
            if lo < ts <= hi:
                r["task"] = label
                break
    return responses


# ----------------------------------------------------------------- report


def collect(slug, pin_ref=None):
    prices = load_prices()
    pin = resolve_pin(pin_ref)
    paths = transcript_paths(slug)
    if not paths:
        raise Abort(f"no transcripts found for {slug}")

    responses = []
    for p in paths:
        responses.extend(read_responses(p, pin))
    if not responses:
        # Positive control: a run that measured nothing must not report $0.00
        # as though it were an answer.
        raise Abort(f"no responses in {len(paths)} transcript(s) — refusing to report")

    for r in responses:
        r["cost"] = price_of(prices, r["model"], r["toks"])

    attribute(responses, commit_index(pin))

    by_task = collections.defaultdict(float)
    by_component = collections.Counter()
    by_component_cost = collections.defaultdict(float)
    by_model = collections.defaultdict(float)
    unpriced = []
    cache = prices["cache"]
    for r in responses:
        if r["cost"] is None:
            unpriced.append(r)
            continue
        by_task[r["task"]] += r["cost"]
        by_model[r["model"]] += r["cost"]
        pr = prices[r["model"]]
        unit = pr["input"] / 1e6
        rates = {
            "input": unit,
            "output": pr["output"] / 1e6,
            "cache_read": unit * cache["read"],
            "write_5m": unit * cache["write_5m"],
            "write_1h": unit * cache["write_1h"],
        }
        for k, n in r["toks"].items():
            by_component[k] += n
            by_component_cost[k] += n * rates[k]

    total = sum(by_task.values())
    # CA-14: reconciliation is asserted, not assumed.
    residual = total - sum(by_component_cost.values())
    if abs(residual) > 0.005:
        raise Abort(
            f"reconciliation failed: task total ${total:,.4f} vs component total "
            f"${sum(by_component_cost.values()):,.4f} (residual ${residual:,.4f})"
        )

    sub = sum(r["cost"] or 0 for r in responses if r["subagent"])
    return {
        "slug": slug,
        "pin": pin,
        "responses": len(responses),
        "transcripts": len(paths),
        "total": total,
        "subagent_total": sub,
        "main_total": total - sub,
        "by_task": dict(by_task),
        "by_model": dict(by_model),
        "tokens": dict(by_component),
        "cost_by_component": dict(by_component_cost),
        "unpriced": [
            {"model": r["model"], "tokens": r["toks"]} for r in unpriced
        ],
        "reconciled": True,
        "residual": residual,
    }


def render(rep, by_task=False, composition=False):
    print(f"M-D2-CST cost report — {rep['slug']}")
    print(f"  pin           {rep['pin'] or '(none — live file, not reproducible)'}")
    print(f"  transcripts   {rep['transcripts']}   responses {rep['responses']}")
    print(f"  main          ${rep['main_total']:>10,.2f}")
    print(f"  subagent tree ${rep['subagent_total']:>10,.2f}")
    print(f"  TOTAL         ${rep['total']:>10,.2f}")

    if composition:
        print("\n  composition")
        tot = rep["total"] or 1
        for k in COMPONENTS:
            c = rep["cost_by_component"].get(k, 0.0)
            print(
                f"    {k:<12}{rep['tokens'].get(k,0):>14,} tok  "
                f"${c:>9,.2f}  {100*c/tot:>5.1f}%"
            )

    if by_task:
        print("\n  by task")
        rows = sorted(rep["by_task"].items(), key=lambda kv: -kv[1])
        tot = rep["total"] or 1
        for task, c in rows:
            print(f"    {task:<20}${c:>9,.2f}  {100*c/tot:>5.1f}%")
        # CA-10: the limit is reported with the number, every time.
        un = rep["by_task"].get(UNATTRIBUTED, 0.0)
        print(
            f"\n    NOTE: {100*un/tot:.0f}% of cost is UNATTRIBUTED — commits whose "
            f"subject carries no T## tag.\n"
            f"    A per-task table is a view over {100*(1-un/tot):.0f}% of spend."
        )

    if rep["unpriced"]:
        print(f"\n  UNPRICED ({len(rep['unpriced'])} responses, model not in sheet):")
        for u in rep["unpriced"]:
            print(f"    {u['model']}  {u['tokens']}")

    print(f"\n  reconciled: ok (residual ${rep['residual']:.6f})")


# -------------------------------------------------------------- self-test


def self_test():
    """AC-5..AC-8. Each asserts a failure mode is actually detected."""
    prices = load_prices()
    checks = []

    def check(name, ok, detail=""):
        checks.append((name, ok, detail))

    # AC-8: per-TTL cache pricing. 5m must not be priced at the 1h rate.
    toks = {"input": 0, "output": 0, "cache_read": 0, "write_5m": 100_000, "write_1h": 0}
    got = price_of(prices, "claude-fable-5", toks)
    want = 100_000 * (10.0 / 1e6) * 1.25
    wrong = 100_000 * (10.0 / 1e6) * 2.0
    check("AC-8 5m cache priced at write_5m", abs(got - want) < 1e-9 and got != wrong,
          f"${got:.4f} (1h would be ${wrong:.4f})")

    # AC-5: dedup invariant is enforced.
    import tempfile
    with tempfile.NamedTemporaryFile("w", suffix=".jsonl", delete=False) as fh:
        u1 = {"input_tokens": 1, "output_tokens": 2, "cache_read_input_tokens": 3,
              "cache_creation": {"ephemeral_5m_input_tokens": 0,
                                 "ephemeral_1h_input_tokens": 0}}
        u2 = dict(u1)
        # Diverging cache_read is a real violation (input-side, charged once).
        u2["cache_read_input_tokens"] = 999
        for u in (u1, u2):
            fh.write(json.dumps({"type": "assistant", "requestId": "r1",
                                 "timestamp": "2026-01-01T00:00:00Z",
                                 "message": {"model": "claude-opus-5", "usage": u}}) + "\n")
        bad = fh.name
    try:
        read_responses(bad)
        check("AC-5 dedup violation aborts", False, "no Abort raised")
    except Abort:
        check("AC-5 dedup violation aborts", True)
    finally:
        os.unlink(bad)

    # AC-9: streamed partial output_tokens must resolve to the final total,
    # not the first line. Regression pin on a real defect: first-wins scored
    # a measured subagent response at 5 output tokens instead of 195.
    with tempfile.NamedTemporaryFile("w", suffix=".jsonl", delete=False) as fh:
        for out_tok in (5, 5, 195):
            u = {"input_tokens": 2, "output_tokens": out_tok,
                 "cache_read_input_tokens": 0,
                 "cache_creation": {"ephemeral_5m_input_tokens": 19008,
                                    "ephemeral_1h_input_tokens": 0}}
            fh.write(json.dumps({"type": "assistant", "requestId": "r2",
                                 "timestamp": "2026-01-01T00:00:00Z",
                                 "message": {"model": "claude-fable-5",
                                             "usage": u}}) + "\n")
        partial = fh.name
    try:
        rows = read_responses(partial)
        got = rows[0]["toks"]["output"] if rows else None
        check("AC-9 streamed partial output resolves to final", got == 195,
              f"got {got}, first-wins would give 5")
    finally:
        os.unlink(partial)

    # AC-6: zero responses must not report $0.00 as an answer.
    with tempfile.NamedTemporaryFile("w", suffix=".jsonl", delete=False) as fh:
        fh.write(json.dumps({"type": "user", "message": {}}) + "\n")
        empty = fh.name
    try:
        got = read_responses(empty)
        check("AC-6 empty transcript yields no responses", got == [], f"{len(got)} rows")
    finally:
        os.unlink(empty)

    # AC-7: the subagent tree is discovered by the path globs.
    slug = "-home-worsch-clay-borg"
    paths = transcript_paths(slug)
    subs = [p for p in paths if "/subagents/" in p]
    check("AC-7 subagent tree enumerated", len(subs) > 0,
          f"{len(subs)} subagent transcript(s) of {len(paths)} total")

    print("cb-cost self-test (positive control)")
    ok = True
    for name, passed, detail in checks:
        print(f"  [{'ok ' if passed else 'FAIL'}] {name}" + (f"  — {detail}" if detail else ""))
        ok &= passed
    return 0 if ok else 1


def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("--slug", default="-home-worsch-clay-borg")
    ap.add_argument("--pin", help="commit-ish or ISO Z instant (CA-07)")
    ap.add_argument("--by-task", action="store_true")
    ap.add_argument("--composition", action="store_true")
    ap.add_argument("--self-test", action="store_true")
    ap.add_argument("--json", action="store_true")
    args = ap.parse_args()

    if args.self_test:
        return self_test()

    try:
        rep = collect(args.slug, args.pin)
    except Abort as e:
        print(f"ABORT — {e}", file=sys.stderr)
        return 1

    if args.json:
        print(json.dumps(rep, indent=2))
    else:
        render(rep, by_task=args.by_task, composition=args.composition)
    return 0


if __name__ == "__main__":
    sys.exit(main())