"""Expose LiteLLM's per-request cost headers to cross-origin browser clients.

MEMBER REQUEST (co-op/support#39, 2026-10-31). Browser JS calling the gateway from
another origin cannot read a response header unless the server names it in
Access-Control-Expose-Headers. LiteLLM sets

    expose_headers=LITELLM_UI_ALLOW_HEADERS

which covers seven names (semantic-filter, guardrail, cache-key, ...) and none of
the cost ones — so `x-litellm-response-cost*` reads as null in JS even though the
proxy sends those headers on the response. Upstream closed the request
(BerriAI/litellm#33123) as stale, so it has to be handled here at the app layer,
exactly like the other patches in this directory.

Additive only. It lets a caller read per-request pricing for requests they made
with their own API key — numbers already present in the response body for
non-streaming calls, and already visible in their dashboard. It exposes no prompt,
key, or account data, and no other member's usage.

Run at BUILD time (the runtime rootfs is read-only under Cloudron). Non-fatal, per
house rule: if upstream moves or rewrites this call, WARN and exit 0 — a missing
convenience header must never keep the gateway from booting.

Regression check: after a deploy, a browser request from an unrelated origin should
see the cost headers listed in Access-Control-Expose-Headers on the response.
"""
from pathlib import Path
import sys

# The header names the proxy can set, taken from the running image rather than
# guessed: grep -rhoE 'x-litellm-[a-z0-9-]*cost[a-z0-9-]*' over the litellm package.
EXPOSED_HEADERS = [
    "x-litellm-response-cost",
    "x-litellm-response-cost-input",
    "x-litellm-response-cost-output",
    "x-litellm-response-cost-original",
    "x-litellm-response-cost-discount-amount",
    "x-litellm-response-cost-margin-amount",
    "x-litellm-response-cost-margin-percent",
    "x-litellm-response-cost-cache-creation",
    "x-litellm-response-cost-cache-read",
    "x-litellm-response-cost-reasoning",
    "x-litellm-response-cost-tool-usage",
    "x-litellm-classifier-cost",
    # Telemetry names, requested in co-op/support#39 (2026-10-31): model identity,
    # call id, the caller's own key spend, timings and retry/fallback counts.
    "x-litellm-model-name",
    "x-litellm-call-id",
    "x-litellm-key-spend",
    "x-litellm-response-duration-ms",
    "x-litellm-overhead-duration-ms",
    "x-litellm-callback-duration-ms",
    "x-litellm-attempted-retries",
    "x-litellm-attempted-fallbacks",
]

OLD = "    expose_headers=LITELLM_UI_ALLOW_HEADERS,\n"
NEW = (
    "    expose_headers=LITELLM_UI_ALLOW_HEADERS\n"
    "    + [\n"
    + "".join(f'        "{h}",\n' for h in EXPOSED_HEADERS)
    + "    ],\n"
)


def main() -> int:
    # Glob rather than pin a Python version: the venv path moves when the base
    # image bumps its interpreter, and a stale path would silently skip the patch.
    candidates = sorted(Path("/app/.venv/lib").glob("python3*/site-packages/litellm/proxy/proxy_server.py"))
    if not candidates:
        print("WARN expose-cost-headers: proxy_server.py not found under /app/.venv/lib — skipping")
        return 0

    target = candidates[-1]
    src = target.read_text()
    if "x-litellm-response-cost-input" in src:
        print("expose-cost-headers: already applied")
        return 0
    found = src.count(OLD)
    if found != 1:
        print(f"WARN expose-cost-headers: expected exactly 1 CORS middleware call, found {found} — skipping")
        return 0

    target.write_text(src.replace(OLD, NEW))
    print(f"expose-cost-headers: appended {len(EXPOSED_HEADERS)} cost header names to expose_headers in {target}")
    return 0


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