import json
import os
import hmac
import time

import requests
from flask import Flask, jsonify, request
from werkzeug.middleware.proxy_fix import ProxyFix

try:
    from recipe_service.metrics import count_since, initialize, record, request_context, usage_json
except ModuleNotFoundError:
    from metrics import count_since, initialize, record, request_context, usage_json


app = Flask(__name__)
app.wsgi_app = ProxyFix(app.wsgi_app, x_for=1, x_proto=1, x_host=1)
MAX_IMAGE_BYTES = 10 * 1024 * 1024
ALLOWED_TYPES = {"image/jpeg", "image/png", "image/webp"}
PROXY_URL = "http://127.0.0.1:8768/gemini"
RATE_LIMIT_REQUESTS_PER_MINUTE = 20

initialize()


def settings() -> dict:
    try:
        config = json.loads(os.environ.get("GEMINI_GENERATION_CONFIG", "{}"))
    except json.JSONDecodeError as exc:
        raise RuntimeError("GEMINI_GENERATION_CONFIG is invalid") from exc
    if not isinstance(config, dict):
        raise RuntimeError("GEMINI_GENERATION_CONFIG must be an object")
    return config


def authorized() -> bool:
    expected = os.environ.get("RECIPE_API_TOKEN")
    authorization = request.headers.get("Authorization", "")
    return bool(expected and hmac.compare_digest(authorization, f"Bearer {expected}"))


def minute_start_utc(epoch_seconds: float) -> str:
    return time.strftime("%Y-%m-%dT%H:%M:00Z", time.gmtime(epoch_seconds))


def is_rate_limited(client_ip: str, now_epoch: float) -> bool:
    if not client_ip:
        return False
    window_start = minute_start_utc(now_epoch)
    return count_since(client_ip=client_ip, started_at_from=window_start) >= RATE_LIMIT_REQUESTS_PER_MINUTE


@app.get("/health")
@app.get("/receipt/health")
def health():
    return jsonify(status="ok")


@app.post("/receipt")
@app.post("/receipt/")
@app.post("/recipe")
@app.post("/recipe/")
def recipe():
    request_id, started_at, started_monotonic = request_context()
    image_mime = None
    image_bytes = None
    prompt_chars = None
    usage = {}
    client_ip = request.remote_addr

    def finalize(response, status_code: int, error: str | None):
        duration_ms = int((time.monotonic() - started_monotonic) * 1000)
        response_bytes = len(response.get_data())
        record(
            request_id=request_id,
            started_at=started_at,
            client_ip=client_ip,
            user_agent=request.user_agent.string,
            method=request.method,
            path=request.path,
            image_mime=image_mime,
            image_bytes=image_bytes,
            prompt_chars=prompt_chars,
            status_code=status_code,
            duration_ms=duration_ms,
            response_bytes=response_bytes,
            usage_json=usage_json(usage),
            error=error,
        )
        return response, status_code

    if not authorized():
        return finalize(jsonify(error="unauthorized"), 401, "unauthorized")

    if is_rate_limited(client_ip=client_ip or "", now_epoch=time.time()):
        return finalize(
            jsonify(error="too many requests", code="rate_limited"),
            429,
            "rate_limited",
        )

    image = request.files.get("image")
    prompt = request.form.get("prompt")
    if image is None or not prompt:
        return finalize(jsonify(error="image and prompt are required"), 400, "image and prompt are required")

    prompt_chars = len(prompt)

    if image.mimetype not in ALLOWED_TYPES:
        image_mime = image.mimetype
        return finalize(jsonify(error="unsupported image type"), 415, "unsupported image type")

    image_data = image.read(MAX_IMAGE_BYTES + 1)
    image_mime = image.mimetype
    image_bytes = len(image_data)

    if len(image_data) > MAX_IMAGE_BYTES:
        return finalize(jsonify(error="image is too large"), 413, "image is too large")

    try:
        config = settings()
        response = requests.post(
            os.environ.get("GEMINI_PROXY_URL", PROXY_URL),
            files={"image": (image.filename or "image", image_data, image.mimetype)},
            data={"prompt": prompt, "generation_config": json.dumps(config)},
            timeout=180,
        )
    except (requests.RequestException, RuntimeError) as exc:
        error = str(exc) if isinstance(exc, RuntimeError) else "Gemini unavailable"
        return finalize(jsonify(error=error), 503, error)

    if response.status_code != 200:
        try:
            detail = response.json().get("error", {}).get("message", "Gemini request failed")
        except ValueError:
            detail = "Gemini request failed"
        app.logger.warning("upstream_failure request_id=%s detail=%s", request_id, detail)
        return finalize(
            jsonify(error="upstream recognition failed", code="upstream_error"),
            502,
            "upstream_error",
        )

    data = response.json()
    usage = data.get("usage", {})
    result = jsonify(text=data.get("text"), usage=usage)
    return finalize(result, 200, None)