zavrsni-rad-otel-app/backend/microservices/api_gateway/main.py

from __future__ import annotations

import logging
from contextlib import asynccontextmanager
from time import perf_counter

import httpx
from fastapi import Depends, FastAPI, HTTPException, Query, Request, Response
from fastapi.middleware.cors import CORSMiddleware

from app.core.config import settings
from app.core.otel import (
    TelemetryProviders,
    configure_otel,
    instrument_fastapi,
    instrument_httpx_clients,
    shutdown_otel,
)
from app.core.security import (
    FrontendPrincipal,
    get_internal_token_manager,
    require_frontend_principal,
)
from microservices.common.http import current_trace_headers, with_internal_service_token

logging.basicConfig(level=settings.log_level)
LOGGER = logging.getLogger(__name__)


def _raise_upstream(exc: httpx.HTTPStatusError) -> None:
    detail = exc.response.text
    raise HTTPException(status_code=exc.response.status_code, detail=detail) from exc


@asynccontextmanager
async def lifespan(app: FastAPI):
    telemetry: TelemetryProviders = configure_otel(settings)
    instrument_httpx_clients()
    app.state.http_client = httpx.Client()
    LOGGER.info("API gateway ready")
    yield
    app.state.http_client.close()
    shutdown_otel(telemetry)


app = FastAPI(title="api-gateway-service", version="0.1.0", lifespan=lifespan)
instrument_fastapi(app)
app.add_middleware(
    CORSMiddleware,
    allow_origins=settings.cors_origins_list,
    allow_credentials=True,
    allow_methods=["GET", "POST"],
    allow_headers=["*"],
    expose_headers=["x-trace-id", "x-span-id"],
)


@app.middleware("http")
async def security_headers(request: Request, call_next):
    response = await call_next(request)
    response.headers["X-Content-Type-Options"] = "nosniff"
    response.headers["X-Frame-Options"] = "DENY"
    response.headers["Referrer-Policy"] = "no-referrer"
    response.headers["Permissions-Policy"] = "camera=(), microphone=(), geolocation=()"
    response.headers["X-Permitted-Cross-Domain-Policies"] = "none"
    response.headers["Strict-Transport-Security"] = (
        "max-age=31536000; includeSubDomains"
    )
    response.headers["Cache-Control"] = "no-store"
    response.headers["Pragma"] = "no-cache"
    return response


def _client() -> httpx.Client:
    return app.state.http_client


def _upstream_headers(principal: FrontendPrincipal) -> dict[str, str]:
    token = get_internal_token_manager().mint(
        subject=principal.subject,
        scopes=principal.scopes,
        source_service="api-gateway",
    )
    return with_internal_service_token(current_trace_headers(), token)


def _get_json(url: str, principal: FrontendPrincipal) -> dict | list:
    try:
        response = _client().get(
            url,
            headers=_upstream_headers(principal),
            timeout=settings.request_timeout_seconds,
        )
        response.raise_for_status()
        return response.json()
    except httpx.HTTPStatusError as exc:
        _raise_upstream(exc)


def _audit_payload(
    request: Request, response: Response, started: float, principal: FrontendPrincipal
) -> dict:
    headers = current_trace_headers()
    return {
        "method": request.method,
        "path": request.url.path,
        "query_string": request.url.query,
        "status_code": response.status_code,
        "duration_ms": (perf_counter() - started) * 1000,
        "trace_id": headers.get("x-trace-id"),
        "span_id": headers.get("x-span-id"),
        "client_ip": request.client.host if request.client else None,
        "user_agent": request.headers.get("user-agent"),
        "details": {
            "subject": principal.subject,
            "scopes": principal.scopes,
        },
    }


def _persist_audit(
    request: Request, response: Response, started: float, principal: FrontendPrincipal
) -> None:
    if not request.url.path.startswith("/api/"):
        return
    try:
        _client().post(
            f"{settings.persistence_service_url.rstrip('/')}/internal/audit-logs",
            headers=_upstream_headers(principal),
            json=_audit_payload(request, response, started, principal),
            timeout=settings.request_timeout_seconds,
        ).raise_for_status()
    except httpx.HTTPError as exc:
        LOGGER.warning("Audit persistence failed: %s", exc)


@app.get("/api/health")
def health(response: Response) -> dict:
    response.headers.update(current_trace_headers())
    return {"status": "ok", "service": "api-gateway-service"}


@app.get("/api/telemetry/status")
def telemetry_status(
    request: Request,
    response: Response,
    principal: FrontendPrincipal = Depends(require_frontend_principal),
) -> dict:
    started = perf_counter()
    response.headers.update(current_trace_headers())
    payload = {
        "status": "instrumented",
        "service_name": "api-gateway-service",
        "collector_endpoint": settings.otel_collector_endpoint,
        "trace_id": current_trace_headers().get("x-trace-id"),
        "span_id": current_trace_headers().get("x-span-id"),
        "trace_headers": ["traceparent", "tracestate", "baggage", "x-trace-id"],
        "subject": principal.subject,
    }
    _persist_audit(request, response, started, principal)
    return payload


@app.get("/api/kpis")
def kpis(
    request: Request,
    response: Response,
    principal: FrontendPrincipal = Depends(require_frontend_principal),
) -> dict:
    started = perf_counter()
    response.headers.update(current_trace_headers())
    payload = _get_json(
        f"{settings.analytics_service_url.rstrip('/')}/internal/kpis", principal
    )
    _persist_audit(request, response, started, principal)
    return payload  # type: ignore[return-value]


@app.get("/api/history")
def history(
    request: Request,
    response: Response,
    days_back: int = Query(default=settings.default_history_days, ge=30, le=1460),
    principal: FrontendPrincipal = Depends(require_frontend_principal),
) -> list[dict]:
    started = perf_counter()
    response.headers.update(current_trace_headers())
    payload = _get_json(
        f"{settings.analytics_service_url.rstrip('/')}/internal/history?days_back={days_back}",
        principal,
    )
    _persist_audit(request, response, started, principal)
    return payload  # type: ignore[return-value]


@app.get("/api/forecasts")
def forecasts(
    request: Request,
    response: Response,
    days: int = Query(default=settings.forecast_horizon_days, ge=7, le=180),
    principal: FrontendPrincipal = Depends(require_frontend_principal),
) -> list[dict]:
    started = perf_counter()
    response.headers.update(current_trace_headers())
    payload = _get_json(
        f"{settings.analytics_service_url.rstrip('/')}/internal/forecasts?days={days}",
        principal,
    )
    _persist_audit(request, response, started, principal)
    return payload  # type: ignore[return-value]


@app.get("/api/rankings")
def rankings(
    request: Request,
    response: Response,
    top_n: int = Query(default=settings.ranking_default_top_n, ge=3, le=100),
    principal: FrontendPrincipal = Depends(require_frontend_principal),
) -> list[dict]:
    started = perf_counter()
    response.headers.update(current_trace_headers())
    payload = _get_json(
        f"{settings.analytics_service_url.rstrip('/')}/internal/rankings?top_n={top_n}",
        principal,
    )
    _persist_audit(request, response, started, principal)
    return payload  # type: ignore[return-value]


@app.get("/api/recommendations")
def recommendations(
    request: Request,
    response: Response,
    principal: FrontendPrincipal = Depends(require_frontend_principal),
) -> list[dict]:
    started = perf_counter()
    response.headers.update(current_trace_headers())
    payload = _get_json(
        f"{settings.analytics_service_url.rstrip('/')}/internal/recommendations",
        principal,
    )
    _persist_audit(request, response, started, principal)
    return payload  # type: ignore[return-value]


@app.get("/api/dashboard")
def dashboard(
    request: Request,
    response: Response,
    principal: FrontendPrincipal = Depends(require_frontend_principal),
) -> dict:
    started = perf_counter()
    response.headers.update(current_trace_headers())
    payload = _get_json(
        f"{settings.analytics_service_url.rstrip('/')}/internal/dashboard", principal
    )
    _persist_audit(request, response, started, principal)
    return payload  # type: ignore[return-value]


@app.get("/api/storage/audit-logs")
def storage_audit_logs(
    request: Request,
    response: Response,
    limit: int = Query(default=settings.storage_default_limit, ge=1, le=500),
    principal: FrontendPrincipal = Depends(require_frontend_principal),
) -> list[dict]:
    started = perf_counter()
    response.headers.update(current_trace_headers())
    payload = _get_json(
        f"{settings.persistence_service_url.rstrip('/')}/internal/audit-logs?limit={limit}",
        principal,
    )
    _persist_audit(request, response, started, principal)
    return payload  # type: ignore[return-value]


@app.get("/api/storage/forecasts")
def storage_forecasts(
    request: Request,
    response: Response,
    limit: int = Query(default=settings.storage_default_limit, ge=1, le=500),
    principal: FrontendPrincipal = Depends(require_frontend_principal),
) -> list[dict]:
    started = perf_counter()
    response.headers.update(current_trace_headers())
    payload = _get_json(
        f"{settings.persistence_service_url.rstrip('/')}/internal/forecast-runs?limit={limit}",
        principal,
    )
    _persist_audit(request, response, started, principal)
    return payload  # type: ignore[return-value]


@app.get("/api/storage/rankings")
def storage_rankings(
    request: Request,
    response: Response,
    limit: int = Query(default=settings.storage_default_limit, ge=1, le=500),
    principal: FrontendPrincipal = Depends(require_frontend_principal),
) -> list[dict]:
    started = perf_counter()
    response.headers.update(current_trace_headers())
    payload = _get_json(
        f"{settings.persistence_service_url.rstrip('/')}/internal/ranking-runs?limit={limit}",
        principal,
    )
    _persist_audit(request, response, started, principal)
    return payload  # type: ignore[return-value]


@app.get("/api/storage/recommendations")
def storage_recommendations(
    request: Request,
    response: Response,
    limit: int = Query(default=settings.storage_default_limit, ge=1, le=500),
    principal: FrontendPrincipal = Depends(require_frontend_principal),
) -> list[dict]:
    started = perf_counter()
    response.headers.update(current_trace_headers())
    payload = _get_json(
        f"{settings.persistence_service_url.rstrip('/')}/internal/recommendation-runs?limit={limit}",
        principal,
    )
    _persist_audit(request, response, started, principal)
    return payload  # type: ignore[return-value]