path: root/fatcat_scholar/web.py

"""
This contains the FastAPI web application and RESTful API.

So far there are few endpoints, so we just put them all here!
"""

import logging
from typing import Optional, Any, List, Dict

from pydantic import BaseModel
import babel.numbers
import babel.support
from fastapi import FastAPI, APIRouter, Request, Depends, Response, HTTPException
from fastapi.staticfiles import StaticFiles
from fastapi.responses import PlainTextResponse, JSONResponse, FileResponse
from fastapi.middleware.cors import CORSMiddleware
import sentry_sdk
from sentry_sdk.integrations.asgi import SentryAsgiMiddleware
from starlette_prometheus import metrics, PrometheusMiddleware
from starlette.exceptions import HTTPException as StarletteHTTPException

from fatcat_scholar.config import settings, GIT_REVISION
from fatcat_scholar.hacks import Jinja2Templates, parse_accept_lang
from fatcat_scholar.search import (
    process_query,
    FulltextQuery,
    FulltextHits,
    es_scholar_index_exists,
)
from fatcat_scholar.schema import ScholarDoc


logger = logging.getLogger()

I18N_LANG_TRANSLATIONS = [
    "ar",
    "de",
    "es",
    "fa",
    "fr",
    "hr",
    "it",
    "nb",
    "nl",
    "pt",
    "ru",
    "zh",
]
I18N_LANG_OPTIONS = I18N_LANG_TRANSLATIONS + [
    settings.I18N_LANG_DEFAULT,
]


class LangPrefix:
    """
    Looks for a two-character language prefix.

    If there is no such prefix, in the future it could also look at the
    Accept-Language header and try to infer a language from that, while not
    setting the prefix code.
    """

    def __init__(self, request: Request):
        self.prefix: str = ""
        self.code: str = settings.I18N_LANG_DEFAULT
        # first try to parse a language code from header
        try:
            accept_code = parse_accept_lang(
                request.headers.get("accept-language", ""), I18N_LANG_OPTIONS,
            )
            if accept_code:
                self.code = accept_code
        except Exception:
            pass

        # then override this with any language code in URL
        for lang_option in I18N_LANG_OPTIONS:
            if request.url.path.startswith(f"/{lang_option}/"):
                self.prefix = f"/{lang_option}"
                self.code = lang_option
                break
        sentry_sdk.set_tag("locale", self.code)


class ContentNegotiation:
    """
    Choses a mimetype to return based on Accept header.

    Intended to be used for RESTful content negotiation from web endpoints to API.
    """

    def __init__(self, request: Request):
        self.mimetype = "text/html"
        if request.headers.get("accept", "").startswith("application/json"):
            self.mimetype = "application/json"


api = APIRouter()


@api.get("/", operation_id="get_home")
async def home() -> Any:
    return {"endpoints": {"/": "this", "/search": "fulltext search"}}


@api.head("/", include_in_schema=False)
async def root_head() -> Any:
    """
    HTTP HEAD only for the root path (and health check below). Requested by,
    eg, uptime monitoring tools. This is distinct from the CORS middleware (for
    OPTION).
    """
    return Response()


@api.get("/_health", operation_id="get_health")
def health_get() -> Any:
    """
    Checks that connection back to elasticsearch index is working.
    """
    if not es_scholar_index_exists():
        raise HTTPException(status_code=503)
    return Response()


@api.head("/_health", include_in_schema=False)
def health_head() -> Any:
    return health_get()


class HitsModel(BaseModel):
    count_returned: int
    count_found: int
    offset: int
    limit: int
    query_time_ms: int
    query_wall_time_ms: int
    results: List[ScholarDoc]


@api.get("/search", operation_id="get_search", response_model=HitsModel)
def search(query: FulltextQuery = Depends(FulltextQuery)) -> FulltextHits:
    hits: Optional[FulltextHits] = None
    if query.q is None:
        raise HTTPException(status_code=400, detail="Expected a 'q' query parameter")
    try:
        hits = process_query(query)
    except ValueError as e:
        sentry_sdk.set_level("warning")
        sentry_sdk.capture_exception(e)
        raise HTTPException(status_code=400, detail=f"Query Error: {e}")
    except IOError as e:
        sentry_sdk.capture_exception(e)
        raise HTTPException(status_code=500, detail=f"Backend Error: {e}")

    # remove internal context from hit objects
    for doc in hits.results:
        doc.pop("_obj", None)

    return hits


web = APIRouter()


def locale_gettext(translations: Any) -> Any:
    def gt(s):  # noqa: ANN001,ANN201
        return translations.ugettext(s)

    return gt


def locale_ngettext(translations: Any) -> Any:
    def ngt(s, p, n):  # noqa: ANN001,ANN201
        return translations.ungettext(s, p, n)

    return ngt


def load_i18n_templates() -> Any:
    """
    This is a hack to work around lack of per-request translation
    (babel/gettext) locale switching in FastAPI and Starlette. Flask (and
    presumably others) get around this using global context (eg, in
    Flask-Babel).

    See related issues:

    - https://github.com/encode/starlette/issues/279
    - https://github.com/aio-libs/aiohttp-jinja2/issues/187
    """

    d = dict()
    for lang_opt in I18N_LANG_OPTIONS:
        translations = babel.support.Translations.load(
            dirname="fatcat_scholar/translations", locales=[lang_opt],
        )
        templates = Jinja2Templates(
            directory="fatcat_scholar/templates", extensions=["jinja2.ext.i18n"],
        )
        templates.env.install_gettext_translations(translations, newstyle=True)
        templates.env.install_gettext_callables(
            locale_gettext(translations), locale_ngettext(translations), newstyle=True,
        )
        # remove a lot of whitespace in HTML output with these configs
        templates.env.trim_blocks = True
        templates.env.lstrip_blocks = True
        # pass-through application settings to be available in templates
        templates.env.globals["settings"] = settings
        templates.env.globals["babel_numbers"] = babel.numbers
        d[lang_opt] = templates
    return d


i18n_templates = load_i18n_templates()


@web.get("/", include_in_schema=False)
async def web_home(
    request: Request,
    lang: LangPrefix = Depends(LangPrefix),
    content: ContentNegotiation = Depends(ContentNegotiation),
) -> Any:
    if content.mimetype == "application/json":
        return await home()
    return i18n_templates[lang.code].TemplateResponse(
        "home.html",
        {"request": request, "locale": lang.code, "lang_prefix": lang.prefix},
    )


@web.get("/about", include_in_schema=False)
async def web_about(request: Request, lang: LangPrefix = Depends(LangPrefix)) -> Any:
    return i18n_templates[lang.code].TemplateResponse(
        "about.html",
        {"request": request, "locale": lang.code, "lang_prefix": lang.prefix},
    )


@web.get("/help", include_in_schema=False)
async def web_help(request: Request, lang: LangPrefix = Depends(LangPrefix)) -> Any:
    return i18n_templates[lang.code].TemplateResponse(
        "help.html",
        {"request": request, "locale": lang.code, "lang_prefix": lang.prefix},
    )


@web.get("/search", include_in_schema=False)
def web_search(
    request: Request,
    response: Response,
    query: FulltextQuery = Depends(FulltextQuery),
    lang: LangPrefix = Depends(LangPrefix),
    content: ContentNegotiation = Depends(ContentNegotiation),
) -> Any:

    if content.mimetype == "application/json":
        return search(query)
    hits: Optional[FulltextHits] = None
    search_error: Optional[dict] = None
    status_code: int = 200
    if query.q is not None:
        try:
            hits = process_query(query)
        except ValueError as e:
            sentry_sdk.set_level("warning")
            sentry_sdk.capture_exception(e)
            search_error = dict(type="query", message=str(e))
            status_code = 400
        except IOError as e:
            sentry_sdk.capture_exception(e)
            search_error = dict(type="backend", message=str(e))
            status_code = 500

    headers = dict()
    if hits and hits.query_wall_time_ms:
        headers[
            "Server-Timing"
        ] = f'es_wall;desc="Search API Request";dur={hits.query_wall_time_ms}'
        if hits.query_time_ms:
            headers[
                "Server-Timing"
            ] += f', es;desc="Search Internal Time";dur={hits.query_time_ms}'
    return i18n_templates[lang.code].TemplateResponse(
        "search.html",
        {
            "request": request,
            "locale": lang.code,
            "lang_prefix": lang.prefix,
            "hits": hits,
            "search_error": search_error,
            "query": query,
        },
        headers=headers,
        status_code=status_code,
    )


app = FastAPI(
    title="Fatcat Scholar",
    description="Fulltext search interface for scholarly web content in the Fatcat catalog. An Internet Archive project.",
    version="0.2.0-dev",
    openapi_url="/api/openapi.json",
    redoc_url="/api/redoc",
    docs_url="/api/docs",
)

app.include_router(web)
for lang_option in I18N_LANG_OPTIONS:
    app.include_router(web, prefix=f"/{lang_option}")

# Becasue we are mounting 'api' after 'web', the web routes will take
# precedence. Requests get passed through the API handlers based on content
# negotiation. This is counter-intuitive here in the code, but does seem to
# work, and results in the OpenAPI docs looking correct.
app.include_router(api)

app.mount("/static", StaticFiles(directory="fatcat_scholar/static"), name="static")


@app.get("/favicon.ico", include_in_schema=False)
async def favicon() -> Any:
    return FileResponse(
        "fatcat_scholar/static/ia-favicon.ico", media_type="image/x-icon"
    )


ROBOTS_ALLOW = open("fatcat_scholar/static/robots.allow.txt", "r").read()
ROBOTS_DISALLOW = open("fatcat_scholar/static/robots.disallow.txt", "r").read()


@app.get("/robots.txt", include_in_schema=False)
async def robots_txt(response_class: Any = PlainTextResponse) -> Any:
    if settings.SCHOLAR_ENV == "prod":
        return PlainTextResponse(ROBOTS_ALLOW)
    else:
        return PlainTextResponse(ROBOTS_DISALLOW)


@app.exception_handler(StarletteHTTPException)
async def http_exception_handler(request: Request, exc: StarletteHTTPException) -> Any:
    """
    This is the generic handler for things like 404 errors.
    """
    # TODO: what if there is an error in any of the detection code?
    content = ContentNegotiation(request)

    if content.mimetype == "text/html":
        lang = LangPrefix(request)
        return i18n_templates[lang.code].TemplateResponse(
            "error.html",
            {
                "request": request,
                "locale": lang.code,
                "lang_prefix": lang.prefix,
                "error": exc,
            },
            status_code=exc.status_code,
        )
    else:
        resp: Dict[str, Any] = {"status_code": exc.status_code}
        if exc.detail:
            resp["detail"] = exc.detail
        return JSONResponse(status_code=exc.status_code, content=resp,)


# configure middleware

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=False,
    allow_methods=["GET"],
    allow_headers=[],  # some defaults always enabled
)

if settings.SENTRY_DSN:
    logger.info("Sentry integration enabled")
    sentry_sdk.init(
        dsn=settings.SENTRY_DSN,
        environment=settings.SCHOLAR_ENV,
        max_breadcrumbs=10,
        release=GIT_REVISION,
    )
    app.add_middleware(SentryAsgiMiddleware)

if settings.ENABLE_PROMETHEUS:
    app.add_middleware(PrometheusMiddleware)
    app.add_route("/prometheus/", metrics)