webfinger/webfinger/lookup.py

"""
Perform WebFinger lookups according to RFC7033
"""

import json

from fastapi import APIRouter
from fastapi.responses import PlainTextResponse, JSONResponse
from fastapi.params import Query

from pydantic import ValidationError

from webfinger.io import get_jrd
from webfinger.models import JRD, JRDResponse


router = APIRouter(
	prefix="/.well-known/webfinger",
	)


# Define required CORS header per RFC7033

HEADERS = {'Access-Control-Allow-Origin': '*'}
# if env.get("CORS_ALLOW_ORIGIN"):
# 	allowed_origins = env.get("CORS_ALLOW_ORIGIN")
# 	headers.update({'Access-Control-Allow-Origin': allowed_origins})


## Example responses for OpenAPI schema

RESOURCE_NOT_PROVIDED = \
	"Query ?resource={resource} to obtain information about that resource."
RESOURCE_NOT_FOUND = \
	"Resource not found"
RESOURCE_NOT_PARSED = \
	"Resource contains invalid JSON or was unreadable"
RESOURCE_NOT_VALID = \
	"Some errors occurred while validating the JRD"

RESPONSES = {
	200: {
		"description": (
			"OK:"
			" The resource you requested was found,"
			" and has the returned resource document."),
		"model": JRD,
		"content": {
			"application/jrd+json": {
				"example": json.loads(JRD.Config.schema_extra['example']),
			},
		},
	},
	400: {
		"description": (
			"Bad Request:"
			" No resource was provided."),
		"content": {
			"text/plain": {
				"example": RESOURCE_NOT_PROVIDED
			},
		},
	},
	404: {
		"description": (
			"Not Found:"
			" Could not find a document for the provided resource."),
		"content": {
			"text/plain": {
				"example": RESOURCE_NOT_FOUND
			},
		},
	},
	500: {
		"description": (
			"Server Error:"
			" The resource exists,"
			" but contains invalid JSON or was unreadable."),
		"content": {
			"text/plain": {
				"example": RESOURCE_NOT_PARSED
			},
		},
	},
}


## The lookup method as described in RFC7033

@router.get(
	"",
	summary = "Lookup a Webfinger resource",
	description = (
		"Query the Webfinger service for a resource URI"
		" and obtain its associated resource document"),
	tags = ["RFC7033"],
	response_model = JRD,
	response_class = JRDResponse,
	responses = {**RESPONSES},
	)
async def lookup(
	resource: str = Query(
		None,
		title = "Resource URI",
		description = (
			"The subject whose document you are looking up."
			" If not provided, you will get a 400 Bad Request."
		),
		),
	rel: list[str] = Query(
		None,
		title = "Link relation",
		description = (
			"If provided, filter the links array for this rel-value only."
			" This parameter may be included multiple times."
		),
		)
	):
	"""
	Respond to a WebFinger query.
	"""
	# If no resource is given, then show a basic hint.
	if not resource:
		return PlainTextResponse(
			content = RESOURCE_NOT_PROVIDED,
			status_code=400,
			headers = HEADERS,
			)

	# Otherwise, try to read the resource document.
	try:
		jrd = get_jrd(resource)
	except FileNotFoundError:
		# JRD file does not exist
		return PlainTextResponse(
			content = RESOURCE_NOT_FOUND,
			status_code = 404,
			headers = HEADERS,
			)
	except (OSError, json.JSONDecodeError):
		# JRD file could not be read or parsed
		return PlainTextResponse(
			content = RESOURCE_NOT_PARSED,
			status_code = 500,
			headers = HEADERS,
			)
	except ValidationError as exception: 
		# JRD was parsed but contained type or value errors
		errors = [RESOURCE_NOT_VALID]
		for error in exception.errors():
			print(error)
			errors.append(f"{error['msg']} for {error['loc'][0]}")
		return PlainTextResponse(
			content = '\n- '.join(errors),
			status_code=500,
			headers = HEADERS,
			)

	# If optional rel is provided, then filter only for links with that rel-type.
	if rel:
		jrd.links = [link for link in jrd.links if link.rel in rel]

	# Construct JSON response and return it.
	return JSONResponse(
		content = jrd.dict(exclude_none=True),
		media_type = "application/jrd+json",
		headers = HEADERS,
		)