#!/usr/bin/env python3
"""Regenerate proxy/nginx.conf from the real deployment's ingress table.

The live instance is a Kubernetes ingress that splits one origin across the
legacy client, the new SPA and several APIs. Which path goes where is not
documented in prose — it is the table in
dof_app_deploy/ansible/group_vars/all/x_ingress.yml plus a per-path ingress in
each service repo. Transcribing 46 rules by hand invites exactly the drift that
would make this instance lie about the real one, so we generate them.

Usage:  python3 scripts/gen-proxy-conf.py > proxy/nginx.conf
Needs the upstream clones in ../vendor (see README.md).
"""
import pathlib
import sys

try:
	import yaml
except ImportError:
	sys.exit('needs PyYAML: pip install pyyaml')

VENDOR = pathlib.Path(__file__).resolve().parents[2] / 'vendor'
INGRESS = VENDOR / 'dof_app_deploy/ansible/group_vars/all/x_ingress.yml'

# Kubernetes service name -> compose upstream. None means the real deployment
# deliberately 404s that path.
UPSTREAM = {
	'client-svc': 'client:3100',
	'nuxtclient-svc': 'nuxt:4000',
	'api-svc': 'api:3030',
	'default-backend-404-svc': None,
	'version-aggregator-svc': None,  # replaced by our own /version below
	None: None,
}

# Routes that live in the individual service repos' own ingress templates
# rather than the shared table, plus the two websocket endpoints.
# (path, upstream, websocket, rewrite-or-None)
EXTRA = [
	('/api/v3/file/', 'file-storage:4444', False, None),
	('/api/v3/wopi/', 'file-storage:4444', False, None),
	('/api/v3/h5p-editor/h5pstatics/', 'h5p-staticfiles:8080', False,
		'^/api/v3/h5p-editor/h5pstatics/(.*)$ /h5pstatics/$1'),
	('/api/v3/h5p-editor/', 'h5p-editor:4448', False, None),
	('/api/v3/', 'api:3030', False, None),
	('/admin/api/v1', 'admin-api:4030', False, None),
	('/board-collaboration', 'board-collaboration:4450', True, None),
	('/tldraw-server', 'tldraw-server:3345', True, None),
	('/api/tldraw', 'tldraw-server:3345', False, None),
]

PREAMBLE = '''# GENERATED by scripts/gen-proxy-conf.py — do not edit by hand.
#
# One origin in front of the whole stack, the way the real instance is fronted
# by its Kubernetes ingress. The path split between the legacy client and the
# new SPA is not cosmetic: get it wrong and you are testing a different
# application from the one the students use.

map $http_upgrade $connection_upgrade {
	default upgrade;
	''      close;
}

server {
	listen 4400;
	server_name localhost;

	# Docker's embedded DNS. Every proxy_pass below goes through a variable so
	# that names resolve per request rather than at startup — otherwise this
	# container refuses to boot whenever an optional profile (tools, av) is
	# down, which is the normal case.
	resolver 127.0.0.11 valid=10s ipv6=off;

	# Course files and H5P uploads are large; the ingress allows the same.
	client_max_body_size 2600m;
	proxy_read_timeout 300s;
	proxy_send_timeout 300s;

	# version-aggregator-svc upstream; /serverversion and /nuxtversion are the
	# real per-app endpoints and are routed below.
	location = /version {
		default_type application/json;
		return 200 '{"local-instance":true,"see":["/serverversion","/nuxtversion"]}';
	}
'''

COMMON = '''		proxy_set_header Host $host;
		proxy_set_header X-Real-IP $remote_addr;
		proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
		proxy_set_header X-Forwarded-Proto $scheme;
'''

WS = '''		proxy_http_version 1.1;
		proxy_set_header Upgrade $http_upgrade;
		proxy_set_header Connection $connection_upgrade;
'''

GONE = '''
	location {path} {{
		return 404;
	}}
'''

# Etherpad is mounted under a prefix it knows nothing about, so the deployment
# runs a dedicated nginx in front of it that rewrites the prefix away and
# proxies socket.io separately. Copied from
# dof_app_deploy/ansible/roles/dof_etherpad/templates/nginx-configmap-files.yml.j2
# — a plain proxy_pass gets you a pad that loads and then never syncs.
ETHERPAD = '''
	location ^~ /etherpad/admin { return 404; }
	location ^~ /etherpad/stats { return 404; }

	location /etherpad/socket.io {
		set $up_etherpad etherpad:9001;
		rewrite /etherpad/socket.io/(.*) /socket.io/$1 break;
		proxy_pass http://$up_etherpad;
		proxy_redirect / /etherpad/;
		proxy_set_header Host $http_host;
		proxy_buffering off;
		proxy_set_header X-Real-IP $remote_addr;
		proxy_set_header X-Forwarded-For $remote_addr;
		proxy_set_header X-Forwarded-Proto $scheme;
		proxy_http_version 1.1;
		proxy_set_header Upgrade $http_upgrade;
		proxy_set_header Connection $connection_upgrade;
	}

	location /etherpad {
		set $up_etherpad etherpad:9001;
		rewrite ^/etherpad$ /etherpad/ permanent;
		rewrite /etherpad/(.*) /$1 break;
		proxy_pass http://$up_etherpad;
		proxy_pass_header Server;
		proxy_redirect / /etherpad/;
		proxy_set_header Host $host;
		proxy_buffering off;
	}
'''


def block(path: str, upstream: str, ws: bool, rewrite: str | None, var: str) -> str:
	out = [f'\n\tlocation {path} {{\n', f'\t\tset ${var} {upstream};\n']
	if rewrite:
		out.append(f'\t\trewrite {rewrite} break;\n')
	out.append(f'\t\tproxy_pass http://${var};\n')
	out.append(COMMON)
	if ws:
		out.append(WS)
	out.append('\t}\n')
	return ''.join(out)


def varname(path: str) -> str:
	safe = ''.join(c if c.isalnum() else '_' for c in path.strip('/')) or 'root'
	return f'up_{safe}'


def main() -> None:
	table = yaml.safe_load(INGRESS.read_text())['default_ingress']

	seen: set[str] = set()
	out = [PREAMBLE]

	out.append('\n\t# --- service-owned ingresses and websockets ---\n')
	for path, upstream, ws, rewrite in EXTRA:
		seen.add(path)
		out.append(block(path, upstream, ws, rewrite, varname(path)))

	out.append('\n\t# --- from dof_app_deploy x_ingress.yml ---\n')
	for name, entry in table.items():
		path = entry.get('path')
		if path is None or path in seen:
			continue
		seen.add(path)
		if path == '/etherpad':
			out.append(ETHERPAD)
			continue
		upstream = UPSTREAM.get(entry.get('serviceName'), 'MISSING')
		if upstream == 'MISSING':
			sys.exit(f'unknown serviceName for {name}: {entry.get("serviceName")}')
		out.append(f'\n\t# {name}')
		out.append(GONE.format(path=path) if upstream is None
			else block(path, upstream, False, None, varname(path)))

	out.append('}\n')
	sys.stdout.write(''.join(out))


if __name__ == '__main__':
	main()