|
1
|
"""Application controller for the deterministic x402 purchase sequence.""" |
|
2
|
|
|
3
|
from __future__ import annotations |
|
4
|
|
|
5
|
from datetime import UTC, datetime |
|
6
|
|
|
7
|
import httpx |
|
8
|
from pydantic import ValidationError |
|
9
|
|
|
10
|
from .audit import AuditTrail |
|
11
|
from .codec import decode_json |
|
12
|
from .errors import MerchantRejectedPayment, PolicyDenied, ProtocolError |
|
13
|
from .merchant import ( |
|
14
|
PAYMENT_REQUIRED_HEADER, |
|
15
|
PAYMENT_RESPONSE_HEADER, |
|
16
|
PAYMENT_SIGNATURE_HEADER, |
|
17
|
) |
|
18
|
from .models import ( |
|
19
|
ApprovalGrant, |
|
20
|
AuditEventType, |
|
21
|
PaymentRequired, |
|
22
|
PurchaseRequest, |
|
23
|
PurchaseResult, |
|
24
|
SettlementResponse, |
|
25
|
SupplierRiskReport, |
|
26
|
) |
|
27
|
from .payments import LocalPaymentProcessor |
|
28
|
from .policy import PolicyEngine |
|
29
|
|
|
30
|
|
|
31
|
class CommerceApplication: |
|
32
|
"""Orchestrate HTTP, authorization, payment, receipt, and audit state.""" |
|
33
|
|
|
34
|
def __init__( |
|
35
|
self, |
|
36
|
*, |
|
37
|
client: httpx.Client, |
|
38
|
policy: PolicyEngine, |
|
39
|
payments: LocalPaymentProcessor, |
|
40
|
audit: AuditTrail | None = None, |
|
41
|
) -> None: |
|
42
|
self.client = client |
|
43
|
self.policy = policy |
|
44
|
self.payments = payments |
|
45
|
self.audit = audit or AuditTrail() |
|
46
|
|
|
47
|
def purchase( |
|
48
|
self, |
|
49
|
request: PurchaseRequest, |
|
50
|
*, |
|
51
|
approval: ApprovalGrant | None = None, |
|
52
|
now: datetime | None = None, |
|
53
|
) -> PurchaseResult: |
|
54
|
now = now or datetime.now(UTC) |
|
55
|
self.audit.append( |
|
56
|
request_id=request.request_id, |
|
57
|
event_type=AuditEventType.RESOURCE_REQUESTED, |
|
58
|
detail={ |
|
59
|
"resource_url": str(request.resource_url), |
|
60
|
"purpose": request.purpose, |
|
61
|
}, |
|
62
|
) |
|
63
|
preflight = self.policy.preflight(request, now=now) |
|
64
|
if not preflight.allowed: |
|
65
|
self.audit.append( |
|
66
|
request_id=request.request_id, |
|
67
|
event_type=AuditEventType.REQUEST_DENIED, |
|
68
|
detail={"code": preflight.code, "stage": "preflight"}, |
|
69
|
) |
|
70
|
raise PolicyDenied(preflight.code, preflight.reason) |
|
71
|
|
|
72
|
initial = self.client.get(str(request.resource_url)) |
|
73
|
if initial.status_code != 402: |
|
74
|
raise ProtocolError( |
|
75
|
"payment_challenge_expected", |
|
76
|
"The paid resource did not return HTTP 402.", |
|
77
|
) |
|
78
|
|
|
79
|
required = self._payment_required(initial) |
|
80
|
requirement = required.accepts[0] |
|
81
|
self.audit.append( |
|
82
|
request_id=request.request_id, |
|
83
|
event_type=AuditEventType.PAYMENT_REQUIRED, |
|
84
|
detail={ |
|
85
|
"merchant_domain": requirement.merchant_domain, |
|
86
|
"amount": str(requirement.decimal_amount), |
|
87
|
"currency": requirement.currency, |
|
88
|
"network": requirement.network, |
|
89
|
}, |
|
90
|
) |
|
91
|
|
|
92
|
decision = self.policy.authorize( |
|
93
|
request, |
|
94
|
required, |
|
95
|
approval=approval, |
|
96
|
now=now, |
|
97
|
) |
|
98
|
self.audit.append( |
|
99
|
request_id=request.request_id, |
|
100
|
event_type=AuditEventType.AUTHORIZATION_CHECKED, |
|
101
|
detail={ |
|
102
|
"allowed": decision.allowed, |
|
103
|
"code": decision.code, |
|
104
|
"requires_human_approval": (decision.requires_human_approval), |
|
105
|
}, |
|
106
|
) |
|
107
|
if not decision.allowed: |
|
108
|
self.audit.append( |
|
109
|
request_id=request.request_id, |
|
110
|
event_type=AuditEventType.REQUEST_DENIED, |
|
111
|
detail={"code": decision.code}, |
|
112
|
) |
|
113
|
raise PolicyDenied(decision.code, decision.reason) |
|
114
|
|
|
115
|
self.audit.append( |
|
116
|
request_id=request.request_id, |
|
117
|
event_type=AuditEventType.PAYMENT_ATTEMPTED, |
|
118
|
detail={"idempotency_key": request.idempotency_key}, |
|
119
|
) |
|
120
|
authorization = self.payments.authorize(request, requirement) |
|
121
|
self.policy.record(authorization.receipt) |
|
122
|
self.audit.append( |
|
123
|
request_id=request.request_id, |
|
124
|
event_type=( |
|
125
|
AuditEventType.PROOF_REUSED |
|
126
|
if authorization.receipt.reused |
|
127
|
else AuditEventType.PROOF_CREATED |
|
128
|
), |
|
129
|
detail={"receipt_id": authorization.receipt.receipt_id}, |
|
130
|
) |
|
131
|
|
|
132
|
self.audit.append( |
|
133
|
request_id=request.request_id, |
|
134
|
event_type=AuditEventType.MERCHANT_RETRY, |
|
135
|
detail={"payment_header": PAYMENT_SIGNATURE_HEADER}, |
|
136
|
) |
|
137
|
paid = self.client.get( |
|
138
|
str(request.resource_url), |
|
139
|
headers={ |
|
140
|
PAYMENT_SIGNATURE_HEADER: authorization.proof_header, |
|
141
|
}, |
|
142
|
) |
|
143
|
if paid.status_code != 200: |
|
144
|
raise MerchantRejectedPayment( |
|
145
|
"merchant_rejected_payment", |
|
146
|
"The merchant did not accept the synthetic payment proof.", |
|
147
|
) |
|
148
|
|
|
149
|
settlement = self._settlement(paid) |
|
150
|
if ( |
|
151
|
not settlement.success |
|
152
|
or settlement.transaction != authorization.receipt.transaction |
|
153
|
): |
|
154
|
raise ProtocolError( |
|
155
|
"settlement_receipt_mismatch", |
|
156
|
"The settlement response does not match the local receipt.", |
|
157
|
) |
|
158
|
try: |
|
159
|
report = SupplierRiskReport.model_validate(paid.json()) |
|
160
|
except (ValueError, ValidationError) as exc: |
|
161
|
raise ProtocolError( |
|
162
|
"invalid_paid_resource", |
|
163
|
"The paid resource did not match the typed report contract.", |
|
164
|
) from exc |
|
165
|
|
|
166
|
self.audit.append( |
|
167
|
request_id=request.request_id, |
|
168
|
event_type=AuditEventType.CONTENT_RETURNED, |
|
169
|
detail={ |
|
170
|
"report_id": report.report_id, |
|
171
|
"receipt_id": authorization.receipt.receipt_id, |
|
172
|
}, |
|
173
|
) |
|
174
|
return PurchaseResult( |
|
175
|
status="completed", |
|
176
|
request_id=request.request_id, |
|
177
|
authorization=decision, |
|
178
|
receipt=authorization.receipt, |
|
179
|
report=report, |
|
180
|
audit_events=self.audit.for_request(request.request_id), |
|
181
|
) |
|
182
|
|
|
183
|
@staticmethod |
|
184
|
def _payment_required(response: httpx.Response) -> PaymentRequired: |
|
185
|
header = response.headers.get(PAYMENT_REQUIRED_HEADER) |
|
186
|
if header is None: |
|
187
|
raise ProtocolError( |
|
188
|
"payment_required_header_missing", |
|
189
|
"HTTP 402 did not include PAYMENT-REQUIRED.", |
|
190
|
) |
|
191
|
payload = decode_json(header, header_name=PAYMENT_REQUIRED_HEADER) |
|
192
|
try: |
|
193
|
return PaymentRequired.model_validate(payload) |
|
194
|
except ValidationError as exc: |
|
195
|
raise ProtocolError( |
|
196
|
"invalid_payment_requirement", |
|
197
|
"PAYMENT-REQUIRED does not match the expected contract.", |
|
198
|
) from exc |
|
199
|
|
|
200
|
@staticmethod |
|
201
|
def _settlement(response: httpx.Response) -> SettlementResponse: |
|
202
|
header = response.headers.get(PAYMENT_RESPONSE_HEADER) |
|
203
|
if header is None: |
|
204
|
raise ProtocolError( |
|
205
|
"payment_response_header_missing", |
|
206
|
"Paid response did not include PAYMENT-RESPONSE.", |
|
207
|
) |
|
208
|
payload = decode_json(header, header_name=PAYMENT_RESPONSE_HEADER) |
|
209
|
try: |
|
210
|
return SettlementResponse.model_validate(payload) |
|
211
|
except ValidationError as exc: |
|
212
|
raise ProtocolError( |
|
213
|
"invalid_settlement_response", |
|
214
|
"PAYMENT-RESPONSE does not match the expected contract.", |
|
215
|
) from exc |