| 1 | """Typed contracts for authorization, x402 transport, receipts, and audit.""" |
| 2 | |
| 3 | from __future__ import annotations |
| 4 | |
| 5 | from datetime import datetime |
| 6 | from decimal import Decimal |
| 7 | from enum import StrEnum |
| 8 | from typing import Any, Literal |
| 9 | |
| 10 | from pydantic import ( |
| 11 | AwareDatetime, |
| 12 | BaseModel, |
| 13 | ConfigDict, |
| 14 | Field, |
| 15 | HttpUrl, |
| 16 | computed_field, |
| 17 | field_validator, |
| 18 | ) |
| 19 | from pydantic_core import PydanticCustomError |
| 20 | |
| 21 | |
| 22 | class FrozenModel(BaseModel): |
| 23 | """Immutable model used for application and protocol contracts.""" |
| 24 | |
| 25 | model_config = ConfigDict(frozen=True, populate_by_name=True) |
| 26 | |
| 27 | |
| 28 | class AuditEventType(StrEnum): |
| 29 | RESOURCE_REQUESTED = "resource_requested" |
| 30 | PAYMENT_REQUIRED = "payment_required" |
| 31 | AUTHORIZATION_CHECKED = "authorization_checked" |
| 32 | PAYMENT_ATTEMPTED = "payment_attempted" |
| 33 | PROOF_CREATED = "proof_created" |
| 34 | PROOF_REUSED = "proof_reused" |
| 35 | MERCHANT_RETRY = "merchant_retry" |
| 36 | CONTENT_RETURNED = "content_returned" |
| 37 | REQUEST_DENIED = "request_denied" |
| 38 | |
| 39 | |
| 40 | class AuditEvent(FrozenModel): |
| 41 | sequence: int = Field(ge=1) |
| 42 | occurred_at: datetime |
| 43 | request_id: str |
| 44 | event_type: AuditEventType |
| 45 | detail: dict[str, Any] = Field(default_factory=dict) |
| 46 | |
| 47 | |
| 48 | class CommercePolicy(FrozenModel): |
| 49 | allowed_merchants: frozenset[str] |
| 50 | allowed_purposes: frozenset[str] |
| 51 | per_request_limit: Decimal = Field(gt=0) |
| 52 | per_run_limit: Decimal = Field(gt=0) |
| 53 | approval_threshold: Decimal = Field(ge=0) |
| 54 | currency: Literal["USDC"] = "USDC" |
| 55 | network: Literal["eip155:84532"] = "eip155:84532" |
| 56 | session_expires_at: datetime |
| 57 | |
| 58 | |
| 59 | class PurchaseRequest(FrozenModel): |
| 60 | request_id: str = Field(min_length=1) |
| 61 | resource_url: HttpUrl |
| 62 | purpose: str = Field(min_length=1) |
| 63 | idempotency_key: str = Field(min_length=8) |
| 64 | |
| 65 | |
| 66 | class ApprovalGrant(FrozenModel): |
| 67 | approval_id: str = Field(min_length=1) |
| 68 | request_id: str = Field(min_length=1) |
| 69 | resource_url: HttpUrl |
| 70 | purpose: str = Field(min_length=1) |
| 71 | maximum_amount: Decimal = Field(gt=0) |
| 72 | currency: Literal["USDC"] = "USDC" |
| 73 | approved_by: str = Field(min_length=1) |
| 74 | approved_at: datetime |
| 75 | expires_at: datetime |
| 76 | |
| 77 | |
| 78 | class ResourceInfo(FrozenModel): |
| 79 | url: HttpUrl |
| 80 | description: str |
| 81 | mime_type: str = Field(alias="mimeType") |
| 82 | |
| 83 | |
| 84 | class PaymentRequirementExtra(FrozenModel): |
| 85 | """Validated x402 metadata used by local policy computed fields.""" |
| 86 | |
| 87 | model_config = ConfigDict(frozen=True, populate_by_name=True, extra="forbid") |
| 88 | |
| 89 | decimals: int = Field(strict=True, ge=0) |
| 90 | currency: Literal["USDC"] |
| 91 | merchant_domain: str = Field( |
| 92 | alias="merchantDomain", |
| 93 | strict=True, |
| 94 | min_length=1, |
| 95 | ) |
| 96 | challenge_id: str = Field( |
| 97 | alias="challengeId", |
| 98 | strict=True, |
| 99 | min_length=1, |
| 100 | ) |
| 101 | issued_at: AwareDatetime | None = Field(default=None, alias="issuedAt") |
| 102 | expires_at: AwareDatetime = Field(alias="expiresAt") |
| 103 | simulation: bool | None = Field(default=None, strict=True) |
| 104 | |
| 105 | @field_validator("issued_at", "expires_at", mode="before") |
| 106 | @classmethod |
| 107 | def require_iso_timestamp_text(cls, value: object) -> object: |
| 108 | if value is None: |
| 109 | return value |
| 110 | if not isinstance(value, str): |
| 111 | raise PydanticCustomError( |
| 112 | "x402_timestamp_type", |
| 113 | "x402 timestamps must be ISO 8601 strings.", |
| 114 | ) |
| 115 | return value |
| 116 | |
| 117 | |
| 118 | class PaymentRequirement(FrozenModel): |
| 119 | """Protocol-shaped x402 V2 exact-payment requirement. |
| 120 | |
| 121 | The local proof is deliberately synthetic. These fields mirror the |
| 122 | current x402 V2 transport shape but do not claim chain conformance. |
| 123 | """ |
| 124 | |
| 125 | scheme: Literal["exact"] = "exact" |
| 126 | network: Literal["eip155:84532"] = "eip155:84532" |
| 127 | amount: str = Field(pattern=r"^[0-9]+$") |
| 128 | asset: str |
| 129 | pay_to: str = Field(alias="payTo") |
| 130 | max_timeout_seconds: int = Field(alias="maxTimeoutSeconds", gt=0) |
| 131 | extra: PaymentRequirementExtra |
| 132 | |
| 133 | @computed_field |
| 134 | @property |
| 135 | def decimal_amount(self) -> Decimal: |
| 136 | return Decimal(self.amount) / (Decimal(10) ** self.extra.decimals) |
| 137 | |
| 138 | @computed_field |
| 139 | @property |
| 140 | def currency(self) -> Literal["USDC"]: |
| 141 | return self.extra.currency |
| 142 | |
| 143 | @computed_field |
| 144 | @property |
| 145 | def merchant_domain(self) -> str: |
| 146 | return self.extra.merchant_domain |
| 147 | |
| 148 | @computed_field |
| 149 | @property |
| 150 | def challenge_id(self) -> str: |
| 151 | return self.extra.challenge_id |
| 152 | |
| 153 | @computed_field |
| 154 | @property |
| 155 | def expires_at(self) -> datetime: |
| 156 | return self.extra.expires_at |
| 157 | |
| 158 | |
| 159 | class PaymentRequired(FrozenModel): |
| 160 | x402_version: Literal[2] = Field(alias="x402Version", default=2) |
| 161 | resource: ResourceInfo |
| 162 | accepts: tuple[PaymentRequirement, ...] = Field(min_length=1) |
| 163 | error: str | None = None |
| 164 | |
| 165 | |
| 166 | class PaymentPayload(FrozenModel): |
| 167 | x402_version: Literal[2] = Field(alias="x402Version", default=2) |
| 168 | accepted: PaymentRequirement |
| 169 | payload: dict[str, str] |
| 170 | |
| 171 | |
| 172 | class SettlementResponse(FrozenModel): |
| 173 | success: bool |
| 174 | transaction: str |
| 175 | network: str |
| 176 | payer: str |
| 177 | |
| 178 | |
| 179 | class AuthorizationDecision(FrozenModel): |
| 180 | allowed: bool |
| 181 | code: str |
| 182 | reason: str |
| 183 | requires_human_approval: bool |
| 184 | approved_amount: Decimal | None = None |
| 185 | |
| 186 | |
| 187 | class PaymentReceipt(FrozenModel): |
| 188 | receipt_id: str |
| 189 | request_id: str |
| 190 | idempotency_key: str |
| 191 | merchant_domain: str |
| 192 | resource_url: HttpUrl |
| 193 | amount: Decimal |
| 194 | currency: Literal["USDC"] |
| 195 | network: str |
| 196 | transaction: str |
| 197 | reused: bool = False |
| 198 | |
| 199 | |
| 200 | class PaymentAuthorization(FrozenModel): |
| 201 | proof_header: str |
| 202 | receipt: PaymentReceipt |
| 203 | |
| 204 | |
| 205 | class SupplierRiskReport(FrozenModel): |
| 206 | report_id: Literal["SYNTH-SUPPLIER-RISK-001"] |
| 207 | supplier: Literal["Northstar Components"] |
| 208 | generated_from: Literal["synthetic data"] |
| 209 | signals: tuple[str, ...] |
| 210 | disclaimer: str |
| 211 | |
| 212 | |
| 213 | class PurchaseResult(FrozenModel): |
| 214 | status: Literal["completed"] |
| 215 | request_id: str |
| 216 | authorization: AuthorizationDecision |
| 217 | receipt: PaymentReceipt |
| 218 | report: SupplierRiskReport |
| 219 | audit_events: tuple[AuditEvent, ...] |
| 220 | |
| 221 | |
| 222 | class AgentPurchaseEvidence(FrozenModel): |
| 223 | """Minimum purchase evidence returned to the model by the function tool.""" |
| 224 | |
| 225 | status: Literal["completed"] |
| 226 | report: SupplierRiskReport |
| 227 | receipt_id: str |
| 228 | amount: Decimal |
| 229 | currency: Literal["USDC"] |
| 230 | requires_human_approval: bool |