feat(cases): link provider-owned evidence references

src/govoplan_cases/backend/evidence_links.py

@@ -0,0 +1,239 @@
+from __future__ import annotations
+
+from collections.abc import Mapping
+from datetime import datetime
+import hashlib
+import json
+from urllib.parse import parse_qs, quote, urlsplit
+
+from sqlalchemy.orm import Session
+
+from govoplan_core.core.institutional import EvidenceReference
+from govoplan_cases.backend.domain import CaseRecord
+from govoplan_cases.backend.service import CaseStoreError, get_case, update_case
+
+
+_SOURCE_CONTRACT = "cases.quick-access-reference.v1"
+_SUPPORTED_REFERENCES = {
+    ("files", "file-version"): "document",
+    ("mail", "message"): "event",
+    ("campaigns", "campaign"): "event",
+}
+
+
+def link_case_evidence(
+    session: Session,
+    principal: object,
+    *,
+    case_id: str,
+    expected_revision: int,
+    reference: Mapping[str, object],
+    recorded_at: datetime,
+    change_reason: str,
+    idempotency_key: str,
+) -> CaseRecord:
+    base = _base_revision(
+        session,
+        principal,
+        case_id=case_id,
+        expected_revision=expected_revision,
+    )
+    evidence = _validated_evidence(reference, tenant_id=base.reference.tenant_id)
+    if any(item.evidence_id == evidence.evidence_id for item in base.evidence_refs):
+        raise CaseStoreError("The owner reference is already linked to this Case.")
+    return update_case(
+        session,
+        principal,
+        case_id=case_id,
+        expected_revision=expected_revision,
+        changes={"evidence_refs": (*base.evidence_refs, evidence)},
+        recorded_at=recorded_at,
+        change_reason=change_reason,
+        idempotency_key=idempotency_key,
+    )
+
+
+def unlink_case_evidence(
+    session: Session,
+    principal: object,
+    *,
+    case_id: str,
+    evidence_id: str,
+    expected_revision: int,
+    recorded_at: datetime,
+    change_reason: str,
+    idempotency_key: str,
+) -> CaseRecord:
+    base = _base_revision(
+        session,
+        principal,
+        case_id=case_id,
+        expected_revision=expected_revision,
+    )
+    evidence = next(
+        (item for item in base.evidence_refs if item.evidence_id == evidence_id),
+        None,
+    )
+    if evidence is None or linked_source(evidence) is None:
+        raise CaseStoreError("The linked owner reference was not found.")
+    return update_case(
+        session,
+        principal,
+        case_id=case_id,
+        expected_revision=expected_revision,
+        changes={
+            "evidence_refs": tuple(
+                item for item in base.evidence_refs if item.evidence_id != evidence_id
+            )
+        },
+        recorded_at=recorded_at,
+        change_reason=change_reason,
+        idempotency_key=idempotency_key,
+    )
+
+
+def linked_source(evidence: EvidenceReference) -> Mapping[str, str] | None:
+    if evidence.source_ref is None:
+        return None
+    try:
+        value = json.loads(evidence.source_ref)
+    except (TypeError, ValueError):
+        return None
+    if not isinstance(value, Mapping) or value.get("contract") != _SOURCE_CONTRACT:
+        return None
+    result = {
+        key: str(value.get(key) or "")
+        for key in ("owner_module", "kind", "object_id", "path")
+    }
+    if (
+        not all(result.values())
+        or (result["owner_module"], result["kind"]) not in _SUPPORTED_REFERENCES
+    ):
+        return None
+    return result
+
+
+def _base_revision(
+    session: Session,
+    principal: object,
+    *,
+    case_id: str,
+    expected_revision: int,
+) -> CaseRecord:
+    base = get_case(
+        session,
+        principal,
+        case_id=case_id,
+        revision=expected_revision,
+    )
+    if base is None:
+        raise LookupError("Case revision not found.")
+    return base
+
+
+def _validated_evidence(
+    value: Mapping[str, object],
+    *,
+    tenant_id: str,
+) -> EvidenceReference:
+    owner_module = _bounded(value.get("owner_module"), "Owner module", 120)
+    reference_kind = _bounded(value.get("kind"), "Owner reference kind", 120)
+    object_id = _bounded(value.get("object_id"), "Owner object id", 1_000)
+    reference_tenant = _bounded(value.get("tenant_id"), "Owner tenant id", 255)
+    version = _bounded(value.get("version"), "Owner version", 255)
+    path = _bounded(value.get("path"), "Owner path", 2_000)
+    evidence_kind = _SUPPORTED_REFERENCES.get((owner_module, reference_kind))
+    if evidence_kind is None:
+        raise CaseStoreError("The owner reference kind is not supported by Cases.")
+    if reference_tenant != tenant_id:
+        raise CaseStoreError("Owner references cannot cross Case tenants.")
+    _validate_owner_path(
+        owner_module=owner_module,
+        reference_kind=reference_kind,
+        object_id=object_id,
+        version=version,
+        path=path,
+    )
+    canonical = {
+        "contract": _SOURCE_CONTRACT,
+        "owner_module": owner_module,
+        "kind": reference_kind,
+        "object_id": object_id,
+        "path": path,
+    }
+    encoded = json.dumps(
+        canonical,
+        ensure_ascii=True,
+        sort_keys=True,
+        separators=(",", ":"),
+    )
+    digest = hashlib.sha256(
+        f"{tenant_id}\x1f{encoded}\x1f{version}".encode()
+    ).hexdigest()
+    return EvidenceReference(
+        kind=evidence_kind,  # type: ignore[arg-type]
+        owner_module=owner_module,
+        evidence_id=f"linked-{digest[:40]}",
+        tenant_id=tenant_id,
+        version=version,
+        source_ref=encoded,
+        derived_from=(_SOURCE_CONTRACT,),
+    )
+
+
+def _validate_owner_path(
+    *,
+    owner_module: str,
+    reference_kind: str,
+    object_id: str,
+    version: str,
+    path: str,
+) -> None:
+    parsed = urlsplit(path)
+    if parsed.scheme or parsed.netloc or not path.startswith("/") or path.startswith("//"):
+        raise CaseStoreError("Owner paths must be local platform routes.")
+    if (owner_module, reference_kind) == ("files", "file-version"):
+        query = parse_qs(parsed.query, keep_blank_values=True)
+        if (
+            parsed.path != "/files"
+            or query.get("versionId") != [object_id]
+            or version != object_id
+            or not query.get("fileId", [""])[0]
+        ):
+            raise CaseStoreError("Files links require an exact authorized version path.")
+        return
+    if (owner_module, reference_kind) == ("mail", "message"):
+        query = parse_qs(parsed.query, keep_blank_values=True)
+        profile = query.get("profile", [""])[0]
+        folder = query.get("folder", [""])[0]
+        message = query.get("message", [""])[0]
+        expected_id = f"{profile}:{folder}:{message}"
+        if (
+            parsed.path != "/mail"
+            or not profile
+            or not folder
+            or not message
+            or object_id != expected_id
+            or version != message
+        ):
+            raise CaseStoreError("Mail links require an exact mailbox message path.")
+        return
+    expected_path = f"/campaigns/{quote(object_id, safe='')}"
+    if path != expected_path:
+        raise CaseStoreError("Campaign links require an exact Campaign path.")
+
+
+def _bounded(value: object, label: str, maximum: int) -> str:
+    result = str(value or "").strip()
+    if not result:
+        raise CaseStoreError(f"{label} is required.")
+    if len(result) > maximum or any(ord(character) < 32 for character in result):
+        raise CaseStoreError(f"{label} is invalid.")
+    return result
+
+
+__all__ = [
+    "link_case_evidence",
+    "linked_source",
+    "unlink_case_evidence",
+]