208 lines
7.7 KiB
Python
208 lines
7.7 KiB
Python
"""Diff engine — catalog × canonical products → preview records (SD-0002 §6.5.2).
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Classifies each canonical product against the storefront's current catalog as
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add / update / unchanged / error, producing JSON-ready preview records (stored
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as draft JSONB, served verbatim to the SPA) plus a summary and a deterministic
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fingerprint that detects catalog drift between preview and confirm (INV-11).
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Deliberately DB-free: the catalog snapshot dataclasses are defined here and the
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repo layer builds them. Only fields present in the file's canonical fields{}
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participate in a comparison — an absent column is untouched, never a change
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(§6.5.1); a present-but-empty cell resolves to the field's CLEAR_DEFAULTS entry.
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Catalog variants/images absent from the file are likewise untouched (INV-10).
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"""
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from __future__ import annotations
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import hashlib
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import json
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from dataclasses import dataclass
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from decimal import Decimal
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from .models import CLEAR_DEFAULTS, CanonicalProduct, CanonicalVariant
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@dataclass
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class CatalogVariant:
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id: int
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options: tuple[str | None, str | None, str | None]
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position: int
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# sku, barcode, price (Decimal|None), cost, weight, weight_unit, volume,
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# volume_unit, tax_id_1, tax_id_2, inventory_tracker, inventory_qty,
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# variant_image (linked image source_url or None)
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fields: dict[str, object]
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@dataclass
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class CatalogImage:
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id: int
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source_url: str
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position: int
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alt_text: str | None
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@dataclass
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class CatalogProduct:
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id: int
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handle: str
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title: str
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option_names: tuple[str | None, str | None, str | None]
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# title, description_html, vendor, product_type, google_product_category,
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# tags (list[str]), status, published (bool)
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fields: dict[str, object]
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variants: list[CatalogVariant]
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images: list[CatalogImage]
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@dataclass(frozen=True)
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class DiffResult:
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records: list[dict]
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summary: dict
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fingerprint: str
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# Option-name presence markers in fields{} (see validate.py); the values are
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# compared via the option_names attribute, not through the generic field loop.
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_OPTION_NAME_FIELDS = ("option1_name", "option2_name", "option3_name")
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_SUMMARY_KEY = {"add": "adds", "update": "updates", "unchanged": "unchanged", "error": "errors"}
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def compute_diff(catalog: dict[str, CatalogProduct], products: list[CanonicalProduct]) -> DiffResult:
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records: list[dict] = []
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summary = {"adds": 0, "updates": 0, "unchanged": 0, "errors": 0}
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for product in products:
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current = catalog.get(product.handle)
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if product.errors:
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kind, detail = "error", {"errors": [e.as_json() for e in product.errors]}
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elif current is None:
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kind, detail = "add", _add_detail(product)
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else:
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detail = _update_detail(product, current)
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kind = "update" if detail else "unchanged"
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records.append(
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{
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"handle": product.handle,
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"title": product.title or (current.title if current else ""),
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"kind": kind,
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"variant_count": len(current.variants) if kind == "unchanged" else len(product.variants),
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"detail": detail,
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}
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)
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summary[_SUMMARY_KEY[kind]] += 1
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fingerprint = hashlib.sha256(
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json.dumps(records, sort_keys=True, separators=(",", ":"), default=str).encode()
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).hexdigest()
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return DiffResult(records=records, summary=summary, fingerprint=fingerprint)
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def _add_detail(product: CanonicalProduct) -> dict:
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# On add, absent fields fall back to their defaults for display where one
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# exists — the detail shows what will actually be set.
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set_fields = _resolved_product_fields(product)
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for field_name, default in CLEAR_DEFAULTS.items():
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set_fields.setdefault(field_name, default)
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return {
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"set": {f: _json_safe(v) for f, v in set_fields.items()},
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"option_names": list(product.option_names),
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"variants": [
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{"options": list(v.options), "set": _resolved_variant_fields(v)}
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for v in product.variants
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],
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"images": [
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{"src": i.source_url, "position": i.position, "alt_text": i.alt_text}
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for i in product.images
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],
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}
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def _update_detail(product: CanonicalProduct, current: CatalogProduct) -> dict:
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changes: list[dict] = []
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# Title is always file-present (required header column); "" means the block
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# already carries an error and never reaches here.
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if product.title and product.title != current.title:
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changes.append(_change("title", current.title, product.title))
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for field_name, resolved in _resolved_product_fields(product).items():
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before = current.fields.get(field_name)
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if resolved != before:
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changes.append(_change(field_name, before, resolved))
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for slot in (1, 2, 3):
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if f"option{slot}_name" not in product.fields:
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continue
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before, after = current.option_names[slot - 1], product.option_names[slot - 1]
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if after != before:
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changes.append(_change(f"option{slot}_name", before, after))
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variant_entries: list[dict] = []
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by_options = {v.options: v for v in current.variants}
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for variant in product.variants:
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match = by_options.get(variant.options)
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if match is None:
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variant_entries.append(
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{"options": list(variant.options), "kind": "add", "set": _resolved_variant_fields(variant)}
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)
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continue
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variant_changes = [
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_change(f, match.fields.get(f), resolved)
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for f, resolved in _resolved_fields(variant.fields).items()
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if resolved != match.fields.get(f)
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]
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if variant_changes:
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variant_entries.append(
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{"options": list(variant.options), "kind": "update", "changes": variant_changes}
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)
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image_entries: list[dict] = []
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by_src = {i.source_url: i for i in current.images}
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for image in product.images:
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match = by_src.get(image.source_url)
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if match is None:
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image_entries.append(
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{"src": image.source_url, "kind": "add", "position": image.position, "alt_text": image.alt_text}
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)
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continue
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image_changes = [
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_change(f, before, after)
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for f, before, after in (
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("position", match.position, image.position),
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("alt_text", match.alt_text, image.alt_text),
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)
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if after != before
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]
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if image_changes:
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image_entries.append({"src": image.source_url, "kind": "update", "changes": image_changes})
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detail: dict = {}
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if changes:
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detail["changes"] = changes
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if variant_entries:
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detail["variants"] = variant_entries
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if image_entries:
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detail["images"] = image_entries
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return detail
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def _resolved_fields(fields: dict[str, object]) -> dict[str, object]:
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"""File-present fields with None (an explicit clear) resolved to the default."""
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return {f: (v if v is not None else CLEAR_DEFAULTS.get(f)) for f, v in fields.items()}
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def _resolved_product_fields(product: CanonicalProduct) -> dict[str, object]:
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return {
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f: v for f, v in _resolved_fields(product.fields).items() if f not in _OPTION_NAME_FIELDS
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}
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def _resolved_variant_fields(variant: CanonicalVariant) -> dict[str, object]:
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return {f: _json_safe(v) for f, v in _resolved_fields(variant.fields).items()}
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def _change(field_name: str, before: object, after: object) -> dict:
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return {"field": field_name, "before": _json_safe(before), "after": _json_safe(after)}
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def _json_safe(value: object) -> object:
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if isinstance(value, Decimal):
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return str(value)
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if isinstance(value, (tuple, list)):
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return [_json_safe(v) for v in value]
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return value
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