feat: add search to crud paginate function (#17)

* feat: add search to crud paginate function

* fixes: comments + tests import

src/fastapi_toolsets/crud/search.py

@@ -0,0 +1,145 @@
+"""Search utilities for AsyncCrud."""
+
+from collections.abc import Sequence
+from dataclasses import dataclass
+from typing import TYPE_CHECKING, Any, Literal
+
+from sqlalchemy import String, or_
+from sqlalchemy.orm import DeclarativeBase
+from sqlalchemy.orm.attributes import InstrumentedAttribute
+
+from ..exceptions import NoSearchableFieldsError
+
+if TYPE_CHECKING:
+    from sqlalchemy.sql.elements import ColumnElement
+
+SearchFieldType = InstrumentedAttribute[Any] | tuple[InstrumentedAttribute[Any], ...]
+
+
+@dataclass
+class SearchConfig:
+    """Advanced search configuration.
+
+    Attributes:
+        query: The search string
+        fields: Fields to search (columns or tuples for relationships)
+        case_sensitive: Case-sensitive search (default: False)
+        match_mode: "any" (OR) or "all" (AND) to combine fields
+    """
+
+    query: str
+    fields: Sequence[SearchFieldType] | None = None
+    case_sensitive: bool = False
+    match_mode: Literal["any", "all"] = "any"
+
+
+def get_searchable_fields(
+    model: type[DeclarativeBase],
+    *,
+    include_relationships: bool = True,
+    max_depth: int = 1,
+) -> list[SearchFieldType]:
+    """Auto-detect String fields on a model and its relationships.
+
+    Args:
+        model: SQLAlchemy model class
+        include_relationships: Include fields from many-to-one/one-to-one relationships
+        max_depth: Max depth for relationship traversal (default: 1)
+
+    Returns:
+        List of columns and tuples (relationship, column)
+    """
+    fields: list[SearchFieldType] = []
+    mapper = model.__mapper__
+
+    # Direct String columns
+    for col in mapper.columns:
+        if isinstance(col.type, String):
+            fields.append(getattr(model, col.key))
+
+    # Relationships (one-to-one, many-to-one only)
+    if include_relationships and max_depth > 0:
+        for rel_name, rel_prop in mapper.relationships.items():
+            if rel_prop.uselist:  # Skip collections (one-to-many, many-to-many)
+                continue
+
+            rel_attr = getattr(model, rel_name)
+            related_model = rel_prop.mapper.class_
+
+            for col in related_model.__mapper__.columns:
+                if isinstance(col.type, String):
+                    fields.append((rel_attr, getattr(related_model, col.key)))
+
+    return fields
+
+
+def build_search_filters(
+    model: type[DeclarativeBase],
+    search: str | SearchConfig,
+    search_fields: Sequence[SearchFieldType] | None = None,
+    default_fields: Sequence[SearchFieldType] | None = None,
+) -> tuple[list["ColumnElement[bool]"], list[InstrumentedAttribute[Any]]]:
+    """Build SQLAlchemy filter conditions for search.
+
+    Args:
+        model: SQLAlchemy model class
+        search: Search string or SearchConfig
+        search_fields: Fields specified per-call (takes priority)
+        default_fields: Default fields (from ClassVar)
+
+    Returns:
+        Tuple of (filter_conditions, joins_needed)
+    """
+    # Normalize input
+    if isinstance(search, str):
+        config = SearchConfig(query=search, fields=search_fields)
+    else:
+        config = search
+        if search_fields is not None:
+            config = SearchConfig(
+                query=config.query,
+                fields=search_fields,
+                case_sensitive=config.case_sensitive,
+                match_mode=config.match_mode,
+            )
+
+    if not config.query or not config.query.strip():
+        return [], []
+
+    # Determine which fields to search
+    fields = config.fields or default_fields or get_searchable_fields(model)
+
+    if not fields:
+        raise NoSearchableFieldsError(model)
+
+    query = config.query.strip()
+    filters: list[ColumnElement[bool]] = []
+    joins: list[InstrumentedAttribute[Any]] = []
+    added_joins: set[str] = set()
+
+    for field in fields:
+        if isinstance(field, tuple):
+            # Relationship: (User.role, Role.name) or deeper
+            for rel in field[:-1]:
+                rel_key = str(rel)
+                if rel_key not in added_joins:
+                    joins.append(rel)
+                    added_joins.add(rel_key)
+            column = field[-1]
+        else:
+            column = field
+
+        # Build the filter
+        if config.case_sensitive:
+            filters.append(column.like(f"%{query}%"))
+        else:
+            filters.append(column.ilike(f"%{query}%"))
+
+    if not filters:
+        return [], []
+
+    # Combine based on match_mode
+    if config.match_mode == "any":
+        return [or_(*filters)], joins
+    else:
+        return filters, joins