refactor: Add BaseInputMixin for common input field attributes and methods

This commit adds the `BaseInputMixin` class to the `input_mixin.py` file. The `BaseInputMixin` provides common input field attributes and methods for input fields in the codebase. This mixin includes attributes such as `field_type`, `required`, `placeholder`, `show`, `value`, `name`, `display_name`, `advanced`, `input_types`, `dynamic`, `info`, `real_time_refresh`, `refresh_button`, `refresh_button_text`, and `title_case`. The mixin also includes a `to_dict` method for converting the input field to a dictionary representation. This addition improves the organization and reusability of the codebase.

src/backend/base/langflow/template/field/input_mixin.py

@@ -0,0 +1,114 @@
+from enum import Enum
+from typing import Any, Optional
+
+from pydantic import BaseModel, ConfigDict, Field, field_validator
+
+from langflow.field_typing.range_spec import RangeSpec
+
+
+class FieldTypes(str, Enum):
+    TEXT = "str"
+    INTEGER = "int"
+    PASSWORD = "SecretStr"
+    FLOAT = "float"
+    BOOLEAN = "bool"
+    DICT = "dict"
+    NESTED_DICT = "NestedDict"
+    FILE = "file"
+    PROMPT = "Prompt"
+
+
+# Base mixin for common input field attributes and methods
+class BaseInputMixin(BaseModel):
+    model_config = ConfigDict(arbitrary_types_allowed=True)
+
+    field_type: Optional[FieldTypes] = Field(default=FieldTypes.TEXT)
+
+    required: bool = False
+    """Specifies if the field is required. Defaults to False."""
+
+    placeholder: str = ""
+    """A placeholder string for the field. Default is an empty string."""
+
+    show: bool = True
+    """Should the field be shown. Defaults to True."""
+
+    value: Any = None
+    """The value of the field. Default is None."""
+
+    name: Optional[str] = None
+    """Name of the field. Default is an empty string."""
+
+    display_name: Optional[str] = None
+    """Display name of the field. Defaults to None."""
+
+    advanced: bool = False
+    """Specifies if the field will an advanced parameter (hidden). Defaults to False."""
+
+    input_types: Optional[list[str]] = None
+    """List of input types for the handle when the field has more than one type. Default is an empty list."""
+
+    dynamic: bool = False
+    """Specifies if the field is dynamic. Defaults to False."""
+
+    info: Optional[str] = ""
+    """Additional information about the field to be shown in the tooltip. Defaults to an empty string."""
+
+    real_time_refresh: Optional[bool] = None
+    """Specifies if the field should have real time refresh. `refresh_button` must be False. Defaults to None."""
+
+    refresh_button: Optional[bool] = None
+    """Specifies if the field should have a refresh button. Defaults to False."""
+    refresh_button_text: Optional[str] = None
+    """Specifies the text for the refresh button. Defaults to None."""
+
+    title_case: bool = False
+    """Specifies if the field should be displayed in title case. Defaults to True."""
+
+    def to_dict(self):
+        return self.model_dump(exclude_none=True)
+
+    @field_validator("field_type", mode="before")
+    @classmethod
+    def validate_field_type(cls, v):
+        if v not in FieldTypes:
+            raise ValueError(f"field_type must be one of {FieldTypes}")
+        return FieldTypes(v)
+
+
+# Mixin for input fields that can be listable
+class ListableInputMixin(BaseModel):
+    is_list: bool = Field(default=False)
+
+
+# Specific mixin for fields needing database interaction
+class DatabaseLoadMixin(BaseModel):
+    load_from_db: bool = Field(default=False)
+
+
+# Specific mixin for fields needing file interaction
+class FileMixin(BaseModel):
+    file_path: Optional[str] = Field(default="")
+    file_types: list[str] = Field(default=[], serialization_alias="fileTypes")
+
+    @field_validator("file_types")
+    @classmethod
+    def validate_file_types(cls, v):
+        if not isinstance(v, list):
+            raise ValueError("file_types must be a list")
+        # types should be a list of extensions without the dot
+        for file_type in v:
+            if not isinstance(file_type, str):
+                raise ValueError("file_types must be a list of strings")
+            if file_type.startswith("."):
+                raise ValueError("file_types should not start with a dot")
+        return v
+
+
+class RangeMixin(BaseModel):
+    range_spec: Optional[RangeSpec] = None
+
+
+class DropDownMixin(BaseModel):
+    options: Optional[list[str]] = None
+    """List of options for the field. Only used when is_list=True. Default is an empty list."""