class TemplateString:
    """
    Replaces {} placeholders in a template with input values, in order.

    Template: "a {subject} on a {surface}, {lighting} lighting, {quality}"
    input_1: "burger"
    input_2: "wooden table"
    input_3: "cinematic"
    input_4: "8k"
    Result:  "a burger on a wooden table, cinematic lighting, 8k"

    Text inside {} is treated as a comment and ignored during substitution.
    Unused placeholders are left as-is. Extra inputs are ignored.
    """

    @classmethod
    def INPUT_TYPES(cls):
        return {
            "required": {
                "template": ("STRING", {
                    "default": "a {}, {}, {}",
                    "multiline": True,
                }),
            },
            "optional": {
                "input_1": ("STRING", {"default": "", "forceInput": True}),
                "input_2": ("STRING", {"default": "", "forceInput": True}),
                "input_3": ("STRING", {"default": "", "forceInput": True}),
                "input_4": ("STRING", {"default": "", "forceInput": True}),
                "input_5": ("STRING", {"default": "", "forceInput": True}),
                "input_6": ("STRING", {"default": "", "forceInput": True}),
                "input_7": ("STRING", {"default": "", "forceInput": True}),
                "input_8": ("STRING", {"default": "", "forceInput": True}),
                "input_9": ("STRING", {"default": "", "forceInput": True}),
                "input_10": ("STRING", {"default": "", "forceInput": True}),
            },
        }

    RETURN_TYPES = ("STRING",)
    RETURN_NAMES = ("text",)
    FUNCTION = "render"
    CATEGORY = "text"

    def render(self, template, **kwargs):
        values = []
        for i in range(1, 11):
            key = f"input_{i}"
            if key in kwargs and kwargs[key] is not None:
                values.append(kwargs[key])

        # Replace {anything} placeholders one at a time, left to right
        # Text inside braces is treated as a comment and discarded
        import re
        result = template
        for val in values:
            result = re.sub(r"\{[^}]*\}", val, result, count=1)

        return (result,)


NODE_CLASS_MAPPINGS = {
    "TemplateString": TemplateString,
}

NODE_DISPLAY_NAME_MAPPINGS = {
    "TemplateString": "Template String",
}