# app.py
# Simple Unit Converter (Gradio) - ready for Hugging Face Spaces
import gradio as gr

# ----------------------------
# Conversion data / helpers
# ----------------------------
CONVERSIONS = {
    "Length": {
        "m": 1.0,
        "cm": 0.01,
        "mm": 0.001,
        "km": 1000.0,
        "in": 0.0254,
        "ft": 0.3048,
        "yd": 0.9144,
        "mi": 1609.344
    },
    "Mass": {
        "kg": 1.0,
        "g": 0.001,
        "mg": 1e-6,
        "lb": 0.45359237,
        "oz": 0.028349523125
    },
    "Volume": {
        "L": 1.0,
        "mL": 0.001,
        "m^3": 1000.0,
        "cup": 0.2365882365,
        "pt": 0.473176473,
        "gal": 3.785411784
    },
    "Temperature": ["C", "F", "K"]
}

def convert_linear(value: float, from_unit: str, to_unit: str, mapping: dict) -> float:
    if from_unit not in mapping or to_unit not in mapping:
        raise ValueError("Unknown unit for this category.")
    value_in_base = value * mapping[from_unit]
    return value_in_base / mapping[to_unit]

def temp_to_c(value: float, unit: str) -> float:
    unit = unit.upper()
    if unit == "C":
        return value
    if unit == "F":
        return (value - 32.0) * 5.0 / 9.0
    if unit == "K":
        return value - 273.15
    raise ValueError("Unsupported temperature unit")

def c_to_temp(celsius: float, unit: str) -> float:
    unit = unit.upper()
    if unit == "C":
        return celsius
    if unit == "F":
        return celsius * 9.0 / 5.0 + 32.0
    if unit == "K":
        return celsius + 273.15
    raise ValueError("Unsupported temperature unit")

def convert_temperature(value: float, from_unit: str, to_unit: str) -> float:
    c = temp_to_c(value, from_unit)
    return c_to_temp(c, to_unit)

# ----------------------------
# Gradio UI callbacks
# ----------------------------
def update_unit_dropdowns(category: str):
    if category == "Temperature":
        units = CONVERSIONS["Temperature"]
    else:
        units = list(CONVERSIONS[category].keys())
    from_default = units[0]
    to_default = units[1] if len(units) > 1 else units[0]
    return gr.update(choices=units, value=from_default), gr.update(choices=units, value=to_default)

def perform_conversion(value, from_unit, to_unit, category):
    try:
        if value is None:
            return "Please enter a numeric value."
        if category == "Temperature":
            result = convert_temperature(float(value), from_unit, to_unit)
            return f"{result:.6g} {to_unit}"
        else:
            mapping = CONVERSIONS[category]
            result = convert_linear(float(value), from_unit, to_unit, mapping)
            return f"{result:.6g} {to_unit}"
    except Exception as e:
        return f"Error: {e}"

# ----------------------------
# Build Gradio Blocks UI
# ----------------------------
with gr.Blocks(title="Simple Unit Converter") as demo:
    gr.Markdown("## Simple Unit Converter\nConvert between Length, Mass, Volume and Temperature units.")
    category_dd = gr.Dropdown(choices=list(CONVERSIONS.keys()), label="Category", value="Length")
    from_dd = gr.Dropdown(choices=list(CONVERSIONS["Length"].keys()), label="From unit")
    to_dd   = gr.Dropdown(choices=list(CONVERSIONS["Length"].keys()), label="To unit")
    val_in = gr.Number(value=1.0, label="Value to convert")
    convert_btn = gr.Button("Convert")
    result_out = gr.Textbox(label="Result", interactive=False)

    category_dd.change(fn=update_unit_dropdowns, inputs=category_dd, outputs=[from_dd, to_dd])
    convert_btn.click(fn=perform_conversion, inputs=[val_in, from_dd, to_dd, category_dd], outputs=result_out)

# IMPORTANT for Spaces: do NOT use share=True (that's for Colab).
if __name__ == "__main__":
    demo.launch()