import gradio as gr

q = 0
q_bar = 1
history = []


def sr_latch(s, r):
    global q, q_bar, history

    s = int(s)
    r = int(r)

    if s == 1 and r == 1:
        state = "INVALID"
    elif s == 1 and r == 0:
        q, q_bar = 1, 0
        state = "SET"
    elif s == 0 and r == 1:
        q, q_bar = 0, 1
        state = "RESET"
    else:
        state = "HOLD"

    q_display = "X" if state == "INVALID" else str(q)
    q_bar_display = "X" if state == "INVALID" else str(q_bar)

    history.append(f"S={s}, R={r}  =>  Q={q_display}, Q'={q_bar_display}  [{state}]")

    log = "\n".join(history)

    return q_display, q_bar_display, state, log


def reset_latch():
    global q, q_bar, history
    q = 0
    q_bar = 1
    history = []
    return "0", "1", "HOLD", ""


custom_css = """
.gradio-container {
    max-width: 720px !important;
    margin: auto;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}
h1 {
    color: #1a1a2e !important;
    font-size: 28px !important;
    font-weight: 700 !important;
    margin-bottom: 4px !important;
}
.subtitle {
    color: #5a5a6e !important;
    font-size: 15px !important;
}
.output-box textarea {
    font-size: 22px !important;
    font-weight: 600 !important;
    text-align: center !important;
    color: #1a1a2e !important;
}
.history-box textarea {
    font-family: "SF Mono", "Fira Code", "Consolas", monospace !important;
    font-size: 13px !important;
    color: #3a3a4e !important;
}
.truth-table-wrap table {
    font-size: 14px !important;
}
.truth-table-wrap th {
    color: #5a5a6e !important;
    font-weight: 600 !important;
}
.truth-table-wrap td {
    color: #1a1a2e !important;
}
button.primary {
    background: #1a1a2e !important;
    color: #ffffff !important;
    border: none !important;
}
button.primary:hover {
    background: #2a2a3e !important;
}
input[type="radio"]:checked {
    accent-color: #1a1a2e !important;
}
"""

with gr.Blocks(title="SR Latch Simulator") as demo:
    gr.Markdown("# SR Latch Simulator")
    gr.Markdown(
        "Toggle the S (set) and R (reset) inputs and click Apply to observe the latch behavior.",
        elem_classes=["subtitle"],
    )

    with gr.Row():
        s_input = gr.Radio(choices=["0", "1"], value="0", label="S (Set)")
        r_input = gr.Radio(choices=["0", "1"], value="0", label="R (Reset)")

    with gr.Row():
        apply_btn = gr.Button("Apply", variant="primary")
        reset_btn = gr.Button("Reset")

    with gr.Row():
        q_output = gr.Textbox(label="Q", value="0", interactive=False, elem_classes=["output-box"])
        q_bar_output = gr.Textbox(label="Q'", value="1", interactive=False, elem_classes=["output-box"])
        state_output = gr.Textbox(label="State", value="HOLD", interactive=False, elem_classes=["output-box"])

    gr.Markdown("### Truth Table")
    gr.Dataframe(
        value=[
            ["0", "0", "Prev", "Prev", "Hold"],
            ["1", "0", "1", "0", "Set"],
            ["0", "1", "0", "1", "Reset"],
            ["1", "1", "X", "X", "Invalid"],
        ],
        headers=["S", "R", "Q", "Q'", "State"],
        interactive=False,
        elem_classes=["truth-table-wrap"],
    )

    gr.Markdown("### History")
    history_box = gr.Textbox(
        label="Log",
        lines=6,
        interactive=False,
        elem_classes=["history-box"],
    )

    apply_btn.click(
        fn=sr_latch,
        inputs=[s_input, r_input],
        outputs=[q_output, q_bar_output, state_output, history_box],
    )

    reset_btn.click(
        fn=reset_latch,
        inputs=[],
        outputs=[q_output, q_bar_output, state_output, history_box],
    )

if __name__ == "__main__":
    demo.launch(css=custom_css, theme=gr.themes.Base())