import pandas as pd
import panel as pn
import numpy as np
import holoviews as hv
from holoviews.streams import Buffer
from bokeh.models import Button, Slider, Spinner
import time
import asyncio

pn.extension(sizing_mode="stretch_width")

class FakeInstrument(object):
    def __init__(self, offset=0.0):
        self.offset = offset

    def set_offset(self, value):
        self.offset = value

    def read_data(self):
        return np.random.random() + self.offset

instrument = FakeInstrument()  # Instantiate your instrument

def make_df(time_sec=0.0, temperature_degC=0.0):
    return pd.DataFrame({'Time (s)': time_sec, 'Temperature (°C)': temperature_degC}, index=[0])

example_df = pd.DataFrame(columns=make_df().columns)
buffer = Buffer(example_df, length=1000, index=False)
plot = hv.DynamicMap(hv.Curve, streams=[buffer]).opts(padding=0.1, height=600, xlim=(0, None), responsive=True)

LABEL_START = 'Start'
LABEL_STOP = 'Stop'
LABEL_CSV_START = "Save to csv"
LABEL_CSV_STOP = "Stop save"
CSV_FILENAME = 'tmp.csv'

button_startstop = Button(label=LABEL_START, button_type="primary")
button_csv = Button(label=LABEL_CSV_START, button_type="success")
offset = Slider(title='Offset', start=-10.0, end=10.0, value=0.0, step=0.1)
interval = Spinner(title="Interval (sec)", value=0.1, step=0.01)

acquisition_task = None
save_to_csv = False

async def acquire_data(interval_sec=0.1):
    global save_to_csv
    t0 = time.time()
    while True:
        instrument.set_offset(offset.value)
        time_elapsed = time.time() - t0
        value = instrument.read_data()
        b = make_df(time_elapsed, value)
        buffer.send(b)

        if save_to_csv:
            b.to_csv(CSV_FILENAME, header=False, index=False, mode='a')

        time_spent_buffering = time.time() - t0 - time_elapsed
        if interval_sec > time_spent_buffering:
            await asyncio.sleep(interval_sec - time_spent_buffering)


def toggle_csv(*events):
    global save_to_csv
    if button_csv.label == LABEL_CSV_START:
        button_csv.label = LABEL_CSV_STOP
        example_df.to_csv(CSV_FILENAME, index=False)  # example_df is empty, so this just writes the header
        save_to_csv = True
    else:
        save_to_csv = False
        button_csv.label = LABEL_CSV_START


def start_stop(*events):
    global acquisition_task, save_to_csv
    if button_startstop.label == LABEL_START:
        button_startstop.label = LABEL_STOP
        buffer.clear()
        acquisition_task = asyncio.get_running_loop().create_task(acquire_data(interval_sec=interval.value))
    else:
        acquisition_task.cancel()
        button_startstop.label = LABEL_START
        if save_to_csv:
            toggle_csv()


button_startstop.on_click(start_stop)
button_csv.on_click(toggle_csv)

hv.extension('bokeh')
hv.renderer('bokeh').theme = 'caliber'
controls = pn.WidgetBox('# Controls',
                        button_startstop,
                        button_csv,
                        interval,
                        offset,
                        )

pn.Row(plot, controls)

pn.template.FastListTemplate(
    site="Panel", 
    title="Hardware Automation, IoT, Streaming and Async", 
    sidebar=[*controls], 
    main=[
        "This app provides a simple example of a graphical interface for **scientific instrument control** using Panel for layout/interaction and [Holoviews](http://holoviews.org) for buffering and plotting data from the instrument.",
        plot,
    ]
).servable();