package main

import (
	"context"
	"errors"
	"fmt"
	"math"
	"sync"
	"time"

	"k8s.io/klog"
)

// daemon is the main state of the succdaemon.
type daemon struct {
	// adcPirani is the adc implementation returning the voltage of the Pfeiffer
	// Pirani gauge.
	adcPirani adc

	gpioDiffusionPump gpio
	gpioRoughingPump  gpio
	gpioBtnPumpDown   gpio
	gpioBtnVent       gpio
	gpioBelowRough    gpio
	gpioBelowHigh     gpio

	// mu guards state variables below.
	mu sync.RWMutex
	// adcPiraniVolts is a moving window of read ADC values, used to calculate a
	// moving average.
	adcPiraniVolts []float32
	rpOn           bool
	dpOn           bool

	vent       momentaryOutput
	pumpdown   momentaryOutput
	aboveRough thresholdOutput
	aboveHigh  thresholdOutput
}

// momentaryOutput is an output that can be triggered for 500ms.
type momentaryOutput struct {
	// output of the block.
	output bool
	// scheduledOff is when the block should be outputting false again.
	scheduledOff time.Time
}

func (m *momentaryOutput) process() {
	m.output = m.scheduledOff.After(time.Now())
}

func (m *momentaryOutput) trigger() {
	m.scheduledOff = time.Now().Add(time.Millisecond * 500)
}

// thresholdOutput outputs true if a given value is above a setpoint/threshold.
// It contains debounce logic for processing noisy analog signals.
type thresholdOutput struct {
	// output of the block.
	output bool
	// debounce is when the debouncer should be inactive again.
	debounce time.Time
	// threshold is the setpoint of the block.
	threshold float64
}

func (t *thresholdOutput) process(value float64) {
	if time.Now().Before(t.debounce) {
		return
	}
	new := value > t.threshold
	if new != t.output {
		t.output = new
		t.debounce = time.Now().Add(time.Second * 5)
	}
}

// process runs the pain acquisition and control loop of succd.
func (d *daemon) process(ctx context.Context) {
	ticker := time.NewTicker(time.Millisecond * 100)
	defer ticker.Stop()
	for {
		select {
		case <-ticker.C:
			if err := d.processOnce(ctx); err != nil {
				if errors.Is(err, ctx.Err()) {
					return
				} else {
					klog.Errorf("Processing error: %v", err)
					time.Sleep(time.Second * 10)
				}
			}
		case <-ctx.Done():
			return
		}
	}
}

// processOnce runs the main loop step of succd.
func (d *daemon) processOnce(_ context.Context) error {
	v, err := d.adcPirani.Read()
	if err != nil {
		return fmt.Errorf("when reading ADC: %w", err)
	}
	d.mu.Lock()
	defer d.mu.Unlock()

	// Process pirani ringbuffer.
	d.adcPiraniVolts = append(d.adcPiraniVolts, v)
	trim := len(d.adcPiraniVolts) - 100
	if trim > 0 {
		d.adcPiraniVolts = d.adcPiraniVolts[trim:]
	}

	d.pumpdown.process()
	d.vent.process()

	_, mbar := d.piraniUnlocked()
	d.aboveRough.process(float64(mbar))
	d.aboveHigh.process(float64(mbar))

	// Update relay outputs.
	for _, rel := range []struct {
		name string
		gpio gpio
		// activeHigh means the relay is active high, ie. a true source will
		// mean that NO/COM get connected, and a false source means that NC/COM
		// get connected.
		activeHigh bool
		source     bool
	}{
		{"rp", d.gpioRoughingPump, false, d.rpOn},
		{"dp", d.gpioDiffusionPump, true, d.dpOn},
		{"pumpdown", d.gpioBtnPumpDown, true, d.pumpdown.output},
		{"vent", d.gpioBtnVent, true, d.vent.output},
		{"rough", d.gpioBelowRough, false, d.aboveRough.output},
		{"high", d.gpioBelowHigh, false, d.aboveHigh.output},
	} {
		val := rel.source
		if rel.activeHigh {
			// Invert because the relays go through logical inversion (ie. a
			// GPIO false is a relay trigger).
			val = !val
		}
		if err := rel.gpio.set(val); err != nil {
			return fmt.Errorf("when outputting %s: %w", rel.name, err)
		}
	}

	return nil
}

// pirani returns the Pirani gauge voltage and pressure.
func (d *daemon) pirani() (volts float32, mbar float32) {
	d.mu.RLock()
	volts, mbar = d.piraniUnlocked()
	d.mu.RUnlock()
	return
}

func (d *daemon) piraniUnlocked() (volts float32, mbar float32) {
	volts = 0.0
	for _, v := range d.adcPiraniVolts {
		volts += v
	}
	if len(d.adcPiraniVolts) != 0 {
		volts /= float32(len(d.adcPiraniVolts))
	}

	// Per Pirani probe docs.
	bar := math.Pow(10.0, float64(volts)-8.5)
	mbar = float32(bar * 1000.0)
	return
}

// rpSet enables/disables the roughing pump.
func (d *daemon) rpSet(state bool) {
	d.mu.Lock()
	defer d.mu.Unlock()
	d.rpOn = state
}

// rpGet returns whether the roughing pump is enabled/disabled.
func (d *daemon) rpGet() bool {
	d.mu.RLock()
	defer d.mu.RUnlock()
	return d.rpOn
}

// dpSet enables/disables the diffusion pump.
func (d *daemon) dpSet(state bool) {
	d.mu.Lock()
	defer d.mu.Unlock()
	d.dpOn = state
}

// dpGet returns whether the diffusion pump is enabled/disabled.
func (d *daemon) dpGet() bool {
	d.mu.RLock()
	defer d.mu.RUnlock()
	return d.dpOn
}

func (d *daemon) vacuumStatusGet() (rough, high bool) {
	d.mu.RLock()
	defer d.mu.RUnlock()
	rough = !d.aboveRough.output
	high = !d.aboveHigh.output
	return
}

// pumpDownPressed toggles the pump down relay for 500ms.
func (d *daemon) pumpDownPress() {
	d.mu.Lock()
	defer d.mu.Unlock()
	d.pumpdown.trigger()
}

// ventPress toggles the vent relay for 500ms.
func (d *daemon) ventPress() {
	d.mu.Lock()
	defer d.mu.Unlock()
	d.vent.trigger()
}