package main

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

	"k8s.io/klog"
)

// daemon is the main service 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 the state below.
	mu sync.RWMutex
	daemonState
}

// 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.daemonState.pirani()
	d.aboveRough.process(float64(mbar))
	d.aboveHigh.process(float64(mbar))

	// Check if the pirani gauge is disconnected. Note: this will assume the
	// pirani gauge is connected for the first couple of processing runs as
	// samples are still being captured.
	if d.piraniDetection() == piraniDetectionDisconnected {
		// Unrealistic result, Pirani probe probably disconnected. Failsafe mode.
		if !d.safety.failsafe {
			d.safety.failsafe = true
			klog.Errorf("Pirani probe seems disconnected; enabling failsafe mode")
		}
	} else {
		if d.safety.failsafe {
			if mbar >= 1e2 {
				d.safety.failsafe = false
				klog.Infof("Values are plausible again; quitting failsafe mode")
			}
		}
	}

	if mbar >= 1e-1 {
		if !d.safety.highPressure {
			d.safety.highPressure = true
			klog.Errorf("Pressure is too high; enabling diffusion pump lockout")
		}
	} else if mbar < (1e-1)-(1e-2) {
		if d.safety.highPressure {
			d.safety.highPressure = false
			klog.Infof("Pressure is low enough for diffusion pump operation; quitting diffusion pump lockout")
		}
	}

	if d.safety.failsafe {
		d.aboveRough.output = true
		d.aboveHigh.output = true
		d.dpOn = false
	}

	if d.safety.highPressure {
		d.dpOn = false
	}

	// 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
}