package main

import (
	_ "embed"
	"fmt"
	"html/template"
	"net/http"
	_ "net/http/pprof"
	"os"
	"strings"
	"time"

	"github.com/coder/websocket"
	"github.com/coder/websocket/wsjson"
	"k8s.io/klog"
)

type httpServer struct {
	d daemonController
}

var (
	//go:embed index.html
	templateIndexText string
	templateIndex     = template.Must(template.New("index").Parse(templateIndexText))
	//go:embed succd.png
	favicon []byte
)

func (s *httpServer) viewFavicon(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "image/png")
	w.Write(favicon)
}

func formatVolts(v float32) string {
	return fmt.Sprintf("%.4f V", v)
}

// formatMbar formats a millibar value using scientific notation and returns a
// HTML fragment (for superscript support).
func formatMbar(v float32) template.HTML {
	exp := 0
	for v < 1 {
		v *= 10
		exp -= 1
	}
	for v >= 10 {
		v /= 10
		exp += 1
	}
	res := fmt.Sprintf("%.3f", v)
	res += fmt.Sprintf(" x 10<sup>%d</sup>", exp)
	res += " mbar"
	return template.HTML(res)
}

// apiData is the data model served to the user via HTTP/WebSockets
type apiData struct {
	// Safety interlocks.
	Safety struct {
		// Failsafe mode enabled - pirani gauge seems disconnected.
		Failsafe bool
		// HighPressure interlock enabled - pressure too high to run diffusion
		// pump.
		HighPressure bool
	}
	// Pirani gauge data.
	Pirani struct {
		// Volts read from the gauge (0-10).
		Volts string
		// Mbar read from the gauge, formatted as HTML.
		Mbar template.HTML
		// MbarFloat read from the gauge.
		MbarFloat float32
	}
	// Pump state.
	Pumps struct {
		// RPOn means the roughing pump is turned on.
		RPOn bool
		// DPOn means the diffusion pump is turned on.
		DPOn bool
	}
	// Pressure feedback into evacuation board.
	Feedback struct {
		// RoughReached is true when the system has reached a rough vacuum
		// stage.
		RoughReached bool
		// HighReached is true when the system has reached a high vacuum stage.
		HighReached bool
	}
	// System junk.
	System struct {
		// Load of the system.
		Load string
		// Hostname of the system.
		Hostname string
	}
}

// apiData returns the user data model for the current state of the system. If
// skipSystem is set, the System subset is ignored (saves system load, and is
// not being served via websockets).
func (s *httpServer) apiData(skipSystem bool) *apiData {
	state := s.d.snapshot()
	volts, mbar := state.pirani()
	rough, high := state.vacuumStatus()

	var hostname, load string
	var err error

	if !skipSystem {
		hostname, err = os.Hostname()
		if err != nil {
			hostname = "unknown"
		}
		loadB, err := os.ReadFile("/proc/loadavg")
		load = "unknown"
		if err == nil {
			parts := strings.Fields(string(loadB))
			load = strings.Join(parts[:3], " ")
		}
	}

	ad := apiData{}
	ad.Safety.Failsafe = state.safety.failsafe
	ad.Safety.HighPressure = state.safety.highPressure
	ad.Pirani.Volts = formatVolts(volts)
	ad.Pirani.Mbar = formatMbar(mbar)
	ad.Pirani.MbarFloat = mbar
	ad.Pumps.RPOn = state.rpOn
	ad.Pumps.DPOn = state.dpOn
	ad.Feedback.RoughReached = rough
	ad.Feedback.HighReached = high
	ad.System.Load = load
	ad.System.Hostname = hostname
	return &ad
}

// httpIndex is the / view.
func (s *httpServer) viewIndex(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/" {
		http.NotFound(w, r)
		return
	}

	data := s.apiData(false)
	//data.Pirani.Mbar = html.St
	templateIndex.Execute(w, data)
}

// httpStream is the websocket clientwards data hose, returning a 10Hz update
// stream of pressure/voltage.
func (s *httpServer) viewStream(w http.ResponseWriter, r *http.Request) {
	c, err := websocket.Accept(w, r, nil)
	if err != nil {
		return
	}
	defer c.CloseNow()

	t := time.NewTicker(time.Second / 10)
	defer t.Stop()

	ctx := c.CloseRead(r.Context())
	for {
		select {
		case <-ctx.Done():
			c.Close(websocket.StatusNormalClosure, "")
			return
		case <-t.C:
			v := s.apiData(true)
			if err := wsjson.Write(ctx, c, v); err != nil {
				klog.Errorf("Websocket write failed: %v", err)
				return
			}
		}
	}
}

// httpMetrics serves minimalistic Prometheus-compatible metrics.
func (s *httpServer) viewMetrics(w http.ResponseWriter, r *http.Request) {
	// TODO(q3k): also serve Go stuff using the actual Prometheus metrics client
	// library.
	// TODO(q3k): serve the rest of the data model
	state := s.d.snapshot()
	_, mbar := state.pirani()
	fmt.Fprintf(w, "# HELP sem_pressure_mbar Pressure in the SEM chamber, in millibar\n")
	fmt.Fprintf(w, "# TYPE sem_pressure_mbar gauge\n")
	fmt.Fprintf(w, "sem_pressure_mbar %f\n", mbar)
}

func (s *httpServer) viewRoughingPumpEnable(w http.ResponseWriter, r *http.Request) {
	s.d.rpSet(true)
	fmt.Fprintf(w, "succ on\n")
}

func (s *httpServer) viewRoughingPumpDisable(w http.ResponseWriter, r *http.Request) {
	s.d.rpSet(false)
	fmt.Fprintf(w, "succ off\n")
}

func (s *httpServer) viewDiffusionPumpEnable(w http.ResponseWriter, r *http.Request) {
	s.d.dpSet(true)
	fmt.Fprintf(w, "deep succ on\n")
}

func (s *httpServer) viewDiffusionPumpDisable(w http.ResponseWriter, r *http.Request) {
	s.d.dpSet(false)
	fmt.Fprintf(w, "deep succ off\n")
}

func (s *httpServer) viewButtonPumpDown(w http.ResponseWriter, r *http.Request) {
	s.d.pumpDownPress()
}

func (s *httpServer) viewButtonVent(w http.ResponseWriter, r *http.Request) {
	s.d.ventPress()
}

func (s *httpServer) setupViews() {
	http.HandleFunc("/", s.viewIndex)
	http.HandleFunc("/favicon.png", s.viewFavicon)
	http.HandleFunc("/stream", s.viewStream)
	http.HandleFunc("/metrics", s.viewMetrics)
	http.HandleFunc("/button/vent", s.viewButtonVent)
	http.HandleFunc("/button/pumpdown", s.viewButtonPumpDown)
	http.HandleFunc("/rp/on", s.viewRoughingPumpEnable)
	http.HandleFunc("/rp/off", s.viewRoughingPumpDisable)
	http.HandleFunc("/dp/on", s.viewDiffusionPumpEnable)
	http.HandleFunc("/dp/off", s.viewDiffusionPumpDisable)
}