/*
Package econetui serves a small admin UI at / for viewing EcoNet devices and
changing their operating mode. It renders server-side HTML (html/template with
embedded assets) and uses HTMX for interactivity; device reads and mode writes
go through the in-process gRPC server, exactly like the MCP packages. Auth is
left to the edge (oauth2-proxy) — this package serves the human surface at /
and the mode-write at /ui/, leaving /health, /metrics, and /api untouched.
*/
package econetui

import (
	"context"
	"embed"
	"fmt"
	"html/template"
	"io/fs"
	"net/http"
	"strings"
	"time"

	"gitea.libretechconsulting.com/rmcguire/go-app/pkg/srv/http/opts"
	"github.com/rs/zerolog"

	"gitea.libretechconsulting.com/rmcguire/econet-exporter/pkg/config"
	"gitea.libretechconsulting.com/rmcguire/econet-exporter/pkg/econet/econetgrpc"
)

//go:embed templates/*.html
var templatesFS embed.FS

//go:embed static
var staticFS embed.FS

// pendingTTL bounds how long an optimistic mode change is shown before the UI
// falls back to the reported state.
const pendingTTL = 90 * time.Second

type EconetUIServer struct {
	ctx        context.Context
	cfg        *config.ServiceConfig
	log        *zerolog.Logger
	econetGRPC *econetgrpc.EconetGRPCServer
	tmpl       *template.Template
	pending    *pendingStore
}

func NewEconetUIServer(ctx context.Context, cfg *config.ServiceConfig,
	grpc *econetgrpc.EconetGRPCServer,
) *EconetUIServer {
	tmpl := template.Must(template.New("").Funcs(template.FuncMap{
		"prettyMode": prettyMode,
		"fillClass":  fillClass,
		"fillWidth":  fillWidth,
	}).ParseFS(templatesFS, "templates/*.html"))

	return &EconetUIServer{
		ctx:        ctx,
		cfg:        cfg,
		log:        zerolog.Ctx(ctx),
		econetGRPC: grpc,
		tmpl:       tmpl,
		pending:    newPendingStore(pendingTTL),
	}
}

func (s *EconetUIServer) GetHandlers() []opts.HTTPHandler {
	staticSub, _ := fs.Sub(staticFS, "static")

	mux := http.NewServeMux()
	mux.HandleFunc("GET /{$}", s.handleIndex)
	mux.HandleFunc("GET /ui/devices", s.handleDevices)
	mux.HandleFunc("GET /ui/devices/{serial}/debug", s.handleDebug)
	mux.HandleFunc("POST /ui/devices/{serial}/mode", s.handleSetMode)
	mux.Handle("GET /static/", http.StripPrefix("/static/", http.FileServer(http.FS(staticSub))))

	s.log.Debug().Msg("Econet admin UI ready at /")

	return []opts.HTTPHandler{{Prefix: "/", Handler: mux}}
}

// prettyMode turns a mode slug ("heat-pump") into a display label ("Heat Pump").
func prettyMode(slug string) string {
	switch slug {
	case "":
		return "Unknown"
	case "electric-gas":
		return "Electric/Gas"
	}
	words := strings.Split(slug, "-")
	for i, w := range words {
		if w != "" {
			words[i] = strings.ToUpper(w[:1]) + w[1:]
		}
	}
	return strings.Join(words, " ")
}

// fillClass buckets a hot-water fill percentage into a color class. It takes
// int32 to match the proto Device field (html/template is strict about types).
func fillClass(pct int32) string {
	switch {
	case pct >= 66:
		return "fill-high"
	case pct >= 33:
		return "fill-mid"
	default:
		return "fill-low"
	}
}

// fillWidth returns a safe CSS width for the fill bar.
func fillWidth(pct int32) template.CSS {
	if pct < 0 {
		pct = 0
	}
	return template.CSS(fmt.Sprintf("width:%d%%", pct))
}