package main

import (
	"context"
	"embed"
	"encoding/json"
	"errors"
	"io/fs"
	"log"
	"net/http"
	"time"

	"go-weatherstation/internal/db"
	"go-weatherstation/internal/providers"
)

//go:embed web/*
var webFS embed.FS

type webServer struct {
	db    *db.DB
	site  providers.Site
	model string
}

type dashboardResponse struct {
	GeneratedAt  time.Time             `json:"generated_at"`
	Site         string                `json:"site"`
	Model        string                `json:"model"`
	OpenMeteoURL string                `json:"open_meteo_url,omitempty"`
	RangeStart   time.Time             `json:"range_start"`
	RangeEnd     time.Time             `json:"range_end"`
	Observations []db.ObservationPoint `json:"observations"`
	Forecast     db.ForecastSeries     `json:"forecast"`
	Latest       *db.ObservationPoint  `json:"latest"`
}

func runWebServer(ctx context.Context, d *db.DB, site providers.Site, model, addr string) error {
	sub, err := fs.Sub(webFS, "web")
	if err != nil {
		return err
	}

	ws := &webServer{
		db:    d,
		site:  site,
		model: model,
	}

	mux := http.NewServeMux()
	mux.HandleFunc("/api/dashboard", ws.handleDashboard)
	mux.HandleFunc("/api/health", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		_, _ = w.Write([]byte(`{"ok":true}`))
	})
	mux.Handle("/", http.FileServer(http.FS(sub)))

	srv := &http.Server{
		Addr:              addr,
		Handler:           mux,
		ReadHeaderTimeout: 5 * time.Second,
	}

	errCh := make(chan error, 1)
	go func() {
		errCh <- srv.ListenAndServe()
	}()

	log.Printf("web ui listening addr=%s", addr)

	select {
	case <-ctx.Done():
		shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer cancel()
		_ = srv.Shutdown(shutdownCtx)
		return nil
	case err := <-errCh:
		if errors.Is(err, http.ErrServerClosed) {
			return nil
		}
		return err
	}
}

func (s *webServer) handleDashboard(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	rangeStr := r.URL.Query().Get("range")
	if rangeStr == "" {
		rangeStr = "24h"
	}
	startStr := r.URL.Query().Get("start")
	endStr := r.URL.Query().Get("end")
	bucket := r.URL.Query().Get("bucket")
	if bucket == "" {
		bucket = "5m"
	}
	if bucket != "1m" && bucket != "5m" {
		http.Error(w, "invalid bucket", http.StatusBadRequest)
		return
	}

	var (
		start time.Time
		end   time.Time
		err   error
	)
	if startStr != "" || endStr != "" {
		if startStr == "" || endStr == "" {
			http.Error(w, "start and end required", http.StatusBadRequest)
			return
		}
		start, err = parseTimeParam(startStr)
		if err != nil {
			http.Error(w, "invalid start", http.StatusBadRequest)
			return
		}
		end, err = parseTimeParam(endStr)
		if err != nil {
			http.Error(w, "invalid end", http.StatusBadRequest)
			return
		}
	} else {
		rangeDur, err := time.ParseDuration(rangeStr)
		if err != nil || rangeDur <= 0 {
			http.Error(w, "invalid range", http.StatusBadRequest)
			return
		}
		end = time.Now().UTC()
		start = end.Add(-rangeDur)
	}

	observations, err := s.db.ObservationSeries(r.Context(), s.site.Name, bucket, start, end)
	if err != nil {
		http.Error(w, "failed to query observations", http.StatusInternalServerError)
		log.Printf("web dashboard observations error: %v", err)
		return
	}

	latest, err := s.db.LatestObservation(r.Context(), s.site.Name)
	if err != nil {
		http.Error(w, "failed to query latest observation", http.StatusInternalServerError)
		log.Printf("web dashboard latest error: %v", err)
		return
	}

	forecast, err := s.db.ForecastSeriesLatest(r.Context(), s.site.Name, s.model)
	if err != nil {
		http.Error(w, "failed to query forecast", http.StatusInternalServerError)
		log.Printf("web dashboard forecast error: %v", err)
		return
	}

	openMeteoURL, err := providers.OpenMeteoRequestURL(s.site, s.model)
	if err != nil {
		log.Printf("web dashboard open-meteo url error: %v", err)
	}

	resp := dashboardResponse{
		GeneratedAt:  time.Now().UTC(),
		Site:         s.site.Name,
		Model:        s.model,
		OpenMeteoURL: openMeteoURL,
		RangeStart:   start,
		RangeEnd:     end,
		Observations: observations,
		Forecast:     forecast,
		Latest:       latest,
	}

	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Cache-Control", "no-store")
	if err := json.NewEncoder(w).Encode(resp); err != nil {
		log.Printf("web dashboard encode error: %v", err)
	}
}

func parseTimeParam(v string) (time.Time, error) {
	if t, err := time.Parse(time.RFC3339, v); err == nil {
		return t, nil
	}
	if t, err := time.Parse("2006-01-02", v); err == nil {
		return t, nil
	}
	return time.Time{}, errors.New("unsupported time format")
}