Method computeResponse

internal/weather/weather.go:252–456

computeResponse performs location resolution, weather fetch, rendering and formatting. Returns ready-to-cache domain.CacheEntry or error. Does NOT write to ResponseWriter — that stays in handler.

(
	ctx context.Context, r *http.Request,
	tracker *TimeTracker,
)

// Returns ready-to-cache domain.CacheEntry or error.
// Does NOT write to ResponseWriter — that stays in handler.
func (s *WeatherService) computeResponse(
	ctx context.Context, r *http.Request,
	tracker *TimeTracker,
) (*domain.CacheEntry, error) {
	debugRequested := r.URL.Query().Get("debug") != ""

	clientIP := getClientIP(r)

	// ── Determine location string ────────────────────────────────────────
	start := time.Now()
	path := r.URL.Path // cleanPath(r.URL.Path) // helper: trim / and extensions
	autoDetect := isAutoDetectPath(path)

	// 0. Locate IP
	var ipData *domain.IPData
	var errIP error
	for _, ipLocator := range s.IPLocators {
		ipData, errIP = ipLocator.GetIPData(clientIP)
		if errIP == nil && ipData != nil {
			break
		}
	}
	tracker.Add("IP locating", time.Since(start))

	// For testing purposes, it is possibe to simulate US-based clients
	// by setting country code in the HTTP headers of the request.
	if countryCode := r.Header.Get("X-Client-Country-Code"); countryCode != "" {
		ipData.CountryCode = countryCode
	}

	/////////////////////
	// This part should be moved to queryparser.
	ipOpts := options.Options{}
	if isClientInUSA(ipData) {
		ipOpts.UseMetric = false
		ipOpts.UseImperial = true
	} else {
		ipOpts.UseMetric = true
		ipOpts.UseImperial = false
	}
	///////////////////

	// 1. Parse options (cheap, always first)
	start = time.Now()
	opts, err := s.QueryParser.Parse(ctx, r, &ipOpts)
	if err != nil {
		return nil, err
	}
	tracker.Add("Options parsing", time.Since(start))

	locStr := opts.Location

	if ipData != nil {
		if autoDetect {
			if ipData.City == "" {
				locStr = fmt.Sprintf("%s,%s", ipData.Latitude, ipData.Longitude)
			} else {
				locStr = fmt.Sprintf("%s, %s, %s", ipData.City, ipData.Region, ipData.CountryCode)