// FILE: ./internal/sources/openweather/observation.go
package openweather

import (
	"context"
	"encoding/json"
	"fmt"
	"time"

	"gitea.maximumdirect.net/ejr/feedkit/config"
	"gitea.maximumdirect.net/ejr/feedkit/event"
	owcommon "gitea.maximumdirect.net/ejr/weatherfeeder/internal/providers/openweather"
	"gitea.maximumdirect.net/ejr/weatherfeeder/internal/sources/common"
	"gitea.maximumdirect.net/ejr/weatherfeeder/internal/standards"
)

type ObservationSource struct {
	http *common.HTTPSource
}

func NewObservationSource(cfg config.SourceConfig) (*ObservationSource, error) {
	const driver = "openweather_observation"

	hs, err := common.NewHTTPSource(driver, cfg, "application/json")
	if err != nil {
		return nil, err
	}

	if err := owcommon.RequireMetricUnits(hs.URL); err != nil {
		return nil, fmt.Errorf("%s %q: %w", hs.Driver, hs.Name, err)
	}

	return &ObservationSource{http: hs}, nil
}

func (s *ObservationSource) Name() string { return s.http.Name }

func (s *ObservationSource) Kind() event.Kind { return event.Kind("observation") }

func (s *ObservationSource) Poll(ctx context.Context) ([]event.Event, error) {
	if err := owcommon.RequireMetricUnits(s.http.URL); err != nil {
		return nil, fmt.Errorf("%s %q: %w", s.http.Driver, s.http.Name, err)
	}

	raw, meta, err := s.fetchRaw(ctx)
	if err != nil {
		return nil, err
	}

	var effectiveAt *time.Time
	if !meta.ParsedTimestamp.IsZero() {
		t := meta.ParsedTimestamp.UTC()
		effectiveAt = &t
	}

	emittedAt := time.Now().UTC()
	eventID := common.ChooseEventID("", s.http.Name, effectiveAt, emittedAt)

	return common.SingleRawEvent(
		s.Kind(),
		s.http.Name,
		standards.SchemaRawOpenWeatherCurrentV1,
		eventID,
		emittedAt,
		effectiveAt,
		raw,
	)
}

// ---- RAW fetch + minimal metadata decode ----

type openWeatherMeta struct {
	Dt int64 `json:"dt"` // unix seconds, UTC

	ParsedTimestamp time.Time `json:"-"`
}

func (s *ObservationSource) fetchRaw(ctx context.Context) (json.RawMessage, openWeatherMeta, error) {
	raw, err := s.http.FetchJSON(ctx)
	if err != nil {
		return nil, openWeatherMeta{}, err
	}

	var meta openWeatherMeta
	if err := json.Unmarshal(raw, &meta); err != nil {
		return raw, openWeatherMeta{}, nil
	}

	if meta.Dt > 0 {
		meta.ParsedTimestamp = time.Unix(meta.Dt, 0).UTC()
	}

	return raw, meta, nil
}