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

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"strings"
	"time"

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

// ObservationSource polls an Open-Meteo endpoint and emits one RAW Observation Event.
type ObservationSource struct {
	name      string
	url       string
	userAgent string
	client    *http.Client
}

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

	// We require params.user_agent for uniformity across sources (even though Open-Meteo
	// itself does not strictly require a special User-Agent).
	c, err := common.RequireHTTPSourceConfig(driver, cfg)
	if err != nil {
		return nil, err
	}

	return &ObservationSource{
		name:      c.Name,
		url:       c.URL,
		userAgent: c.UserAgent,
		client:    common.NewHTTPClient(common.DefaultHTTPTimeout),
	}, nil
}

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

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

// Poll fetches Open-Meteo "current" and emits exactly one RAW Event.
func (s *ObservationSource) Poll(ctx context.Context) ([]event.Event, error) {
	raw, meta, err := s.fetchRaw(ctx)
	if err != nil {
		return nil, err
	}

	eventID := buildEventID(s.name, meta)
	if strings.TrimSpace(eventID) == "" {
		// Extremely defensive fallback: keep the envelope valid no matter what.
		eventID = fmt.Sprintf("openmeteo:current:%s:%s", s.name, time.Now().UTC().Format(time.RFC3339Nano))
	}

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

	return common.SingleRawEvent(
		s.Kind(),
		s.name,
		standards.SchemaRawOpenMeteoCurrentV1,
		eventID,
		effectiveAt,
		raw,
	)
}

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

type openMeteoMeta struct {
	Latitude         float64 `json:"latitude"`
	Longitude        float64 `json:"longitude"`
	Timezone         string  `json:"timezone"`
	UTCOffsetSeconds int     `json:"utc_offset_seconds"`

	Current struct {
		Time string `json:"time"`
	} `json:"current"`

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

func (s *ObservationSource) fetchRaw(ctx context.Context) (json.RawMessage, openMeteoMeta, error) {
	b, err := common.FetchBody(ctx, s.client, s.url, s.userAgent, "application/json")
	if err != nil {
		return nil, openMeteoMeta{}, fmt.Errorf("openmeteo_observation %q: %w", s.name, err)
	}

	raw := json.RawMessage(b)

	var meta openMeteoMeta
	if err := json.Unmarshal(b, &meta); err != nil {
		// If metadata decode fails, still return raw; envelope will fall back to computed ID without EffectiveAt.
		return raw, openMeteoMeta{}, nil
	}

	// Best effort: compute a stable EffectiveAt + event ID component.
	// If parsing fails, we simply omit EffectiveAt and fall back to time.Now() in buildEventID.
	if t, err := openmeteo.ParseTime(meta.Current.Time, meta.Timezone, meta.UTCOffsetSeconds); err == nil {
		meta.ParsedTimestamp = t.UTC()
	}

	return raw, meta, nil
}

func buildEventID(sourceName string, meta openMeteoMeta) string {
	locKey := ""
	if meta.Latitude != 0 || meta.Longitude != 0 {
		locKey = fmt.Sprintf("coord:%.5f,%.5f", meta.Latitude, meta.Longitude)
	} else {
		locKey = "loc:unknown"
	}

	ts := meta.ParsedTimestamp
	if ts.IsZero() {
		ts = time.Now().UTC()
	}

	return fmt.Sprintf("openmeteo:current:%s:%s:%s", sourceName, locKey, ts.Format(time.RFC3339Nano))
}