package openmeteo

import (
	"context"
	"fmt"
	"strings"
	"time"

	"gitea.maximumdirect.net/ejr/feedkit/event"
	"gitea.maximumdirect.net/ejr/weatherfeeder/internal/model"
	normcommon "gitea.maximumdirect.net/ejr/weatherfeeder/internal/normalizers/common"
	omcommon "gitea.maximumdirect.net/ejr/weatherfeeder/internal/providers/openmeteo"
	"gitea.maximumdirect.net/ejr/weatherfeeder/internal/standards"
)

// ForecastNormalizer converts:
//
//	standards.SchemaRawOpenMeteoHourlyForecastV1 -> standards.SchemaWeatherForecastV1
//
// It interprets Open-Meteo hourly forecast JSON and maps it into the canonical
// model.WeatherForecastRun representation.
//
// Caveats / assumptions:
//   - Open-Meteo does not provide a true "issued at" timestamp; IssuedAt uses
//     Event.EmittedAt when present, otherwise the first hourly time.
//   - Hourly payloads are array-oriented; missing fields are treated as nil per-period.
//   - Snowfall is provided in centimeters and is converted to millimeters.
//   - apparent_temperature is mapped to ApparentTemperatureC when present.
type ForecastNormalizer struct{}

func (ForecastNormalizer) Match(e event.Event) bool {
	return strings.TrimSpace(e.Schema) == standards.SchemaRawOpenMeteoHourlyForecastV1
}

func (ForecastNormalizer) Normalize(ctx context.Context, in event.Event) (*event.Event, error) {
	_ = ctx // normalization is pure/CPU; keep ctx for future expensive steps

	// If present, prefer the existing event EmittedAt as IssuedAt.
	var fallbackIssued time.Time
	if !in.EmittedAt.IsZero() {
		fallbackIssued = in.EmittedAt.UTC()
	}

	return normcommon.NormalizeJSON(
		in,
		"openmeteo hourly forecast",
		standards.SchemaWeatherForecastV1,
		func(parsed omForecastResponse) (model.WeatherForecastRun, time.Time, error) {
			return buildForecast(parsed, fallbackIssued)
		},
	)
}

// buildForecast contains the domain mapping logic (provider -> canonical model).
func buildForecast(parsed omForecastResponse, fallbackIssued time.Time) (model.WeatherForecastRun, time.Time, error) {
	times := parsed.Hourly.Time
	if len(times) == 0 {
		return model.WeatherForecastRun{}, time.Time{}, fmt.Errorf("missing hourly.time")
	}
	issuedAt := fallbackIssued.UTC()

	run := model.WeatherForecastRun{
		LocationID:   normcommon.SynthStationIDPtr("OPENMETEO", parsed.Latitude, parsed.Longitude),
		LocationName: "Open-Meteo",

		IssuedAt:  time.Time{},
		UpdatedAt: nil,
		Product:   model.ForecastProductHourly,

		Latitude:        floatCopy(parsed.Latitude),
		Longitude:       floatCopy(parsed.Longitude),
		ElevationMeters: floatCopy(parsed.Elevation),

		Periods: nil,
	}

	periods := make([]model.WeatherForecastPeriod, 0, len(times))
	var prevStart time.Time
	for i := range times {
		start, err := parseHourlyTime(parsed, i)
		if err != nil {
			return model.WeatherForecastRun{}, time.Time{}, err
		}
		if issuedAt.IsZero() && i == 0 {
			issuedAt = start
		}

		end, err := parsePeriodEnd(parsed, i, start, prevStart)
		if err != nil {
			return model.WeatherForecastRun{}, time.Time{}, err
		}
		prevStart = start

		var isDay *bool
		if v := intAt(parsed.Hourly.IsDay, i); v != nil {
			b := *v == 1
			isDay = &b
		}

		wmo := wmoAt(parsed.Hourly.WeatherCode, i)
		canonicalText := standards.WMOText(wmo, isDay)

		period := model.WeatherForecastPeriod{
			StartTime: start,
			EndTime:   end,

			Name:  "",
			IsDay: isDay,

			ConditionCode: wmo,
			ConditionText: canonicalText,

			ProviderRawDescription: "",

			TextDescription: canonicalText,
			DetailedText:    "",

			IconURL: "",
		}

		if v := floatAt(parsed.Hourly.Temperature2m, i); v != nil {
			period.TemperatureC = v
		}
		if v := floatAt(parsed.Hourly.ApparentTemp, i); v != nil {
			period.ApparentTemperatureC = v
		}
		if v := floatAt(parsed.Hourly.DewPoint2m, i); v != nil {
			period.DewpointC = v
		}
		if v := floatAt(parsed.Hourly.RelativeHumidity2m, i); v != nil {
			period.RelativeHumidityPercent = v
		}
		if v := floatAt(parsed.Hourly.WindDirection10m, i); v != nil {
			period.WindDirectionDegrees = v
		}
		if v := floatAt(parsed.Hourly.WindSpeed10m, i); v != nil {
			period.WindSpeedKmh = v
		}
		if v := floatAt(parsed.Hourly.WindGusts10m, i); v != nil {
			period.WindGustKmh = v
		}
		if v := floatAt(parsed.Hourly.Visibility, i); v != nil {
			period.VisibilityMeters = v
		}
		if v := floatAt(parsed.Hourly.CloudCover, i); v != nil {
			period.CloudCoverPercent = v
		}
		if v := floatAt(parsed.Hourly.UVIndex, i); v != nil {
			period.UVIndex = v
		}

		if v := floatAt(parsed.Hourly.PrecipProbability, i); v != nil {
			period.ProbabilityOfPrecipitationPercent = v
		}
		if v := floatAt(parsed.Hourly.Precipitation, i); v != nil {
			period.PrecipitationAmountMm = v
		}
		if v := floatAt(parsed.Hourly.Snowfall, i); v != nil {
			mm := *v * 10.0
			period.SnowfallDepthMM = &mm
		}

		if v := floatAt(parsed.Hourly.SurfacePressure, i); v != nil {
			pa := normcommon.PressurePaFromHPa(*v)
			period.BarometricPressurePa = &pa
		} else if v := floatAt(parsed.Hourly.PressureMSL, i); v != nil {
			pa := normcommon.PressurePaFromHPa(*v)
			period.BarometricPressurePa = &pa
		}

		periods = append(periods, period)
	}

	run.Periods = periods

	if issuedAt.IsZero() {
		return model.WeatherForecastRun{}, time.Time{}, fmt.Errorf("missing issuedAt")
	}
	run.IssuedAt = issuedAt

	// EffectiveAt policy for forecasts: treat IssuedAt as the effective time (dedupe-friendly).
	return run, issuedAt, nil
}

func parseHourlyTime(parsed omForecastResponse, idx int) (time.Time, error) {
	if idx < 0 || idx >= len(parsed.Hourly.Time) {
		return time.Time{}, fmt.Errorf("hourly.time[%d] missing", idx)
	}
	raw := strings.TrimSpace(parsed.Hourly.Time[idx])
	if raw == "" {
		return time.Time{}, fmt.Errorf("hourly.time[%d] empty", idx)
	}

	t, err := omcommon.ParseTime(raw, parsed.Timezone, parsed.UTCOffsetSeconds)
	if err != nil {
		return time.Time{}, fmt.Errorf("hourly.time[%d] invalid %q: %w", idx, raw, err)
	}
	return t.UTC(), nil
}

func parsePeriodEnd(parsed omForecastResponse, idx int, start, prevStart time.Time) (time.Time, error) {
	if idx+1 < len(parsed.Hourly.Time) {
		return parseHourlyTime(parsed, idx+1)
	}

	step := time.Hour
	if !prevStart.IsZero() {
		if d := start.Sub(prevStart); d > 0 {
			step = d
		}
	}
	return start.Add(step), nil
}

func floatCopy(v *float64) *float64 {
	if v == nil {
		return nil
	}
	out := *v
	return &out
}

func floatAt(vals []*float64, idx int) *float64 {
	if idx < 0 || idx >= len(vals) {
		return nil
	}
	return floatCopy(vals[idx])
}

func intAt(vals []*int, idx int) *int {
	if idx < 0 || idx >= len(vals) {
		return nil
	}
	if vals[idx] == nil {
		return nil
	}
	out := *vals[idx]
	return &out
}

func wmoAt(vals []*int, idx int) model.WMOCode {
	if v := intAt(vals, idx); v != nil {
		return model.WMOCode(*v)
	}
	return model.WMOUnknown
}