// FILE: internal/model/forecast.go
package model

import "time"

// ForecastProduct distinguishes *what kind* of forecast a provider is offering.
// This is intentionally canonical and not provider-nomenclature.
type ForecastProduct string

const (
	// ForecastProductHourly is a sub-daily forecast where each period is typically ~1 hour.
	ForecastProductHourly ForecastProduct = "hourly"

	// ForecastProductNarrative is a human-oriented sequence of periods like
	// "Tonight", "Friday", "Friday Night" with variable duration.
	//
	// (NWS "/forecast" looks like this; it is not strictly “daily”.)
	ForecastProductNarrative ForecastProduct = "narrative"

	// ForecastProductDaily is a calendar-day (or day-bucketed) forecast where a period
	// commonly carries min/max values (Open-Meteo daily, many others).
	ForecastProductDaily ForecastProduct = "daily"
)

// WeatherForecastRun is a single issued forecast snapshot for a location and product.
//
// Design goals:
//   - Immutable snapshot semantics: “provider asserted X at IssuedAt”.
//   - Provider-independent schema: normalize many upstreams into one shape.
//   - Retrieval-friendly: periods are inside the run, but can be stored/indexed separately.
type WeatherForecastRun struct {
	// Identity / metadata (aligned with WeatherObservation’s StationID/StationName/Timestamp).
	LocationID   string    `json:"locationId,omitempty"`
	LocationName string    `json:"locationName,omitempty"`
	IssuedAt     time.Time `json:"issuedAt"` // required: when this run was generated/issued

	// Some providers include both a generated time and a later update time.
	// Keep UpdatedAt optional; many providers won’t supply it.
	UpdatedAt *time.Time `json:"updatedAt,omitempty"`

	// What sort of forecast this run represents (hourly vs narrative vs daily).
	Product ForecastProduct `json:"product"`

	// Optional spatial context. Many providers are fundamentally lat/lon-based.
	Latitude  *float64 `json:"latitude,omitempty"`
	Longitude *float64 `json:"longitude,omitempty"`

	// Kept to align with WeatherObservation and because elevation is sometimes important
	// for interpreting temps/precip, even if not always supplied by the provider.
	ElevationMeters *float64 `json:"elevationMeters,omitempty"`

	// The forecast periods contained in this issued run. Order should be chronological.
	Periods []WeatherForecastPeriod `json:"periods"`
}

// WeatherForecastPeriod is a forecast for a specific valid interval [StartTime, EndTime).
//
// Conceptually, it mirrors WeatherObservation (condition + measurements), but:
// /  - It has a time *range* (start/end) instead of a single timestamp.
// /  - It adds forecast-specific fields like probability/amount of precip.
// /  - It supports min/max for “daily” products (and other aggregated periods).
type WeatherForecastPeriod struct {
	// Identity / validity window (required)
	StartTime time.Time `json:"startTime"`
	EndTime   time.Time `json:"endTime"`

	// Human-facing period label (e.g., "Tonight", "Friday"). Often empty for hourly.
	Name string `json:"name,omitempty"`

	// Canonical day/night hint (aligned with WeatherObservation.IsDay).
	// Providers vary in whether they explicitly include this.
	IsDay *bool `json:"isDay,omitempty"`

	// Canonical internal representation (provider-independent).
	// Like WeatherObservation, this is required; use an “unknown” WMOCode if unmappable.
	ConditionCode WMOCode `json:"conditionCode"`

	// Provider-independent short text describing the conditions (normalized, if possible).
	ConditionText string `json:"conditionText,omitempty"`

	// Provider-specific “evidence” for troubleshooting mapping and drift.
	ProviderRawDescription string `json:"providerRawDescription,omitempty"`

	// Human-facing narrative. Not all providers supply rich text (Open-Meteo often won’t).
	TextDescription string `json:"textDescription,omitempty"` // short phrase / summary
	DetailedText    string `json:"detailedText,omitempty"`    // longer narrative, if available

	// Provider-specific (legacy / transitional)
	IconURL string `json:"iconUrl,omitempty"`

	// Core predicted measurements (nullable; units align with WeatherObservation)
	TemperatureC *float64 `json:"temperatureC,omitempty"`

	// For aggregated products (notably “daily”), providers may supply min/max.
	TemperatureCMin *float64 `json:"temperatureCMin,omitempty"`
	TemperatureCMax *float64 `json:"temperatureCMax,omitempty"`

	DewpointC               *float64 `json:"dewpointC,omitempty"`
	RelativeHumidityPercent *float64 `json:"relativeHumidityPercent,omitempty"`
	WindDirectionDegrees    *float64 `json:"windDirectionDegrees,omitempty"`
	WindSpeedKmh            *float64 `json:"windSpeedKmh,omitempty"`
	WindGustKmh             *float64 `json:"windGustKmh,omitempty"`
	BarometricPressurePa    *float64 `json:"barometricPressurePa,omitempty"`
	VisibilityMeters        *float64 `json:"visibilityMeters,omitempty"`
	ApparentTemperatureC    *float64 `json:"apparentTemperatureC,omitempty"`
	CloudCoverPercent       *float64 `json:"cloudCoverPercent,omitempty"`

	// Precipitation (forecast-specific). Keep these generic and provider-independent.
	ProbabilityOfPrecipitationPercent *float64 `json:"probabilityOfPrecipitationPercent,omitempty"`

	// Quantitative precip is not universally available, but OpenWeather/Open-Meteo often supply it.
	// Use liquid-equivalent mm for interoperability.
	PrecipitationAmountMm *float64 `json:"precipitationAmountMm,omitempty"`
	SnowfallDepthMM       *float64 `json:"snowfallDepthMm,omitempty"`

	// Optional extras that some providers supply and downstream might care about.
	UVIndex *float64 `json:"uvIndex,omitempty"`
}