package freshness

import (
	"errors"
	"time"

	"github.com/itworx/pulse/internal/datasource"
)

type Input struct {
	SourceID string
	Required bool
	Health   datasource.SourceHealth
	Previous datasource.HealthState
	Now      time.Time
}
type Result struct {
	State       datasource.HealthState
	Age         *time.Duration
	LastKnownAt time.Time
	Recovery    bool
	Event       string
	Warning     string
}

func Evaluate(input Input) (Result, error) {
	if input.SourceID == "" {
		return Result{}, errors.New("source id is required")
	}
	now := input.Now
	if now.IsZero() {
		now = time.Now().UTC()
	}
	if err := input.Health.Validate(now); err != nil {
		return Result{}, err
	}
	result := Result{State: input.Health.EffectiveState(now), LastKnownAt: input.Health.ObservedAt}
	if !input.Health.ObservedAt.IsZero() {
		age := now.Sub(input.Health.ObservedAt)
		if age < 0 {
			age = 0
		}
		result.Age = &age
	}
	if input.Required && result.State != datasource.HealthHealthy && result.State != datasource.HealthDegraded {
		result.State = datasource.HealthUnknown
		result.Warning = "REQUIRED_SOURCE_UNKNOWN"
	}
	if input.Previous == datasource.HealthUnknown && (result.State == datasource.HealthHealthy || result.State == datasource.HealthDegraded) {
		result.Recovery = true
		result.Event = "DATASOURCE_RECOVERED"
	}
	return result, nil
}