package state

import (
	"context"
	"errors"

	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/codes"
	"go.opentelemetry.io/otel/trace"

	"gitea.libretechconsulting.com/rmcguire/ambient-local-exporter/pkg/weather"
)

// Returns last requested number of weather updates
func (w *WeatherState) Get(ctx context.Context, last int) (
	[]*weather.WeatherUpdate, error,
) {
	if last < 1 {
		last = 1
	}

	ctx, span := w.tracer.Start(ctx, "getWeatherState")
	span.SetAttributes(
		attribute.Int("last", last),
		attribute.Int("keep", w.keep),
		attribute.Int("currentSize", w.Count()),
	)
	defer span.End()

	updates, err := w.get(ctx, last)
	if err != nil {
		span.RecordError(err)
		span.SetStatus(codes.Error, err.Error())
	} else {
		span.SetStatus(codes.Ok, "")
	}

	return updates, err
}

func (w *WeatherState) get(ctx context.Context, last int) (
	[]*weather.WeatherUpdate, error,
) {
	span := trace.SpanFromContext(ctx)

	w.RLock()
	defer w.Unlock()

	span.AddEvent("acquired lock on state cache")

	updates := w.updates

	if w.count() == 0 {
		err := errors.New("no state to get")
		span.RecordError(err)
		return nil, err
	} else if w.count() <= last {
		span.RecordError(errors.New("requested more state than exists"))
	} else {
		updates = updates[len(updates)-last:]
	}

	span.SetAttributes(attribute.Int("retrieved", len(updates)))
	span.SetStatus(codes.Ok, "")

	return updates, nil
}

// Returns count of retained weather updates
func (w *WeatherState) Count() int {
	_, span := w.tracer.Start(w.ctx, "countWeatherState")
	defer span.End()

	count := w.count()

	span.SetAttributes(attribute.Int("count", count))
	span.SetStatus(codes.Ok, "")

	return count
}

func (w *WeatherState) count() int {
	w.RLock()
	defer w.RUnlock()

	return len(w.updates)
}