package telemetry

import (
	"context"

	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/metric"

	"github.com/fujin/anthropic-proxy/internal/ratelimit"
)

var (
	RequestCounter      metric.Int64Counter
	RequestDuration     metric.Float64Histogram
	RequestBodySize     metric.Int64Histogram
	UpstreamErrors      metric.Int64Counter
	TokensInput         metric.Int64Counter
	TokensOutput        metric.Int64Counter
	CredentialCooldowns metric.Int64Counter
	ActiveCredentials   metric.Int64UpDownCounter
	StreamRequests      metric.Int64Counter
)

// InitMetrics creates all metric instruments from the given meter.
// If tracker is non-nil, registers observable gauges for per-window usage.
func InitMetrics(meter metric.Meter, tracker *ratelimit.Tracker) {
	RequestCounter, _ = meter.Int64Counter("proxy.request.count",
		metric.WithDescription("Total proxy requests"),
	)
	RequestDuration, _ = meter.Float64Histogram("proxy.request.duration_ms",
		metric.WithDescription("Request latency in milliseconds"),
		metric.WithUnit("ms"),
	)
	RequestBodySize, _ = meter.Int64Histogram("proxy.request.body_size_bytes",
		metric.WithDescription("Request body size in bytes"),
		metric.WithUnit("By"),
	)
	UpstreamErrors, _ = meter.Int64Counter("proxy.upstream.errors",
		metric.WithDescription("Upstream error count"),
	)
	TokensInput, _ = meter.Int64Counter("proxy.tokens.input",
		metric.WithDescription("Input tokens consumed"),
	)
	TokensOutput, _ = meter.Int64Counter("proxy.tokens.output",
		metric.WithDescription("Output tokens consumed"),
	)
	CredentialCooldowns, _ = meter.Int64Counter("proxy.credential.cooldowns",
		metric.WithDescription("Credential cooldown activations"),
	)
	ActiveCredentials, _ = meter.Int64UpDownCounter("proxy.credential.active",
		metric.WithDescription("Currently active (non-cooldown) credentials"),
	)
	StreamRequests, _ = meter.Int64Counter("proxy.stream.requests",
		metric.WithDescription("Streaming request count"),
	)

	if tracker == nil {
		return
	}

	attr5h := attribute.String("window", "5h")
	attr7d := attribute.String("window", "7d")
	attrSonnet := attribute.String("window", "7d_sonnet")

	meter.Float64ObservableGauge("proxy.usage.utilization",
		metric.WithDescription("Current utilization % from API"),
		metric.WithFloat64Callback(func(_ context.Context, o metric.Float64Observer) error {
			o.Observe(tracker.FiveHour().Utilization, metric.WithAttributes(attr5h))
			o.Observe(tracker.SevenDay().Utilization, metric.WithAttributes(attr7d))
			o.Observe(tracker.Sonnet().Utilization, metric.WithAttributes(attrSonnet))
			return nil
		}),
	)

	meter.Int64ObservableGauge("proxy.usage.resets_at",
		metric.WithDescription("Unix seconds when window resets"),
		metric.WithInt64Callback(func(_ context.Context, o metric.Int64Observer) error {
			o.Observe(tracker.FiveHour().ResetsAt.Unix(), metric.WithAttributes(attr5h))
			o.Observe(tracker.SevenDay().ResetsAt.Unix(), metric.WithAttributes(attr7d))
			o.Observe(tracker.Sonnet().ResetsAt.Unix(), metric.WithAttributes(attrSonnet))
			return nil
		}),
	)

}