package observability

import (
	"net/http"
	"strconv"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promauto"
)

var (
	httpRequestsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "ultid_http_requests_total",
		Help: "Total number of HTTP requests.",
	}, []string{"method", "path", "status"})

	httpRequestDurationSeconds = promauto.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "ultid_http_request_duration_seconds",
		Help:    "HTTP request latency in seconds.",
		Buckets: []float64{0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2, 5, 10},
	}, []string{"method", "path", "status"})

	httpErrorsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "ultid_http_errors_total",
		Help: "Total number of HTTP requests ending with 5xx.",
	}, []string{"method", "path", "status"})

	imapSyncRunsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "ultid_imap_sync_runs_total",
		Help: "Total number of IMAP sync cycles.",
	}, []string{"outcome"})

	imapSyncDurationSeconds = promauto.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "ultid_imap_sync_duration_seconds",
		Help:    "Duration of IMAP sync cycles.",
		Buckets: []float64{0.1, 0.25, 0.5, 1, 2, 5, 10, 30, 60, 120, 300},
	}, []string{"outcome"})

	imapLastSuccessUnix = promauto.NewGauge(prometheus.GaugeOpts{
		Name: "ultid_imap_sync_last_success_timestamp_seconds",
		Help: "Unix timestamp of last successful IMAP sync cycle.",
	})

	outboxQueueDepth = promauto.NewGauge(prometheus.GaugeOpts{
		Name: "ultid_outbox_queue_depth",
		Help: "Current number of queued/sending/scheduled outbox items.",
	})

	outboxProcessedTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "ultid_outbox_processed_total",
		Help: "Total number of outbox jobs processed.",
	}, []string{"outcome"})

	webhookExecutionsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "ultid_webhook_executions_total",
		Help: "Total number of webhook executions.",
	}, []string{"outcome", "status_class"})

	webhookDurationSeconds = promauto.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "ultid_webhook_duration_seconds",
		Help:    "Webhook execution latency in seconds.",
		Buckets: []float64{0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2, 5, 10},
	}, []string{"outcome"})

	webhookRetriesTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "ultid_webhook_retries_total",
		Help: "Total number of webhook retries.",
	}, []string{"reason"})

	webhookDeadLettersTotal = promauto.NewCounter(prometheus.CounterOpts{
		Name: "ultid_webhook_dead_letters_total",
		Help: "Total number of webhook executions moved to dead-letter.",
	})

	webhookPayloadTruncatedTotal = promauto.NewCounter(prometheus.CounterOpts{
		Name: "ultid_webhook_payload_truncated_total",
		Help: "Total number of webhook payloads truncated in logs.",
	})

	migrationJobsProcessedTotal = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "ultid_migration_jobs_processed_total",
		Help: "Total number of migration worker job runs.",
	}, []string{"service", "outcome"})

	migrationJobDurationSeconds = promauto.NewHistogramVec(prometheus.HistogramOpts{
		Name:    "ultid_migration_job_duration_seconds",
		Help:    "Migration worker job run duration in seconds.",
		Buckets: []float64{0.1, 0.25, 0.5, 1, 2, 5, 10, 30, 60, 120, 300},
	}, []string{"service", "outcome"})

	migrationPendingJobs = promauto.NewGauge(prometheus.GaugeOpts{
		Name: "ultid_migration_pending_jobs",
		Help: "Migration jobs picked up on the latest worker tick.",
	})

	migrationRateLimitRetriesTotal = promauto.NewCounter(prometheus.CounterOpts{
		Name: "ultid_migration_rate_limit_retries_total",
		Help: "Total number of migration provider API 429 retries.",
	})
)

type metricsResponseWriter struct {
	http.ResponseWriter
	status int
}

func (rw *metricsResponseWriter) WriteHeader(code int) {
	rw.status = code
	rw.ResponseWriter.WriteHeader(code)
}

func (rw *metricsResponseWriter) Flush() {
	if f, ok := rw.ResponseWriter.(http.Flusher); ok {
		f.Flush()
	}
}

func HTTPMetrics(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		rw := &metricsResponseWriter{ResponseWriter: w, status: http.StatusOK}
		next.ServeHTTP(rw, r)

		status := strconv.Itoa(rw.status)
		labels := []string{r.Method, r.URL.Path, status}

		httpRequestsTotal.WithLabelValues(labels...).Inc()
		httpRequestDurationSeconds.WithLabelValues(labels...).Observe(time.Since(start).Seconds())
		if rw.status >= http.StatusInternalServerError {
			httpErrorsTotal.WithLabelValues(labels...).Inc()
		}
	})
}

func ObserveIMAPSync(outcome string, duration time.Duration) {
	imapSyncRunsTotal.WithLabelValues(outcome).Inc()
	imapSyncDurationSeconds.WithLabelValues(outcome).Observe(duration.Seconds())
	if outcome == "success" {
		imapLastSuccessUnix.SetToCurrentTime()
	}
}

func SetOutboxQueueDepth(depth int64) {
	outboxQueueDepth.Set(float64(depth))
}

func IncOutboxProcessed(outcome string) {
	outboxProcessedTotal.WithLabelValues(outcome).Inc()
}

func ObserveWebhookExecution(outcome string, statusCode int, duration time.Duration) {
	statusClass := "none"
	if statusCode > 0 {
		statusClass = strconv.Itoa(statusCode/100) + "xx"
	}
	webhookExecutionsTotal.WithLabelValues(outcome, statusClass).Inc()
	webhookDurationSeconds.WithLabelValues(outcome).Observe(duration.Seconds())
}

func IncWebhookRetry(reason string) {
	webhookRetriesTotal.WithLabelValues(reason).Inc()
}

func IncWebhookDeadLetter() {
	webhookDeadLettersTotal.Inc()
}

func IncWebhookPayloadTruncated() {
	webhookPayloadTruncatedTotal.Inc()
}

func ObserveMigrationJob(service, outcome string, duration time.Duration) {
	if service == "" {
		service = "unknown"
	}
	if outcome == "" {
		outcome = "unknown"
	}
	migrationJobsProcessedTotal.WithLabelValues(service, outcome).Inc()
	migrationJobDurationSeconds.WithLabelValues(service, outcome).Observe(duration.Seconds())
}

func SetMigrationPendingJobs(count int) {
	migrationPendingJobs.Set(float64(count))
}

func IncMigrationRateLimitRetry() {
	migrationRateLimitRetriesTotal.Inc()
}