package monitoring

import (
	"context"
	"fmt"
	"strings"
)

// PrometheusExporter exports metrics in Prometheus format
type PrometheusExporter struct {
	Collectors []Collector
}

func NewPrometheusExporter(collectors ...Collector) *PrometheusExporter {
	return &PrometheusExporter{Collectors: collectors}
}

// Export collects all metrics and formats them as Prometheus text format
func (e *PrometheusExporter) Export(ctx context.Context) string {
	var builder strings.Builder
	allErrors := []string{}

	for _, collector := range e.Collectors {
		collection := collector.Collect(ctx)
		allErrors = append(allErrors, collection.Errors...)

		for _, metric := range collection.Metrics {
			// Format: metric_name{label1="value1",label2="value2"} value
			builder.WriteString(metric.Name)
			if len(metric.Labels) > 0 {
				builder.WriteString("{")
				first := true
				for k, v := range metric.Labels {
					if !first {
						builder.WriteString(",")
					}
					builder.WriteString(fmt.Sprintf(`%s="%s"`, k, escapeLabelValue(v)))
					first = false
				}
				builder.WriteString("}")
			}
			builder.WriteString(fmt.Sprintf(" %v\n", metric.Value))
		}
	}

	// Add error metrics if any
	if len(allErrors) > 0 {
		builder.WriteString(fmt.Sprintf("monitoring_collector_errors_total %d\n", len(allErrors)))
	}

	return builder.String()
}

func escapeLabelValue(v string) string {
	v = strings.ReplaceAll(v, "\\", "\\\\")
	v = strings.ReplaceAll(v, "\"", "\\\"")
	v = strings.ReplaceAll(v, "\n", "\\n")
	return v
}