package meter

import (
	"context"
	"fmt"
	"os"
	"path/filepath"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/sdk/metric"
	"go.opentelemetry.io/otel/sdk/resource"
	semconv "go.opentelemetry.io/otel/semconv/v1.17.0"
)

func WithServiceName(name string) func(*Option) error {
	return func(o *Option) error {
		o.serviceName = name

		return nil
	}
}

func WithAttributes(attrs ...attribute.KeyValue) func(context.Context, *Option) error {
	return func(_ context.Context, o *Option) error {
		o.attributes = attrs

		return nil
	}
}

func WithExtraResource(opts ...resource.Option) func(context.Context, *Option) error {
	return func(_ context.Context, o *Option) error {
		o.extraResource = opts

		return nil
	}
}

func WithReader(reader metric.Reader) func(context.Context, *Option) error {
	return func(_ context.Context, o *Option) error {
		o.reader = reader

		return nil
	}
}

type Option struct {
	reader        metric.Reader
	serviceName   string
	attributes    []attribute.KeyValue
	extraResource []resource.Option
}

func newOptions(ctx context.Context, opts ...func(context.Context, *Option) error) (Option, error) {
	option := Option{
		serviceName: filepath.Base(os.Args[0]),
		extraResource: []resource.Option{
			resource.WithOS(),
			resource.WithProcess(),
			resource.WithContainer(),
			resource.WithHost(),
		},
	}

	for idx, opt := range opts {
		if err := opt(ctx, &option); err != nil {
			return option, fmt.Errorf("option[%d]:%w", idx, err)
		}
	}

	return option, nil
}

func New(ctx context.Context, opts ...func(context.Context, *Option) error) (*metric.MeterProvider, error) {
	option, err := newOptions(ctx, opts...)
	if err != nil {
		return nil, fmt.Errorf("configure:%w", err)
	}

	extraResources, eerr := resource.New(
		ctx,
		append(
			option.extraResource,
			resource.WithAttributes(
				append(
					option.attributes,
					semconv.ServiceName(option.serviceName),
				)...,
			),
		)...,
	)
	if eerr != nil {
		return nil, fmt.Errorf("create extra resource: %w", eerr)
	}

	res, rerr := resource.Merge(
		resource.Default(),
		extraResources,
	)
	if rerr != nil {
		return nil, fmt.Errorf("merge resource: %w", rerr)
	}

	provOption := make([]metric.Option, 0, 2)

	if option.reader != nil {
		provOption = append(provOption, metric.WithReader(option.reader))
	}

	meterProvider := metric.NewMeterProvider(append(provOption, metric.WithResource(res))...)
	otel.SetMeterProvider(meterProvider)

	return meterProvider, nil
}