go-emlid/reach/client/client.go

package client

import (
	"context"
	"sync"

	"forge.cadoles.com/cadoles/go-emlid/reach/client/protocol"
	"github.com/pkg/errors"
)

type Client struct {
	addr string
	opts *Options

	proto protocol.Identifier
	ops   protocol.Operations

	getProtocolOnce    sync.Once
	getProtocolOnceErr error
}

func (c *Client) Protocol(ctx context.Context) (protocol.Identifier, protocol.Operations, error) {
	id, ops, err := c.getProtocol(ctx)
	if err != nil {
		return "", nil, errors.WithStack(err)
	}

	return id, ops, nil
}

func (c *Client) getProtocol(ctx context.Context) (protocol.Identifier, protocol.Operations, error) {
	c.getProtocolOnce.Do(func() {
		availables, err := c.opts.Protocols.Availables(ctx, c.addr)
		if err != nil {
			c.getProtocolOnceErr = errors.WithStack(err)
			return
		}

		var preferred protocol.Protocol
		var fallback protocol.Protocol

		for _, proto := range availables {
			if proto.Identifier() == c.opts.FallbackProtocol {
				fallback = proto
			}

			if proto.Identifier() == c.opts.PreferredProtocol {
				preferred = proto
				break
			}
		}

		if preferred != nil {
			c.proto = preferred.Identifier()
			c.ops = preferred.Operations(c.addr)
			return
		}

		if fallback != nil {
			c.proto = fallback.Identifier()
			c.ops = fallback.Operations(c.addr)
			return
		}

		for _, proto := range availables {
			if proto.Identifier() != c.opts.FallbackProtocol {
				continue
			}

			fallback = proto
			break
		}

		if fallback == nil {
			c.getProtocolOnceErr = errors.Errorf("neither preferred protocol '%v' or fallback '%v' are available", c.opts.PreferredProtocol, c.opts.FallbackProtocol)
			return
		}

		c.proto = fallback.Identifier()
		c.ops = fallback.Operations(c.addr)
	})
	if c.getProtocolOnceErr != nil {
		return "", nil, errors.WithStack(c.getProtocolOnceErr)
	}

	return c.proto, c.ops, nil
}

func NewClient(addr string, funcs ...OptionFunc) *Client {
	opts := NewOptions(funcs...)
	client := &Client{
		addr: addr,
		opts: opts,
	}
	return client
}