package sinks

import (
	"fmt"
	"strings"

	"gitea.maximumdirect.net/ejr/feedkit/config"
)

// Factory constructs a sink instance from config.
//
// This is the mechanism that lets concrete daemons wire in whatever sinks they
// want without main.go being full of switch statements.
type Factory func(cfg config.SinkConfig) (Sink, error)

type Registry struct {
	byDriver map[string]Factory
}

func NewRegistry() *Registry {
	return &Registry{byDriver: map[string]Factory{}}
}

func (r *Registry) Register(driver string, f Factory) {
	if r == nil {
		panic("sinks.Registry.Register: registry cannot be nil")
	}
	driver = strings.TrimSpace(driver)
	if driver == "" {
		panic("sinks.Registry.Register: driver cannot be empty")
	}
	if f == nil {
		panic(fmt.Sprintf("sinks.Registry.Register: factory cannot be nil (driver=%q)", driver))
	}
	if r.byDriver == nil {
		r.byDriver = map[string]Factory{}
	}
	if _, exists := r.byDriver[driver]; exists {
		panic(fmt.Sprintf("sinks.Registry.Register: driver %q already registered", driver))
	}
	r.byDriver[driver] = f
}

func (r *Registry) Build(cfg config.SinkConfig) (Sink, error) {
	if r == nil {
		return nil, fmt.Errorf("sinks registry is nil")
	}
	driver := strings.TrimSpace(cfg.Driver)
	f, ok := r.byDriver[driver]
	if !ok {
		return nil, fmt.Errorf("unknown sink driver: %q", driver)
	}
	sink, err := f(cfg)
	if err != nil {
		return nil, fmt.Errorf("build sink %q: %w", driver, err)
	}
	if sink == nil {
		return nil, fmt.Errorf("build sink %q: factory returned nil sink", driver)
	}
	return sink, nil
}