package plugin

import (
	"fmt"
	"sync"
)

// Registry holds all registered collector plugins.
type Registry struct {
	mu      sync.RWMutex
	plugins map[string]Collector
}

// NewRegistry creates an empty plugin registry.
func NewRegistry() *Registry {
	return &Registry{plugins: make(map[string]Collector)}
}

// Register adds a collector to the registry. Panics on duplicate name.
func (r *Registry) Register(c Collector) {
	r.mu.Lock()
	defer r.mu.Unlock()
	name := c.Name()
	if _, exists := r.plugins[name]; exists {
		panic(fmt.Sprintf("plugin %q already registered", name))
	}
	r.plugins[name] = c
}

// Get returns a collector by name, or an error if not found.
func (r *Registry) Get(name string) (Collector, error) {
	r.mu.RLock()
	defer r.mu.RUnlock()
	c, ok := r.plugins[name]
	if !ok {
		return nil, fmt.Errorf("plugin %q not registered", name)
	}
	return c, nil
}

// List returns all registered plugin names.
func (r *Registry) List() []string {
	r.mu.RLock()
	defer r.mu.RUnlock()
	names := make([]string, 0, len(r.plugins))
	for name := range r.plugins {
		names = append(names, name)
	}
	return names
}