package extractorregistry

import (
	"fmt"
	"sort"
	"strings"

	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
)

type Constructor func() (contracts.Extractor, error)

type Registry struct {
	constructors map[string]Constructor
}

func New() *Registry {
	return &Registry{
		constructors: make(map[string]Constructor),
	}
}

func (r *Registry) Register(key string, constructor Constructor) error {
	if r == nil {
		return fmt.Errorf("extractor registry must not be nil")
	}

	normalizedKey := strings.TrimSpace(key)
	if normalizedKey == "" {
		return fmt.Errorf("extractor key must not be empty")
	}
	if constructor == nil {
		return fmt.Errorf("extractor constructor for %q must not be nil", normalizedKey)
	}
	if _, ok := r.constructors[normalizedKey]; ok {
		return fmt.Errorf("extractor %q is already registered", normalizedKey)
	}

	r.constructors[normalizedKey] = constructor
	return nil
}

func (r *Registry) Build(key string) (contracts.Extractor, error) {
	if r == nil {
		return nil, fmt.Errorf("extractor registry must not be nil")
	}

	normalizedKey := strings.TrimSpace(key)
	if normalizedKey == "" {
		return nil, fmt.Errorf("extractor key must not be empty")
	}

	constructor, ok := r.constructors[normalizedKey]
	if !ok {
		return nil, fmt.Errorf("extractor %q is not registered", normalizedKey)
	}

	extractor, err := constructor()
	if err != nil {
		return nil, fmt.Errorf("build extractor %q: %w", normalizedKey, err)
	}
	if extractor == nil {
		return nil, fmt.Errorf("extractor %q constructor returned nil", normalizedKey)
	}
	if extractor.Key() != normalizedKey {
		return nil, fmt.Errorf("extractor %q returned key %q", normalizedKey, extractor.Key())
	}

	return extractor, nil
}

func (r *Registry) RegisteredKeys() []string {
	if r == nil {
		return nil
	}

	keys := make([]string, 0, len(r.constructors))
	for key := range r.constructors {
		keys = append(keys, key)
	}
	sort.Strings(keys)
	return keys
}