package pipeline

import (
	"fmt"
	"strings"

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

type MergerConstructor func() (contracts.Merger, error)

type MergerRegistry struct {
	constructors map[string]MergerConstructor
	specs        map[string]ModuleSpec
}

func NewMergerRegistry() *MergerRegistry {
	return &MergerRegistry{
		constructors: make(map[string]MergerConstructor),
		specs:        make(map[string]ModuleSpec),
	}
}

func (r *MergerRegistry) Register(key string, constructor MergerConstructor) error {
	return r.RegisterWithSpec(defaultModuleSpec(key, StageMerge), constructor)
}

func (r *MergerRegistry) RegisterWithSpec(spec ModuleSpec, constructor MergerConstructor) error {
	if r == nil {
		return fmt.Errorf("merger registry must not be nil")
	}

	normalizedSpec := normalizeModuleSpec(spec)
	if err := validateModuleSpec("merger", StageMerge, normalizedSpec); err != nil {
		return err
	}
	if constructor == nil {
		return fmt.Errorf("merger constructor for %q must not be nil", normalizedSpec.Key)
	}
	if _, ok := r.constructors[normalizedSpec.Key]; ok {
		return fmt.Errorf("merger %q is already registered", normalizedSpec.Key)
	}

	if r.constructors == nil {
		r.constructors = make(map[string]MergerConstructor)
	}
	if r.specs == nil {
		r.specs = make(map[string]ModuleSpec)
	}
	r.constructors[normalizedSpec.Key] = constructor
	r.specs[normalizedSpec.Key] = cloneModuleSpec(normalizedSpec)
	return nil
}

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

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

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

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

	return merger, nil
}

func (r *MergerRegistry) Spec(key string) (ModuleSpec, bool) {
	if r == nil {
		return ModuleSpec{}, false
	}

	spec, ok := r.specs[strings.TrimSpace(key)]
	if !ok {
		return ModuleSpec{}, false
	}
	return cloneModuleSpec(spec), true
}

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

	return sortedRegistryKeys(r.constructors)
}