package promptkit

import (
	"context"
	"fmt"

	internalengine "gitea.maximumdirect.net/eric/promptkit/internal/engine"
)

// NamespaceFilterMode selects namespace membership for an identity listing.
type NamespaceFilterMode uint8

const (
	// NamespaceDefault uses the engine view's scope, or all IDs if it is unset.
	NamespaceDefault NamespaceFilterMode = iota
	// NamespaceNamed selects IDs whose exact namespace matches Name.
	NamespaceNamed
	// NamespaceUnqualified selects IDs without a namespace.
	NamespaceUnqualified
	// NamespaceAll selects IDs from every namespace, overriding the view scope.
	NamespaceAll
)

// NamespaceFilter optionally overrides the namespace used for one listing.
// NamespaceNamed requires a nonempty valid namespace in Name; other modes
// ignore Name.
type NamespaceFilter struct {
	Mode NamespaceFilterMode
	Name string
}

// ResourceKind selects one identity type for [Engine.ListNamespaces].
type ResourceKind string

const (
	// ResourcePrompt selects namespaces containing prompt IDs.
	ResourcePrompt ResourceKind = "prompt"
	// ResourceProfile selects namespaces containing profile IDs.
	ResourceProfile ResourceKind = "profile"
	// ResourceBackend selects namespaces containing backend IDs.
	ResourceBackend ResourceKind = "backend"
)

// CollectionInfo describes one effective collections declaration.
type CollectionInfo struct {
	// Namespace is the exact collection key.
	Namespace string
	// ReleaseVersion is nil when absent or null and points to the exact value
	// when present, including an explicitly empty string.
	ReleaseVersion *string
}

// PromptIdentity identifies one prompt ID and its optional descriptive version
// label in the effective configuration captured when an Engine is constructed.
// Version is metadata only and never participates in prompt selection. A nil
// Version means no label was declared; a non-nil empty string is an explicit
// label. It has no stable JSON representation.
type PromptIdentity struct {
	ID      string
	Version *string
}

// ListProfiles returns profile IDs in the effective configuration captured
// when the engine was constructed. Maintained and consumer profiles are
// included; an inherited profile retains its own ID. IDs are preserved exactly
// and sorted lexically. An omitted filter or NamespaceDefault uses the view's
// profile namespace, or all profiles when unset. NamespaceNamed selects the
// exact named namespace, NamespaceUnqualified selects IDs without a slash, and
// NamespaceAll selects every profile. An explicit filter replaces the view's
// default for this call. At most one filter is accepted.
//
// The returned slice is caller-owned and safe to mutate while the engine is
// used concurrently. Empty inventories succeed.
//
// Listing reports membership, not execution readiness. It does not reload
// configuration or perform resource, credential, provider, or execution work.
// Profile IDs are application data and may be sensitive. A nil or zero-value
// engine returns an error matching ErrInvalidConfig. Cancellation or deadline
// expiration returns the context error and no partial result. Multiple
// filters, an unknown mode, or an invalid named namespace returns an error
// matching ErrInvalidRequest.
func (e *Engine) ListProfiles(ctx context.Context, filters ...NamespaceFilter) ([]string, error) {
	if e == nil || e.internal == nil {
		return nil, fmt.Errorf("%w: engine is nil", ErrInvalidConfig)
	}

	profiles, err := e.internal.ListProfiles(ctx, internalListingFilters(filters)...)
	if err != nil {
		return nil, mapPublicError(err)
	}
	return profiles, nil
}

// ListPrompts returns prompt IDs in the effective configuration captured when
// the engine was constructed, sorted lexically by ID. Each identity may include
// its descriptive version label. Its optional filter follows the same
// NamespaceDefault, NamespaceNamed, NamespaceUnqualified, and NamespaceAll
// behavior as [Engine.ListProfiles], using the prompt namespace by default.
// At most one filter is accepted.
//
// The returned slice and each Version pointer are caller-owned and safe to
// mutate while the engine is used concurrently. Empty inventories succeed.
//
// Listing reports membership, not execution readiness. It does not reload
// configuration or perform resource, credential, provider, or execution work.
// Prompt identities are application data and may be sensitive. A nil or
// zero-value engine returns an error matching ErrInvalidConfig. Cancellation
// or deadline expiration returns the context error and no partial result.
// Multiple filters, an unknown mode, or an invalid named namespace returns an
// error matching ErrInvalidRequest.
func (e *Engine) ListPrompts(ctx context.Context, filters ...NamespaceFilter) ([]PromptIdentity, error) {
	if e == nil || e.internal == nil {
		return nil, fmt.Errorf("%w: engine is nil", ErrInvalidConfig)
	}

	identities, err := e.internal.ListPrompts(ctx, internalListingFilters(filters)...)
	if err != nil {
		return nil, mapPublicError(err)
	}
	public := make([]PromptIdentity, len(identities))
	for i, identity := range identities {
		public[i] = PromptIdentity{ID: identity.ID, Version: copyStringPtr(identity.Version)}
	}
	if err := ctx.Err(); err != nil {
		return nil, mapPublicError(err)
	}
	return public, nil
}

// ListBackends returns backend IDs in the effective configuration captured
// when the engine was constructed, sorted lexically by full ID. Its optional
// filter follows the same namespace behavior as [Engine.ListProfiles], using
// the backend namespace by default. At most one filter is accepted. The
// returned slice is caller-owned and safe to mutate while the engine is used
// concurrently. Empty inventories succeed.
//
// Listing reports membership, not execution readiness, and performs no
// provider or execution work. A nil or zero-value engine returns an error
// matching ErrInvalidConfig. Cancellation or deadline expiration returns the
// context error and no partial result. Multiple filters, an unknown mode, or
// an invalid named namespace returns an error matching ErrInvalidRequest.
func (e *Engine) ListBackends(ctx context.Context, filters ...NamespaceFilter) ([]string, error) {
	if e == nil || e.internal == nil {
		return nil, fmt.Errorf("%w: engine is nil", ErrInvalidConfig)
	}
	backends, err := e.internal.ListBackends(ctx, internalListingFilters(filters)...)
	if err != nil {
		return nil, mapPublicError(err)
	}
	return backends, nil
}

func internalListingFilters(filters []NamespaceFilter) []internalengine.ListingFilter {
	if filters == nil {
		return nil
	}
	internal := make([]internalengine.ListingFilter, len(filters))
	for index, filter := range filters {
		internal[index] = internalengine.ListingFilter{
			Mode: internalengine.ListingFilterMode(filter.Mode),
			Name: filter.Name,
		}
	}
	return internal
}

// ListNamespaces returns the sorted, distinct namespaces that contain the
// selected resource kinds. With no kinds, it returns the union across prompts,
// profiles, and backends. Repeated kinds have no effect; an unknown kind
// returns an error matching ErrInvalidRequest. The inventory is global and is
// not restricted by this engine view's scopes. Unqualified resource IDs do
// not contribute a namespace.
//
// The returned slice is caller-owned. A nil or zero-value engine returns an
// error matching ErrInvalidConfig. Cancellation or deadline expiration
// returns the context error and no partial result.
func (e *Engine) ListNamespaces(ctx context.Context, kinds ...ResourceKind) ([]string, error) {
	if e == nil || e.internal == nil {
		return nil, fmt.Errorf("%w: engine is nil", ErrInvalidConfig)
	}
	internalKinds := make([]string, len(kinds))
	for index, kind := range kinds {
		internalKinds[index] = string(kind)
	}
	namespaces, err := e.internal.ListNamespaces(ctx, internalKinds)
	if err != nil {
		return nil, mapPublicError(err)
	}
	return namespaces, nil
}

// ListCollections returns the sorted collection declarations from the
// effective configuration captured when the engine was constructed. It
// includes metadata-only and resource-only declarations and is independent of
// namespace view scopes. It does not infer collections from resource IDs or
// configuration source history.
//
// The returned slice and each ReleaseVersion pointer are caller-owned. Nil
// means the label was absent or null; a non-nil empty string is preserved. A
// nil or zero-value engine returns an error matching ErrInvalidConfig.
// Cancellation or deadline expiration returns the context error and no partial
// result.
func (e *Engine) ListCollections(ctx context.Context) ([]CollectionInfo, error) {
	if e == nil || e.internal == nil {
		return nil, fmt.Errorf("%w: engine is nil", ErrInvalidConfig)
	}
	collections, err := e.internal.ListCollections(ctx)
	if err != nil {
		return nil, mapPublicError(err)
	}
	public := make([]CollectionInfo, len(collections))
	for index, collection := range collections {
		public[index] = CollectionInfo{
			Namespace:      collection.Namespace,
			ReleaseVersion: copyStringPtr(collection.ReleaseVersion),
		}
	}
	if err := ctx.Err(); err != nil {
		return nil, mapPublicError(err)
	}
	return public, nil
}